Commit Graph

623 Commits

Author SHA1 Message Date
Al Viro 37c17e1f37 untangling do_lookup() - expand the area under ->i_mutex
keep holding ->i_mutex over revalidation parts

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-03-31 16:03:16 -04:00
Al Viro 3f6c7c71a2 untangling do_lookup() - isolate !dentry stuff from the rest of it.
Duplicate the revalidation-related parts into if (!dentry) branch.
Next step will be to pull them under i_mutex.

This and the next 8 commits are more or less a splitup of patch
by Miklos; folks, when you are working with something that convoluted,
carve your patches up into easily reviewed steps, especially when
a lot of codepaths involved are rarely hit...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-03-31 16:03:16 -04:00
Miklos Szeredi cda309de25 vfs: move MAY_EXEC check from __lookup_hash()
The only caller of __lookup_hash() that needs the exec permission check on
parent is lookup_one_len().

All lookup_hash() callers already checked permission in LOOKUP_PARENT walk.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-03-31 16:03:16 -04:00
Miklos Szeredi 3637c05d88 vfs: don't revalidate just looked up dentry
__lookup_hash() calls ->lookup() if the dentry needs lookup and on success
revalidates the dentry (all under dir->i_mutex).

While this is harmless it doesn't make a lot of sense.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-03-31 16:03:16 -04:00
Miklos Szeredi fa4ee15951 vfs: fix d_need_lookup/d_revalidate order in do_lookup
Doing revalidate on a dentry which has not yet been looked up makes no sense.

Move the d_need_lookup() check before d_revalidate().

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-03-31 16:03:16 -04:00
Linus Torvalds 11bcb32848 The following text was taken from the original review request:
"[PATCH 0/3] RFC - module.h usage cleanups in fs/ and lib/"
 		https://lkml.org/lkml/2012/2/29/589
 --
 
 Fix up files in fs/ and lib/ dirs to only use module.h if they really
 need it.
 
 These are trivial in scope vs. the work done previously.  We now have
 things where any few remaining cleanups can be farmed out to arch or
 subsystem maintainers, and I have done so when possible.  What is
 remaining here represents the bits that don't clearly lie within a
 single arch/subsystem boundary, like the fs dir and the lib dir.
 
 Some duplicate includes arising from overlapping fixes from
 independent subsystem maintainer submissions are also quashed.
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Merge tag 'module-for-3.4' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux

Pull cleanup of fs/ and lib/ users of module.h from Paul Gortmaker:
 "Fix up files in fs/ and lib/ dirs to only use module.h if they really
  need it.

  These are trivial in scope vs the work done previously.  We now have
  things where any few remaining cleanups can be farmed out to arch or
  subsystem maintainers, and I have done so when possible.  What is
  remaining here represents the bits that don't clearly lie within a
  single arch/subsystem boundary, like the fs dir and the lib dir.

  Some duplicate includes arising from overlapping fixes from
  independent subsystem maintainer submissions are also quashed."

Fix up trivial conflicts due to clashes with other include file cleanups
(including some due to the previous bug.h cleanup pull).

* tag 'module-for-3.4' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux:
  lib: reduce the use of module.h wherever possible
  fs: reduce the use of module.h wherever possible
  includecheck: delete any duplicate instances of module.h
2012-03-24 10:24:31 -07:00
Linus Torvalds f7493e5d9c vfs: tidy up sparse warnings in fs/namei.c
While doing the fs/namei.c cleanups, I ran sparse on it, and it pointed
out other large integers and a couple of cases of us using '0' instead
of the proper 'NULL'.

Sparse still doesn't understand some of the conditional locking going
on, but that's no excuse for not fixing up the trivial stuff.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-03-22 16:10:40 -07:00
Linus Torvalds 989412bbd2 vfs: tidy up fs/namei.c byte-repeat word constants
In commit commit 1de5b41cd3 ("fs/namei.c: fix warnings on 32-bit")
Andrew said that there must be a tidier way of doing this.

This is that tidier way.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-03-22 15:58:27 -07:00
Al Viro f132c5be05 Fix full_name_hash() behaviour when length is a multiple of 8
We want it to match what hash_name() is doing, which means extra
multiply by 9 in this case...

Reported-and-Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-03-22 15:10:43 -07:00
Linus Torvalds 95211279c5 Merge branch 'akpm' (Andrew's patch-bomb)
Merge first batch of patches from Andrew Morton:
 "A few misc things and all the MM queue"

* emailed from Andrew Morton <akpm@linux-foundation.org>: (92 commits)
  memcg: avoid THP split in task migration
  thp: add HPAGE_PMD_* definitions for !CONFIG_TRANSPARENT_HUGEPAGE
  memcg: clean up existing move charge code
  mm/memcontrol.c: remove unnecessary 'break' in mem_cgroup_read()
  mm/memcontrol.c: remove redundant BUG_ON() in mem_cgroup_usage_unregister_event()
  mm/memcontrol.c: s/stealed/stolen/
  memcg: fix performance of mem_cgroup_begin_update_page_stat()
  memcg: remove PCG_FILE_MAPPED
  memcg: use new logic for page stat accounting
  memcg: remove PCG_MOVE_LOCK flag from page_cgroup
  memcg: simplify move_account() check
  memcg: remove EXPORT_SYMBOL(mem_cgroup_update_page_stat)
  memcg: kill dead prev_priority stubs
  memcg: remove PCG_CACHE page_cgroup flag
  memcg: let css_get_next() rely upon rcu_read_lock()
  cgroup: revert ss_id_lock to spinlock
  idr: make idr_get_next() good for rcu_read_lock()
  memcg: remove unnecessary thp check in page stat accounting
  memcg: remove redundant returns
  memcg: enum lru_list lru
  ...
2012-03-22 09:04:48 -07:00
Andrew Morton 1de5b41cd3 fs/namei.c: fix warnings on 32-bit
i386 allnoconfig:

  fs/namei.c: In function 'has_zero':
  fs/namei.c:1617: warning: integer constant is too large for 'unsigned long' type
  fs/namei.c:1617: warning: integer constant is too large for 'unsigned long' type
  fs/namei.c: In function 'hash_name':
  fs/namei.c:1635: warning: integer constant is too large for 'unsigned long' type

There must be a tidier way of doing this.

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-03-21 17:54:54 -07:00
Linus Torvalds e2a0883e40 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs pile 1 from Al Viro:
 "This is _not_ all; in particular, Miklos' and Jan's stuff is not there
  yet."

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (64 commits)
  ext4: initialization of ext4_li_mtx needs to be done earlier
  debugfs-related mode_t whack-a-mole
  hfsplus: add an ioctl to bless files
  hfsplus: change finder_info to u32
  hfsplus: initialise userflags
  qnx4: new helper - try_extent()
  qnx4: get rid of qnx4_bread/qnx4_getblk
  take removal of PF_FORKNOEXEC to flush_old_exec()
  trim includes in inode.c
  um: uml_dup_mmap() relies on ->mmap_sem being held, but activate_mm() doesn't hold it
  um: embed ->stub_pages[] into mmu_context
  gadgetfs: list_for_each_safe() misuse
  ocfs2: fix leaks on failure exits in module_init
  ecryptfs: make register_filesystem() the last potential failure exit
  ntfs: forgets to unregister sysctls on register_filesystem() failure
  logfs: missing cleanup on register_filesystem() failure
  jfs: mising cleanup on register_filesystem() failure
  make configfs_pin_fs() return root dentry on success
  configfs: configfs_create_dir() has parent dentry in dentry->d_parent
  configfs: sanitize configfs_create()
  ...
2012-03-21 13:36:41 -07:00
Linus Torvalds 9f3938346a Merge branch 'kmap_atomic' of git://github.com/congwang/linux
Pull kmap_atomic cleanup from Cong Wang.

It's been in -next for a long time, and it gets rid of the (no longer
used) second argument to k[un]map_atomic().

Fix up a few trivial conflicts in various drivers, and do an "evil
merge" to catch some new uses that have come in since Cong's tree.

* 'kmap_atomic' of git://github.com/congwang/linux: (59 commits)
  feature-removal-schedule.txt: schedule the deprecated form of kmap_atomic() for removal
  highmem: kill all __kmap_atomic() [swarren@nvidia.com: highmem: Fix ARM build break due to __kmap_atomic rename]
  drbd: remove the second argument of k[un]map_atomic()
  zcache: remove the second argument of k[un]map_atomic()
  gma500: remove the second argument of k[un]map_atomic()
  dm: remove the second argument of k[un]map_atomic()
  tomoyo: remove the second argument of k[un]map_atomic()
  sunrpc: remove the second argument of k[un]map_atomic()
  rds: remove the second argument of k[un]map_atomic()
  net: remove the second argument of k[un]map_atomic()
  mm: remove the second argument of k[un]map_atomic()
  lib: remove the second argument of k[un]map_atomic()
  power: remove the second argument of k[un]map_atomic()
  kdb: remove the second argument of k[un]map_atomic()
  udf: remove the second argument of k[un]map_atomic()
  ubifs: remove the second argument of k[un]map_atomic()
  squashfs: remove the second argument of k[un]map_atomic()
  reiserfs: remove the second argument of k[un]map_atomic()
  ocfs2: remove the second argument of k[un]map_atomic()
  ntfs: remove the second argument of k[un]map_atomic()
  ...
2012-03-21 09:40:26 -07:00
Al Viro 68ac1234fb switch touch_atime to struct path
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-03-20 21:29:41 -04:00
Al Viro 8de5277879 vfs: check i_nlink limits in vfs_{mkdir,rename_dir,link}
New field of struct super_block - ->s_max_links.  Maximal allowed
value of ->i_nlink or 0; in the latter case all checks still need
to be done in ->link/->mkdir/->rename instances.  Note that this
limit applies both to directoris and to non-directories.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-03-20 21:29:32 -04:00
Cong Wang e8e3c3d66f fs: remove the second argument of k[un]map_atomic()
Acked-by: Benjamin LaHaise <bcrl@kvack.org>
Signed-off-by: Cong Wang <amwang@redhat.com>
2012-03-20 21:48:21 +08:00
Linus Torvalds b0e37d7ac6 Merge branch 'dcache-word-accesses'
* branch 'dcache-word-accesses':
  vfs: use 'unsigned long' accesses for dcache name comparison and hashing

This does the name hashing and lookup using word-sized accesses when
that is efficient, namely on x86 (although any little-endian machine
with good unaligned accesses would do).

It does very much depend on little-endian logic, but it's a very hot
couple of functions under some real loads, and this patch improves the
performance of __d_lookup_rcu() and link_path_walk() by up to about 30%.
Giving a 10% improvement on some very pathname-heavy benchmarks.

Because we do make unaligned accesses past the filename, the
optimization is disabled when CONFIG_DEBUG_PAGEALLOC is active, and we
effectively depend on the fact that on x86 we don't really ever have the
last page of usable RAM followed immediately by any IO memory (due to
ACPI tables, BIOS buffer areas etc).

Some of the bit operations we do are a bit "subtle".  It's commented,
but you do need to really think about the code.  Or just consider it
black magic.

Thanks to people on G+ for some of the optimized bit tricks.
2012-03-19 16:37:28 -07:00
Miklos Szeredi 7f6c7e62fc vfs: fix return value from do_last()
complete_walk() returns either ECHILD or ESTALE.  do_last() turns this into
ECHILD unconditionally.  If not in RCU mode, this error will reach userspace
which is complete nonsense.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
CC: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-03-10 17:05:30 -05:00
Miklos Szeredi 097b180ca0 vfs: fix double put after complete_walk()
complete_walk() already puts nd->path, no need to do it again at cleanup time.

This would result in Oopses if triggered, apparently the codepath is not too
well exercised.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
CC: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-03-10 17:05:30 -05:00
Linus Torvalds bfcfaa77bd vfs: use 'unsigned long' accesses for dcache name comparison and hashing
Ok, this is hacky, and only works on little-endian machines with goo
unaligned handling.  And even then only with CONFIG_DEBUG_PAGEALLOC
disabled, since it can access up to 7 bytes after the pathname.

But it runs like a bat out of hell.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-03-08 18:08:44 -08:00
Linus Torvalds ae942ae719 vfs: export full_name_hash() function to modules
Commit 5707c87f "vfs: uninline full_name_hash()" broke the modular
build, because it needs exporting now that it isn't inlined any more.

Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-03-02 19:40:57 -08:00
Linus Torvalds 200e9ef7ab vfs: split up name hashing in link_path_walk() into helper function
The code in link_path_walk() that finds out the length and the hash of
the next path component is some of the hottest code in the kernel.  And
I have a version of it that does things at the full width of the CPU
wordsize at a time, but that means that we *really* want to split it up
into a separate helper function.

So this re-organizes the code a bit and splits the hashing part into a
helper function called "hash_name()".  It returns the length of the
pathname component, while at the same time computing and writing the
hash to the appropriate location.

The code generation is slightly changed by this patch, but generally for
the better - and the added abstraction actually makes the code easier to
read too.  And the new interface is well suited for replacing just the
"hash_name()" function with alternative implementations.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-03-02 14:49:24 -08:00
Linus Torvalds 0145acc202 vfs: uninline full_name_hash()
.. and also use it in lookup_one_len() rather than open-coding it.

There aren't any performance-critical users, so inlining it is silly.
But it wouldn't matter if it wasn't for the fact that the word-at-a-time
dentry name patches want to conditionally replace the function, and
uninlining it sets the stage for that.

So again, this is a preparatory patch that doesn't change any semantics,
and only prepares for a much cleaner and testable word-at-a-time dentry
name accessor patch.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-03-02 14:32:59 -08:00
Paul Gortmaker 630d9c4727 fs: reduce the use of module.h wherever possible
For files only using THIS_MODULE and/or EXPORT_SYMBOL, map
them onto including export.h -- or if the file isn't even
using those, then just delete the include.  Fix up any implicit
include dependencies that were being masked by module.h along
the way.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2012-02-28 19:31:58 -05:00
Miklos Szeredi e188dc02d3 vfs: fix d_inode_lookup() dentry ref leak
d_inode_lookup() leaks a dentry reference on IS_DEADDIR().

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
CC: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-02-13 20:45:37 -05:00
Eric Paris 4043cde8ec audit: do not call audit_getname on error
Just a code cleanup really.  We don't need to make a function call just for
it to return on error.  This also makes the VFS function even easier to follow
and removes a conditional on a hot path.

Signed-off-by: Eric Paris <eparis@redhat.com>
2012-01-17 16:17:01 -05:00
Al Viro ece2ccb668 Merge branches 'vfsmount-guts', 'umode_t' and 'partitions' into Z 2012-01-06 23:15:54 -05:00
Al Viro a73324da7a vfs: move mnt_mountpoint to struct mount
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-03 22:57:05 -05:00
Al Viro 0714a53380 vfs: now it can be done - make mnt_parent point to struct mount
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-03 22:57:05 -05:00
Al Viro 3376f34fff vfs: mnt_parent moved to struct mount
the second victim...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-03 22:57:04 -05:00
Al Viro c71053659e vfs: spread struct mount - __lookup_mnt() result
switch __lookup_mnt() to returning struct mount *; callers adjusted.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-03 22:56:58 -05:00
Al Viro a218d0fdc5 switch open and mkdir syscalls to umode_t
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-03 22:55:19 -05:00
Al Viro f69aac0006 switch may_mknod() to umode_t
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-03 22:55:14 -05:00
Al Viro 1a67aafb5f switch ->mknod() to umode_t
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-03 22:54:54 -05:00
Al Viro 4acdaf27eb switch ->create() to umode_t
vfs_create() ignores everything outside of 16bit subset of its
mode argument; switching it to umode_t is obviously equivalent
and it's the only caller of the method

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-03 22:54:53 -05:00
Al Viro 18bb1db3e7 switch vfs_mkdir() and ->mkdir() to umode_t
vfs_mkdir() gets int, but immediately drops everything that might not
fit into umode_t and that's the only caller of ->mkdir()...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-03 22:54:53 -05:00
Al Viro 8208a22bb8 switch sys_mknodat(2) to umode_t
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-01-03 22:54:52 -05:00
Al Viro a3fbbde70a VFS: we need to set LOOKUP_JUMPED on mountpoint crossing
Mountpoint crossing is similar to following procfs symlinks - we do
not get ->d_revalidate() called for dentry we have arrived at, with
unpleasant consequences for NFS4.

Simple way to reproduce the problem in mainline:

    cat >/tmp/a.c <<'EOF'
    #include <unistd.h>
    #include <fcntl.h>
    #include <stdio.h>
    main()
    {
            struct flock fl = {.l_type = F_RDLCK, .l_whence = SEEK_SET, .l_len = 1};
            if (fcntl(0, F_SETLK, &fl))
                    perror("setlk");
    }
    EOF
    cc /tmp/a.c -o /tmp/test

then on nfs4:

    mount --bind file1 file2
    /tmp/test < file1		# ok
    /tmp/test < file2		# spews "setlk: No locks available"...

What happens is the missing call of ->d_revalidate() after mountpoint
crossing and that's where NFS4 would issue OPEN request to server.

The fix is simple - treat mountpoint crossing the same way we deal with
following procfs-style symlinks.  I.e.  set LOOKUP_JUMPED...

Cc: stable@kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-11-07 14:58:06 -08:00
Andy Whitcroft 1fa1e7f615 readlinkat: ensure we return ENOENT for the empty pathname for normal lookups
Since the commit below which added O_PATH support to the *at() calls, the
error return for readlink/readlinkat for the empty pathname has switched
from ENOENT to EINVAL:

  commit 65cfc67223
  Author: Al Viro <viro@zeniv.linux.org.uk>
  Date:   Sun Mar 13 15:56:26 2011 -0400

    readlinkat(), fchownat() and fstatat() with empty relative pathnames

This is both unexpected for userspace and makes readlink/readlinkat
inconsistant with all other interfaces; and inconsistant with our stated
return for these pathnames.

As the readlinkat call does not have a flags parameter we cannot use the
AT_EMPTY_PATH approach used in the other calls.  Therefore expose whether
the original path is infact entry via a new user_path_at_empty() path
lookup function.  Use this to determine whether to default to EINVAL or
ENOENT for failures.

Addresses http://bugs.launchpad.net/bugs/817187

[akpm@linux-foundation.org: remove unused getname_flags()]
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: <stable@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
2011-11-02 12:53:42 +01:00
J. Bruce Fields f3c7691e8d leases: fix write-open/read-lease race
In setlease, we use i_writecount to decide whether we can give out a
read lease.

In open, we break leases before incrementing i_writecount.

There is therefore a window between the break lease and the i_writecount
increment when setlease could add a new read lease.

This would leave us with a simultaneous write open and read lease, which
shouldn't happen.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
2011-10-28 14:59:00 +02:00
Andreas Gruenbacher 948409c74d vfs: add a comment to inode_permission()
Acked-by: J. Bruce Fields <bfields@redhat.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruen@kernel.org>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
2011-10-28 14:58:55 +02:00
Andreas Gruenbacher d124b60a83 vfs: pass all mask flags check_acl and posix_acl_permission
Acked-by: J. Bruce Fields <bfields@redhat.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruen@kernel.org>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
2011-10-28 14:58:54 +02:00
Andreas Gruenbacher 8fd90c8d1d vfs: indicate that the permission functions take all the MAY_* flags
Acked-by: J. Bruce Fields <bfields@redhat.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruen@kernel.org>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
2011-10-28 14:58:54 +02:00
Linus Torvalds b6c8069d35 vfs: remove LOOKUP_NO_AUTOMOUNT flag
That flag no longer makes sense, since we don't look up automount points
as eagerly any more.  Additionally, it turns out that the NO_AUTOMOUNT
handling was buggy to begin with: it would avoid automounting even for
cases where we really *needed* to do the automount handling, and could
return ENOENT for autofs entries that hadn't been instantiated yet.

With our new non-eager automount semantics, one discussion has been
about adding a AT_AUTOMOUNT flag to vfs_fstatat (and thus the
newfstatat() and fstatat64() system calls), but it's probably not worth
it: you can always force at least directory automounting by simply
adding the final '/' to the filename, which works for *all* of the stat
family system calls, old and new.

So AT_NO_AUTOMOUNT (and thus LOOKUP_NO_AUTOMOUNT) really were just a
result of our bad default behavior.

Acked-by: Ian Kent <raven@themaw.net>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-09-27 08:12:33 -07:00
Linus Torvalds d94c177bee vfs pathname lookup: Add LOOKUP_AUTOMOUNT flag
Since we've now turned around and made LOOKUP_FOLLOW *not* force an
automount, we want to add the ability to force an automount event on
lookup even if we don't happen to have one of the other flags that force
it implicitly (LOOKUP_OPEN, LOOKUP_DIRECTORY, LOOKUP_PARENT..)

Most cases will never want to use this, since you'd normally want to
delay automounting as long as possible, which usually implies
LOOKUP_OPEN (when we open a file or directory, we really cannot avoid
the automount any more).

But Trond argued sufficiently forcefully that at a minimum bind mounting
a file and quotactl will want to force the automount lookup.  Some other
cases (like nfs_follow_remote_path()) could use it too, although
LOOKUP_DIRECTORY would work there as well.

This commit just adds the flag and logic, no users yet, though.  It also
doesn't actually touch the LOOKUP_NO_AUTOMOUNT flag that is related, and
was made irrelevant by the same change that made us not follow on
LOOKUP_FOLLOW.

Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Ian Kent <raven@themaw.net>
Cc: Jeff Layton <jlayton@redhat.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Greg KH <gregkh@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-09-26 17:44:55 -07:00
Al Viro 1d2ef59014 restore pinning the victim dentry in vfs_rmdir()/vfs_rename_dir()
We used to get the victim pinned by dentry_unhash() prior to commit
64252c75a2 ("vfs: remove dget() from dentry_unhash()") and ->rmdir()
and ->rename() instances relied on that; most of them don't care, but
ones that used d_delete() themselves do.  As the result, we are getting
rmdir() oopses on NFS now.

Just grab the reference before locking the victim and drop it explicitly
after unlocking, same as vfs_rename_other() does.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Simon Kirby <sim@hostway.ca>
Cc: stable@kernel.org (3.0.x)
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-09-14 11:31:55 -07:00
Miklos Szeredi 0ec26fd069 vfs: automount should ignore LOOKUP_FOLLOW
Prior to 2.6.38 automount would not trigger on either stat(2) or
lstat(2) on the automount point.

After 2.6.38, with the introduction of the ->d_automount()
infrastructure, stat(2) and others would start triggering automount
while lstat(2), etc. still would not.  This is a regression and a
userspace ABI change.

Problem originally reported here:

  http://thread.gmane.org/gmane.linux.kernel.autofs/6098

It appears that there was an attempt at fixing various userspace tools
to not trigger the automount.  But since the stat system call is
rather common it is impossible to "fix" all userspace.

This patch reverts the original behavior, which is to not trigger on
stat(2) and other symlink following syscalls.

[ It's not really clear what the right behavior is.  Apparently Solaris
  does the "automount on stat, leave alone on lstat".  And some programs
  can get unhappy when "stat+open+fstat" ends up giving a different
  result from the fstat than from the initial stat.

  But the change in 2.6.38 resulted in problems for some people, so
  we're going back to old behavior.  Maybe we can re-visit this
  discussion at some future date  - Linus ]

Reported-by: Leonardo Chiquitto <leonardo.lists@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Acked-by: Ian Kent <raven@themaw.net>
Cc: David Howells <dhowells@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-09-09 15:42:34 -07:00
Linus Torvalds 7813b94a54 vfs: rename 'do_follow_link' to 'should_follow_link'
Al points out that the do_follow_link() helper function really is
misnamed - it's about whether we should try to follow a symlink or not,
not about actually doing the following.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-08-07 13:42:25 -07:00
Ari Savolainen 206b1d09a5 Fix POSIX ACL permission check
After commit 3567866bf261: "RCUify freeing acls, let check_acl() go ahead in
RCU mode if acl is cached" posix_acl_permission is being called with an
unsupported flag and the permission check fails. This patch fixes the issue.

Signed-off-by: Ari Savolainen <ari.m.savolainen@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-08-07 04:52:23 -04:00
Linus Torvalds 3ddcd0569c vfs: optimize inode cache access patterns
The inode structure layout is largely random, and some of the vfs paths
really do care.  The path lookup in particular is already quite D$
intensive, and profiles show that accessing the 'inode->i_op->xyz'
fields is quite costly.

We already optimized the dcache to not unnecessarily load the d_op
structure for members that are often NULL using the DCACHE_OP_xyz bits
in dentry->d_flags, and this does something very similar for the inode
ops that are used during pathname lookup.

It also re-orders the fields so that the fields accessed by 'stat' are
together at the beginning of the inode structure, and roughly in the
order accessed.

The effect of this seems to be in the 1-2% range for an empty kernel
"make -j" run (which is fairly kernel-intensive, mostly in filename
lookup), so it's visible.  The numbers are fairly noisy, though, and
likely depend a lot on exact microarchitecture.  So there's more tuning
to be done.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-08-06 22:53:23 -07:00
Al Viro 3567866bf2 RCUify freeing acls, let check_acl() go ahead in RCU mode if acl is cached
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-08-03 00:58:42 -04:00
David Howells 5a30d8a2b8 VFS: Fix automount for negative autofs dentries
Autofs may set the DCACHE_NEED_AUTOMOUNT flag on negative dentries.  These
need attention from the automounter daemon regardless of the LOOKUP_FOLLOW flag.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Ian Kent <raven@themaw.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-08-01 01:38:01 -04:00
Linus Torvalds 84635d68be vfs: fix check_acl compile error when CONFIG_FS_POSIX_ACL is not set
Commit e77819e57f ("vfs: move ACL cache lookup into generic code")
didn't take the FS_POSIX_ACL config variable into account - when that is
not set, ACL's go away, and the cache helper functions do not exist,
causing compile errors like

  fs/namei.c: In function 'check_acl':
  fs/namei.c:191:10: error: implicit declaration of function 'negative_cached_acl'
  fs/namei.c:196:2: error: implicit declaration of function 'get_cached_acl'
  fs/namei.c:196:6: warning: assignment makes pointer from integer without a cast
  fs/namei.c:212:11: error: implicit declaration of function 'set_cached_acl'

Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Acked-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-07-25 22:47:03 -07:00
Linus Torvalds 14067ff536 vfs: make gcc generate more obvious code for acl permission checking
The "fsuid is the inode owner" case is not necessarily always the likely
case, but it's the case that doesn't do anything odd and that we want in
straight-line code.  Make gcc not generate random "jump around for the
fun of it" code.

This just helps me read profiles.  That thing is one of the hottest
parts of the whole pathname lookup.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-07-25 19:55:52 -07:00
Christoph Hellwig 4e34e719e4 fs: take the ACL checks to common code
Replace the ->check_acl method with a ->get_acl method that simply reads an
ACL from disk after having a cache miss.  This means we can replace the ACL
checking boilerplate code with a single implementation in namei.c.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-25 14:30:23 -04:00
Linus Torvalds e77819e57f vfs: move ACL cache lookup into generic code
This moves logic for checking the cached ACL values from low-level
filesystems into generic code.  The end result is a streamlined ACL
check that doesn't need to load the inode->i_op->check_acl pointer at
all for the common cached case.

The filesystems also don't need to check for a non-blocking RCU walk
case in their acl_check() functions, because that is all handled at a
VFS layer.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-25 14:23:39 -04:00
Tobias Klauser 8c5dc70aae VFS: Fixup kerneldoc for generic_permission()
The flags parameter went away in
d749519b444db985e40b897f73ce1898b11f997e

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-20 20:47:43 -04:00
Al Viro e3c3d9c838 unexport kern_path_parent()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-20 01:44:16 -04:00
Al Viro e0a0124936 switch vfs_path_lookup() to struct path
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-20 01:44:14 -04:00
Al Viro ed75e95de5 kill lookup_create()
folded into the only caller (kern_path_create())

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-20 01:44:12 -04:00
Al Viro dae6ad8f37 new helpers: kern_path_create/user_path_create
combination of kern_path_parent() and lookup_create().  Does *not*
expose struct nameidata to caller.  Syscalls converted to that...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-20 01:44:05 -04:00
Al Viro 49084c3bb2 kill LOOKUP_CONTINUE
LOOKUP_PARENT is equivalent to it now

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-20 01:44:03 -04:00
Al Viro 8a5e929dd2 don't transliterate lower bits of ->intent.open.flags to FMODE_...
->create() instances are much happier that way...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-20 01:43:52 -04:00
Al Viro 554a8b9f54 Don't pass nameidata when calling vfs_create() from mknod()
All instances can cope with that now (and ceph one actually
starts working properly).

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-20 01:43:49 -04:00
Al Viro d2d9e9fbc2 merge do_revalidate() into its only caller
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-20 01:43:34 -04:00
Al Viro 4ad5abb3d0 no reason to keep exec_permission() separate now
cache footprint alone makes it a bad idea...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-20 01:43:32 -04:00
Al Viro d594e7ec4d massage generic_permission() to treat directories on a separate path
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-20 01:43:30 -04:00
Al Viro eecdd358b4 ->permission() sanitizing: don't pass flags to exec_permission()
pass mask instead; kill security_inode_exec_permission() since we can use
security_inode_permission() instead.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-20 01:43:29 -04:00
Al Viro 10556cb21a ->permission() sanitizing: don't pass flags to ->permission()
not used by the instances anymore.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-20 01:43:24 -04:00
Al Viro 2830ba7f34 ->permission() sanitizing: don't pass flags to generic_permission()
redundant; all callers get it duplicated in mask & MAY_NOT_BLOCK and none of
them removes that bit.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-20 01:43:22 -04:00
Al Viro 7e40145eb1 ->permission() sanitizing: don't pass flags to ->check_acl()
not used in the instances anymore.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-20 01:43:21 -04:00
Al Viro 9c2c703929 ->permission() sanitizing: pass MAY_NOT_BLOCK to ->check_acl()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-20 01:43:19 -04:00
Al Viro 1fc0f78ca9 ->permission() sanitizing: MAY_NOT_BLOCK
Duplicate the flags argument into mask bitmap.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-20 01:43:18 -04:00
Al Viro 178ea73521 kill check_acl callback of generic_permission()
its value depends only on inode and does not change; we might as
well store it in ->i_op->check_acl and be done with that.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-20 01:43:16 -04:00
Al Viro 07b8ce1ee8 lockless get_write_access/deny_write_access
new helpers: atomic_inc_unless_negative()/atomic_dec_unless_positive()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-20 01:43:14 -04:00
Al Viro f4d6ff89d8 move exec_permission() up to the rest of permission-related functions
... and convert the comment before it into linuxdoc form.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-20 01:43:13 -04:00
Al Viro 3bfa784a65 kill file_permission() completely
convert the last remaining caller to inode_permission()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-20 01:43:11 -04:00
Al Viro 78f32a9b47 switch path_init() to exec_permission()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-20 01:43:08 -04:00
Al Viro 4cf27141cb make exec_permission(dir) really equivalent to inode_permission(dir, MAY_EXEC)
capability overrides apply only to the default case; if fs has ->permission()
that does _not_ call generic_permission(), we have no business doing them.
Moreover, if it has ->permission() that does call generic_permission(), we
have no need to recheck capabilities.

Besides, the capability overrides should apply only if we got EACCES from
acl_permission_check(); any other value (-EIO, etc.) should be returned
to caller, capabilities or not capabilities.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-20 01:43:05 -04:00
Josef Bacik 44396f4b5c fs: add a DCACHE_NEED_LOOKUP flag for d_flags
Btrfs (and I'd venture most other fs's) stores its indexes in nice disk order
for readdir, but unfortunately in the case of anything that stats the files in
order that readdir spits back (like oh say ls) that means we still have to do
the normal lookup of the file, which means looking up our other index and then
looking up the inode.  What I want is a way to create dummy dentries when we
find them in readdir so that when ls or anything else subsequently does a
stat(), we already have the location information in the dentry and can go
straight to the inode itself.  The lookup stuff just assumes that if it finds a
dentry it is done, it doesn't perform a lookup.  So add a DCACHE_NEED_LOOKUP
flag so that the lookup code knows it still needs to run i_op->lookup() on the
parent to get the inode for the dentry.  I have tested this with btrfs and I
went from something that looks like this

http://people.redhat.com/jwhiter/ls-noreada.png

To this

http://people.redhat.com/jwhiter/ls-good.png

Thats a savings of 1300 seconds, or 22 minutes.  That is a significant savings.
Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-20 01:43:03 -04:00
Linus Torvalds 5943026240 vfs: fix race in rcu lookup of pruned dentry
Don't update *inode in __follow_mount_rcu() until we'd verified that
there is mountpoint there.  Kudos to Hugh Dickins for catching that
one in the first place and eventually figuring out the solution (and
catching a braino in the earlier version of patch).

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-19 21:49:01 -07:00
Al Viro 94c0d4ecbe Fix ->d_lock locking order in unlazy_walk()
Make sure that child is still a child of parent before nested locking
of child->d_lock in unlazy_walk(); otherwise we are risking a violation
of locking order and deadlocks.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-07-12 21:40:23 -04:00
Al Viro 8e833fd2e1 fix comment in generic_permission()
CAP_DAC_OVERRIDE is enough for MAY_EXEC on directory, even if
no exec bits are set.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-06-20 10:45:56 -04:00
Al Viro 6291176bcd kill obsolete comment for follow_down()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-06-20 10:45:49 -04:00
Al Viro 8aef188452 VFS: Fix vfsmount overput on simultaneous automount
[Kudos to dhowells for tracking that crap down]

If two processes attempt to cause automounting on the same mountpoint at the
same time, the vfsmount holding the mountpoint will be left with one too few
references on it, causing a BUG when the kernel tries to clean up.

The problem is that lock_mount() drops the caller's reference to the
mountpoint's vfsmount in the case where it finds something already mounted on
the mountpoint as it transits to the mounted filesystem and replaces path->mnt
with the new mountpoint vfsmount.

During a pathwalk, however, we don't take a reference on the vfsmount if it is
the same as the one in the nameidata struct, but do_add_mount() doesn't know
this.

The fix is to make sure we have a ref on the vfsmount of the mountpoint before
calling do_add_mount().  However, if lock_mount() doesn't transit, we're then
left with an extra ref on the mountpoint vfsmount which needs releasing.
We can handle that in follow_managed() by not making assumptions about what
we can and what we cannot get from lookup_mnt() as the current code does.

The callers of follow_managed() expect that reference to path->mnt will be
grabbed iff path->mnt has been changed.  follow_managed() and follow_automount()
keep track of whether such reference has been grabbed and assume that it'll
happen in those and only those cases that'll have us return with changed
path->mnt.  That assumption is almost correct - it breaks in case of
racing automounts and in even harder to hit race between following a mountpoint
and a couple of mount --move.  The thing is, we don't need to make that
assumption at all - after the end of loop in follow_manage() we can check
if path->mnt has ended up unchanged and do mntput() if needed.

The BUG can be reproduced with the following test program:

	#include <stdio.h>
	#include <sys/types.h>
	#include <sys/stat.h>
	#include <unistd.h>
	#include <sys/wait.h>
	int main(int argc, char **argv)
	{
		int pid, ws;
		struct stat buf;
		pid = fork();
		stat(argv[1], &buf);
		if (pid > 0) wait(&ws);
		return 0;
	}

and the following procedure:

 (1) Mount an NFS volume that on the server has something else mounted on a
     subdirectory.  For instance, I can mount / from my server:

	mount warthog:/ /mnt -t nfs4 -r

     On the server /data has another filesystem mounted on it, so NFS will see
     a change in FSID as it walks down the path, and will mark /mnt/data as
     being a mountpoint.  This will cause the automount code to be triggered.

     !!! Do not look inside the mounted fs at this point !!!

 (2) Run the above program on a file within the submount to generate two
     simultaneous automount requests:

	/tmp/forkstat /mnt/data/testfile

 (3) Unmount the automounted submount:

	umount /mnt/data

 (4) Unmount the original mount:

	umount /mnt

     At this point the kernel should throw a BUG with something like the
     following:

	BUG: Dentry ffff880032e3c5c0{i=2,n=} still in use (1) [unmount of nfs4 0:12]

Note that the bug appears on the root dentry of the original mount, not the
mountpoint and not the submount because sys_umount() hasn't got to its final
mntput_no_expire() yet, but this isn't so obvious from the call trace:

 [<ffffffff8117cd82>] shrink_dcache_for_umount+0x69/0x82
 [<ffffffff8116160e>] generic_shutdown_super+0x37/0x15b
 [<ffffffffa00fae56>] ? nfs_super_return_all_delegations+0x2e/0x1b1 [nfs]
 [<ffffffff811617f3>] kill_anon_super+0x1d/0x7e
 [<ffffffffa00d0be1>] nfs4_kill_super+0x60/0xb6 [nfs]
 [<ffffffff81161c17>] deactivate_locked_super+0x34/0x83
 [<ffffffff811629ff>] deactivate_super+0x6f/0x7b
 [<ffffffff81186261>] mntput_no_expire+0x18d/0x199
 [<ffffffff811862a8>] mntput+0x3b/0x44
 [<ffffffff81186d87>] release_mounts+0xa2/0xbf
 [<ffffffff811876af>] sys_umount+0x47a/0x4ba
 [<ffffffff8109e1ca>] ? trace_hardirqs_on_caller+0x1fd/0x22f
 [<ffffffff816ea86b>] system_call_fastpath+0x16/0x1b

as do_umount() is inlined.  However, you can see release_mounts() in there.

Note also that it may be necessary to have multiple CPU cores to be able to
trigger this bug.

Tested-by: Jeff Layton <jlayton@redhat.com>
Tested-by: Ian Kent <raven@themaw.net>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-06-16 11:28:16 -04:00
Török Edwin 50338b889d fix wrong iput on d_inode introduced by e6bc45d65d
Git bisection shows that commit e6bc45d65d causes
BUG_ONs under high I/O load:

kernel BUG at fs/inode.c:1368!
[ 2862.501007] Call Trace:
[ 2862.501007]  [<ffffffff811691d8>] d_kill+0xf8/0x140
[ 2862.501007]  [<ffffffff81169c19>] dput+0xc9/0x190
[ 2862.501007]  [<ffffffff8115577f>] fput+0x15f/0x210
[ 2862.501007]  [<ffffffff81152171>] filp_close+0x61/0x90
[ 2862.501007]  [<ffffffff81152251>] sys_close+0xb1/0x110
[ 2862.501007]  [<ffffffff814c14fb>] system_call_fastpath+0x16/0x1b

A reliable way to reproduce this bug is:
Login to KDE, run 'rsnapshot sync', and apt-get install openjdk-6-jdk,
and apt-get remove openjdk-6-jdk.

The buggy part of the patch is this:
	struct inode *inode = NULL;
.....
-               if (nd.last.name[nd.last.len])
-                       goto slashes;
                inode = dentry->d_inode;
-               if (inode)
-                       ihold(inode);
+               if (nd.last.name[nd.last.len] || !inode)
+                       goto slashes;
+               ihold(inode)
...
	if (inode)
		iput(inode);	/* truncate the inode here */

If nd.last.name[nd.last.len] is nonzero (and thus goto slashes branch is taken),
and dentry->d_inode is non-NULL, then this code now does an additional iput on
the inode, which is wrong.

Fix this by only setting the inode variable if nd.last.name[nd.last.len] is 0.

Reference: https://lkml.org/lkml/2011/6/15/50
Reported-by: Norbert Preining <preining@logic.at>
Reported-by: Török Edwin <edwintorok@gmail.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Török Edwin <edwintorok@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-06-16 11:27:39 -04:00
Theodore Ts'o e6bc45d65d vfs: make unlink() and rmdir() return ENOENT in preference to EROFS
If user space attempts to remove a non-existent file or directory, and
the file system is mounted read-only, return ENOENT instead of EROFS.
Either error code is arguably valid/correct, but ENOENT is a more
specific error message.

Reported-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-06-07 08:51:14 -04:00
Sage Weil 3cebde2413 vfs: shrink_dcache_parent before rmdir, dir rename
The dentry_unhash push-down series missed that shink_dcache_parent needs to
be called prior to rmdir or dir rename to clear DCACHE_REFERENCED and
allow efficient dentry reclaim.

Reported-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-05-30 01:48:27 -04:00
Al Viro d6e9bd256c Lift the check for automount points into do_lookup()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-05-27 07:03:15 -04:00
Al Viro dea3937619 Trim excessive arguments of follow_mount_rcu()
... and kill a useless local variable in follow_dotdot_rcu(), while
we are at it - follow_mount_rcu(nd, path, inode) *always* assigned
value to *inode, and always it had been path->dentry->d_inode (aka
nd->path.dentry->d_inode, since it always got &nd->path as the second
argument).

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-05-27 07:01:49 -04:00
Al Viro 287548e46a split __follow_mount_rcu() into normal and .. cases
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-05-27 06:51:56 -04:00
Linus Torvalds 32e51f141f Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6: (25 commits)
  cifs: remove unnecessary dentry_unhash on rmdir/rename_dir
  ocfs2: remove unnecessary dentry_unhash on rmdir/rename_dir
  exofs: remove unnecessary dentry_unhash on rmdir/rename_dir
  nfs: remove unnecessary dentry_unhash on rmdir/rename_dir
  ext2: remove unnecessary dentry_unhash on rmdir/rename_dir
  ext3: remove unnecessary dentry_unhash on rmdir/rename_dir
  ext4: remove unnecessary dentry_unhash on rmdir/rename_dir
  btrfs: remove unnecessary dentry_unhash in rmdir/rename_dir
  ceph: remove unnecessary dentry_unhash calls
  vfs: clean up vfs_rename_other
  vfs: clean up vfs_rename_dir
  vfs: clean up vfs_rmdir
  vfs: fix vfs_rename_dir for FS_RENAME_DOES_D_MOVE filesystems
  libfs: drop unneeded dentry_unhash
  vfs: update dentry_unhash() comment
  vfs: push dentry_unhash on rename_dir into file systems
  vfs: push dentry_unhash on rmdir into file systems
  vfs: remove dget() from dentry_unhash()
  vfs: dentry_unhash immediately prior to rmdir
  vfs: Block mmapped writes while the fs is frozen
  ...
2011-05-26 09:52:14 -07:00
Sage Weil 51892bbb57 vfs: clean up vfs_rename_other
Simplify control flow to match vfs_rename_dir.

Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-05-26 07:26:53 -04:00
Sage Weil 9055cba711 vfs: clean up vfs_rename_dir
Simplify control flow through vfs_rename_dir.

Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-05-26 07:26:52 -04:00
Sage Weil 912dbc15d9 vfs: clean up vfs_rmdir
Simplify the control flow with an out label.

Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-05-26 07:26:51 -04:00
Miklos Szeredi b5afd2c406 vfs: fix vfs_rename_dir for FS_RENAME_DOES_D_MOVE filesystems
vfs_rename_dir() doesn't properly account for filesystems with
FS_RENAME_DOES_D_MOVE.  If new_dentry has a target inode attached, it
unhashes the new_dentry prior to the rename() iop and rehashes it after,
but doesn't account for the possibility that rename() may have swapped
{old,new}_dentry.  For FS_RENAME_DOES_D_MOVE filesystems, it rehashes
new_dentry (now the old renamed-from name, which d_move() expected to go
away), such that a subsequent lookup will find it.  Currently all
FS_RENAME_DOES_D_MOVE filesystems compensate for this by failing in
d_revalidate.

The bug was introduced by: commit 349457ccf2
"[PATCH] Allow file systems to manually d_move() inside of ->rename()"

Fix by not rehashing the new dentry.  Rehashing used to be needed by
d_move() but isn't anymore.

Reported-by: Sage Weil <sage@newdream.net>
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-05-26 07:26:50 -04:00
Sage Weil a71905f0db vfs: update dentry_unhash() comment
The helper is now only called by file systems, not the VFS.

Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-05-26 07:26:49 -04:00
Sage Weil e4eaac06bc vfs: push dentry_unhash on rename_dir into file systems
Only a few file systems need this.  Start by pushing it down into each
rename method (except gfs2 and xfs) so that it can be dealt with on a
per-fs basis.

Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-05-26 07:26:48 -04:00
Sage Weil 79bf7c732b vfs: push dentry_unhash on rmdir into file systems
Only a few file systems need this.  Start by pushing it down into each
fs rmdir method (except gfs2 and xfs) so it can be dealt with on a per-fs
basis.

This does not change behavior for any in-tree file systems.

Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-05-26 07:26:47 -04:00
Sage Weil 64252c75a2 vfs: remove dget() from dentry_unhash()
This serves no useful purpose that I can discern.  All callers (rename,
rmdir) hold their own reference to the dentry.

A quick audit of all file systems showed no relevant checks on the value
of d_count in vfs_rmdir/vfs_rename_dir paths.

Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-05-26 07:26:46 -04:00
Sage Weil 48293699a0 vfs: dentry_unhash immediately prior to rmdir
This presumes that there is no reason to unhash a dentry if we fail because
it is a mountpoint or the LSM check fails, and that the LSM checks do not
depend on the dentry being unhashed.

Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-05-26 07:26:46 -04:00
Al Viro 9f1fafee9e merge handle_reval_dot and nameidata_drop_rcu_last
new helper: complete_walk().  Done on successful completion
of walk, drops out of RCU mode, does d_revalidate of final
result if that hadn't been done already.

handle_reval_dot() and nameidata_drop_rcu_last() subsumed into
that one; callers converted to use of complete_walk().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-05-26 07:26:32 -04:00
Al Viro 19660af736 consolidate nameidata_..._drop_rcu()
Merge these into a single function (unlazy_walk(nd, dentry)),
kill ..._maybe variants

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-05-26 07:26:02 -04:00
Erez Zadok 1a4022f88d VFS: move BUG_ON test for symlink nd->depth after current->link_count test
This solves a serious VFS-level bug in nested_symlink (which was
rewritten from do_follow_link), and follows the order of depth tests
that existed before.

The bug triggers a BUG_ON in fs/namei.c:1381, when running racer with
symlink and rename ops.

Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
Acked-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-05-21 00:12:16 -07:00
Linus Torvalds 26cf46be95 vfs: micro-optimize acl_permission_check()
It's a hot function, and we're better off not mixing types in the mask
calculations.  The compiler just ends up mixing 16-bit and 32-bit
operations, for no good reason.

So do everything in 'unsigned int' rather than mixing 'unsigned int'
masking with a 'umode_t' (16-bit) mode variable.

This, together with the parent commit (47a150edc2ae: "Cache user_ns in
struct cred") makes acl_permission_check() much nicer.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-05-13 11:51:01 -07:00
Tim Chen c1530019e3 vfs: Fix absolute RCU path walk failures due to uninitialized seq number
During RCU walk in path_lookupat and path_openat, the rcu lookup
frequently failed if looking up an absolute path, because when root
directory was looked up, seq number was not properly set in nameidata.

We dropped out of RCU walk in nameidata_drop_rcu due to mismatch in
directory entry's seq number.  We reverted to slow path walk that need
to take references.

With the following patch, I saw a 50% increase in an exim mail server
benchmark throughput on a 4-socket Nehalem-EX system.

Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Cc: stable@kernel.org (v2.6.38)
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-04-15 15:28:12 -07:00
Lucas De Marchi 25985edced Fix common misspellings
Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
2011-03-31 11:26:23 -03:00
Ian Kent 62a7375e5d vfs - check non-mountpoint dentry might block in __follow_mount_rcu()
When following a mount in rcu-walk mode we must check if the incoming dentry
is telling us it may need to block, even if it isn't actually a mountpoint.

Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-24 14:24:32 -04:00
Linus Torvalds b81a618dcd Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6:
  deal with races in /proc/*/{syscall,stack,personality}
  proc: enable writing to /proc/pid/mem
  proc: make check_mem_permission() return an mm_struct on success
  proc: hold cred_guard_mutex in check_mem_permission()
  proc: disable mem_write after exec
  mm: implement access_remote_vm
  mm: factor out main logic of access_process_vm
  mm: use mm_struct to resolve gate vma's in __get_user_pages
  mm: arch: rename in_gate_area_no_task to in_gate_area_no_mm
  mm: arch: make in_gate_area take an mm_struct instead of a task_struct
  mm: arch: make get_gate_vma take an mm_struct instead of a task_struct
  x86: mark associated mm when running a task in 32 bit compatibility mode
  x86: add context tag to mark mm when running a task in 32-bit compatibility mode
  auxv: require the target to be tracable (or yourself)
  close race in /proc/*/environ
  report errors in /proc/*/*map* sanely
  pagemap: close races with suid execve
  make sessionid permissions in /proc/*/task/* match those in /proc/*
  fix leaks in path_lookupat()

Fix up trivial conflicts in fs/proc/base.c
2011-03-23 20:51:42 -07:00
Serge E. Hallyn 2e14967075 userns: rename is_owner_or_cap to inode_owner_or_capable
And give it a kernel-doc comment.

[akpm@linux-foundation.org: btrfs changed in linux-next]
Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Daniel Lezcano <daniel.lezcano@free.fr>
Acked-by: David Howells <dhowells@redhat.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-23 19:47:13 -07:00
Serge E. Hallyn e795b71799 userns: userns: check user namespace for task->file uid equivalence checks
Cheat for now and say all files belong to init_user_ns.  Next step will be
to let superblocks belong to a user_ns, and derive inode_userns(inode)
from inode->i_sb->s_user_ns.  Finally we'll introduce more flexible
arrangements.

Changelog:
	Feb 15: make is_owner_or_cap take const struct inode
	Feb 23: make is_owner_or_cap bool

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Serge E. Hallyn <serge.hallyn@canonical.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Daniel Lezcano <daniel.lezcano@free.fr>
Acked-by: David Howells <dhowells@redhat.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-23 19:47:08 -07:00
Al Viro bd23a539d0 fix leaks in path_lookupat()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-23 09:56:55 -04:00
Al Viro 1aed3e4204 lose 'mounting_here' argument in ->d_manage()
it's always false...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-18 10:01:59 -04:00
Al Viro 7cc90cc3ff don't pass 'mounting_here' flag to follow_down()
it's always false now

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-18 09:04:20 -04:00
Al Viro 0e794589e5 fix follow_link() breakage
commit 574197e0de had a missing
piece, breaking the loop detection ;-/

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-16 04:57:03 -04:00
Al Viro 574197e0de tidy the trailing symlinks traversal up
* pull the handling of current->total_link_count into
__do_follow_link()
* put the common "do ->put_link() if needed and path_put() the link"
  stuff into a helper (put_link(nd, link, cookie))
* rename __do_follow_link() to follow_link(), while we are at it

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-15 17:16:25 -04:00
Al Viro b356379a02 Turn resolution of trailing symlinks iterative everywhere
The last remaining place (resolution of nested symlink) converted
to the loop of the same kind we have in path_lookupat() and
path_openat().

Note that we still *do* have a recursion in pathname resolution;
can't avoid it, really.  However, it's strictly for nested symlinks
now - i.e. ones in the middle of a pathname.

link_path_walk() has lost the tail now - it always walks everything
except the last component.

do_follow_link() renamed to nested_symlink() and moved down.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-15 17:16:25 -04:00
Al Viro ce0525449d simplify link_path_walk() tail
Now that link_path_walk() is called without LOOKUP_PARENT
only from do_follow_link(), we can simplify the checks in
last component handling.  First of all, checking if we'd
arrived to a directory is not needed - the caller will check
it anyway.  And LOOKUP_FOLLOW is guaranteed to be there,
since we only get to that place with nd->depth > 0.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-15 17:16:25 -04:00
Al Viro bd92d7fed8 Make trailing symlink resolution in path_lookupat() iterative
Now the only caller of link_path_walk() that does *not* pass
LOOKUP_PARENT is do_follow_link()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-15 17:16:25 -04:00
Al Viro b21041d0f7 update nd->inode in __do_follow_link() instead of after do_follow_link()
... and note that we only need to do it for LAST_BIND symlinks

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-15 17:16:25 -04:00
Al Viro ce57dfc179 pull handling of one pathname component into a helper
new helper: walk_component().  Handles everything except symlinks;
returns negative on error, 0 on success and 1 on symlinks we decided
to follow.  Drops out of RCU mode on such symlinks.

link_path_walk() and do_last() switched to using that.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-15 17:16:20 -04:00
Aneesh Kumar K.V 11a7b371b6 fs: allow AT_EMPTY_PATH in linkat(), limit that to CAP_DAC_READ_SEARCH
We don't want to allow creation of private hardlinks by different application
using the fd passed to them via SCM_RIGHTS. So limit the null relative name
usage in linkat syscall to CAP_DAC_READ_SEARCH

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
2011-03-15 17:16:05 -04:00
Al Viro bcda76524c Allow O_PATH for symlinks
At that point we can't do almost nothing with them.  They can be opened
with O_PATH, we can manipulate such descriptors with dup(), etc. and
we can see them in /proc/*/{fd,fdinfo}/*.

We can't (and won't be able to) follow /proc/*/fd/* symlinks for those;
there's simply not enough information for pathname resolution to go on
from such point - to resolve a symlink we need to know which directory
does it live in.

We will be able to do useful things with them after the next commit, though -
readlinkat() and fchownat() will be possible to use with dfd being an
O_PATH-opened symlink and empty relative pathname.  Combined with
open_by_handle() it'll give us a way to do realink-by-handle and
lchown-by-handle without messing with more redundant syscalls.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-15 02:21:45 -04:00
Al Viro 1abf0c718f New kind of open files - "location only".
New flag for open(2) - O_PATH.  Semantics:
	* pathname is resolved, but the file itself is _NOT_ opened
as far as filesystem is concerned.
	* almost all operations on the resulting descriptors shall
fail with -EBADF.  Exceptions are:
	1) operations on descriptors themselves (i.e.
		close(), dup(), dup2(), dup3(), fcntl(fd, F_DUPFD),
		fcntl(fd, F_DUPFD_CLOEXEC, ...), fcntl(fd, F_GETFD),
		fcntl(fd, F_SETFD, ...))
	2) fcntl(fd, F_GETFL), for a common non-destructive way to
		check if descriptor is open
	3) "dfd" arguments of ...at(2) syscalls, i.e. the starting
		points of pathname resolution
	* closing such descriptor does *NOT* affect dnotify or
posix locks.
	* permissions are checked as usual along the way to file;
no permission checks are applied to the file itself.  Of course,
giving such thing to syscall will result in permission checks (at
the moment it means checking that starting point of ....at() is
a directory and caller has exec permissions on it).

fget() and fget_light() return NULL on such descriptors; use of
fget_raw() and fget_raw_light() is needed to get them.  That protects
existing code from dealing with those things.

There are two things still missing (they come in the next commits):
one is handling of symlinks (right now we refuse to open them that
way; see the next commit for semantics related to those) and another
is descriptor passing via SCM_RIGHTS datagrams.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-15 02:21:45 -04:00
Aneesh Kumar K.V aae8a97d3e fs: Don't allow to create hardlink for deleted file
Add inode->i_nlink == 0 check in VFS. Some of the file systems
do this internally. A followup patch will remove those instance.
This is needed to ensure that with link by handle we don't allow
to create hardlink of an unlinked file. The check also prevent a race
between unlink and link

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-15 02:21:44 -04:00
Al Viro f52e0c1130 New AT_... flag: AT_EMPTY_PATH
For name_to_handle_at(2) we'll want both ...at()-style syscall that
would be usable for non-directory descriptors (with empty relative
pathname).  Introduce new flag (AT_EMPTY_PATH) to deal with that and
corresponding LOOKUP_EMPTY; teach user_path_at() and path_init() to
deal with the latter.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 19:12:20 -04:00
Al Viro 73d049a40f open-style analog of vfs_path_lookup()
new function: file_open_root(dentry, mnt, name, flags) opens the file
vfs_path_lookup would arrive to.

Note that name can be empty; in that case the usual requirement that
dentry should be a directory is lifted.

open-coded equivalents switched to it, may_open() got down exactly
one caller and became static.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:28 -04:00
Al Viro 5b6ca027d8 reduce vfs_path_lookup() to do_path_lookup()
New lookup flag: LOOKUP_ROOT.  nd->root is set (and held) by caller,
path_init() starts walking from that place and all pathname resolution
machinery never drops nd->root if that flag is set.  That turns
vfs_path_lookup() into a special case of do_path_lookup() *and*
gets us down to 3 callers of link_path_walk(), making it finally
feasible to rip the handling of trailing symlink out of link_path_walk().
That will not only simply the living hell out of it, but make life
much simpler for unionfs merge.  Trailing symlink handling will
become iterative, which is a good thing for stack footprint in
a lot of situations as well.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:27 -04:00
Al Viro 5a18fff209 untangle do_lookup()
That thing has devolved into rats nest of gotos; sane use of unlikely()
gets rid of that horror and gives much more readable structure:
	* make a fast attempt to find a dentry; false negatives are OK.
In RCU mode if everything went fine, we are done, otherwise just drop
out of RCU.  If we'd done (RCU) ->d_revalidate() and it had not refused
outright (i.e. didn't give us -ECHILD), remember its result.
	* now we are not in RCU mode and hopefully have a dentry.  If we
do not, lock parent, do full d_lookup() and if that has not found anything,
allocate and call ->lookup().  If we'd done that ->lookup(), remember that
dentry is good and we don't need to revalidate it.
	* now we have a dentry.  If it has ->d_revalidate() and we can't
skip it, call it.
	* hopefully dentry is good; if not, either fail (in case of error)
or try to invalidate it.  If d_invalidate() has succeeded, drop it and
retry everything as if original attempt had not found a dentry.
	* now we can finish it up - deal with mountpoint crossing and
automount.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:27 -04:00
Al Viro 40b39136f0 path_openat: clean ELOOP handling a bit
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:27 -04:00
Al Viro f374ed5fa8 do_last: kill a rudiment of old ->d_revalidate() workaround
There used to be time when ->d_revalidate() couldn't return an error.
So intents code had lookup_instantiate_filp() stash ERR_PTR(error)
in nd->intent.open.filp and had it checked after lookup_hash(), to
catch the otherwise silent failures.  That had been introduced by
commit 4af4c52f34.  These days
->d_revalidate() can and does propagate errors back to callers
explicitly, so this check isn't needed anymore.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:27 -04:00
Al Viro 6c0d46c493 fold __open_namei_create() and open_will_truncate() into do_last()
... and clean up a bit more

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:27 -04:00
Al Viro ca344a894b do_last: unify may_open() call and everyting after it
We have a bunch of diverging codepaths in do_last(); some of
them converge, but the case of having to create a new file
duplicates large part of common tail of the rest and exits
separately.  Massage them so that they could be merged.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:27 -04:00
Al Viro 9b44f1b392 move may_open() from __open_name_create() to do_last()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:26 -04:00
Al Viro 0f9d1a10c3 expand finish_open() in its only caller
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:26 -04:00
Al Viro 5a202bcd75 sanitize pathname component hash calculation
Lift it to lookup_one_len() and link_path_walk() resp. into the
same place where we calculated default hash function of the same
name.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:26 -04:00
Al Viro 6a96ba5441 kill __lookup_one_len()
only one caller left

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:26 -04:00
Al Viro fe2d35ff0d switch non-create side of open() to use of do_last()
Instead of path_lookupat() doing trailing symlink resolution,
use the same scheme as on the O_CREAT side.  Walk with
LOOKUP_PARENT, then (in do_last()) look the final component
up, then either open it or return error or, if it's a symlink,
give the symlink back to path_openat() to be resolved there.

The really messy complication here is RCU.  We don't want to drop
out of RCU mode before the final lookup, since we don't want to
bounce parent directory ->d_count without a good reason.

Result is _not_ pretty; later in the series we'll clean it up.
For now we are roughly back where we'd been before the revert
done by Nick's series - top-level logics of path_openat() is
cleaned up, do_last() does actual opening, symlink resolution is
done uniformly.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:26 -04:00
Al Viro 70e9b35711 get rid of nd->file
Don't stash the struct file * used as starting point of walk in nameidata;
pass file ** to path_init() instead.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:26 -04:00
Al Viro 951361f954 get rid of the last LOOKUP_RCU dependencies in link_path_walk()
New helper: terminate_walk().  An error has happened during pathname
resolution and we either drop nd->path or terminate RCU, depending
the mode we had been in.  After that, nd is essentially empty.
Switch link_path_walk() to using that for cleanup.

Now the top-level logics in link_path_walk() is back to sanity.  RCU
dependencies are in the lower-level functions.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:26 -04:00
Al Viro a7472baba2 make nameidata_dentry_drop_rcu_maybe() always leave RCU mode
Now we have do_follow_link() guaranteed to leave without dangling RCU
and the next step will get LOOKUP_RCU logics completely out of
link_path_walk().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:25 -04:00
Al Viro ef7562d528 make handle_dots() leave RCU mode on error
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:25 -04:00
Al Viro 4455ca6223 clear RCU on all failure exits from link_path_walk()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:25 -04:00
Al Viro 9856fa1b28 pull handling of . and .. into inlined helper
getting LOOKUP_RCU checks out of link_path_walk()...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:25 -04:00
Al Viro 7bc055d1d5 kill out_dput: in link_path_walk()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:25 -04:00
Al Viro 13aab428a7 separate -ESTALE/-ECHILD retries in do_filp_open() from real work
new helper: path_openat().  Does what do_filp_open() does, except
that it tries only the walk mode (RCU/normal/force revalidation)
it had been told to.

Both create and non-create branches are using path_lookupat() now.
Fixed the double audit_inode() in non-create branch.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:25 -04:00
Al Viro 47c805dc2d switch do_filp_open() to struct open_flags
take calculation of open_flags by open(2) arguments into new helper
in fs/open.c, move filp_open() over there, have it and do_sys_open()
use that helper, switch exec.c callers of do_filp_open() to explicit
(and constant) struct open_flags.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:25 -04:00
Al Viro c3e380b0b3 Collect "operation mode" arguments of do_last() into a structure
No point messing with passing shitloads of "operation mode" arguments
to do_open() one by one, especially since they are not going to change
during do_filp_open().  Collect them into a struct, fill it and pass
to do_last() by reference.

Make sure that lookup intent flags are correctly set and removed - we
want them for do_last(), but they make no sense for __do_follow_link().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:25 -04:00
Al Viro f1afe9efc8 clean up the failure exits after __do_follow_link() in do_filp_open()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:24 -04:00
Al Viro 36f3b4f690 pull security_inode_follow_link() into __do_follow_link()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:24 -04:00
Al Viro 086e183a64 pull dropping RCU on success of link_path_walk() into path_lookupat()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:24 -04:00
Al Viro 16c2cd7179 untangle the "need_reval_dot" mess
instead of ad-hackery around need_reval_dot(), do the following:
set a flag (LOOKUP_JUMPED) in the beginning of path, on absolute
symlink traversal, on ".." and on procfs-style symlinks.  Clear on
normal components, leave unchanged on ".".  Non-nested callers of
link_path_walk() call handle_reval_path(), which checks that flag
is set and that fs does want the final revalidate thing, then does
->d_revalidate().  In link_path_walk() all the return_reval stuff
is gone.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:24 -04:00
Al Viro fe479a580d merge component type recognition
no need to do it in three places...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:24 -04:00
Al Viro e41f7d4ee5 merge path_init and path_init_rcu
Actual dependency on whether we want RCU or not is in 3 small areas
(as it ought to be) and everything around those is the same in both
versions.  Since each function has only one caller and those callers
are on two sides of if (flags & LOOKUP_RCU), it's easier and cleaner
to merge them and pull the checks inside.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:24 -04:00
Al Viro ee0827cd6b sanitize path_walk() mess
New helper: path_lookupat().  Basically, what do_path_lookup() boils to
modulo -ECHILD/-ESTALE handler.  path_walk* family is gone; vfs_path_lookup()
is using link_path_walk() directly, do_path_lookup() and do_filp_open()
are using path_lookupat().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:24 -04:00
Al Viro 52094c8a06 take RCU-dependent stuff around exec_permission() into a new helper
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:23 -04:00
Al Viro c9c6cac0c2 kill path_lookup()
all remaining callers pass LOOKUP_PARENT to it, so
flags argument can die; renamed to kern_path_parent()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-14 09:15:23 -04:00
Al Viro b306419ae0 nd->inode is not set on the second attempt in path_walk()
We leave it at whatever it had been pointing to after the
first link_path_walk() had failed with -ESTALE.  Things
do not work well after that...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-08 21:16:28 -05:00
Al Viro 1858efd471 minimal fix for do_filp_open() race
failure exits on the no-O_CREAT side of do_filp_open() merge with
those of O_CREAT one; unfortunately, if do_path_lookup() returns
-ESTALE, we'll get out_filp:, notice that we are about to return
-ESTALE without having trying to create the sucker with LOOKUP_REVAL
and jump right into the O_CREAT side of code.  And proceed to try
and create a file.  Usually that'll fail with -ESTALE again, but
we can race and get that attempt of pathname resolution to succeed.

open() without O_CREAT really shouldn't end up creating files, races
or not.  The real fix is to rearchitect the whole do_filp_open(),
but for now splitting the failure exits will do.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-03-04 13:14:21 -05:00
Linus Torvalds 3abb17e82f vfs: fix BUG_ON() in fs/namei.c:1461
When Al moved the nameidata_dentry_drop_rcu_maybe() call into the
do_follow_link function in commit 844a391799 ("nothing in
do_follow_link() is going to see RCU"), he mistakenly left the

	BUG_ON(inode != path->dentry->d_inode);

behind.  Which would otherwise be ok, but that BUG_ON() really needs to
be _after_ dropping RCU, since the dentry isn't necessarily stable
otherwise.

So complete the code movement in that commit, and move the BUG_ON() into
do_follow_link() too.  This means that we need to pass in 'inode' as an
argument (just for this one use), but that's a small thing.  And
eventually we may be confident enough in our path lookup that we can
just remove the BUG_ON() and the unnecessary inode argument.

Reported-and-tested-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-02-16 08:56:55 -08:00
Al Viro 4e924a4f53 get rid of nameidata_dentry_drop_rcu() calling nameidata_drop_rcu()
can't happen anymore and didn't work right anyway

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-02-15 02:26:54 -05:00
Al Viro f60aef7ec6 drop out of RCU in return_reval
... thus killing the need to handle drop-from-RCU in d_revalidate()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-02-15 02:26:54 -05:00
Al Viro f5e1c1c1af split do_revalidate() into RCU and non-RCU cases
fixing oopsen in lookup_one_len()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-02-15 02:26:54 -05:00
Al Viro 24643087e7 in do_lookup() split RCU and non-RCU cases of need_revalidate
and use unlikely() instead of gotos, for fsck sake...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-02-15 02:26:54 -05:00
Al Viro 844a391799 nothing in do_follow_link() is going to see RCU
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-02-15 02:26:53 -05:00
Linus Torvalds 2dab597441 Fix possible filp_cachep memory corruption
In commit 31e6b01f41 ("fs: rcu-walk for path lookup") we started doing
path lookup using RCU, which then falls back to a careful non-RCU lookup
in case of problems (LOOKUP_REVAL).  So do_filp_open() has this "re-do
the lookup carefully" looping case.

However, that means that we must not release the open-intent file data
if we are going to loop around and use it once more!

Fix this by moving the release of the open-intent data to the function
that allocates it (do_filp_open() itself) rather than the helper
functions that can get called multiple times (finish_open() and
do_last()).  This makes the logic for the lifetime of that field much
more obvious, and avoids the possible double free.

Reported-by: J. R. Okajima <hooanon05@yahoo.co.jp>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-02-11 15:53:38 -08:00
Ian Kent 8931221411 vfs - fix dentry ref count in do_lookup()
There is a ref count problem in fs/namei.c:do_lookup().

When walking in ref-walk mode, if follow_managed() returns a fail we
need to drop dentry and possibly vfsmount.  Clean up properly,
as we do in the other caller of follow_managed().

Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-01-18 01:21:26 -05:00
Al Viro 19a167af7c Take the completion of automount into new helper
... and shift it from namei.c to namespace.c

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-01-17 01:35:23 -05:00
Al Viro f03c65993b sanitize vfsmount refcounting changes
Instead of splitting refcount between (per-cpu) mnt_count
and (SMP-only) mnt_longrefs, make all references contribute
to mnt_count again and keep track of how many are longterm
ones.

Accounting rules for longterm count:
	* 1 for each fs_struct.root.mnt
	* 1 for each fs_struct.pwd.mnt
	* 1 for having non-NULL ->mnt_ns
	* decrement to 0 happens only under vfsmount lock exclusive

That allows nice common case for mntput() - since we can't drop the
final reference until after mnt_longterm has reached 0 due to the rules
above, mntput() can grab vfsmount lock shared and check mnt_longterm.
If it turns out to be non-zero (which is the common case), we know
that this is not the final mntput() and can just blindly decrement
percpu mnt_count.  Otherwise we grab vfsmount lock exclusive and
do usual decrement-and-check of percpu mnt_count.

For fs_struct.c we have mnt_make_longterm() and mnt_make_shortterm();
namespace.c uses the latter in places where we don't already hold
vfsmount lock exclusive and opencodes a few remaining spots where
we need to manipulate mnt_longterm.

Note that we mostly revert the code outside of fs/namespace.c back
to what we used to have; in particular, normal code doesn't need
to care about two kinds of references, etc.  And we get to keep
the optimization Nick's variant had bought us...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-01-16 13:47:07 -05:00
David Howells ea5b778a8b Unexport do_add_mount() and add in follow_automount(), not ->d_automount()
Unexport do_add_mount() and make ->d_automount() return the vfsmount to be
added rather than calling do_add_mount() itself.  follow_automount() will then
do the addition.

This slightly complicates things as ->d_automount() normally wants to add the
new vfsmount to an expiration list and start an expiration timer.  The problem
with that is that the vfsmount will be deleted if it has a refcount of 1 and
the timer will not repeat if the expiration list is empty.

To this end, we require the vfsmount to be returned from d_automount() with a
refcount of (at least) 2.  One of these refs will be dropped unconditionally.
In addition, follow_automount() must get a 3rd ref around the call to
do_add_mount() lest it eat a ref and return an error, leaving the mount we
have open to being expired as we would otherwise have only 1 ref on it.

d_automount() should also add the the vfsmount to the expiration list (by
calling mnt_set_expiry()) and start the expiration timer before returning, if
this mechanism is to be used.  The vfsmount will be unlinked from the
expiration list by follow_automount() if do_add_mount() fails.

This patch also fixes the call to do_add_mount() for AFS to propagate the mount
flags from the parent vfsmount.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-01-15 20:07:48 -05:00
David Howells ab90911ff9 Allow d_manage() to be used in RCU-walk mode
Allow d_manage() to be called from pathwalk when it is in RCU-walk mode as well
as when it is in Ref-walk mode.  This permits __follow_mount_rcu() to call
d_manage() directly.  d_manage() needs a parameter to indicate that it is in
RCU-walk mode as it isn't allowed to sleep if in that mode (but should return
-ECHILD instead).

autofs4_d_manage() can then be set to retain RCU-walk mode if the daemon
accesses it and otherwise request dropping back to ref-walk mode.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-01-15 20:07:47 -05:00
David Howells 87556ef199 Remove a further kludge from __do_follow_link()
Remove a further kludge from __do_follow_link() as it's no longer required with
the automount code.

This reverts the non-helper-function parts of
051d381259, which breaks union mounts.

Reported-by: vaurora@redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-01-15 20:07:46 -05:00
David Howells db3729153e Remove the automount through follow_link() kludge code from pathwalk
Remove the automount through follow_link() kludge code from pathwalk in favour
of using d_automount().

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Ian Kent <raven@themaw.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-01-15 20:07:36 -05:00
David Howells 6f45b65672 Add an AT_NO_AUTOMOUNT flag to suppress terminal automount
Add an AT_NO_AUTOMOUNT flag to suppress terminal automounting of automount
point directories.  This can be used by fstatat() users to permit the
gathering of attributes on an automount point and also prevent
mass-automounting of a directory of automount points by ls.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Ian Kent <raven@themaw.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-01-15 20:07:33 -05:00
David Howells cc53ce53c8 Add a dentry op to allow processes to be held during pathwalk transit
Add a dentry op (d_manage) to permit a filesystem to hold a process and make it
sleep when it tries to transit away from one of that filesystem's directories
during a pathwalk.  The operation is keyed off a new dentry flag
(DCACHE_MANAGE_TRANSIT).

The filesystem is allowed to be selective about which processes it holds and
which it permits to continue on or prohibits from transiting from each flagged
directory.  This will allow autofs to hold up client processes whilst letting
its userspace daemon through to maintain the directory or the stuff behind it
or mounted upon it.

The ->d_manage() dentry operation:

	int (*d_manage)(struct path *path, bool mounting_here);

takes a pointer to the directory about to be transited away from and a flag
indicating whether the transit is undertaken by do_add_mount() or
do_move_mount() skipping through a pile of filesystems mounted on a mountpoint.

It should return 0 if successful and to let the process continue on its way;
-EISDIR to prohibit the caller from skipping to overmounted filesystems or
automounting, and to use this directory; or some other error code to return to
the user.

->d_manage() is called with namespace_sem writelocked if mounting_here is true
and no other locks held, so it may sleep.  However, if mounting_here is true,
it may not initiate or wait for a mount or unmount upon the parameter
directory, even if the act is actually performed by userspace.

Within fs/namei.c, follow_managed() is extended to check with d_manage() first
on each managed directory, before transiting away from it or attempting to
automount upon it.

follow_down() is renamed follow_down_one() and should only be used where the
filesystem deliberately intends to avoid management steps (e.g. autofs).

A new follow_down() is added that incorporates the loop done by all other
callers of follow_down() (do_add/move_mount(), autofs and NFSD; whilst AFS, NFS
and CIFS do use it, their use is removed by converting them to use
d_automount()).  The new follow_down() calls d_manage() as appropriate.  It
also takes an extra parameter to indicate if it is being called from mount code
(with namespace_sem writelocked) which it passes to d_manage().  follow_down()
ignores automount points so that it can be used to mount on them.

__follow_mount_rcu() is made to abort rcu-walk mode if it hits a directory with
DCACHE_MANAGE_TRANSIT set on the basis that we're probably going to have to
sleep.  It would be possible to enter d_manage() in rcu-walk mode too, and have
that determine whether to abort or not itself.  That would allow the autofs
daemon to continue on in rcu-walk mode.

Note that DCACHE_MANAGE_TRANSIT on a directory should be cleared when it isn't
required as every tranist from that directory will cause d_manage() to be
invoked.  It can always be set again when necessary.

==========================
WHAT THIS MEANS FOR AUTOFS
==========================

Autofs currently uses the lookup() inode op and the d_revalidate() dentry op to
trigger the automounting of indirect mounts, and both of these can be called
with i_mutex held.

autofs knows that the i_mutex will be held by the caller in lookup(), and so
can drop it before invoking the daemon - but this isn't so for d_revalidate(),
since the lock is only held on _some_ of the code paths that call it.  This
means that autofs can't risk dropping i_mutex from its d_revalidate() function
before it calls the daemon.

The bug could manifest itself as, for example, a process that's trying to
validate an automount dentry that gets made to wait because that dentry is
expired and needs cleaning up:

	mkdir         S ffffffff8014e05a     0 32580  24956
	Call Trace:
	 [<ffffffff885371fd>] :autofs4:autofs4_wait+0x674/0x897
	 [<ffffffff80127f7d>] avc_has_perm+0x46/0x58
	 [<ffffffff8009fdcf>] autoremove_wake_function+0x0/0x2e
	 [<ffffffff88537be6>] :autofs4:autofs4_expire_wait+0x41/0x6b
	 [<ffffffff88535cfc>] :autofs4:autofs4_revalidate+0x91/0x149
	 [<ffffffff80036d96>] __lookup_hash+0xa0/0x12f
	 [<ffffffff80057a2f>] lookup_create+0x46/0x80
	 [<ffffffff800e6e31>] sys_mkdirat+0x56/0xe4

versus the automount daemon which wants to remove that dentry, but can't
because the normal process is holding the i_mutex lock:

	automount     D ffffffff8014e05a     0 32581      1              32561
	Call Trace:
	 [<ffffffff80063c3f>] __mutex_lock_slowpath+0x60/0x9b
	 [<ffffffff8000ccf1>] do_path_lookup+0x2ca/0x2f1
	 [<ffffffff80063c89>] .text.lock.mutex+0xf/0x14
	 [<ffffffff800e6d55>] do_rmdir+0x77/0xde
	 [<ffffffff8005d229>] tracesys+0x71/0xe0
	 [<ffffffff8005d28d>] tracesys+0xd5/0xe0

which means that the system is deadlocked.

This patch allows autofs to hold up normal processes whilst the daemon goes
ahead and does things to the dentry tree behind the automouter point without
risking a deadlock as almost no locks are held in d_manage() and none in
d_automount().

Signed-off-by: David Howells <dhowells@redhat.com>
Was-Acked-by: Ian Kent <raven@themaw.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-01-15 20:07:31 -05:00
David Howells 9875cf8064 Add a dentry op to handle automounting rather than abusing follow_link()
Add a dentry op (d_automount) to handle automounting directories rather than
abusing the follow_link() inode operation.  The operation is keyed off a new
dentry flag (DCACHE_NEED_AUTOMOUNT).

This also makes it easier to add an AT_ flag to suppress terminal segment
automount during pathwalk and removes the need for the kludge code in the
pathwalk algorithm to handle directories with follow_link() semantics.

The ->d_automount() dentry operation:

	struct vfsmount *(*d_automount)(struct path *mountpoint);

takes a pointer to the directory to be mounted upon, which is expected to
provide sufficient data to determine what should be mounted.  If successful, it
should return the vfsmount struct it creates (which it should also have added
to the namespace using do_add_mount() or similar).  If there's a collision with
another automount attempt, NULL should be returned.  If the directory specified
by the parameter should be used directly rather than being mounted upon,
-EISDIR should be returned.  In any other case, an error code should be
returned.

The ->d_automount() operation is called with no locks held and may sleep.  At
this point the pathwalk algorithm will be in ref-walk mode.

Within fs/namei.c itself, a new pathwalk subroutine (follow_automount()) is
added to handle mountpoints.  It will return -EREMOTE if the automount flag was
set, but no d_automount() op was supplied, -ELOOP if we've encountered too many
symlinks or mountpoints, -EISDIR if the walk point should be used without
mounting and 0 if successful.  The path will be updated to point to the mounted
filesystem if a successful automount took place.

__follow_mount() is replaced by follow_managed() which is more generic
(especially with the patch that adds ->d_manage()).  This handles transits from
directories during pathwalk, including automounting and skipping over
mountpoints (and holding processes with the next patch).

__follow_mount_rcu() will jump out of RCU-walk mode if it encounters an
automount point with nothing mounted on it.

follow_dotdot*() does not handle automounts as you don't want to trigger them
whilst following "..".

I've also extracted the mount/don't-mount logic from autofs4 and included it
here.  It makes the mount go ahead anyway if someone calls open() or creat(),
tries to traverse the directory, tries to chdir/chroot/etc. into the directory,
or sticks a '/' on the end of the pathname.  If they do a stat(), however,
they'll only trigger the automount if they didn't also say O_NOFOLLOW.

I've also added an inode flag (S_AUTOMOUNT) so that filesystems can mark their
inodes as automount points.  This flag is automatically propagated to the
dentry as DCACHE_NEED_AUTOMOUNT by __d_instantiate().  This saves NFS and could
save AFS a private flag bit apiece, but is not strictly necessary.  It would be
preferable to do the propagation in d_set_d_op(), but that doesn't normally
have access to the inode.

[AV: fixed breakage in case if __follow_mount_rcu() fails and nameidata_drop_rcu()
succeeds in RCU case of do_lookup(); we need to fall through to non-RCU case after
that, rather than just returning with ungrabbed *path]

Signed-off-by: David Howells <dhowells@redhat.com>
Was-Acked-by: Ian Kent <raven@themaw.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-01-15 20:05:03 -05:00
Al Viro 1a8edf40e7 do_lookup() fix
do_lookup() has a path leading from LOOKUP_RCU case to non-RCU
crossing of mountpoints, which breaks things badly.  If we
hit need_revalidate: and do nothing in there, we need to come
back into LOOKUP_RCU half of things, not to done: in non-RCU
one.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-01-15 20:03:39 -05:00
Linus Torvalds acda4721ae Merge branch 'vfs-scale-working' of git://git.kernel.org/pub/scm/linux/kernel/git/npiggin/linux-npiggin
* 'vfs-scale-working' of git://git.kernel.org/pub/scm/linux/kernel/git/npiggin/linux-npiggin:
  kernel: fix hlist_bl again
  cgroups: Fix a lockdep warning at cgroup removal
  fs: namei fix ->put_link on wrong inode in do_filp_open
2011-01-14 09:08:29 -08:00
Nick Piggin 7b9337aaf9 fs: namei fix ->put_link on wrong inode in do_filp_open
J. R. Okajima noticed that ->put_link is being attempted on the
wrong inode, and suggested the way to fix it. I changed it a bit
according to Al's suggestion to keep an explicit link path around.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-14 08:42:43 +00:00
Linus Torvalds db9effe99a Merge branch 'vfs-scale-working' of git://git.kernel.org/pub/scm/linux/kernel/git/npiggin/linux-npiggin
* 'vfs-scale-working' of git://git.kernel.org/pub/scm/linux/kernel/git/npiggin/linux-npiggin:
  fs: fix do_last error case when need_reval_dot
  nfs: add missing rcu-walk check
  fs: hlist UP debug fixup
  fs: fix dropping of rcu-walk from force_reval_path
  fs: force_reval_path drop rcu-walk before d_invalidate
  fs: small rcu-walk documentation fixes

Fixed up trivial conflicts in Documentation/filesystems/porting
2011-01-13 20:14:13 -08:00
J. R. Okajima f20877d94a fs: fix do_last error case when need_reval_dot
When open(2) without O_DIRECTORY opens an existing dir, it should return
EISDIR. In do_last(), the variable 'error' is initialized EISDIR, but it
is changed by d_revalidate() which returns any positive to represent
'the target dir is valid.'

Should we keep and return the initialized 'error' in this case.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-14 03:56:04 +00:00
Nick Piggin 90dbb77ba4 fs: fix dropping of rcu-walk from force_reval_path
As J. R. Okajima noted, force_reval_path passes in the same dentry to
d_revalidate as the one in the nameidata structure (other callers pass in a
child), so the locking breaks. This can oops with a chrooted nfs mount, for
example. Similarly there can be other problems with revalidating a dentry
which is already in nameidata of the path walk.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-14 02:36:19 +00:00
Nick Piggin bb20c18db6 fs: force_reval_path drop rcu-walk before d_invalidate
d_revalidate can return in rcu-walk mode even when it returns 0.  We can't just
call any old dcache function on rcu-walk dentry (the dentry is unstable, so
even through d_lock can safely be taken, the result may no longer be what we
expect -- careful re-checks would be required). So just drop rcu in this case.

(I missed this conversion when switching to the rcu-walk convention that Linus
suggested)

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-14 02:35:53 +00:00
Jeff Layton e1181ee657 vfs: pass struct file to do_truncate on O_TRUNC opens (try #2)
When a file is opened with O_TRUNC, the truncate processing is handled
by handle_truncate(). This function however doesn't receive any info
about the newly instantiated filp, and therefore can't pass that info
along so that the setattr can use it.

This makes NFSv4 misbehave. The client does an open and gets a valid
stateid, and then doesn't use that stateid on the subsequent truncate.
It uses the zero-stateid instead. Most servers ignore this fact and
just do the truncate anyway, but some don't like it (notably, RHEL4).

It seems more correct that since we have a fully instantiated file at
the time that handle_truncate is called, that we pass that along so
that the truncate operation can properly use it.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2011-01-12 20:06:59 -05:00
Randy Dunlap 39191628ed fs: fix namei.c kernel-doc notation
Fix new kernel-doc notation warnings in fs/namei.c and spell
ECHILD correctly.

  Warning(fs/namei.c:218): No description found for parameter 'flags'
  Warning(fs/namei.c:425): Excess function parameter 'Returns' description in 'nameidata_drop_rcu'
  Warning(fs/namei.c:478): Excess function parameter 'Returns' description in 'nameidata_dentry_drop_rcu'
  Warning(fs/namei.c:540): Excess function parameter 'Returns' description in 'nameidata_drop_rcu_last'

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc:	Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-01-10 07:38:53 -08:00
Nick Piggin b3e19d924b fs: scale mntget/mntput
The problem that this patch aims to fix is vfsmount refcounting scalability.
We need to take a reference on the vfsmount for every successful path lookup,
which often go to the same mount point.

The fundamental difficulty is that a "simple" reference count can never be made
scalable, because any time a reference is dropped, we must check whether that
was the last reference. To do that requires communication with all other CPUs
that may have taken a reference count.

We can make refcounts more scalable in a couple of ways, involving keeping
distributed counters, and checking for the global-zero condition less
frequently.

- check the global sum once every interval (this will delay zero detection
  for some interval, so it's probably a showstopper for vfsmounts).

- keep a local count and only taking the global sum when local reaches 0 (this
  is difficult for vfsmounts, because we can't hold preempt off for the life of
  a reference, so a counter would need to be per-thread or tied strongly to a
  particular CPU which requires more locking).

- keep a local difference of increments and decrements, which allows us to sum
  the total difference and hence find the refcount when summing all CPUs. Then,
  keep a single integer "long" refcount for slow and long lasting references,
  and only take the global sum of local counters when the long refcount is 0.

This last scheme is what I implemented here. Attached mounts and process root
and working directory references are "long" references, and everything else is
a short reference.

This allows scalable vfsmount references during path walking over mounted
subtrees and unattached (lazy umounted) mounts with processes still running
in them.

This results in one fewer atomic op in the fastpath: mntget is now just a
per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock
and non-atomic decrement in the common case. However code is otherwise bigger
and heavier, so single threaded performance is basically a wash.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:33 +11:00
Nick Piggin b74c79e993 fs: provide rcu-walk aware permission i_ops
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:29 +11:00
Nick Piggin 34286d6662 fs: rcu-walk aware d_revalidate method
Require filesystems be aware of .d_revalidate being called in rcu-walk
mode (nd->flags & LOOKUP_RCU). For now do a simple push down, returning
-ECHILD from all implementations.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:29 +11:00
Nick Piggin fb045adb99 fs: dcache reduce branches in lookup path
Reduce some branches and memory accesses in dcache lookup by adding dentry
flags to indicate common d_ops are set, rather than having to check them.
This saves a pointer memory access (dentry->d_op) in common path lookup
situations, and saves another pointer load and branch in cases where we
have d_op but not the particular operation.

Patched with:

git grep -E '[.>]([[:space:]])*d_op([[:space:]])*=' | xargs sed -e 's/\([^\t ]*\)->d_op = \(.*\);/d_set_d_op(\1, \2);/' -e 's/\([^\t ]*\)\.d_op = \(.*\);/d_set_d_op(\&\1, \2);/' -i

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:28 +11:00
Nick Piggin c28cc36469 fs: fs_struct use seqlock
Use a seqlock in the fs_struct to enable us to take an atomic copy of the
complete cwd and root paths. Use this in the RCU lookup path to avoid a
thread-shared spinlock in RCU lookup operations.

Multi-threaded apps may now perform path lookups with scalability matching
multi-process apps. Operations such as stat(2) become very scalable for
multi-threaded workload.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:27 +11:00
Nick Piggin 31e6b01f41 fs: rcu-walk for path lookup
Perform common cases of path lookups without any stores or locking in the
ancestor dentry elements. This is called rcu-walk, as opposed to the current
algorithm which is a refcount based walk, or ref-walk.

This results in far fewer atomic operations on every path element,
significantly improving path lookup performance. It also avoids cacheline
bouncing on common dentries, significantly improving scalability.

The overall design is like this:
* LOOKUP_RCU is set in nd->flags, which distinguishes rcu-walk from ref-walk.
* Take the RCU lock for the entire path walk, starting with the acquiring
  of the starting path (eg. root/cwd/fd-path). So now dentry refcounts are
  not required for dentry persistence.
* synchronize_rcu is called when unregistering a filesystem, so we can
  access d_ops and i_ops during rcu-walk.
* Similarly take the vfsmount lock for the entire path walk. So now mnt
  refcounts are not required for persistence. Also we are free to perform mount
  lookups, and to assume dentry mount points and mount roots are stable up and
  down the path.
* Have a per-dentry seqlock to protect the dentry name, parent, and inode,
  so we can load this tuple atomically, and also check whether any of its
  members have changed.
* Dentry lookups (based on parent, candidate string tuple) recheck the parent
  sequence after the child is found in case anything changed in the parent
  during the path walk.
* inode is also RCU protected so we can load d_inode and use the inode for
  limited things.
* i_mode, i_uid, i_gid can be tested for exec permissions during path walk.
* i_op can be loaded.

When we reach the destination dentry, we lock it, recheck lookup sequence,
and increment its refcount and mountpoint refcount. RCU and vfsmount locks
are dropped. This is termed "dropping rcu-walk". If the dentry refcount does
not match, we can not drop rcu-walk gracefully at the current point in the
lokup, so instead return -ECHILD (for want of a better errno). This signals the
path walking code to re-do the entire lookup with a ref-walk.

Aside from the final dentry, there are other situations that may be encounted
where we cannot continue rcu-walk. In that case, we drop rcu-walk (ie. take
a reference on the last good dentry) and continue with a ref-walk. Again, if
we can drop rcu-walk gracefully, we return -ECHILD and do the whole lookup
using ref-walk. But it is very important that we can continue with ref-walk
for most cases, particularly to avoid the overhead of double lookups, and to
gain the scalability advantages on common path elements (like cwd and root).

The cases where rcu-walk cannot continue are:
* NULL dentry (ie. any uncached path element)
* parent with d_inode->i_op->permission or ACLs
* dentries with d_revalidate
* Following links

In future patches, permission checks and d_revalidate become rcu-walk aware. It
may be possible eventually to make following links rcu-walk aware.

Uncached path elements will always require dropping to ref-walk mode, at the
very least because i_mutex needs to be grabbed, and objects allocated.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:27 +11:00
Nick Piggin b5c84bf6f6 fs: dcache remove dcache_lock
dcache_lock no longer protects anything. remove it.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:23 +11:00
Nick Piggin b7ab39f631 fs: dcache scale dentry refcount
Make d_count non-atomic and protect it with d_lock. This allows us to ensure a
0 refcount dentry remains 0 without dcache_lock. It is also fairly natural when
we start protecting many other dentry members with d_lock.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:21 +11:00
Nick Piggin b1e6a015a5 fs: change d_hash for rcu-walk
Change d_hash so it may be called from lock-free RCU lookups. See similar
patch for d_compare for details.

For in-tree filesystems, this is just a mechanical change.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
2011-01-07 17:50:20 +11:00
Lino Sanfilippo b1085ba80c fanotify: if set by user unset FMODE_NONOTIFY before fsnotify_perm() is called
Unsetting FMODE_NONOTIFY in fsnotify_open() is too late, since fsnotify_perm()
is called before. If FMODE_NONOTIFY is set fsnotify_perm() will skip permission
checks, so a user can still disable permission checks by setting this flag
in an open() call.
This patch corrects this by unsetting the flag before fsnotify_perm is called.

Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Signed-off-by: Eric Paris <eparis@redhat.com>
2010-12-07 16:14:21 -05:00
Al Viro d893f1bc2a fix open/umount race
nameidata_to_filp() drops nd->path or transfers it to opened
file.  In the former case it's a Bad Idea(tm) to do mnt_drop_write()
on nd->path.mnt, since we might race with umount and vfsmount in
question might be gone already.

Fix: don't drop it, then...  IOW, have nameidata_to_filp() grab nd->path
in case it transfers it to file and do path_drop() in callers.  After
they are through with accessing nd->path...

Reported-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-10-29 04:14:56 -04:00
Al Viro 7de9c6ee3e new helper: ihold()
Clones an existing reference to inode; caller must already hold one.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-10-25 21:26:11 -04:00
Christoph Hellwig 81fca44400 fs: move permission check back into __lookup_hash
The caller that didn't need it is gone.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-10-25 21:18:19 -04:00
Nick Piggin 99b7db7b8f fs: brlock vfsmount_lock
fs: brlock vfsmount_lock

Use a brlock for the vfsmount lock. It must be taken for write whenever
modifying the mount hash or associated fields, and may be taken for read when
performing mount hash lookups.

A new lock is added for the mnt-id allocator, so it doesn't need to take
the heavy vfsmount write-lock.

The number of atomics should remain the same for fastpath rlock cases, though
code would be slightly slower due to per-cpu access. Scalability is not not be
much improved in common cases yet, due to other locks (ie. dcache_lock) getting
in the way. However path lookups crossing mountpoints should be one case where
scalability is improved (currently requiring the global lock).

The slowpath is slower due to use of brlock. On a 64 core, 64 socket, 32 node
Altix system (high latency to remote nodes), a simple umount microbenchmark
(mount --bind mnt mnt2 ; umount mnt2 loop 1000 times), before this patch it
took 6.8s, afterwards took 7.1s, about 5% slower.

Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-18 08:35:48 -04:00
Nick Piggin b04f784e5d fs: remove extra lookup in __lookup_hash
fs: remove extra lookup in __lookup_hash

Optimize lookup for create operations, where no dentry should often be
common-case. In cases where it is not, such as unlink, the added overhead
is much smaller than the removed.

Also, move comments about __d_lookup racyness to the __d_lookup call site.
d_lookup is intuitive; __d_lookup is what needs commenting. So in that same
vein, add kerneldoc comments to __d_lookup and clean up some of the comments:

- We are interested in how the RCU lookup works here, particularly with
  renames. Make that explicit, and point to the document where it is explained
  in more detail.
- RCU is pretty standard now, and macros make implementations pretty mindless.
  If we want to know about RCU barrier details, we look in RCU code.
- Delete some boring legacy comments because we don't care much about how the
  code used to work, more about the interesting parts of how it works now. So
  comments about lazy LRU may be interesting, but would better be done in the
  LRU or refcount management code.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-18 08:35:47 -04:00