Commit Graph

535 Commits

Author SHA1 Message Date
Linus Torvalds 18253e034d Merge branch 'work.dcache2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull dcache and mountpoint updates from Al Viro:
 "Saner handling of refcounts to mountpoints.

  Transfer the counting reference from struct mount ->mnt_mountpoint
  over to struct mountpoint ->m_dentry. That allows us to get rid of the
  convoluted games with ordering of mount shutdowns.

  The cost is in teaching shrink_dcache_{parent,for_umount} to cope with
  mixed-filesystem shrink lists, which we'll also need for the Slab
  Movable Objects patchset"

* 'work.dcache2' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  switch the remnants of releasing the mountpoint away from fs_pin
  get rid of detach_mnt()
  make struct mountpoint bear the dentry reference to mountpoint, not struct mount
  Teach shrink_dcache_parent() to cope with mixed-filesystem shrink lists
  fs/namespace.c: shift put_mountpoint() to callers of unhash_mnt()
  __detach_mounts(): lookup_mountpoint() can't return ERR_PTR() anymore
  nfs: dget_parent() never returns NULL
  ceph: don't open-code the check for dead lockref
2019-07-20 09:15:51 -07:00
Al Viro 9bdebc2bd1 Teach shrink_dcache_parent() to cope with mixed-filesystem shrink lists
Currently, running into a shrink list that contains dentries from different
filesystems can cause several unpleasant things for shrink_dcache_parent()
and for umount(2).

The first problem is that there's a window during shrink_dentry_list() between
__dentry_kill() takes a victim out and dropping reference to its parent.  During
that window the parent looks like a genuine busy dentry.  shrink_dcache_parent()
(or, worse yet, shrink_dcache_for_umount()) coming at that time will see no
eviction candidates and no indication that it needs to wait for some
shrink_dentry_list() to proceed further.

That applies for any shrink list that might intersect with the subtree we are
trying to shrink; the only reason it does not blow on umount(2) in the mainline
is that we unregister the memory shrinker before hitting shrink_dcache_for_umount().

Another problem happens if something in a mixed-filesystem shrink list gets
be stuck in e.g. iput(), getting umount of unrelated fs to spin waiting for
the stuck shrinker to get around to our dentries.

Solution:
        1) have shrink_dentry_list() decrement the parent's refcount and
make sure it's on a shrink list (ours unless it already had been on some
other) before calling __dentry_kill().  That eliminates the window when
shrink_dcache_parent() would've blown past the entire subtree without
noticing anything with zero refcount not on shrink lists.
	2) when shrink_dcache_parent() has found no eviction candidates,
but some dentries are still sitting on shrink lists, rather than
repeating the scan in hope that shrinkers have progressed, scan looking
for something on shrink lists with zero refcount.  If such a thing is
found, grab rcu_read_lock() and stop the scan, with caller locking
it for eviction, dropping out of RCU and doing __dentry_kill(), with
the same treatment for parent as shrink_dentry_list() would do.

Note that right now mixed-filesystem shrink lists do not occur, so this
is not a mainline bug.  Howevere, there's a bunch of uses for such
beasts (e.g. the "try and evict everything we can out of given page"
patches; there are potential uses in mount-related code, considerably
simplifying the life in fs/namespace.c, etc.)

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2019-07-10 07:32:22 -04:00
Amir Goldstein 49246466a9 fsnotify: move fsnotify_nameremove() hook out of d_delete()
d_delete() was piggy backed for the fsnotify_nameremove() hook when
in fact not all callers of d_delete() care about fsnotify events.

For all callers of d_delete() that may be interested in fsnotify events,
we made sure to call one of fsnotify_{unlink,rmdir}() hooks before
calling d_delete().

Now we can move the fsnotify_nameremove() call from d_delete() to the
fsnotify_{unlink,rmdir}() hooks.

Two explicit calls to fsnotify_nameremove() from nfs/afs sillyrename
are also removed. This will cause a change of behavior - nfs/afs will
NOT generate an fsnotify delete event when renaming over a positive
dentry.  This change is desirable, because it is consistent with the
behavior of all other filesystems.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
2019-06-20 14:47:44 +02:00
Thomas Gleixner 457c899653 treewide: Add SPDX license identifier for missed files
Add SPDX license identifiers to all files which:

 - Have no license information of any form

 - Have EXPORT_.*_SYMBOL_GPL inside which was used in the
   initial scan/conversion to ignore the file

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

  GPL-2.0-only

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-05-21 10:50:45 +02:00
Linus Torvalds a9fbcd6728 Clean up fscrypt's dcache revalidation support, and other
miscellaneous cleanups.
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Merge tag 'fscrypt_for_linus' of git://git.kernel.org/pub/scm/fs/fscrypt/fscrypt

Pull fscrypt updates from Ted Ts'o:
 "Clean up fscrypt's dcache revalidation support, and other
  miscellaneous cleanups"

* tag 'fscrypt_for_linus' of git://git.kernel.org/pub/scm/fs/fscrypt/fscrypt:
  fscrypt: cache decrypted symlink target in ->i_link
  vfs: use READ_ONCE() to access ->i_link
  fscrypt: fix race where ->lookup() marks plaintext dentry as ciphertext
  fscrypt: only set dentry_operations on ciphertext dentries
  fs, fscrypt: clear DCACHE_ENCRYPTED_NAME when unaliasing directory
  fscrypt: fix race allowing rename() and link() of ciphertext dentries
  fscrypt: clean up and improve dentry revalidation
  fscrypt: use READ_ONCE() to access ->i_crypt_info
  fscrypt: remove WARN_ON_ONCE() when decryption fails
  fscrypt: drop inode argument from fscrypt_get_ctx()
2019-05-07 21:28:04 -07:00
Al Viro 230c6402b1 ovl_lookup_real_one(): don't bother with strlen()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2019-04-26 13:13:33 -04:00
Eric Biggers 0bf3d5c160 fs, fscrypt: clear DCACHE_ENCRYPTED_NAME when unaliasing directory
Make __d_move() clear DCACHE_ENCRYPTED_NAME on the source dentry.  This
is needed for when d_splice_alias() moves a directory's encrypted alias
to its decrypted alias as a result of the encryption key being added.

Otherwise, the decrypted alias will incorrectly be invalidated on the
next lookup, causing problems such as unmounting a mount the user just
mount()ed there.

Note that we don't have to support arbitrary moves of this flag because
fscrypt doesn't allow dentries with DCACHE_ENCRYPTED_NAME to be the
source or target of a rename().

Fixes: 28b4c26396 ("ext4 crypto: revalidate dentry after adding or removing the key")
Reported-by: Sarthak Kukreti <sarthakkukreti@chromium.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2019-04-17 10:05:51 -04:00
Al Viro ab1152dd56 unexport d_alloc_pseudo()
No modular uses since introducion of alloc_file_pseudo(),
and the only non-modular user not in alloc_file_pseudo()
had actually been wrong - should've been d_alloc_anon().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2019-04-09 19:20:46 -04:00
Al Viro 5467a68cbf dcache: sort the freeing-without-RCU-delay mess for good.
For lockless accesses to dentries we don't have pinned we rely
(among other things) upon having an RCU delay between dropping
the last reference and actually freeing the memory.

On the other hand, for things like pipes and sockets we neither
do that kind of lockless access, nor want to deal with the
overhead of an RCU delay every time a socket gets closed.

So delay was made optional - setting DCACHE_RCUACCESS in ->d_flags
made sure it would happen.  We tried to avoid setting it unless
we knew we need it.  Unfortunately, that had led to recurring
class of bugs, in which we missed the need to set it.

We only really need it for dentries that are created by
d_alloc_pseudo(), so let's not bother with trying to be smart -
just make having an RCU delay the default.  The ones that do
*not* get it set the replacement flag (DCACHE_NORCU) and we'd
better use that sparingly.  d_alloc_pseudo() is the only
such user right now.

FWIW, the race that finally prompted that switch had been
between __lock_parent() of immediate subdirectory of what's
currently the root of a disconnected tree (e.g. from
open-by-handle in progress) racing with d_splice_alias()
elsewhere picking another alias for the same inode, either
on outright corrupted fs image, or (in case of open-by-handle
on NFS) that subdirectory having been just moved on server.
It's not easy to hit, so the sky is not falling, but that's
not the first race on similar missed cases and the logics
for settinf DCACHE_RCUACCESS has gotten ridiculously
convoluted.

Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2019-04-09 19:18:04 -04:00
Waiman Long af0c9af1b3 fs/dcache: Track & report number of negative dentries
The current dentry number tracking code doesn't distinguish between
positive & negative dentries.  It just reports the total number of
dentries in the LRU lists.

As excessive number of negative dentries can have an impact on system
performance, it will be wise to track the number of positive and
negative dentries separately.

This patch adds tracking for the total number of negative dentries in
the system LRU lists and reports it in the 5th field in the
/proc/sys/fs/dentry-state file.  The number, however, does not include
negative dentries that are in flight but not in the LRU yet as well as
those in the shrinker lists which are on the way out anyway.

The number of positive dentries in the LRU lists can be roughly found by
subtracting the number of negative dentries from the unused count.

Matthew Wilcox had confirmed that since the introduction of the
dentry_stat structure in 2.1.60, the dummy array was there, probably for
future extension.  They were not replacements of pre-existing fields.
So no sane applications that read the value of /proc/sys/fs/dentry-state
will do dummy thing if the last 2 fields of the sysctl parameter are not
zero.  IOW, it will be safe to use one of the dummy array entry for
negative dentry count.

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-01-30 11:02:11 -08:00
Waiman Long 1dbd449c99 fs/dcache: Fix incorrect nr_dentry_unused accounting in shrink_dcache_sb()
The nr_dentry_unused per-cpu counter tracks dentries in both the LRU
lists and the shrink lists where the DCACHE_LRU_LIST bit is set.

The shrink_dcache_sb() function moves dentries from the LRU list to a
shrink list and subtracts the dentry count from nr_dentry_unused.  This
is incorrect as the nr_dentry_unused count will also be decremented in
shrink_dentry_list() via d_shrink_del().

To fix this double decrement, the decrement in the shrink_dcache_sb()
function is taken out.

Fixes: 4e717f5c10 ("list_lru: remove special case function list_lru_dispose_all."
Cc: stable@kernel.org
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-01-30 11:02:11 -08:00
Mike Rapoport 57c8a661d9 mm: remove include/linux/bootmem.h
Move remaining definitions and declarations from include/linux/bootmem.h
into include/linux/memblock.h and remove the redundant header.

The includes were replaced with the semantic patch below and then
semi-automated removal of duplicated '#include <linux/memblock.h>

@@
@@
- #include <linux/bootmem.h>
+ #include <linux/memblock.h>

[sfr@canb.auug.org.au: dma-direct: fix up for the removal of linux/bootmem.h]
  Link: http://lkml.kernel.org/r/20181002185342.133d1680@canb.auug.org.au
[sfr@canb.auug.org.au: powerpc: fix up for removal of linux/bootmem.h]
  Link: http://lkml.kernel.org/r/20181005161406.73ef8727@canb.auug.org.au
[sfr@canb.auug.org.au: x86/kaslr, ACPI/NUMA: fix for linux/bootmem.h removal]
  Link: http://lkml.kernel.org/r/20181008190341.5e396491@canb.auug.org.au
Link: http://lkml.kernel.org/r/1536927045-23536-30-git-send-email-rppt@linux.vnet.ibm.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Greentime Hu <green.hu@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Guan Xuetao <gxt@pku.edu.cn>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: Jonas Bonn <jonas@southpole.se>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Ley Foon Tan <lftan@altera.com>
Cc: Mark Salter <msalter@redhat.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Richard Kuo <rkuo@codeaurora.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Rich Felker <dalias@libc.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Serge Semin <fancer.lancer@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-10-31 08:54:16 -07:00
Vlastimil Babka 2e03b4bc4a dcache: allocate external names from reclaimable kmalloc caches
We can use the newly introduced kmalloc-reclaimable-X caches, to allocate
external names in dcache, which will take care of the proper accounting
automatically, and also improve anti-fragmentation page grouping.

This effectively reverts commit f1782c9bc5 ("dcache: account external
names as indirectly reclaimable memory") and instead passes
__GFP_RECLAIMABLE to kmalloc().  The accounting thus moves from
NR_INDIRECTLY_RECLAIMABLE_BYTES to NR_SLAB_RECLAIMABLE, which is also
considered in MemAvailable calculation and overcommit decisions.

Link: http://lkml.kernel.org/r/20180731090649.16028-4-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Roman Gushchin <guro@fb.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Vijayanand Jitta <vjitta@codeaurora.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-10-26 16:26:32 -07:00
Tetsuo Handa 6cd00a01f0 fs/dcache.c: fix kmemcheck splat at take_dentry_name_snapshot()
Since only dentry->d_name.len + 1 bytes out of DNAME_INLINE_LEN bytes
are initialized at __d_alloc(), we can't copy the whole size
unconditionally.

 WARNING: kmemcheck: Caught 32-bit read from uninitialized memory (ffff8fa27465ac50)
 636f6e66696766732e746d70000000000010000000000000020000000188ffff
  i i i i i i i i i i i i i u u u u u u u u u u i i i i i u u u u
                                  ^
 RIP: 0010:take_dentry_name_snapshot+0x28/0x50
 RSP: 0018:ffffa83000f5bdf8 EFLAGS: 00010246
 RAX: 0000000000000020 RBX: ffff8fa274b20550 RCX: 0000000000000002
 RDX: ffffa83000f5be40 RSI: ffff8fa27465ac50 RDI: ffffa83000f5be60
 RBP: ffffa83000f5bdf8 R08: ffffa83000f5be48 R09: 0000000000000001
 R10: ffff8fa27465ac00 R11: ffff8fa27465acc0 R12: ffff8fa27465ac00
 R13: ffff8fa27465acc0 R14: 0000000000000000 R15: 0000000000000000
 FS:  00007f79737ac8c0(0000) GS:ffffffff8fc30000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: ffff8fa274c0b000 CR3: 0000000134aa7002 CR4: 00000000000606f0
  take_dentry_name_snapshot+0x28/0x50
  vfs_rename+0x128/0x870
  SyS_rename+0x3b2/0x3d0
  entry_SYSCALL_64_fastpath+0x1a/0xa4
  0xffffffffffffffff

Link: http://lkml.kernel.org/r/201709131912.GBG39012.QMJLOVFSFFOOtH@I-love.SAKURA.ne.jp
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Vegard Nossum <vegard.nossum@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-17 16:20:28 -07:00
Linus Torvalds 4591343e35 Merge branches 'work.misc' and 'work.dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull misc vfs updates from Al Viro:
 "Misc cleanups from various folks all over the place

  I expected more fs/dcache.c cleanups this cycle, so that went into a
  separate branch. Said cleanups have missed the window, so in the
  hindsight it could've gone into work.misc instead. Decided not to
  cherry-pick, thus the 'work.dcache' branch"

* 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  fs: dcache: Use true and false for boolean values
  fold generic_readlink() into its only caller
  fs: shave 8 bytes off of struct inode
  fs: Add more kernel-doc to the produced documentation
  fs: Fix attr.c kernel-doc
  removed extra extern file_fdatawait_range

* 'work.dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  kill dentry_update_name_case()
2018-08-13 21:28:25 -07:00
Linus Torvalds 0ea97a2d61 Merge branch 'work.mkdir' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs icache updates from Al Viro:

 - NFS mkdir/open_by_handle race fix

 - analogous solution for FUSE, replacing the one currently in mainline

 - new primitive to be used when discarding halfway set up inodes on
   failed object creation; gives sane warranties re icache lookups not
   returning such doomed by still not freed inodes. A bunch of
   filesystems switched to that animal.

 - Miklos' fix for last cycle regression in iget5_locked(); -stable will
   need a slightly different variant, unfortunately.

 - misc bits and pieces around things icache-related (in adfs and jfs).

* 'work.mkdir' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  jfs: don't bother with make_bad_inode() in ialloc()
  adfs: don't put inodes into icache
  new helper: inode_fake_hash()
  vfs: don't evict uninitialized inode
  jfs: switch to discard_new_inode()
  ext2: make sure that partially set up inodes won't be returned by ext2_iget()
  udf: switch to discard_new_inode()
  ufs: switch to discard_new_inode()
  btrfs: switch to discard_new_inode()
  new primitive: discard_new_inode()
  kill d_instantiate_no_diralias()
  nfs_instantiate(): prevent multiple aliases for directory inode
2018-08-13 20:25:58 -07:00
Al Viro 4c0d7cd5c8 make sure that __dentry_kill() always invalidates d_seq, unhashed or not
RCU pathwalk relies upon the assumption that anything that changes
->d_inode of a dentry will invalidate its ->d_seq.  That's almost
true - the one exception is that the final dput() of already unhashed
dentry does *not* touch ->d_seq at all.  Unhashing does, though,
so for anything we'd found by RCU dcache lookup we are fine.
Unfortunately, we can *start* with an unhashed dentry or jump into
it.

We could try and be careful in the (few) places where that could
happen.  Or we could just make the final dput() invalidate the damn
thing, unhashed or not.  The latter is much simpler and easier to
backport, so let's do it that way.

Reported-by: "Dae R. Jeong" <threeearcat@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-08-09 18:07:15 -04:00
Al Viro 90bad5e05b root dentries need RCU-delayed freeing
Since mountpoint crossing can happen without leaving lazy mode,
root dentries do need the same protection against having their
memory freed without RCU delay as everything else in the tree.

It's partially hidden by RCU delay between detaching from the
mount tree and dropping the vfsmount reference, but the starting
point of pathwalk can be on an already detached mount, in which
case umount-caused RCU delay has already passed by the time the
lazy pathwalk grabs rcu_read_lock().  If the starting point
happens to be at the root of that vfsmount *and* that vfsmount
covers the entire filesystem, we get trouble.

Fixes: 48a066e72d ("RCU'd vsfmounts")
Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-08-06 09:13:32 -04:00
Gustavo A. R. Silva 7964410fcf fs: dcache: Use true and false for boolean values
Return statements in functions returning bool should use true or false
instead of an integer value.

This issue was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-08-05 15:52:44 -04:00
Al Viro c2b6d621c4 new primitive: discard_new_inode()
We don't want open-by-handle picking half-set-up in-core
struct inode from e.g. mkdir() having failed halfway through.
In other words, we don't want such inodes returned by iget_locked()
on their way to extinction.  However, we can't just have them
unhashed - otherwise open-by-handle immediately *after* that would've
ended up creating a new in-core inode over the on-disk one that
is in process of being freed right under us.

	Solution: new flag (I_CREATING) set by insert_inode_locked() and
removed by unlock_new_inode() and a new primitive (discard_new_inode())
to be used by such halfway-through-setup failure exits instead of
unlock_new_inode() / iput() combinations.  That primitive unlocks new
inode, but leaves I_CREATING in place.

	iget_locked() treats finding an I_CREATING inode as failure
(-ESTALE, once we sort out the error propagation).
	insert_inode_locked() treats the same as instant -EBUSY.
	ilookup() treats those as icache miss.

[Fix by Dan Carpenter <dan.carpenter@oracle.com> folded in]

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-08-03 15:55:30 -04:00
Al Viro c971e6a006 kill d_instantiate_no_diralias()
The only user is fuse_create_new_entry(), and there it's used to
mitigate the same mkdir/open-by-handle race as in nfs_mkdir().
The same solution applies - unhash the mkdir argument, then
call d_splice_alias() and if that returns a reference to preexisting
alias, dput() and report success.  ->mkdir() argument left unhashed
negative with the preexisting alias moved in the right place is just
fine from the ->mkdir() callers point of view.

Cc: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-08-01 23:18:53 -04:00
Al Viro 63a67a926e kill dentry_update_name_case()
the last user is gone

Spotted-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-06-23 17:16:44 -04:00
Linus Torvalds f956d08a56 Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull misc vfs updates from Al Viro:
 "Misc bits and pieces not fitting into anything more specific"

* 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  vfs: delete unnecessary assignment in vfs_listxattr
  Documentation: filesystems: update filesystem locking documentation
  vfs: namei: use path_equal() in follow_dotdot()
  fs.h: fix outdated comment about file flags
  __inode_security_revalidate() never gets NULL opt_dentry
  make xattr_getsecurity() static
  vfat: simplify checks in vfat_lookup()
  get rid of dead code in d_find_alias()
  it's SB_BORN, not MS_BORN...
  msdos_rmdir(): kill BS comment
  remove rpc_rmdir()
  fs: avoid fdput() after failed fdget() in vfs_dedupe_file_range()
2018-06-04 10:14:28 -07:00
Linus Torvalds 06c86e66d6 Merge branch 'work.dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull dcache updates from Al Viro:
 "This is the first part of dealing with livelocks etc around
  shrink_dcache_parent()."

* 'work.dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  restore cond_resched() in shrink_dcache_parent()
  dput(): turn into explicit while() loop
  dcache: move cond_resched() into the end of __dentry_kill()
  d_walk(): kill 'finish' callback
  d_invalidate(): unhash immediately
2018-06-04 08:57:36 -07:00
Al Viro 61fec493c9 get rid of dead code in d_find_alias()
All "try disconnected alias if nothing else fits" logics in d_find_alias()
got accidentally disabled by Neil a while ago; for most of the callers it
was the right thing to do, so fixes belong in few callers that *do* want
disconnected aliases.  This just takes the now-dead code in d_find_alias()
out.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-05-13 12:08:32 -04:00
Al Viro 1e2e547a93 do d_instantiate/unlock_new_inode combinations safely
For anything NFS-exported we do _not_ want to unlock new inode
before it has grown an alias; original set of fixes got the
ordering right, but missed the nasty complication in case of
lockdep being enabled - unlock_new_inode() does
	lockdep_annotate_inode_mutex_key(inode)
which can only be done before anyone gets a chance to touch
->i_mutex.  Unfortunately, flipping the order and doing
unlock_new_inode() before d_instantiate() opens a window when
mkdir can race with open-by-fhandle on a guessed fhandle, leading
to multiple aliases for a directory inode and all the breakage
that follows from that.

	Correct solution: a new primitive (d_instantiate_new())
combining these two in the right order - lockdep annotate, then
d_instantiate(), then the rest of unlock_new_inode().  All
combinations of d_instantiate() with unlock_new_inode() should
be converted to that.

Cc: stable@kernel.org	# 2.6.29 and later
Tested-by: Mike Marshall <hubcap@omnibond.com>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-05-11 15:36:37 -04:00
Al Viro 4fb4887140 restore cond_resched() in shrink_dcache_parent()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-04-19 23:58:48 -04:00
Al Viro 1088a6408c dput(): turn into explicit while() loop
No need to mess with gotos when the code yielded by straight while()
isn't any worse...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-04-15 23:36:58 -04:00
Al Viro 9c5f1d3019 dcache: move cond_resched() into the end of __dentry_kill()
cond_resched() in shrink_dentry_list() is too early

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-04-15 23:36:58 -04:00
Al Viro 3a8e3611e0 d_walk(): kill 'finish' callback
no users left

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-04-15 23:36:57 -04:00
Al Viro ff17fa561a d_invalidate(): unhash immediately
Once that is done, we can just hunt mountpoints down one by one;
no new mountpoints can be added from now on, so we don't need
anything tricky in finish() callback, etc.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-04-15 23:36:57 -04:00
Nikolay Borisov 32785c0539 fs/dcache.c: add cond_resched() in shrink_dentry_list()
As previously reported (https://patchwork.kernel.org/patch/8642031/)
it's possible to call shrink_dentry_list with a large number of dentries
(> 10000).  This, in turn, could trigger the softlockup detector and
possibly trigger a panic.  In addition to the unmount path being
vulnerable to this scenario, at SuSE we've observed similar situation
happening during process exit on processes that touch a lot of dentries.
Here is an excerpt from a crash dump.  The number after the colon are
the number of dentries on the list passed to shrink_dentry_list:

PID 99760: 10722
PID 107530: 215
PID 108809: 24134
PID 108877: 21331
PID 141708: 16487

So we want to kill between 15k-25k dentries without yielding.

And one possible call stack looks like:

4 [ffff8839ece41db0] _raw_spin_lock at ffffffff8152a5f8
5 [ffff8839ece41db0] evict at ffffffff811c3026
6 [ffff8839ece41dd0] __dentry_kill at ffffffff811bf258
7 [ffff8839ece41df0] shrink_dentry_list at ffffffff811bf593
8 [ffff8839ece41e18] shrink_dcache_parent at ffffffff811bf830
9 [ffff8839ece41e50] proc_flush_task at ffffffff8120dd61
10 [ffff8839ece41ec0] release_task at ffffffff81059ebd
11 [ffff8839ece41f08] do_exit at ffffffff8105b8ce
12 [ffff8839ece41f78] sys_exit at ffffffff8105bd53
13 [ffff8839ece41f80] system_call_fastpath at ffffffff81532909

While some of the callers of shrink_dentry_list do use cond_resched,
this is not sufficient to prevent softlockups.  So just move
cond_resched into shrink_dentry_list from its callers.

David said: I've found hundreds of occurrences of warnings that we emit
when need_resched stays set for a prolonged period of time with the
stack trace that is included in the change log.

Link: http://lkml.kernel.org/r/1521718946-31521-1-git-send-email-nborisov@suse.com
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Goldwyn Rodrigues <rgoldwyn@suse.de>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-04-11 10:28:38 -07:00
Roman Gushchin f1782c9bc5 dcache: account external names as indirectly reclaimable memory
I received a report about suspicious growth of unreclaimable slabs on
some machines.  I've found that it happens on machines with low memory
pressure, and these unreclaimable slabs are external names attached to
dentries.

External names are allocated using generic kmalloc() function, so they
are accounted as unreclaimable.  But they are held by dentries, which
are reclaimable, and they will be reclaimed under the memory pressure.

In particular, this breaks MemAvailable calculation, as it doesn't take
unreclaimable slabs into account.  This leads to a silly situation, when
a machine is almost idle, has no memory pressure and therefore has a big
dentry cache.  And the resulting MemAvailable is too low to start a new
workload.

To address the issue, the NR_INDIRECTLY_RECLAIMABLE_BYTES counter is
used to track the amount of memory, consumed by external names.  The
counter is increased in the dentry allocation path, if an external name
structure is allocated; and it's decreased in the dentry freeing path.

To reproduce the problem I've used the following Python script:

  import os

  for iter in range (0, 10000000):
      try:
          name = ("/some_long_name_%d" % iter) + "_" * 220
          os.stat(name)
      except Exception:
          pass

Without this patch:
  $ cat /proc/meminfo | grep MemAvailable
  MemAvailable:    7811688 kB
  $ python indirect.py
  $ cat /proc/meminfo | grep MemAvailable
  MemAvailable:    2753052 kB

With the patch:
  $ cat /proc/meminfo | grep MemAvailable
  MemAvailable:    7809516 kB
  $ python indirect.py
  $ cat /proc/meminfo | grep MemAvailable
  MemAvailable:    7749144 kB

[guro@fb.com: fix indirectly reclaimable memory accounting for CONFIG_SLOB]
  Link: http://lkml.kernel.org/r/20180312194140.19517-1-guro@fb.com
[guro@fb.com: fix indirectly reclaimable memory accounting]
  Link: http://lkml.kernel.org/r/20180313125701.7955-1-guro@fb.com
Link: http://lkml.kernel.org/r/20180305133743.12746-5-guro@fb.com
Signed-off-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-04-11 10:28:29 -07:00
Al Viro cbd4a5bcb2 d_genocide: move export to definition
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-03-29 15:08:21 -04:00
Al Viro 42177007aa fold dentry_lock_for_move() into its sole caller and clean it up
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-03-29 15:07:49 -04:00
Al Viro 076515fc92 make non-exchanging __d_move() copy ->d_parent rather than swap them
Currently d_move(from, to) does the following:
	* name/parent of from <- old name/parent of to, from hashed there
	* to is unhashed
	* name of to is preserved
	* if from used to be detached, to gets detached
	* if from used to be attached, parent of to <- old parent of from.

That's both user-visibly bogus and complicates reasoning a lot.
Much saner semantics would be
	* name/parent of from <- name/parent of to, from hashed there.
	* to is unhashed
	* name/parent of to is unchanged.

The price, of course, is that old parent of from might lose a reference.
However,
	* all potentially cross-directory callers of d_move() have both
parents pinned directly; typically, dentries themselves are grabbed
only after we have grabbed and locked both parents.  IOW, the decrement
of old parent's refcount in case of d_move() won't reach zero.
	* __d_move() from d_splice_alias() is done to detached alias.
No refcount decrements in that case
	* __d_move() from __d_unalias() *can* get the refcount to zero.
So let's grab a reference to alias' old parent before calling __d_unalias()
and dput() it after we'd dropped rename_lock.

That does make d_splice_alias() potentially blocking.  However, it has
no callers in non-sleepable contexts (and the case where we'd grown
that dget/dput pair is _very_ rare, so performance is not an issue).

Another thing that needs adjustment is unlocking in the end of __d_move();
folded it in.  And cleaned the remnants of bogus ordering from the
"lock them in the beginning" counterpart - it's never been right and
now (well, for 7 years now) we have that thing always serialized on
rename_lock anyway.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-03-29 15:07:49 -04:00
Al Viro 7a5cf791a7 split d_path() and friends into a separate file
Those parts of fs/dcache.c are pretty much self-contained.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-03-29 15:07:46 -04:00
Al Viro 43986d63b6 dcache.c: trim includes
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-03-29 15:07:45 -04:00
John Ogness 8f04da2adb fs/dcache: Avoid a try_lock loop in shrink_dentry_list()
shrink_dentry_list() holds dentry->d_lock and needs to acquire
dentry->d_inode->i_lock. This cannot be done with a spin_lock()
operation because it's the reverse of the regular lock order.
To avoid ABBA deadlocks it is done with a trylock loop.

Trylock loops are problematic in two scenarios:

  1) PREEMPT_RT converts spinlocks to 'sleeping' spinlocks, which are
     preemptible. As a consequence the i_lock holder can be preempted
     by a higher priority task. If that task executes the trylock loop
     it will do so forever and live lock.

  2) In virtual machines trylock loops are problematic as well. The
     VCPU on which the i_lock holder runs can be scheduled out and a
     task on a different VCPU can loop for a whole time slice. In the
     worst case this can lead to starvation. Commits 47be61845c
     ("fs/dcache.c: avoid soft-lockup in dput()") and 046b961b45
     ("shrink_dentry_list(): take parent's d_lock earlier") are
     addressing exactly those symptoms.

Avoid the trylock loop by using dentry_kill(). When pruning ancestors,
the same code applies that is used to kill a dentry in dput(). This
also has the benefit that the locking order is now the same. First
the inode is locked, then the parent.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-03-29 15:07:44 -04:00
Al Viro f657a666fd get rid of trylock loop around dentry_kill()
In case when trylock in there fails, deal with it directly in
dentry_kill().  Note that in cases when we drop and retake
->d_lock, we need to recheck whether to retain the dentry.
Another thing is that dropping/retaking ->d_lock might have
ended up with negative dentry turning into positive; that,
of course, can happen only once...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-03-29 15:07:44 -04:00
Al Viro 62d9956cef handle move to LRU in retain_dentry()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-03-29 15:07:43 -04:00
Al Viro a338579f2f dput(): consolidate the "do we need to retain it?" into an inlined helper
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-03-29 15:07:43 -04:00
Al Viro 8b987a46a1 split the slow part of lock_parent() off
Turn the "trylock failed" part into uninlined __lock_parent().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-03-29 15:07:42 -04:00
Al Viro 65d8eb5a8f now lock_parent() can't run into killed dentry
all remaining callers hold either a reference or ->i_lock

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-03-29 15:07:42 -04:00
Al Viro 3b3f09f48b get rid of trylock loop in locking dentries on shrink list
In case of trylock failure don't re-add to the list - drop the locks
and carefully get them in the right order.  For shrink_dentry_list(),
somebody having grabbed a reference to dentry means that we can
kick it off-list, so if we find dentry being modified under us we
don't need to play silly buggers with retries anyway - off the list
it is.

The locking logics taken out into a helper of its own; lock_parent()
is no longer used for dentries that can be killed under us.

[fix from Eric Biggers folded]

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-03-29 15:07:02 -04:00
Al Viro c19457f0ae d_delete(): get rid of trylock loop
just grab ->i_lock first; we have a positive dentry, nothing's going
to happen to inode

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-03-12 11:59:14 -04:00
John Ogness c1d0c1a2b5 fs/dcache: Move dentry_kill() below lock_parent()
A subsequent patch will modify dentry_kill() to call lock_parent().
Move the dentry_kill() implementation "as is" below lock_parent()
first. This will help simplify the review of the subsequent patch
with dentry_kill() changes.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-03-12 11:59:13 -04:00
John Ogness 06080d100d fs/dcache: Remove stale comment from dentry_kill()
Commit 0d98439ea3 ("vfs: use lockred "dead" flag to mark unrecoverably
dead dentries") removed the `ref' parameter in dentry_kill() but its
documentation remained. Remove it.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-03-12 11:59:13 -04:00
Al Viro 0632a9ac7b take write_seqcount_invalidate() into __d_drop()
... and reorder it with making d_unhashed() true.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-03-12 11:59:12 -04:00
Will Deacon 8cc07c808c fs: dcache: Use READ_ONCE when accessing i_dir_seq
i_dir_seq is subject to concurrent modification by a cmpxchg or
store-release operation, so ensure that the relaxed access in
d_alloc_parallel uses READ_ONCE.

Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-02-25 12:51:10 -05:00