SYNOPSIS
size[4] Tsetattr tag[2] attr[n]
size[4] Rsetattr tag[2]
DESCRIPTION
The setattr command changes some of the file status information.
attr resembles the iattr structure used in Linux kernel. It
specifies which status parameter is to be changed and to what
value. It is laid out as follows:
valid[4]
specifies which status information is to be changed. Possible
values are:
ATTR_MODE (1 << 0)
ATTR_UID (1 << 1)
ATTR_GID (1 << 2)
ATTR_SIZE (1 << 3)
ATTR_ATIME (1 << 4)
ATTR_MTIME (1 << 5)
ATTR_ATIME_SET (1 << 7)
ATTR_MTIME_SET (1 << 8)
The last two bits represent whether the time information
is being sent by the client's user space. In the absense
of these bits the server always uses server's time.
mode[4]
File permission bits
uid[4]
Owner id of file
gid[4]
Group id of the file
size[8]
File size
atime_sec[8]
Time of last file access, seconds
atime_nsec[8]
Time of last file access, nanoseconds
mtime_sec[8]
Time of last file modification, seconds
mtime_nsec[8]
Time of last file modification, nanoseconds
Explanation of the patches:
--------------------------
*) The kernel just copies relevent contents of iattr structure to
p9_iattr_dotl structure and passes it down to the client. The
only check it has is calling inode_change_ok()
*) The p9_iattr_dotl structure does not have ctime and ia_file
parameters because I don't think these are needed in our case.
The client user space can request updating just ctime by calling
chown(fd, -1, -1). This is handled on server side without a need
for putting ctime on the wire.
*) The server currently supports changing mode, time, ownership and
size of the file.
*) 9P RFC says "Either all the changes in wstat request happen, or
none of them does: if the request succeeds, all changes were made;
if it fails, none were."
I have not done anything to implement this specifically because I
don't see a reason.
Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
SYNOPSIS
size[4] Tgetattr tag[2] fid[4] request_mask[8]
size[4] Rgetattr tag[2] lstat[n]
DESCRIPTION
The getattr transaction inquires about the file identified by fid.
request_mask is a bit mask that specifies which fields of the
stat structure is the client interested in.
The reply will contain a machine-independent directory entry,
laid out as follows:
st_result_mask[8]
Bit mask that indicates which fields in the stat structure
have been populated by the server
qid.type[1]
the type of the file (directory, etc.), represented as a bit
vector corresponding to the high 8 bits of the file's mode
word.
qid.vers[4]
version number for given path
qid.path[8]
the file server's unique identification for the file
st_mode[4]
Permission and flags
st_uid[4]
User id of owner
st_gid[4]
Group ID of owner
st_nlink[8]
Number of hard links
st_rdev[8]
Device ID (if special file)
st_size[8]
Size, in bytes
st_blksize[8]
Block size for file system IO
st_blocks[8]
Number of file system blocks allocated
st_atime_sec[8]
Time of last access, seconds
st_atime_nsec[8]
Time of last access, nanoseconds
st_mtime_sec[8]
Time of last modification, seconds
st_mtime_nsec[8]
Time of last modification, nanoseconds
st_ctime_sec[8]
Time of last status change, seconds
st_ctime_nsec[8]
Time of last status change, nanoseconds
st_btime_sec[8]
Time of creation (birth) of file, seconds
st_btime_nsec[8]
Time of creation (birth) of file, nanoseconds
st_gen[8]
Inode generation
st_data_version[8]
Data version number
request_mask and result_mask bit masks contain the following bits
#define P9_STATS_MODE 0x00000001ULL
#define P9_STATS_NLINK 0x00000002ULL
#define P9_STATS_UID 0x00000004ULL
#define P9_STATS_GID 0x00000008ULL
#define P9_STATS_RDEV 0x00000010ULL
#define P9_STATS_ATIME 0x00000020ULL
#define P9_STATS_MTIME 0x00000040ULL
#define P9_STATS_CTIME 0x00000080ULL
#define P9_STATS_INO 0x00000100ULL
#define P9_STATS_SIZE 0x00000200ULL
#define P9_STATS_BLOCKS 0x00000400ULL
#define P9_STATS_BTIME 0x00000800ULL
#define P9_STATS_GEN 0x00001000ULL
#define P9_STATS_DATA_VERSION 0x00002000ULL
#define P9_STATS_BASIC 0x000007ffULL
#define P9_STATS_ALL 0x00003fffULL
This patch implements the client side of getattr implementation for
9P2000.L. It introduces a new structure p9_stat_dotl for getting
Linux stat information along with QID. The data layout is similar to
stat structure in Linux user space with the following major
differences:
inode (st_ino) is not part of data. Instead qid is.
device (st_dev) is not part of data because this doesn't make sense
on the client.
All time variables are 64 bit wide on the wire. The kernel seems to use
32 bit variables for these variables. However, some of the architectures
have used 64 bit variables and glibc exposes 64 bit variables to user
space on some architectures. Hence to be on the safer side we have made
these 64 bit in the protocol. Refer to the comments in
include/asm-generic/stat.h
There are some additional fields: st_btime_sec, st_btime_nsec, st_gen,
st_data_version apart from the bitmask, st_result_mask. The bit mask
is filled by the server to indicate which stat fields have been
populated by the server. Currently there is no clean way for the
server to obtain these additional fields, so it sends back just the
basic fields.
Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
Signed-off-by: Eric Van Hensbegren <ericvh@gmail.com>
We need to make sure we pass the right uid value
during attach. dotl is similar to dotu in this regard.
Without this mapped security model on dotl doesn't work
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
This patch implements the kernel part of readdir() implementation for 9p2000.L
Change from V3: Instead of inode, server now sends qids for each dirent
SYNOPSIS
size[4] Treaddir tag[2] fid[4] offset[8] count[4]
size[4] Rreaddir tag[2] count[4] data[count]
DESCRIPTION
The readdir request asks the server to read the directory specified by 'fid'
at an offset specified by 'offset' and return as many dirent structures as
possible that fit into count bytes. Each dirent structure is laid out as
follows.
qid.type[1]
the type of the file (directory, etc.), represented as a bit
vector corresponding to the high 8 bits of the file's mode
word.
qid.vers[4]
version number for given path
qid.path[8]
the file server's unique identification for the file
offset[8]
offset into the next dirent.
type[1]
type of this directory entry.
name[256]
name of this directory entry.
This patch adds v9fs_dir_readdir_dotl() as the readdir() call for 9p2000.L.
This function sends P9_TREADDIR command to the server. In response the server
sends a buffer filled with dirent structures. This is different from the
existing v9fs_dir_readdir() call which receives stat structures from the server.
This results in significant speedup of readdir() on large directories.
For example, doing 'ls >/dev/null' on a directory with 10000 files on my
laptop takes 1.088 seconds with the existing code, but only takes 0.339 seconds
with the new readdir.
Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
Change the v9fs_file_readn function to limit the maximum transfer size
based on the iounit or msize.
Also remove the redundant check for limiting the transfer size in
v9fs_file_write. This check is done by p9_client_write.
Signed-off-by: M. Mohan Kumar <mohan@in.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
Pass the correct end of the buffer to p9stat_read.
Signed-off-by: Latchesar Ionkov <lucho@ionkov.net>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
This patch removes a redundant fid clone on the directory fid and hence
reduces a server transaction while creating new filesystem object.
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
Without this patch, an attempt to mksock will get an EINVAL.
Before this patch:
[root@localhost 1dir]# mksock mysock
mksock: error making mysock: Invalid argument
With this patch:
[root@localhost 1dir]# mksock mysock
[root@localhost 1dir]# ls -l mysock
s--------- 1 root root 0 2010-03-31 17:44 mysock
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
For lookup if we get ENOENT error from the server we still
instantiate the dentry. We need to make sure we have dentry
operations set in that case so that a later dput on the dentry
does the expected. Without the patch we get the below error
#ln -sf abc abclink
ln: creating symbolic link `abclink': No such file or directory
Now on the host do
$ touch abclink
Guest now gives ENOENT error.
# ls
ls: cannot access abclink: No such file or directory
Debugged-by:Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
I made a V2 of this patch on top of my patches for VFS switches.
All the changes were due to change in some offsets.
rename - change name of file or directory
size[4] Trename tag[2] fid[4] newdirfid[4] name[s]
size[4] Rrename tag[2]
The rename message is used to change the name of a file, possibly moving it
to a new directory. The 9P wstat message can only rename a file within the
same directory.
Signed-off-by: Jim Garlick <garlick@llnl.gov>
Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
I made a V2 of this patch on top of my patches for VFS switches. The
change was adding v9fs_statfs pointer to v9fs_super_ops_dotl
instead of v9fs_super_ops.
statfs - get file system statistics
size[4] Tstatfs tag[2] fid[4]
size[4] Rstatfs tag[2] type[4] bsize[4] blocks[8] bfree[8] bavail[8]
files[8] ffree[8] fsid[8] namelen[4]
The statfs message is used to request file system information returned
by the statfs(2) system call, which is used by df(1) to report file
system and disk space usage.
Signed-off-by: Jim Garlick <garlick@llnl.gov>
Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
Implements VFS switches for 9p2000.L protocol.
Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ericvh/v9fs:
9p: saving negative to unsigned char
9p: return on mutex_lock_interruptible()
9p: Creating files with names too long should fail with ENAMETOOLONG.
9p: Make sure we are able to clunk the cached fid on umount
9p: drop nlink remove
fs/9p: Clunk the fid resulting from partial walk of the name
9p: documentation update
9p: Fix setting of protocol flags in v9fs_session_info structure.
If "err" is -EINTR here the original code calls mutex_unlock() and then
returns, but it should just return directly.
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
------------------------------------------------------------------------------
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dcache prune happen on umount. So we cannot mark the client
satus disconnect. That will prevent a 9p call to the server
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
We need to drop the link count on the inode of a sucessfull remove
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
This patch fixes a simple bug I left behind in my earlier protocol
negotiation patch.
Thanks,
Sripathi.
Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
percpu.h is included by sched.h and module.h and thus ends up being
included when building most .c files. percpu.h includes slab.h which
in turn includes gfp.h making everything defined by the two files
universally available and complicating inclusion dependencies.
percpu.h -> slab.h dependency is about to be removed. Prepare for
this change by updating users of gfp and slab facilities include those
headers directly instead of assuming availability. As this conversion
needs to touch large number of source files, the following script is
used as the basis of conversion.
http://userweb.kernel.org/~tj/misc/slabh-sweep.py
The script does the followings.
* Scan files for gfp and slab usages and update includes such that
only the necessary includes are there. ie. if only gfp is used,
gfp.h, if slab is used, slab.h.
* When the script inserts a new include, it looks at the include
blocks and try to put the new include such that its order conforms
to its surrounding. It's put in the include block which contains
core kernel includes, in the same order that the rest are ordered -
alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
doesn't seem to be any matching order.
* If the script can't find a place to put a new include (mostly
because the file doesn't have fitting include block), it prints out
an error message indicating which .h file needs to be added to the
file.
The conversion was done in the following steps.
1. The initial automatic conversion of all .c files updated slightly
over 4000 files, deleting around 700 includes and adding ~480 gfp.h
and ~3000 slab.h inclusions. The script emitted errors for ~400
files.
2. Each error was manually checked. Some didn't need the inclusion,
some needed manual addition while adding it to implementation .h or
embedding .c file was more appropriate for others. This step added
inclusions to around 150 files.
3. The script was run again and the output was compared to the edits
from #2 to make sure no file was left behind.
4. Several build tests were done and a couple of problems were fixed.
e.g. lib/decompress_*.c used malloc/free() wrappers around slab
APIs requiring slab.h to be added manually.
5. The script was run on all .h files but without automatically
editing them as sprinkling gfp.h and slab.h inclusions around .h
files could easily lead to inclusion dependency hell. Most gfp.h
inclusion directives were ignored as stuff from gfp.h was usually
wildly available and often used in preprocessor macros. Each
slab.h inclusion directive was examined and added manually as
necessary.
6. percpu.h was updated not to include slab.h.
7. Build test were done on the following configurations and failures
were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my
distributed build env didn't work with gcov compiles) and a few
more options had to be turned off depending on archs to make things
build (like ipr on powerpc/64 which failed due to missing writeq).
* x86 and x86_64 UP and SMP allmodconfig and a custom test config.
* powerpc and powerpc64 SMP allmodconfig
* sparc and sparc64 SMP allmodconfig
* ia64 SMP allmodconfig
* s390 SMP allmodconfig
* alpha SMP allmodconfig
* um on x86_64 SMP allmodconfig
8. percpu.h modifications were reverted so that it could be applied as
a separate patch and serve as bisection point.
Given the fact that I had only a couple of failures from tests on step
6, I'm fairly confident about the coverage of this conversion patch.
If there is a breakage, it's likely to be something in one of the arch
headers which should be easily discoverable easily on most builds of
the specific arch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
While investigating a bug, I came across a possible bug in v9fs. The
problem is similar to the one reported for NFS by ASANO Masahiro in
http://lkml.org/lkml/2005/12/21/334.
v9fs_file_lock() will skip locks on file which has mode set to 02666.
This is a problem in cases where the mode of the file is changed after
a process has obtained a lock on the file. Such a lock will be skipped
during unlock and the machine will end up with a BUG in
locks_remove_flock().
v9fs_file_lock() should skip the check for mandatory locks when
unlocking a file.
Signed-off-by: Sachin Prabhu <sprabhu@redhat.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
Fixes a simple bug so that large files beyond 2GB can be created.
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
This patch changes the name of the new 9P protocol from 9p2010.L to
9p2000.u. This is because we learnt that the name 9p2010 is already
being used by others.
Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
This ensure that on failure when we free the stat buf we don't end up
freeing an already freed pointer in the earlier loop
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
For regular file and directories we put the link
count in th extension field in a tagged string format.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
Removes 'dotu' variable and make everything dependent
on 'proto_version' field.
Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
Add 9P2000.u and 9P2010.L protocol flags to V9FS VFS
This patch adds 9P2000.u and 9P2010.L protocol flags into V9FS VFS side code
and removes the single flag used for 'extended'.
Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
If match_strdup() fail this function exits without freeing the options string.
Signed-off-by: Venkateswararao Jujjuri <jvrao@us.ibm.com>
Sigend-off-by: Eric Van Hensbergen <ericvh@gmail.com>
Options pointer is being moved before calling kfree() which seems
to cause problems. This uses a separate pointer to track and free
original allocation.
Signed-off-by: Venkateswararao Jujjuri <jvrao@us.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>w
Implement the fsync in the client side by marking stat field values to 'don't touch' so that server may
interpret it as a request to guarantee that the contents of the associated file are committed to stable
storage before the Rwstat message is returned.
Without this patch, calling fsync on a 9p file results in "Invalid argument" error. Please check the attached
C program.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: M. Mohan Kumar <mohan@in.ibm.com>
Acked-by: Venkateswararao Jujjuri (JV) <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
if 9P ->get_sb() fails late (at root inode or root dentry
allocation), we'll hit its ->kill_sb() with NULL ->s_root
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
For symlinks generic_readlink() will work just fine and for directories
we don't want ->readlink() at all.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
While building 2.6.32-rc8-git2 for Fedora I noticed the following thinko
in commit 201a15428b ("FS-Cache: Handle
pages pending storage that get evicted under OOM conditions"):
fs/9p/cache.c: In function '__v9fs_fscache_release_page':
fs/9p/cache.c:346: error: 'vnode' undeclared (first use in this function)
fs/9p/cache.c:346: error: (Each undeclared identifier is reported only once
fs/9p/cache.c:346: error: for each function it appears in.)
make[2]: *** [fs/9p/cache.o] Error 1
Fix the 9P filesystem to correctly construct the argument to
fscache_maybe_release_page().
Signed-off-by: Kyle McMartin <kyle@redhat.com>
Signed-off-by: Xiaotian Feng <dfeng@redhat.com> [from identical patch]
Signed-off-by: Stefan Lippers-Hollmann <s.l-h@gmx.de> [from identical patch]
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Handle netfs pages that the vmscan algorithm wants to evict from the pagecache
under OOM conditions, but that are waiting for write to the cache. Under these
conditions, vmscan calls the releasepage() function of the netfs, asking if a
page can be discarded.
The problem is typified by the following trace of a stuck process:
kslowd005 D 0000000000000000 0 4253 2 0x00000080
ffff88001b14f370 0000000000000046 ffff880020d0d000 0000000000000007
0000000000000006 0000000000000001 ffff88001b14ffd8 ffff880020d0d2a8
000000000000ddf0 00000000000118c0 00000000000118c0 ffff880020d0d2a8
Call Trace:
[<ffffffffa00782d8>] __fscache_wait_on_page_write+0x8b/0xa7 [fscache]
[<ffffffff8104c0f1>] ? autoremove_wake_function+0x0/0x34
[<ffffffffa0078240>] ? __fscache_check_page_write+0x63/0x70 [fscache]
[<ffffffffa00b671d>] nfs_fscache_release_page+0x4e/0xc4 [nfs]
[<ffffffffa00927f0>] nfs_release_page+0x3c/0x41 [nfs]
[<ffffffff810885d3>] try_to_release_page+0x32/0x3b
[<ffffffff81093203>] shrink_page_list+0x316/0x4ac
[<ffffffff8109372b>] shrink_inactive_list+0x392/0x67c
[<ffffffff813532fa>] ? __mutex_unlock_slowpath+0x100/0x10b
[<ffffffff81058df0>] ? trace_hardirqs_on_caller+0x10c/0x130
[<ffffffff8135330e>] ? mutex_unlock+0x9/0xb
[<ffffffff81093aa2>] shrink_list+0x8d/0x8f
[<ffffffff81093d1c>] shrink_zone+0x278/0x33c
[<ffffffff81052d6c>] ? ktime_get_ts+0xad/0xba
[<ffffffff81094b13>] try_to_free_pages+0x22e/0x392
[<ffffffff81091e24>] ? isolate_pages_global+0x0/0x212
[<ffffffff8108e743>] __alloc_pages_nodemask+0x3dc/0x5cf
[<ffffffff81089529>] grab_cache_page_write_begin+0x65/0xaa
[<ffffffff8110f8c0>] ext3_write_begin+0x78/0x1eb
[<ffffffff81089ec5>] generic_file_buffered_write+0x109/0x28c
[<ffffffff8103cb69>] ? current_fs_time+0x22/0x29
[<ffffffff8108a509>] __generic_file_aio_write+0x350/0x385
[<ffffffff8108a588>] ? generic_file_aio_write+0x4a/0xae
[<ffffffff8108a59e>] generic_file_aio_write+0x60/0xae
[<ffffffff810b2e82>] do_sync_write+0xe3/0x120
[<ffffffff8104c0f1>] ? autoremove_wake_function+0x0/0x34
[<ffffffff810b18e1>] ? __dentry_open+0x1a5/0x2b8
[<ffffffff810b1a76>] ? dentry_open+0x82/0x89
[<ffffffffa00e693c>] cachefiles_write_page+0x298/0x335 [cachefiles]
[<ffffffffa0077147>] fscache_write_op+0x178/0x2c2 [fscache]
[<ffffffffa0075656>] fscache_op_execute+0x7a/0xd1 [fscache]
[<ffffffff81082093>] slow_work_execute+0x18f/0x2d1
[<ffffffff8108239a>] slow_work_thread+0x1c5/0x308
[<ffffffff8104c0f1>] ? autoremove_wake_function+0x0/0x34
[<ffffffff810821d5>] ? slow_work_thread+0x0/0x308
[<ffffffff8104be91>] kthread+0x7a/0x82
[<ffffffff8100beda>] child_rip+0xa/0x20
[<ffffffff8100b87c>] ? restore_args+0x0/0x30
[<ffffffff8102ef83>] ? tg_shares_up+0x171/0x227
[<ffffffff8104be17>] ? kthread+0x0/0x82
[<ffffffff8100bed0>] ? child_rip+0x0/0x20
In the above backtrace, the following is happening:
(1) A page storage operation is being executed by a slow-work thread
(fscache_write_op()).
(2) FS-Cache farms the operation out to the cache to perform
(cachefiles_write_page()).
(3) CacheFiles is then calling Ext3 to perform the actual write, using Ext3's
standard write (do_sync_write()) under KERNEL_DS directly from the netfs
page.
(4) However, for Ext3 to perform the write, it must allocate some memory, in
particular, it must allocate at least one page cache page into which it
can copy the data from the netfs page.
(5) Under OOM conditions, the memory allocator can't immediately come up with
a page, so it uses vmscan to find something to discard
(try_to_free_pages()).
(6) vmscan finds a clean netfs page it might be able to discard (possibly the
one it's trying to write out).
(7) The netfs is called to throw the page away (nfs_release_page()) - but it's
called with __GFP_WAIT, so the netfs decides to wait for the store to
complete (__fscache_wait_on_page_write()).
(8) This blocks a slow-work processing thread - possibly against itself.
The system ends up stuck because it can't write out any netfs pages to the
cache without allocating more memory.
To avoid this, we make FS-Cache cancel some writes that aren't in the middle of
actually being performed. This means that some data won't make it into the
cache this time. To support this, a new FS-Cache function is added
fscache_maybe_release_page() that replaces what the netfs releasepage()
functions used to do with respect to the cache.
The decisions fscache_maybe_release_page() makes are counted and displayed
through /proc/fs/fscache/stats on a line labelled "VmScan". There are four
counters provided: "nos=N" - pages that weren't pending storage; "gon=N" -
pages that were pending storage when we first looked, but weren't by the time
we got the object lock; "bsy=N" - pages that we ignored as they were actively
being written when we looked; and "can=N" - pages that we cancelled the storage
of.
What I'd really like to do is alter the behaviour of the cancellation
heuristics, depending on how necessary it is to expel pages. If there are
plenty of other pages that aren't waiting to be written to the cache that
could be ejected first, then it would be nice to hold up on immediate
cancellation of cache writes - but I don't see a way of doing that.
Signed-off-by: David Howells <dhowells@redhat.com>
The patch below also addresses a couple of other corner cases in readdir
seen with a large (e.g. 64k) msize. I'm not sure what people think of
my co-opting of fid->aux here. I'd be happy to rework if there's a better
way.
When the size of the user supplied buffer passed to readdir is smaller
than the data returned in one go by the 9P read request, v9fs_dir_readdir()
currently discards extra data so that, on the next call, a 9P read
request will be issued with offset < previous offset + bytes returned,
which voilates the constraint described in paragraph 3 of read(5) description.
This patch preseves the leftover data in fid->aux for use in the next call.
Signed-off-by: Jim Garlick <garlick@llnl.gov>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
I do not know if you've looked on the patch, but unfortunately it is
incorrect. A suggested better version is in this email (the old
version didn't work in case the user provided buffer was not long
enough - it incorrectly appended null byte on a position of last char,
and thus broke the contract of the readlink method). However, I'm
still not sure this is 100% correct thing to do, I think readlink is
supposed to return buffer without last null byte in all cases, but we
do return last null byte (even the old version).. on the other hand it
is likely unspecified what is in the remaining part of the buffer, so
null character may be fine there ;):
Signed-off-by: Martin Stava <martin.stava@gmail.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
Here is a proposed patch for bug in readdir. Listing of dirs with
many files fails without this patch.
Signed-off-by: Martin Stava <martin.stava@gmail.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
This patch adds a persistent, read-only caching facility for
9p clients using the FS-Cache caching backend.
When the fscache facility is enabled, each inode is associated
with a corresponding vcookie which is an index into the FS-Cache
indexing tree. The FS-Cache indexing tree is indexed at 3 levels:
- session object associated with each mount.
- inode/vcookie
- actual data (pages)
A cache tag is chosen randomly for each session. These tags can
be read off /sys/fs/9p/caches and can be passed as a mount-time
parameter to re-attach to the specified caching session.
Signed-off-by: Abhishek Kulkarni <adkulkar@umail.iu.edu>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
When using the cache=loose flags, the inode's size was not being
updated correctly on a remote write. Thus subsequent reads of
the whole file resulted in a truncated read. Fix it.
Signed-off-by: Abhishek Kulkarni <adkulkar@umail.iu.edu>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
Change all occurrence of inode->i_size with i_size_read() or i_size_write()
as appropriate.
Signed-off-by: Abhishek Kulkarni <adkulkar@umail.iu.edu>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
The mount options string is saved in sb->s_options. This patch removes
the redundant duplicating of the mount options. Also, since we are not
displaying anything special in show options, we replace v9fs_show_options
with generic_show_options for now.
Signed-off-by: Abhishek Kulkarni <adkulkar@umail.iu.edu>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
Cast the error return value (ENOMEM) in v9fs_get_inode() to its
correct type using ERR_PTR.
Signed-off-by: Abhishek Kulkarni <adkulkar@umail.iu.edu>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
Remove a redundant update of inode's i_uid and i_gid
after v9fs_get_inode() since the latter already sets up
a new inode and sets the proper uid and gid values.
Signed-off-by: Abhishek Kulkarni <adkulkar@umail.iu.edu>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
->get_sb can fail causing some badness. this patch fixes
* clear sb->fs_s_info in kill_sb.
* deactivate_locked_super() calls kill_sb (v9fs_kill_super) which closes the
destroys the client, clunks all its fids and closes the v9fs session.
Attempting to do it twice will cause an oops.
Signed-off-by: Abhishek Kulkarni <adkulkar@umail.iu.edu>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
Add the delimiter ',' before the options when they are passed
and check if no option parameters are passed to prevent displaying
NULL in /proc/mounts.
Signed-off-by: Abhishek Kulkarni <adkulkar@umail.iu.edu>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
