Commit graph

390 commits

Author SHA1 Message Date
Hugh Dickins
98f32602d4 hugh: update email address
My old address will shut down in a few days time: remove it from the tree,
and add a tmpfs (shmem filesystem) maintainer entry with the new address.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-05-21 13:14:32 -07:00
Nick Piggin
b827e496c8 mm: close page_mkwrite races
Change page_mkwrite to allow implementations to return with the page
locked, and also change it's callers (in page fault paths) to hold the
lock until the page is marked dirty.  This allows the filesystem to have
full control of page dirtying events coming from the VM.

Rather than simply hold the page locked over the page_mkwrite call, we
call page_mkwrite with the page unlocked and allow callers to return with
it locked, so filesystems can avoid LOR conditions with page lock.

The problem with the current scheme is this: a filesystem that wants to
associate some metadata with a page as long as the page is dirty, will
perform this manipulation in its ->page_mkwrite.  It currently then must
return with the page unlocked and may not hold any other locks (according
to existing page_mkwrite convention).

In this window, the VM could write out the page, clearing page-dirty.  The
filesystem has no good way to detect that a dirty pte is about to be
attached, so it will happily write out the page, at which point, the
filesystem may manipulate the metadata to reflect that the page is no
longer dirty.

It is not always possible to perform the required metadata manipulation in
->set_page_dirty, because that function cannot block or fail.  The
filesystem may need to allocate some data structure, for example.

And the VM cannot mark the pte dirty before page_mkwrite, because
page_mkwrite is allowed to fail, so we must not allow any window where the
page could be written to if page_mkwrite does fail.

This solution of holding the page locked over the 3 critical operations
(page_mkwrite, setting the pte dirty, and finally setting the page dirty)
closes out races nicely, preventing page cleaning for writeout being
initiated in that window.  This provides the filesystem with a strong
synchronisation against the VM here.

- Sage needs this race closed for ceph filesystem.
- Trond for NFS (http://bugzilla.kernel.org/show_bug.cgi?id=12913).
- I need it for fsblock.
- I suspect other filesystems may need it too (eg. btrfs).
- I have converted buffer.c to the new locking. Even simple block allocation
  under dirty pages might be susceptible to i_size changing under partial page
  at the end of file (we also have a buffer.c-side problem here, but it cannot
  be fixed properly without this patch).
- Other filesystems (eg. NFS, maybe btrfs) will need to change their
  page_mkwrite functions themselves.

[ This also moves page_mkwrite another step closer to fault, which should
  eventually allow page_mkwrite to be moved into ->fault, and thus avoiding a
  filesystem calldown and page lock/unlock cycle in __do_fault. ]

[akpm@linux-foundation.org: fix derefs of NULL ->mapping]
Cc: Sage Weil <sage@newdream.net>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-05-02 15:36:09 -07:00
Marc Dionne
91ac033d83 CacheFiles: Fix the documentation to use the correct credential pointer names
Adjust the CacheFiles documentation to use the correct names of the credential
pointers in task_struct.

The documentation was using names from the old versions of the credentials
patches.

Signed-off-by: Marc Dionne <marc.c.dionne@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-04-24 13:28:30 -07:00
Adrian McMenamin
66672fefaa Documentation/filesystems: remove out of date reference to BKL being held
Documentation/filesystems/vfs.txt incorrectly states that the kernel is
locked during the call to statfs (Documentation/filesystems/Locking
correctly says it is not). This patch removes the offending sentence.

remove reference to BKL being held in statfs

Signed-off-by: Adrian McMenamin <adrian@mcmen.demon.co.uk>
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2009-04-20 23:01:16 -04:00
Evgeniy Polyakov
e0ca873916 Staging: Pohmelfs: Added IO permissions and priorities.
Signed-off-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-04-17 11:06:30 -07:00
Ryusuke Konishi
458c5b0822 nilfs2: clean up sketch file
The sketch file is a file to mark checkpoints with user data.  It was
experimentally introduced in the original implementation, and now
obsolete.  The file was handled differently with regular files; the file
size got truncated when a checkpoint was created.

This stops the special treatment and will treat it as a regular file.
Most users are not affected because mkfs.nilfs2 no longer makes this file.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-04-07 08:31:19 -07:00
Ryusuke Konishi
962281a7ab nilfs2: add document
This adds a document describing the features, mount options, userland
tools, usage, disk format, and related URLs for the nilfs2 file system.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-04-07 08:31:12 -07:00
Linus Torvalds
a63856252d Merge branch 'for-2.6.30' of git://linux-nfs.org/~bfields/linux
* 'for-2.6.30' of git://linux-nfs.org/~bfields/linux: (81 commits)
  nfsd41: define nfsd4_set_statp as noop for !CONFIG_NFSD_V4
  nfsd41: define NFSD_DRC_SIZE_SHIFT in set_max_drc
  nfsd41: Documentation/filesystems/nfs41-server.txt
  nfsd41: CREATE_EXCLUSIVE4_1
  nfsd41: SUPPATTR_EXCLCREAT attribute
  nfsd41: support for 3-word long attribute bitmask
  nfsd: dynamically skip encoded fattr bitmap in _nfsd4_verify
  nfsd41: pass writable attrs mask to nfsd4_decode_fattr
  nfsd41: provide support for minor version 1 at rpc level
  nfsd41: control nfsv4.1 svc via /proc/fs/nfsd/versions
  nfsd41: add OPEN4_SHARE_ACCESS_WANT nfs4_stateid bmap
  nfsd41: access_valid
  nfsd41: clientid handling
  nfsd41: check encode size for sessions maxresponse cached
  nfsd41: stateid handling
  nfsd: pass nfsd4_compound_state* to nfs4_preprocess_{state,seq}id_op
  nfsd41: destroy_session operation
  nfsd41: non-page DRC for solo sequence responses
  nfsd41: Add a create session replay cache
  nfsd41: create_session operation
  ...
2009-04-06 13:25:56 -07:00
Linus Torvalds
3516c6a8dc Merge git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging-2.6
* git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging-2.6: (714 commits)
  Staging: sxg: slicoss: Specify the license for Sahara SXG and Slicoss drivers
  Staging: serqt_usb: fix build due to proc tty changes
  Staging: serqt_usb: fix checkpatch errors
  Staging: serqt_usb: add TODO file
  Staging: serqt_usb: Lindent the code
  Staging: add USB serial Quatech driver
  staging: document that the wifi staging drivers a bit better
  Staging: echo cleanup
  Staging: BUG to BUG_ON changes
  Staging: remove some pointless conditionals before kfree_skb()
  Staging: line6: fix build error, select SND_RAWMIDI
  Staging: line6: fix checkpatch errors in variax.c
  Staging: line6: fix checkpatch errors in toneport.c
  Staging: line6: fix checkpatch errors in pcm.c
  Staging: line6: fix checkpatch errors in midibuf.c
  Staging: line6: fix checkpatch errors in midi.c
  Staging: line6: fix checkpatch errors in dumprequest.c
  Staging: line6: fix checkpatch errors in driver.c
  Staging: line6: fix checkpatch errors in audio.c
  Staging: line6: fix checkpatch errors in pod.c
  ...
2009-04-05 11:06:45 -07:00
Benny Halevy
3ef1728898 nfsd41: Documentation/filesystems/nfs41-server.txt
Initial nfs41 server write up describing the status of the linux
server implementation.

[nfsd41: document unenforced nfs41 compound ordering rules.]
[get rid of CONFIG_NFSD_V4_1]
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2009-04-03 17:41:24 -07:00
Linus Torvalds
811158b147 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial: (28 commits)
  trivial: Update my email address
  trivial: NULL noise: drivers/mtd/tests/mtd_*test.c
  trivial: NULL noise: drivers/media/dvb/frontends/drx397xD_fw.h
  trivial: Fix misspelling of "Celsius".
  trivial: remove unused variable 'path' in alloc_file()
  trivial: fix a pdlfush -> pdflush typo in comment
  trivial: jbd header comment typo fix for JBD_PARANOID_IOFAIL
  trivial: wusb: Storage class should be before const qualifier
  trivial: drivers/char/bsr.c: Storage class should be before const qualifier
  trivial: h8300: Storage class should be before const qualifier
  trivial: fix where cgroup documentation is not correctly referred to
  trivial: Give the right path in Documentation example
  trivial: MTD: remove EOL from MODULE_DESCRIPTION
  trivial: Fix typo in bio_split()'s documentation
  trivial: PWM: fix of #endif comment
  trivial: fix typos/grammar errors in Kconfig texts
  trivial: Fix misspelling of firmware
  trivial: cgroups: documentation typo and spelling corrections
  trivial: Update contact info for Jochen Hein
  trivial: fix typo "resgister" -> "register"
  ...
2009-04-03 15:24:35 -07:00
Evgeniy Polyakov
b8523c40d5 Staging: pohmelfs: documentation.
This patch includes POHMELFS design and implementation description.
Separate file includes mount options, default parameters and usage examples.

Signed-off-by: Eveniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2009-04-03 14:53:33 -07:00
Linus Torvalds
3cc50ac0db Merge git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-2.6-fscache
* git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-2.6-fscache: (41 commits)
  NFS: Add mount options to enable local caching on NFS
  NFS: Display local caching state
  NFS: Store pages from an NFS inode into a local cache
  NFS: Read pages from FS-Cache into an NFS inode
  NFS: nfs_readpage_async() needs to be accessible as a fallback for local caching
  NFS: Add read context retention for FS-Cache to call back with
  NFS: FS-Cache page management
  NFS: Add some new I/O counters for FS-Cache doing things for NFS
  NFS: Invalidate FsCache page flags when cache removed
  NFS: Use local disk inode cache
  NFS: Define and create inode-level cache objects
  NFS: Define and create superblock-level objects
  NFS: Define and create server-level objects
  NFS: Register NFS for caching and retrieve the top-level index
  NFS: Permit local filesystem caching to be enabled for NFS
  NFS: Add FS-Cache option bit and debug bit
  NFS: Add comment banners to some NFS functions
  FS-Cache: Make kAFS use FS-Cache
  CacheFiles: A cache that backs onto a mounted filesystem
  CacheFiles: Export things for CacheFiles
  ...
2009-04-03 10:07:43 -07:00
Linus Torvalds
9b59f0316b Merge branch 'for-linus' of git://git.open-osd.org/linux-open-osd
* 'for-linus' of git://git.open-osd.org/linux-open-osd:
  fs: Add exofs to Kernel build
  exofs: Documentation
  exofs: export_operations
  exofs: super_operations and file_system_type
  exofs: dir_inode and directory operations
  exofs: address_space_operations
  exofs: symlink_inode and fast_symlink_inode operations
  exofs: file and file_inode operations
  exofs: Kbuild, Headers and osd utils
2009-04-03 09:53:22 -07:00
Linus Torvalds
03c3fa0a3b Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-udf-2.6
* 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-udf-2.6:
  udf: Don't write integrity descriptor too often
  udf: Try anchor in block 256 first
  udf: Some type fixes and cleanups
  udf: use hardware sector size
  udf: fix novrs mount option
  udf: Fix oops when invalid character in filename occurs
  udf: return f_fsid for statfs(2)
  udf: Add checks to not underflow sector_t
  udf: fix default mode and dmode options handling
  udf: fix sparse warnings:
  udf: unsigned last[i] cannot be less than 0
  udf: implement mode and dmode mounting options
  udf: reduce stack usage of udf_get_filename
  udf: reduce stack usage of udf_load_pvoldesc
  Fix the udf code not to pass structs on stack where possible.
  Remove struct typedefs from fs/udf/ecma_167.h et al.
2009-04-03 09:50:39 -07:00
David Howells
9ae326a690 CacheFiles: A cache that backs onto a mounted filesystem
Add an FS-Cache cache-backend that permits a mounted filesystem to be used as a
backing store for the cache.

CacheFiles uses a userspace daemon to do some of the cache management - such as
reaping stale nodes and culling.  This is called cachefilesd and lives in
/sbin.  The source for the daemon can be downloaded from:

	http://people.redhat.com/~dhowells/cachefs/cachefilesd.c

And an example configuration from:

	http://people.redhat.com/~dhowells/cachefs/cachefilesd.conf

The filesystem and data integrity of the cache are only as good as those of the
filesystem providing the backing services.  Note that CacheFiles does not
attempt to journal anything since the journalling interfaces of the various
filesystems are very specific in nature.

CacheFiles creates a misc character device - "/dev/cachefiles" - that is used
to communication with the daemon.  Only one thing may have this open at once,
and whilst it is open, a cache is at least partially in existence.  The daemon
opens this and sends commands down it to control the cache.

CacheFiles is currently limited to a single cache.

CacheFiles attempts to maintain at least a certain percentage of free space on
the filesystem, shrinking the cache by culling the objects it contains to make
space if necessary - see the "Cache Culling" section.  This means it can be
placed on the same medium as a live set of data, and will expand to make use of
spare space and automatically contract when the set of data requires more
space.

============
REQUIREMENTS
============

The use of CacheFiles and its daemon requires the following features to be
available in the system and in the cache filesystem:

	- dnotify.

	- extended attributes (xattrs).

	- openat() and friends.

	- bmap() support on files in the filesystem (FIBMAP ioctl).

	- The use of bmap() to detect a partial page at the end of the file.

It is strongly recommended that the "dir_index" option is enabled on Ext3
filesystems being used as a cache.

=============
CONFIGURATION
=============

The cache is configured by a script in /etc/cachefilesd.conf.  These commands
set up cache ready for use.  The following script commands are available:

 (*) brun <N>%
 (*) bcull <N>%
 (*) bstop <N>%
 (*) frun <N>%
 (*) fcull <N>%
 (*) fstop <N>%

	Configure the culling limits.  Optional.  See the section on culling
	The defaults are 7% (run), 5% (cull) and 1% (stop) respectively.

	The commands beginning with a 'b' are file space (block) limits, those
	beginning with an 'f' are file count limits.

 (*) dir <path>

	Specify the directory containing the root of the cache.  Mandatory.

 (*) tag <name>

	Specify a tag to FS-Cache to use in distinguishing multiple caches.
	Optional.  The default is "CacheFiles".

 (*) debug <mask>

	Specify a numeric bitmask to control debugging in the kernel module.
	Optional.  The default is zero (all off).  The following values can be
	OR'd into the mask to collect various information:

		1	Turn on trace of function entry (_enter() macros)
		2	Turn on trace of function exit (_leave() macros)
		4	Turn on trace of internal debug points (_debug())

	This mask can also be set through sysfs, eg:

		echo 5 >/sys/modules/cachefiles/parameters/debug

==================
STARTING THE CACHE
==================

The cache is started by running the daemon.  The daemon opens the cache device,
configures the cache and tells it to begin caching.  At that point the cache
binds to fscache and the cache becomes live.

The daemon is run as follows:

	/sbin/cachefilesd [-d]* [-s] [-n] [-f <configfile>]

The flags are:

 (*) -d

	Increase the debugging level.  This can be specified multiple times and
	is cumulative with itself.

 (*) -s

	Send messages to stderr instead of syslog.

 (*) -n

	Don't daemonise and go into background.

 (*) -f <configfile>

	Use an alternative configuration file rather than the default one.

===============
THINGS TO AVOID
===============

Do not mount other things within the cache as this will cause problems.  The
kernel module contains its own very cut-down path walking facility that ignores
mountpoints, but the daemon can't avoid them.

Do not create, rename or unlink files and directories in the cache whilst the
cache is active, as this may cause the state to become uncertain.

Renaming files in the cache might make objects appear to be other objects (the
filename is part of the lookup key).

Do not change or remove the extended attributes attached to cache files by the
cache as this will cause the cache state management to get confused.

Do not create files or directories in the cache, lest the cache get confused or
serve incorrect data.

Do not chmod files in the cache.  The module creates things with minimal
permissions to prevent random users being able to access them directly.

=============
CACHE CULLING
=============

The cache may need culling occasionally to make space.  This involves
discarding objects from the cache that have been used less recently than
anything else.  Culling is based on the access time of data objects.  Empty
directories are culled if not in use.

Cache culling is done on the basis of the percentage of blocks and the
percentage of files available in the underlying filesystem.  There are six
"limits":

 (*) brun
 (*) frun

     If the amount of free space and the number of available files in the cache
     rises above both these limits, then culling is turned off.

 (*) bcull
 (*) fcull

     If the amount of available space or the number of available files in the
     cache falls below either of these limits, then culling is started.

 (*) bstop
 (*) fstop

     If the amount of available space or the number of available files in the
     cache falls below either of these limits, then no further allocation of
     disk space or files is permitted until culling has raised things above
     these limits again.

These must be configured thusly:

	0 <= bstop < bcull < brun < 100
	0 <= fstop < fcull < frun < 100

Note that these are percentages of available space and available files, and do
_not_ appear as 100 minus the percentage displayed by the "df" program.

The userspace daemon scans the cache to build up a table of cullable objects.
These are then culled in least recently used order.  A new scan of the cache is
started as soon as space is made in the table.  Objects will be skipped if
their atimes have changed or if the kernel module says it is still using them.

===============
CACHE STRUCTURE
===============

The CacheFiles module will create two directories in the directory it was
given:

 (*) cache/

 (*) graveyard/

The active cache objects all reside in the first directory.  The CacheFiles
kernel module moves any retired or culled objects that it can't simply unlink
to the graveyard from which the daemon will actually delete them.

The daemon uses dnotify to monitor the graveyard directory, and will delete
anything that appears therein.

The module represents index objects as directories with the filename "I..." or
"J...".  Note that the "cache/" directory is itself a special index.

Data objects are represented as files if they have no children, or directories
if they do.  Their filenames all begin "D..." or "E...".  If represented as a
directory, data objects will have a file in the directory called "data" that
actually holds the data.

Special objects are similar to data objects, except their filenames begin
"S..." or "T...".

If an object has children, then it will be represented as a directory.
Immediately in the representative directory are a collection of directories
named for hash values of the child object keys with an '@' prepended.  Into
this directory, if possible, will be placed the representations of the child
objects:

	INDEX     INDEX      INDEX                             DATA FILES
	========= ========== ================================= ================
	cache/@4a/I03nfs/@30/Ji000000000000000--fHg8hi8400
	cache/@4a/I03nfs/@30/Ji000000000000000--fHg8hi8400/@75/Es0g000w...DB1ry
	cache/@4a/I03nfs/@30/Ji000000000000000--fHg8hi8400/@75/Es0g000w...N22ry
	cache/@4a/I03nfs/@30/Ji000000000000000--fHg8hi8400/@75/Es0g000w...FP1ry

If the key is so long that it exceeds NAME_MAX with the decorations added on to
it, then it will be cut into pieces, the first few of which will be used to
make a nest of directories, and the last one of which will be the objects
inside the last directory.  The names of the intermediate directories will have
'+' prepended:

	J1223/@23/+xy...z/+kl...m/Epqr

Note that keys are raw data, and not only may they exceed NAME_MAX in size,
they may also contain things like '/' and NUL characters, and so they may not
be suitable for turning directly into a filename.

To handle this, CacheFiles will use a suitably printable filename directly and
"base-64" encode ones that aren't directly suitable.  The two versions of
object filenames indicate the encoding:

	OBJECT TYPE	PRINTABLE	ENCODED
	===============	===============	===============
	Index		"I..."		"J..."
	Data		"D..."		"E..."
	Special		"S..."		"T..."

Intermediate directories are always "@" or "+" as appropriate.

Each object in the cache has an extended attribute label that holds the object
type ID (required to distinguish special objects) and the auxiliary data from
the netfs.  The latter is used to detect stale objects in the cache and update
or retire them.

Note that CacheFiles will erase from the cache any file it doesn't recognise or
any file of an incorrect type (such as a FIFO file or a device file).

==========================
SECURITY MODEL AND SELINUX
==========================

CacheFiles is implemented to deal properly with the LSM security features of
the Linux kernel and the SELinux facility.

One of the problems that CacheFiles faces is that it is generally acting on
behalf of a process, and running in that process's context, and that includes a
security context that is not appropriate for accessing the cache - either
because the files in the cache are inaccessible to that process, or because if
the process creates a file in the cache, that file may be inaccessible to other
processes.

The way CacheFiles works is to temporarily change the security context (fsuid,
fsgid and actor security label) that the process acts as - without changing the
security context of the process when it the target of an operation performed by
some other process (so signalling and suchlike still work correctly).

When the CacheFiles module is asked to bind to its cache, it:

 (1) Finds the security label attached to the root cache directory and uses
     that as the security label with which it will create files.  By default,
     this is:

	cachefiles_var_t

 (2) Finds the security label of the process which issued the bind request
     (presumed to be the cachefilesd daemon), which by default will be:

	cachefilesd_t

     and asks LSM to supply a security ID as which it should act given the
     daemon's label.  By default, this will be:

	cachefiles_kernel_t

     SELinux transitions the daemon's security ID to the module's security ID
     based on a rule of this form in the policy.

	type_transition <daemon's-ID> kernel_t : process <module's-ID>;

     For instance:

	type_transition cachefilesd_t kernel_t : process cachefiles_kernel_t;

The module's security ID gives it permission to create, move and remove files
and directories in the cache, to find and access directories and files in the
cache, to set and access extended attributes on cache objects, and to read and
write files in the cache.

The daemon's security ID gives it only a very restricted set of permissions: it
may scan directories, stat files and erase files and directories.  It may
not read or write files in the cache, and so it is precluded from accessing the
data cached therein; nor is it permitted to create new files in the cache.

There are policy source files available in:

	http://people.redhat.com/~dhowells/fscache/cachefilesd-0.8.tar.bz2

and later versions.  In that tarball, see the files:

	cachefilesd.te
	cachefilesd.fc
	cachefilesd.if

They are built and installed directly by the RPM.

If a non-RPM based system is being used, then copy the above files to their own
directory and run:

	make -f /usr/share/selinux/devel/Makefile
	semodule -i cachefilesd.pp

You will need checkpolicy and selinux-policy-devel installed prior to the
build.

By default, the cache is located in /var/fscache, but if it is desirable that
it should be elsewhere, than either the above policy files must be altered, or
an auxiliary policy must be installed to label the alternate location of the
cache.

For instructions on how to add an auxiliary policy to enable the cache to be
located elsewhere when SELinux is in enforcing mode, please see:

	/usr/share/doc/cachefilesd-*/move-cache.txt

When the cachefilesd rpm is installed; alternatively, the document can be found
in the sources.

==================
A NOTE ON SECURITY
==================

CacheFiles makes use of the split security in the task_struct.  It allocates
its own task_security structure, and redirects current->act_as to point to it
when it acts on behalf of another process, in that process's context.

The reason it does this is that it calls vfs_mkdir() and suchlike rather than
bypassing security and calling inode ops directly.  Therefore the VFS and LSM
may deny the CacheFiles access to the cache data because under some
circumstances the caching code is running in the security context of whatever
process issued the original syscall on the netfs.

Furthermore, should CacheFiles create a file or directory, the security
parameters with that object is created (UID, GID, security label) would be
derived from that process that issued the system call, thus potentially
preventing other processes from accessing the cache - including CacheFiles's
cache management daemon (cachefilesd).

What is required is to temporarily override the security of the process that
issued the system call.  We can't, however, just do an in-place change of the
security data as that affects the process as an object, not just as a subject.
This means it may lose signals or ptrace events for example, and affects what
the process looks like in /proc.

So CacheFiles makes use of a logical split in the security between the
objective security (task->sec) and the subjective security (task->act_as).  The
objective security holds the intrinsic security properties of a process and is
never overridden.  This is what appears in /proc, and is what is used when a
process is the target of an operation by some other process (SIGKILL for
example).

The subjective security holds the active security properties of a process, and
may be overridden.  This is not seen externally, and is used whan a process
acts upon another object, for example SIGKILLing another process or opening a
file.

LSM hooks exist that allow SELinux (or Smack or whatever) to reject a request
for CacheFiles to run in a context of a specific security label, or to create
files and directories with another security label.

This documentation is added by the patch to:

	Documentation/filesystems/caching/cachefiles.txt

Signed-Off-By: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Daire Byrne <Daire.Byrne@framestore.com>
2009-04-03 16:42:41 +01:00
David Howells
952efe7b78 FS-Cache: Add and document asynchronous operation handling
Add and document asynchronous operation handling for use by FS-Cache's data
storage and retrieval routines.

The following documentation is added to:

	Documentation/filesystems/caching/operations.txt

		       ================================
		       ASYNCHRONOUS OPERATIONS HANDLING
		       ================================

========
OVERVIEW
========

FS-Cache has an asynchronous operations handling facility that it uses for its
data storage and retrieval routines.  Its operations are represented by
fscache_operation structs, though these are usually embedded into some other
structure.

This facility is available to and expected to be be used by the cache backends,
and FS-Cache will create operations and pass them off to the appropriate cache
backend for completion.

To make use of this facility, <linux/fscache-cache.h> should be #included.

===============================
OPERATION RECORD INITIALISATION
===============================

An operation is recorded in an fscache_operation struct:

	struct fscache_operation {
		union {
			struct work_struct fast_work;
			struct slow_work slow_work;
		};
		unsigned long		flags;
		fscache_operation_processor_t processor;
		...
	};

Someone wanting to issue an operation should allocate something with this
struct embedded in it.  They should initialise it by calling:

	void fscache_operation_init(struct fscache_operation *op,
				    fscache_operation_release_t release);

with the operation to be initialised and the release function to use.

The op->flags parameter should be set to indicate the CPU time provision and
the exclusivity (see the Parameters section).

The op->fast_work, op->slow_work and op->processor flags should be set as
appropriate for the CPU time provision (see the Parameters section).

FSCACHE_OP_WAITING may be set in op->flags prior to each submission of the
operation and waited for afterwards.

==========
PARAMETERS
==========

There are a number of parameters that can be set in the operation record's flag
parameter.  There are three options for the provision of CPU time in these
operations:

 (1) The operation may be done synchronously (FSCACHE_OP_MYTHREAD).  A thread
     may decide it wants to handle an operation itself without deferring it to
     another thread.

     This is, for example, used in read operations for calling readpages() on
     the backing filesystem in CacheFiles.  Although readpages() does an
     asynchronous data fetch, the determination of whether pages exist is done
     synchronously - and the netfs does not proceed until this has been
     determined.

     If this option is to be used, FSCACHE_OP_WAITING must be set in op->flags
     before submitting the operation, and the operating thread must wait for it
     to be cleared before proceeding:

		wait_on_bit(&op->flags, FSCACHE_OP_WAITING,
			    fscache_wait_bit, TASK_UNINTERRUPTIBLE);

 (2) The operation may be fast asynchronous (FSCACHE_OP_FAST), in which case it
     will be given to keventd to process.  Such an operation is not permitted
     to sleep on I/O.

     This is, for example, used by CacheFiles to copy data from a backing fs
     page to a netfs page after the backing fs has read the page in.

     If this option is used, op->fast_work and op->processor must be
     initialised before submitting the operation:

		INIT_WORK(&op->fast_work, do_some_work);

 (3) The operation may be slow asynchronous (FSCACHE_OP_SLOW), in which case it
     will be given to the slow work facility to process.  Such an operation is
     permitted to sleep on I/O.

     This is, for example, used by FS-Cache to handle background writes of
     pages that have just been fetched from a remote server.

     If this option is used, op->slow_work and op->processor must be
     initialised before submitting the operation:

		fscache_operation_init_slow(op, processor)

Furthermore, operations may be one of two types:

 (1) Exclusive (FSCACHE_OP_EXCLUSIVE).  Operations of this type may not run in
     conjunction with any other operation on the object being operated upon.

     An example of this is the attribute change operation, in which the file
     being written to may need truncation.

 (2) Shareable.  Operations of this type may be running simultaneously.  It's
     up to the operation implementation to prevent interference between other
     operations running at the same time.

=========
PROCEDURE
=========

Operations are used through the following procedure:

 (1) The submitting thread must allocate the operation and initialise it
     itself.  Normally this would be part of a more specific structure with the
     generic op embedded within.

 (2) The submitting thread must then submit the operation for processing using
     one of the following two functions:

	int fscache_submit_op(struct fscache_object *object,
			      struct fscache_operation *op);

	int fscache_submit_exclusive_op(struct fscache_object *object,
					struct fscache_operation *op);

     The first function should be used to submit non-exclusive ops and the
     second to submit exclusive ones.  The caller must still set the
     FSCACHE_OP_EXCLUSIVE flag.

     If successful, both functions will assign the operation to the specified
     object and return 0.  -ENOBUFS will be returned if the object specified is
     permanently unavailable.

     The operation manager will defer operations on an object that is still
     undergoing lookup or creation.  The operation will also be deferred if an
     operation of conflicting exclusivity is in progress on the object.

     If the operation is asynchronous, the manager will retain a reference to
     it, so the caller should put their reference to it by passing it to:

	void fscache_put_operation(struct fscache_operation *op);

 (3) If the submitting thread wants to do the work itself, and has marked the
     operation with FSCACHE_OP_MYTHREAD, then it should monitor
     FSCACHE_OP_WAITING as described above and check the state of the object if
     necessary (the object might have died whilst the thread was waiting).

     When it has finished doing its processing, it should call
     fscache_put_operation() on it.

 (4) The operation holds an effective lock upon the object, preventing other
     exclusive ops conflicting until it is released.  The operation can be
     enqueued for further immediate asynchronous processing by adjusting the
     CPU time provisioning option if necessary, eg:

	op->flags &= ~FSCACHE_OP_TYPE;
	op->flags |= ~FSCACHE_OP_FAST;

     and calling:

	void fscache_enqueue_operation(struct fscache_operation *op)

     This can be used to allow other things to have use of the worker thread
     pools.

=====================
ASYNCHRONOUS CALLBACK
=====================

When used in asynchronous mode, the worker thread pool will invoke the
processor method with a pointer to the operation.  This should then get at the
container struct by using container_of():

	static void fscache_write_op(struct fscache_operation *_op)
	{
		struct fscache_storage *op =
			container_of(_op, struct fscache_storage, op);
	...
	}

The caller holds a reference on the operation, and will invoke
fscache_put_operation() when the processor function returns.  The processor
function is at liberty to call fscache_enqueue_operation() or to take extra
references.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Daire Byrne <Daire.Byrne@framestore.com>
2009-04-03 16:42:39 +01:00
David Howells
36c9559022 FS-Cache: Object management state machine
Implement the cache object management state machine.

The following documentation is added to illuminate the working of this state
machine.  It will also be added as:

	Documentation/filesystems/caching/object.txt

	     ====================================================
	     IN-KERNEL CACHE OBJECT REPRESENTATION AND MANAGEMENT
	     ====================================================

==============
REPRESENTATION
==============

FS-Cache maintains an in-kernel representation of each object that a netfs is
currently interested in.  Such objects are represented by the fscache_cookie
struct and are referred to as cookies.

FS-Cache also maintains a separate in-kernel representation of the objects that
a cache backend is currently actively caching.  Such objects are represented by
the fscache_object struct.  The cache backends allocate these upon request, and
are expected to embed them in their own representations.  These are referred to
as objects.

There is a 1:N relationship between cookies and objects.  A cookie may be
represented by multiple objects - an index may exist in more than one cache -
or even by no objects (it may not be cached).

Furthermore, both cookies and objects are hierarchical.  The two hierarchies
correspond, but the cookies tree is a superset of the union of the object trees
of multiple caches:

	    NETFS INDEX TREE               :      CACHE 1     :      CACHE 2
	                                   :                  :
	                                   :   +-----------+  :
	                          +----------->|  IObject  |  :
	      +-----------+       |        :   +-----------+  :
	      |  ICookie  |-------+        :         |        :
	      +-----------+       |        :         |        :   +-----------+
	            |             +------------------------------>|  IObject  |
	            |                      :         |        :   +-----------+
	            |                      :         V        :         |
	            |                      :   +-----------+  :         |
	            V             +----------->|  IObject  |  :         |
	      +-----------+       |        :   +-----------+  :         |
	      |  ICookie  |-------+        :         |        :         V
	      +-----------+       |        :         |        :   +-----------+
	            |             +------------------------------>|  IObject  |
	      +-----+-----+                :         |        :   +-----------+
	      |           |                :         |        :         |
	      V           |                :         V        :         |
	+-----------+     |                :   +-----------+  :         |
	|  ICookie  |------------------------->|  IObject  |  :         |
	+-----------+     |                :   +-----------+  :         |
	      |           V                :         |        :         V
	      |     +-----------+          :         |        :   +-----------+
	      |     |  ICookie  |-------------------------------->|  IObject  |
	      |     +-----------+          :         |        :   +-----------+
	      V           |                :         V        :         |
	+-----------+     |                :   +-----------+  :         |
	|  DCookie  |------------------------->|  DObject  |  :         |
	+-----------+     |                :   +-----------+  :         |
	                  |                :                  :         |
	          +-------+-------+        :                  :         |
	          |               |        :                  :         |
	          V               V        :                  :         V
	    +-----------+   +-----------+  :                  :   +-----------+
	    |  DCookie  |   |  DCookie  |------------------------>|  DObject  |
	    +-----------+   +-----------+  :                  :   +-----------+
	                                   :                  :

In the above illustration, ICookie and IObject represent indices and DCookie
and DObject represent data storage objects.  Indices may have representation in
multiple caches, but currently, non-index objects may not.  Objects of any type
may also be entirely unrepresented.

As far as the netfs API goes, the netfs is only actually permitted to see
pointers to the cookies.  The cookies themselves and any objects attached to
those cookies are hidden from it.

===============================
OBJECT MANAGEMENT STATE MACHINE
===============================

Within FS-Cache, each active object is managed by its own individual state
machine.  The state for an object is kept in the fscache_object struct, in
object->state.  A cookie may point to a set of objects that are in different
states.

Each state has an action associated with it that is invoked when the machine
wakes up in that state.  There are four logical sets of states:

 (1) Preparation: states that wait for the parent objects to become ready.  The
     representations are hierarchical, and it is expected that an object must
     be created or accessed with respect to its parent object.

 (2) Initialisation: states that perform lookups in the cache and validate
     what's found and that create on disk any missing metadata.

 (3) Normal running: states that allow netfs operations on objects to proceed
     and that update the state of objects.

 (4) Termination: states that detach objects from their netfs cookies, that
     delete objects from disk, that handle disk and system errors and that free
     up in-memory resources.

In most cases, transitioning between states is in response to signalled events.
When a state has finished processing, it will usually set the mask of events in
which it is interested (object->event_mask) and relinquish the worker thread.
Then when an event is raised (by calling fscache_raise_event()), if the event
is not masked, the object will be queued for processing (by calling
fscache_enqueue_object()).

PROVISION OF CPU TIME
---------------------

The work to be done by the various states is given CPU time by the threads of
the slow work facility (see Documentation/slow-work.txt).  This is used in
preference to the workqueue facility because:

 (1) Threads may be completely occupied for very long periods of time by a
     particular work item.  These state actions may be doing sequences of
     synchronous, journalled disk accesses (lookup, mkdir, create, setxattr,
     getxattr, truncate, unlink, rmdir, rename).

 (2) Threads may do little actual work, but may rather spend a lot of time
     sleeping on I/O.  This means that single-threaded and 1-per-CPU-threaded
     workqueues don't necessarily have the right numbers of threads.

LOCKING SIMPLIFICATION
----------------------

Because only one worker thread may be operating on any particular object's
state machine at once, this simplifies the locking, particularly with respect
to disconnecting the netfs's representation of a cache object (fscache_cookie)
from the cache backend's representation (fscache_object) - which may be
requested from either end.

=================
THE SET OF STATES
=================

The object state machine has a set of states that it can be in.  There are
preparation states in which the object sets itself up and waits for its parent
object to transit to a state that allows access to its children:

 (1) State FSCACHE_OBJECT_INIT.

     Initialise the object and wait for the parent object to become active.  In
     the cache, it is expected that it will not be possible to look an object
     up from the parent object, until that parent object itself has been looked
     up.

There are initialisation states in which the object sets itself up and accesses
disk for the object metadata:

 (2) State FSCACHE_OBJECT_LOOKING_UP.

     Look up the object on disk, using the parent as a starting point.
     FS-Cache expects the cache backend to probe the cache to see whether this
     object is represented there, and if it is, to see if it's valid (coherency
     management).

     The cache should call fscache_object_lookup_negative() to indicate lookup
     failure for whatever reason, and should call fscache_obtained_object() to
     indicate success.

     At the completion of lookup, FS-Cache will let the netfs go ahead with
     read operations, no matter whether the file is yet cached.  If not yet
     cached, read operations will be immediately rejected with ENODATA until
     the first known page is uncached - as to that point there can be no data
     to be read out of the cache for that file that isn't currently also held
     in the pagecache.

 (3) State FSCACHE_OBJECT_CREATING.

     Create an object on disk, using the parent as a starting point.  This
     happens if the lookup failed to find the object, or if the object's
     coherency data indicated what's on disk is out of date.  In this state,
     FS-Cache expects the cache to create

     The cache should call fscache_obtained_object() if creation completes
     successfully, fscache_object_lookup_negative() otherwise.

     At the completion of creation, FS-Cache will start processing write
     operations the netfs has queued for an object.  If creation failed, the
     write ops will be transparently discarded, and nothing recorded in the
     cache.

There are some normal running states in which the object spends its time
servicing netfs requests:

 (4) State FSCACHE_OBJECT_AVAILABLE.

     A transient state in which pending operations are started, child objects
     are permitted to advance from FSCACHE_OBJECT_INIT state, and temporary
     lookup data is freed.

 (5) State FSCACHE_OBJECT_ACTIVE.

     The normal running state.  In this state, requests the netfs makes will be
     passed on to the cache.

 (6) State FSCACHE_OBJECT_UPDATING.

     The state machine comes here to update the object in the cache from the
     netfs's records.  This involves updating the auxiliary data that is used
     to maintain coherency.

And there are terminal states in which an object cleans itself up, deallocates
memory and potentially deletes stuff from disk:

 (7) State FSCACHE_OBJECT_LC_DYING.

     The object comes here if it is dying because of a lookup or creation
     error.  This would be due to a disk error or system error of some sort.
     Temporary data is cleaned up, and the parent is released.

 (8) State FSCACHE_OBJECT_DYING.

     The object comes here if it is dying due to an error, because its parent
     cookie has been relinquished by the netfs or because the cache is being
     withdrawn.

     Any child objects waiting on this one are given CPU time so that they too
     can destroy themselves.  This object waits for all its children to go away
     before advancing to the next state.

 (9) State FSCACHE_OBJECT_ABORT_INIT.

     The object comes to this state if it was waiting on its parent in
     FSCACHE_OBJECT_INIT, but its parent died.  The object will destroy itself
     so that the parent may proceed from the FSCACHE_OBJECT_DYING state.

(10) State FSCACHE_OBJECT_RELEASING.
(11) State FSCACHE_OBJECT_RECYCLING.

     The object comes to one of these two states when dying once it is rid of
     all its children, if it is dying because the netfs relinquished its
     cookie.  In the first state, the cached data is expected to persist, and
     in the second it will be deleted.

(12) State FSCACHE_OBJECT_WITHDRAWING.

     The object transits to this state if the cache decides it wants to
     withdraw the object from service, perhaps to make space, but also due to
     error or just because the whole cache is being withdrawn.

(13) State FSCACHE_OBJECT_DEAD.

     The object transits to this state when the in-memory object record is
     ready to be deleted.  The object processor shouldn't ever see an object in
     this state.

THE SET OF EVENTS
-----------------

There are a number of events that can be raised to an object state machine:

 (*) FSCACHE_OBJECT_EV_UPDATE

     The netfs requested that an object be updated.  The state machine will ask
     the cache backend to update the object, and the cache backend will ask the
     netfs for details of the change through its cookie definition ops.

 (*) FSCACHE_OBJECT_EV_CLEARED

     This is signalled in two circumstances:

     (a) when an object's last child object is dropped and

     (b) when the last operation outstanding on an object is completed.

     This is used to proceed from the dying state.

 (*) FSCACHE_OBJECT_EV_ERROR

     This is signalled when an I/O error occurs during the processing of some
     object.

 (*) FSCACHE_OBJECT_EV_RELEASE
 (*) FSCACHE_OBJECT_EV_RETIRE

     These are signalled when the netfs relinquishes a cookie it was using.
     The event selected depends on whether the netfs asks for the backing
     object to be retired (deleted) or retained.

 (*) FSCACHE_OBJECT_EV_WITHDRAW

     This is signalled when the cache backend wants to withdraw an object.
     This means that the object will have to be detached from the netfs's
     cookie.

Because the withdrawing releasing/retiring events are all handled by the object
state machine, it doesn't matter if there's a collision with both ends trying
to sever the connection at the same time.  The state machine can just pick
which one it wants to honour, and that effects the other.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Daire Byrne <Daire.Byrne@framestore.com>
2009-04-03 16:42:38 +01:00
David Howells
7394daa8c6 FS-Cache: Add use of /proc and presentation of statistics
Make FS-Cache create its /proc interface and present various statistical
information through it.  Also provide the functions for updating this
information.

These features are enabled by:

	CONFIG_FSCACHE_PROC
	CONFIG_FSCACHE_STATS
	CONFIG_FSCACHE_HISTOGRAM

The /proc directory for FS-Cache is also exported so that caching modules can
add their own statistics there too.

The FS-Cache module is loadable at this point, and the statistics files can be
examined by userspace:

	cat /proc/fs/fscache/stats
	cat /proc/fs/fscache/histogram

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Daire Byrne <Daire.Byrne@framestore.com>
2009-04-03 16:42:37 +01:00
David Howells
0dfc41d1ef FS-Cache: Add the FS-Cache cache backend API and documentation
Add the API for a generic facility (FS-Cache) by which caches may declare them
selves open for business, and may obtain work to be done from network
filesystems.  The header file is included by:

	#include <linux/fscache-cache.h>

Documentation for the API is also added to:

	Documentation/filesystems/caching/backend-api.txt

This API is not usable without the implementation of the utility functions
which will be added in further patches.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Daire Byrne <Daire.Byrne@framestore.com>
2009-04-03 16:42:36 +01:00
David Howells
2d6fff6370 FS-Cache: Add the FS-Cache netfs API and documentation
Add the API for a generic facility (FS-Cache) by which filesystems (such as AFS
or NFS) may call on local caching capabilities without having to know anything
about how the cache works, or even if there is a cache:

	+---------+
	|         |                        +--------------+
	|   NFS   |--+                     |              |
	|         |  |                 +-->|   CacheFS    |
	+---------+  |   +----------+  |   |  /dev/hda5   |
	             |   |          |  |   +--------------+
	+---------+  +-->|          |  |
	|         |      |          |--+
	|   AFS   |----->| FS-Cache |
	|         |      |          |--+
	+---------+  +-->|          |  |
	             |   |          |  |   +--------------+
	+---------+  |   +----------+  |   |              |
	|         |  |                 +-->|  CacheFiles  |
	|  ISOFS  |--+                     |  /var/cache  |
	|         |                        +--------------+
	+---------+

General documentation and documentation of the netfs specific API are provided
in addition to the header files.

As this patch stands, it is possible to build a filesystem against the facility
and attempt to use it.  All that will happen is that all requests will be
immediately denied as if no cache is present.

Further patches will implement the core of the facility.  The facility will
transfer requests from networking filesystems to appropriate caches if
possible, or else gracefully deny them.

If this facility is disabled in the kernel configuration, then all its
operations will trivially reduce to nothing during compilation.

WHY NOT I_MAPPING?
==================

I have added my own API to implement caching rather than using i_mapping to do
this for a number of reasons.  These have been discussed a lot on the LKML and
CacheFS mailing lists, but to summarise the basics:

 (1) Most filesystems don't do hole reportage.  Holes in files are treated as
     blocks of zeros and can't be distinguished otherwise, making it difficult
     to distinguish blocks that have been read from the network and cached from
     those that haven't.

 (2) The backing inode must be fully populated before being exposed to
     userspace through the main inode because the VM/VFS goes directly to the
     backing inode and does not interrogate the front inode's VM ops.

     Therefore:

     (a) The backing inode must fit entirely within the cache.

     (b) All backed files currently open must fit entirely within the cache at
     	 the same time.

     (c) A working set of files in total larger than the cache may not be
     	 cached.

     (d) A file may not grow larger than the available space in the cache.

     (e) A file that's open and cached, and remotely grows larger than the
     	 cache is potentially stuffed.

 (3) Writes go to the backing filesystem, and can only be transferred to the
     network when the file is closed.

 (4) There's no record of what changes have been made, so the whole file must
     be written back.

 (5) The pages belong to the backing filesystem, and all metadata associated
     with that page are relevant only to the backing filesystem, and not
     anything stacked atop it.

OVERVIEW
========

FS-Cache provides (or will provide) the following facilities:

 (1) Caches can be added / removed at any time, even whilst in use.

 (2) Adds a facility by which tags can be used to refer to caches, even if
     they're not available yet.

 (3) More than one cache can be used at once.  Caches can be selected
     explicitly by use of tags.

 (4) The netfs is provided with an interface that allows either party to
     withdraw caching facilities from a file (required for (1)).

 (5) A netfs may annotate cache objects that belongs to it.  This permits the
     storage of coherency maintenance data.

 (6) Cache objects will be pinnable and space reservations will be possible.

 (7) The interface to the netfs returns as few errors as possible, preferring
     rather to let the netfs remain oblivious.

 (8) Cookies are used to represent indices, files and other objects to the
     netfs.  The simplest cookie is just a NULL pointer - indicating nothing
     cached there.

 (9) The netfs is allowed to propose - dynamically - any index hierarchy it
     desires, though it must be aware that the index search function is
     recursive, stack space is limited, and indices can only be children of
     indices.

(10) Indices can be used to group files together to reduce key size and to make
     group invalidation easier.  The use of indices may make lookup quicker,
     but that's cache dependent.

(11) Data I/O is effectively done directly to and from the netfs's pages.  The
     netfs indicates that page A is at index B of the data-file represented by
     cookie C, and that it should be read or written.  The cache backend may or
     may not start I/O on that page, but if it does, a netfs callback will be
     invoked to indicate completion.  The I/O may be either synchronous or
     asynchronous.

(12) Cookies can be "retired" upon release.  At this point FS-Cache will mark
     them as obsolete and the index hierarchy rooted at that point will get
     recycled.

(13) The netfs provides a "match" function for index searches.  In addition to
     saying whether a match was made or not, this can also specify that an
     entry should be updated or deleted.

FS-Cache maintains a virtual index tree in which all indices, files, objects
and pages are kept.  Bits of this tree may actually reside in one or more
caches.

                                           FSDEF
                                             |
                        +------------------------------------+
                        |                                    |
                       NFS                                  AFS
                        |                                    |
           +--------------------------+                +-----------+
           |                          |                |           |
        homedir                     mirror          afs.org   redhat.com
           |                          |                            |
     +------------+           +---------------+              +----------+
     |            |           |               |              |          |
   00001        00002       00007           00125        vol00001   vol00002
     |            |           |               |                         |
 +---+---+     +-----+      +---+      +------+------+            +-----+----+
 |   |   |     |     |      |   |      |      |      |            |     |    |
PG0 PG1 PG2   PG0  XATTR   PG0 PG1   DIRENT DIRENT DIRENT        R/W   R/O  Bak
                     |                                            |
                    PG0                                       +-------+
                                                              |       |
                                                            00001   00003
                                                              |
                                                          +---+---+
                                                          |   |   |
                                                         PG0 PG1 PG2

In the example above, two netfs's can be seen to be backed: NFS and AFS.  These
have different index hierarchies:

 (*) The NFS primary index will probably contain per-server indices.  Each
     server index is indexed by NFS file handles to get data file objects.
     Each data file objects can have an array of pages, but may also have
     further child objects, such as extended attributes and directory entries.
     Extended attribute objects themselves have page-array contents.

 (*) The AFS primary index contains per-cell indices.  Each cell index contains
     per-logical-volume indices.  Each of volume index contains up to three
     indices for the read-write, read-only and backup mirrors of those volumes.
     Each of these contains vnode data file objects, each of which contains an
     array of pages.

The very top index is the FS-Cache master index in which individual netfs's
have entries.

Any index object may reside in more than one cache, provided it only has index
children.  Any index with non-index object children will be assumed to only
reside in one cache.

The FS-Cache overview can be found in:

	Documentation/filesystems/caching/fscache.txt

The netfs API to FS-Cache can be found in:

	Documentation/filesystems/caching/netfs-api.txt

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Daire Byrne <Daire.Byrne@framestore.com>
2009-04-03 16:42:36 +01:00
Shen Feng
760df93ecd documentation: update Documentation/filesystem/proc.txt and Documentation/sysctls
Now /proc/sys is described in many places and much information is
redundant.  This patch updates the proc.txt and move the /proc/sys
desciption out to the files in Documentation/sysctls.

Details are:

merge
-  2.1  /proc/sys/fs - File system data
-  2.11 /proc/sys/fs/mqueue - POSIX message queues filesystem
-  2.17 /proc/sys/fs/epoll - Configuration options for the epoll interface
with Documentation/sysctls/fs.txt.

remove
-  2.2  /proc/sys/fs/binfmt_misc - Miscellaneous binary formats
since it's not better then the Documentation/binfmt_misc.txt.

merge
-  2.3  /proc/sys/kernel - general kernel parameters
with Documentation/sysctls/kernel.txt

remove
-  2.5  /proc/sys/dev - Device specific parameters
since it's obsolete the sysfs is used now.

remove
-  2.6  /proc/sys/sunrpc - Remote procedure calls
since it's not better then the Documentation/sysctls/sunrpc.txt

move
-  2.7  /proc/sys/net - Networking stuff
-  2.9  Appletalk
-  2.10 IPX
to newly created Documentation/sysctls/net.txt.

remove
-  2.8  /proc/sys/net/ipv4 - IPV4 settings
since it's not better then the Documentation/networking/ip-sysctl.txt.

add
- Chapter 3 Per-Process Parameters
to descibe /proc/<pid>/xxx parameters.

Signed-off-by: Shen Feng <shen@cn.fujitsu.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-04-02 19:04:53 -07:00
Marcin Slusarz
7ac9bcd5da udf: implement mode and dmode mounting options
"dmode" allows overriding permissions of directories and
"mode" allows overriding permissions of files.

Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Jan Kara <jack@suse.cz>
2009-04-02 12:29:50 +02:00
Linus Torvalds
395d73413c Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4
* 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: (33 commits)
  ext4: Regularize mount options
  ext4: fix locking typo in mballoc which could cause soft lockup hangs
  ext4: fix typo which causes a memory leak on error path
  jbd2: Update locking coments
  ext4: Rename pa_linear to pa_type
  ext4: add checks of block references for non-extent inodes
  ext4: Check for an valid i_mode when reading the inode from disk
  ext4: Use WRITE_SYNC for commits which are caused by fsync()
  ext4: Add auto_da_alloc mount option
  ext4: Use struct flex_groups to calculate get_orlov_stats()
  ext4: Use atomic_t's in struct flex_groups
  ext4: remove /proc tuning knobs
  ext4: Add sysfs support
  ext4: Track lifetime disk writes
  ext4: Fix discard of inode prealloc space with delayed allocation.
  ext4: Automatically allocate delay allocated blocks on rename
  ext4: Automatically allocate delay allocated blocks on close
  ext4: add EXT4_IOC_ALLOC_DA_BLKS ioctl
  ext4: Simplify delalloc code by removing mpage_da_writepages()
  ext4: Save stack space by removing fake buffer heads
  ...
2009-04-01 10:57:49 -07:00
Linus Torvalds
e76e5b2c66 Merge branch 'linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci-2.6
* 'linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci-2.6: (88 commits)
  PCI: fix HT MSI mapping fix
  PCI: don't enable too much HT MSI mapping
  x86/PCI: make pci=lastbus=255 work when acpi is on
  PCI: save and restore PCIe 2.0 registers
  PCI: update fakephp for bus_id removal
  PCI: fix kernel oops on bridge removal
  PCI: fix conflict between SR-IOV and config space sizing
  powerpc/PCI: include pci.h in powerpc MSI implementation
  PCI Hotplug: schedule fakephp for feature removal
  PCI Hotplug: rename legacy_fakephp to fakephp
  PCI Hotplug: restore fakephp interface with complete reimplementation
  PCI: Introduce /sys/bus/pci/devices/.../rescan
  PCI: Introduce /sys/bus/pci/devices/.../remove
  PCI: Introduce /sys/bus/pci/rescan
  PCI: Introduce pci_rescan_bus()
  PCI: do not enable bridges more than once
  PCI: do not initialize bridges more than once
  PCI: always scan child buses
  PCI: pci_scan_slot() returns newly found devices
  PCI: don't scan existing devices
  ...

Fix trivial append-only conflict in Documentation/feature-removal-schedule.txt
2009-04-01 09:47:12 -07:00
Nick Piggin
c2ec175c39 mm: page_mkwrite change prototype to match fault
Change the page_mkwrite prototype to take a struct vm_fault, and return
VM_FAULT_xxx flags.  There should be no functional change.

This makes it possible to return much more detailed error information to
the VM (and also can provide more information eg.  virtual_address to the
driver, which might be important in some special cases).

This is required for a subsequent fix.  And will also make it easier to
merge page_mkwrite() with fault() in future.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <joel.becker@oracle.com>
Cc: Artem Bityutskiy <dedekind@infradead.org>
Cc: Felix Blyakher <felixb@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-04-01 08:59:14 -07:00
Boaz Harrosh
214c8adb87 exofs: Documentation
Added some documentation in exofs.txt, as well as a BUGS file.

For further reading, operation instructions, example scripts
and up to date infomation and code please see:
http://open-osd.org

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
2009-03-31 19:44:38 +03:00
Pavel Machek
e3375ac767 trivial: document ext3 semantics of 'ro' option a bit better
ext3 has quite unexpected semantics or "ro" and defaults are
not what they are documented to be, due to mkfs override.

Signed-off-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2009-03-30 15:21:56 +02:00
Theodore Ts'o
06705bff91 ext4: Regularize mount options
Add support for using the mount options "barrier" and "nobarrier", and
"auto_da_alloc" and "noauto_da_alloc", which is more consistent than
"barrier=<0|1>" or "auto_da_alloc=<0|1>".  Most other ext3/ext4 mount
options use the foo/nofoo naming convention.  We allow the old forms
of these mount options for backwards compatibility.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2009-03-28 10:59:57 -04:00
Greg Banks
b5cbc369db Document /proc/fs/nfsd/pool_stats
Document the format and semantics of the /proc/fs/nfsd/pool_stats file.

Signed-off-by: Greg Banks <gnb@sgi.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2009-03-27 19:24:27 -04:00
Linus Torvalds
8e9d208972 Merge branch 'bkl-removal' of git://git.lwn.net/linux-2.6
* 'bkl-removal' of git://git.lwn.net/linux-2.6:
  Rationalize fasync return values
  Move FASYNC bit handling to f_op->fasync()
  Use f_lock to protect f_flags
  Rename struct file->f_ep_lock
2009-03-26 16:14:02 -07:00
Jody McIntyre
1db4b2d221 trivial: fix orphan dates in ext2 documentation
Revert the change to the orphan dates of Windows 95, DOS, compression.
Add a new orphan date for OS/2.

Signed-off-by: Jody McIntyre <scjody@sun.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-03-23 14:21:26 -07:00
Linus Torvalds
d56ffd38a9 Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6: (32 commits)
  ucc_geth: Fix oops when using fixed-link support
  dm9000: locking bugfix
  net: update dnet.c for bus_id removal
  dnet: DNET should depend on HAS_IOMEM
  dca: add missing copyright/license headers
  nl80211: Check that function pointer != NULL before using it
  sungem: missing net_device_ops
  be2net: fix to restore vlan ids into BE2 during a IF DOWN->UP cycle
  be2net: replenish when posting to rx-queue is starved in out of mem conditions
  bas_gigaset: correctly allocate USB interrupt transfer buffer
  smsc911x: reset last known duplex and carrier on open
  sh_eth: Fix mistake of the address of SH7763
  sh_eth: Change handling of IRQ
  netns: oops in ip[6]_frag_reasm incrementing stats
  net: kfree(napi->skb) => kfree_skb
  net: fix sctp breakage
  ipv6: fix display of local and remote sit endpoints
  net: Document /proc/sys/net/core/netdev_budget
  tulip: fix crash on iface up with shirq debug
  virtio_net: Make virtio_net support carrier detection
  ...
2009-03-23 09:25:58 -07:00
Alex Chiang
77c27c7b49 PCI: Introduce /sys/bus/pci/devices/.../remove
This patch adds an attribute named "remove" to a PCI device's sysfs
directory.  Writing a non-zero value to this attribute will remove the PCI
device and any children of it.

Trent Piepho wrote the original implementation and documentation.

Thanks to Vegard Nossum for testing under kmemcheck and finding locking
issues with the sysfs interface.

Cc: Trent Piepho <xyzzy@speakeasy.org>
Tested-by: Vegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: Alex Chiang <achiang@hp.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
2009-03-20 14:58:48 -07:00
Stanislaw Gruszka
e9c6a586f5 net: Document /proc/sys/net/core/netdev_budget
The NAPI poll parameter netdev_budget is not documented in
kernel-docs. Since it may have a substantial effect on at least some
network loads, it should be.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com> 
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-03-18 18:51:06 -07:00
Jonathan Corbet
76398425bb Move FASYNC bit handling to f_op->fasync()
Removing the BKL from FASYNC handling ran into the challenge of keeping the
setting of the FASYNC bit in filp->f_flags atomic with regard to calls to
the underlying fasync() function.  Andi Kleen suggested moving the handling
of that bit into fasync(); this patch does exactly that.  As a result, we
have a couple of internal API changes: fasync() must now manage the FASYNC
bit, and it will be called without the BKL held.

As it happens, every fasync() implementation in the kernel with one
exception calls fasync_helper().  So, if we make fasync_helper() set the
FASYNC bit, we can avoid making any changes to the other fasync()
functions - as long as those functions, themselves, have proper locking.
Most fasync() implementations do nothing but call fasync_helper() - which
has its own lock - so they are easily verified as correct.  The BKL had
already been pushed down into the rest.

The networking code has its own version of fasync_helper(), so that code
has been augmented with explicit FASYNC bit handling.

Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: David Miller <davem@davemloft.net>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2009-03-16 08:32:27 -06:00
Jody McIntyre
ab03eca8d4 trivial: fix bad links in the ext2 and ext3 documentation
Trivial patch to fix bad links in the ext2 and ext3 documentation.

Signed-off-by: Jody McIntyre <scjody@sun.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-03-12 16:24:25 -07:00
Phillip Lougher
edf2e2811e Squashfs: fix documentation typo, Cramfs filesystem limit is 256 MiB
Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
2009-03-05 00:40:13 +00:00
Theodore Ts'o
b713a5ec55 ext4: remove /proc tuning knobs
Remove tuning knobs in /proc/fs/ext4/<dev/* since they have been
replaced by knobs in sysfs at /sys/fs/ext4/<dev>/*.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2009-03-31 09:11:14 -04:00
Theodore Ts'o
722bde6875 ext4: Add fine print for the 32000 subdirectory limit
Some poeple are reading the ext4 feature list too literally and create
dubious test cases involving very long filenames and 1k blocksize and
then complain when they run into an htree-imposed limit.  So add fine
print to the "fix 32000 subdirectory limit" ext4 feature.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2009-02-23 00:51:57 -05:00
Mike Murphy
f8a1af6bbc PATCH [2/2] Documentation/filesystems/sysfs.txt: fix descriptions of device attributes
Fix descriptions of device attributes to be consistent with the actual
implementations in include/linux/device.h

Signed-off-by: Mike Murphy <mamurph[at]cs.clemson.edu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-02-22 09:28:15 -08:00
Timothy S. Nelson
97c44836cd PCI: return error on failure to read PCI ROMs
This patch makes the ROM reading code return an error to user space if
the size of the ROM read is equal to 0.

The patch also emits a warnings if the contents of the ROM are invalid,
and documents the effects of the "enable" file on ROM reading.

Signed-off-by: Timothy S. Nelson <wayland@wayland.id.au>
Acked-by: Alex Villacis-Lasso <a_villacis@palosanto.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
2009-02-04 16:58:41 -08:00
Linus Torvalds
f96c08e8c5 Merge branch 'linux-next' of git://git.infradead.org/ubifs-2.6
* 'linux-next' of git://git.infradead.org/ubifs-2.6:
  UBIFS: remove fast unmounting
  UBIFS: return sensible error codes
  UBIFS: remount ro fixes
  UBIFS: spelling fix 'date' -> 'data'
  UBIFS: sync wbufs after syncing inodes and pages
  UBIFS: fix LPT out-of-space bug (again)
  UBIFS: fix no_chk_data_crc
  UBIFS: fix assertions
  UBIFS: ensure orphan area head is initialized
  UBIFS: always clean up GC LEB space
  UBIFS: add re-mount debugging checks
  UBIFS: fix LEB list freeing
  UBIFS: simplify locking
  UBIFS: document dark_wm and dead_wm better
  UBIFS: do not treat all data as short term
  UBIFS: constify operations
  UBIFS: do not commit twice
2009-02-03 16:52:44 -08:00
Evgeniy Polyakov
9e9e3cbc62 mm: OOM documentation update
Signed-off-by: Evgeniy Polyakov <zbr@ioremap.net>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-01-29 18:04:43 -08:00
Artem Bityutskiy
27ad279933 UBIFS: remove fast unmounting
This UBIFS feature has never worked properly, and it was a mistake
to add it because we simply have no use-cases. So, lets still accept
the fast_unmount mount option, but ignore it. This does not change
much, because UBIFS commit in sync_fs anyway, and sync_fs is called
while unmounting.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2009-01-29 16:34:30 +02:00
James Lentini
096abd7703 update port number in NFS/RDMA documentation
Update the NFS/RDMA documentation to use the new port number assigned
by IANA.

Signed-off-by: James Lentini <jlentini@netapp.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
2009-01-27 17:20:14 -05:00
Peter W Morreale
db0fb1848a Update of Documentation: vm.txt and proc.txt
Update Documentation/sysctl/vm.txt and Documentation/filesystems/proc.txt.
 More specifically, the section on /proc/sys/vm in
Documentation/filesystems/proc.txt was removed and a link to
Documentation/sysctl/vm.txt added.

Most of the verbiage from proc.txt was simply moved in vm.txt, with new
addtional text for "swappiness" and "stat_interval".

Signed-off-by: Peter W Morreale <pmorreale@novell.com>
Acked-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-01-15 16:39:35 -08:00
Takashi Sato
c4be0c1dc4 filesystem freeze: add error handling of write_super_lockfs/unlockfs
Currently, ext3 in mainline Linux doesn't have the freeze feature which
suspends write requests.  So, we cannot take a backup which keeps the
filesystem's consistency with the storage device's features (snapshot and
replication) while it is mounted.

In many case, a commercial filesystem (e.g.  VxFS) has the freeze feature
and it would be used to get the consistent backup.

If Linux's standard filesystem ext3 has the freeze feature, we can do it
without a commercial filesystem.

So I have implemented the ioctls of the freeze feature.
I think we can take the consistent backup with the following steps.
1. Freeze the filesystem with the freeze ioctl.
2. Separate the replication volume or create the snapshot
   with the storage device's feature.
3. Unfreeze the filesystem with the unfreeze ioctl.
4. Take the backup from the separated replication volume
   or the snapshot.

This patch:

VFS:
Changed the type of write_super_lockfs and unlockfs from "void"
to "int" so that they can return an error.
Rename write_super_lockfs and unlockfs of the super block operation
freeze_fs and unfreeze_fs to avoid a confusion.

ext3, ext4, xfs, gfs2, jfs:
Changed the type of write_super_lockfs and unlockfs from "void"
to "int" so that write_super_lockfs returns an error if needed,
and unlockfs always returns 0.

reiserfs:
Changed the type of write_super_lockfs and unlockfs from "void"
to "int" so that they always return 0 (success) to keep a current behavior.

Signed-off-by: Takashi Sato <t-sato@yk.jp.nec.com>
Signed-off-by: Masayuki Hamaguchi <m-hamaguchi@ys.jp.nec.com>
Cc: <xfs-masters@oss.sgi.com>
Cc: <linux-ext4@vger.kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dave Kleikamp <shaggy@austin.ibm.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Alasdair G Kergon <agk@redhat.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>
2009-01-09 16:54:42 -08:00
Linus Torvalds
31aeb6c815 Merge git://git.kernel.org/pub/scm/linux/kernel/git/pkl/squashfs-linus
* git://git.kernel.org/pub/scm/linux/kernel/git/pkl/squashfs-linus:
  MAINTAINERS: squashfs entry
  Squashfs: documentation
  Squashfs: initrd support
  Squashfs: Kconfig entry
  Squashfs: Makefiles
  Squashfs: header files
  Squashfs: block operations
  Squashfs: cache operations
  Squashfs: uid/gid lookup operations
  Squashfs: fragment block operations
  Squashfs: export operations
  Squashfs: super block operations
  Squashfs: symlink operations
  Squashfs: regular file operations
  Squashfs: directory readdir operations
  Squashfs: directory lookup operations
  Squashfs: inode operations
2009-01-09 15:18:49 -08:00
Linus Torvalds
73d59314e6 Merge git://git.kernel.org/pub/scm/linux/kernel/git/mason/btrfs-unstable
* git://git.kernel.org/pub/scm/linux/kernel/git/mason/btrfs-unstable: (864 commits)
  Btrfs: explicitly mark the tree log root for writeback
  Btrfs: Drop the hardware crc32c asm code
  Btrfs: Add Documentation/filesystem/btrfs.txt, remove old COPYING
  Btrfs: kmap_atomic(KM_USER0) is safe for btrfs_readpage_end_io_hook
  Btrfs: Don't use kmap_atomic(..., KM_IRQ0) during checksum verifies
  Btrfs: tree logging checksum fixes
  Btrfs: don't change file extent's ram_bytes in btrfs_drop_extents
  Btrfs: Use btrfs_join_transaction to avoid deadlocks during snapshot creation
  Btrfs: drop remaining LINUX_KERNEL_VERSION checks and compat code
  Btrfs: drop EXPORT symbols from extent_io.c
  Btrfs: Fix checkpatch.pl warnings
  Btrfs: Fix free block discard calls down to the block layer
  Btrfs: avoid orphan inode caused by log replay
  Btrfs: avoid potential super block corruption
  Btrfs: do not call kfree if kmalloc failed in btrfs_sysfs_add_super
  Btrfs: fix a memory leak in btrfs_get_sb
  Btrfs: Fix typo in clear_state_cb
  Btrfs: Fix memset length in btrfs_file_write
  Btrfs: update directory's size when creating subvol/snapshot
  Btrfs: add permission checks to the ioctls
  ...
2009-01-09 13:01:38 -08:00