Commit Graph

1095 Commits

Author SHA1 Message Date
Theodore Ts'o 673c610033 ext4: Move struct ext4_mount_options from ext4.h to super.c
Move the ext4_mount_options structure definition from ext4.h, since it
is only used in super.c.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-12-15 20:28:48 -05:00
Theodore Ts'o fd8c37eccd ext4: Simplify the usage of clear_opt() and set_opt() macros
Change clear_opt() and set_opt() to take a superblock pointer instead
of a pointer to EXT4_SB(sb)->s_mount_opt.  This makes it easier for us
to support a second mount option field.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-12-15 20:26:48 -05:00
Aaro Koskinen 6d5c3aa84b ext4: fix typo which broke '..' detection in ext4_find_entry()
There should be a check for the NUL character instead of '0'.

Fortunately the only thing that cares about this is NFS serving, which
is why we didn't notice this in the merge window testing.

Reported-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
Signed-off-by: Aaro Koskinen <aaro.koskinen@nokia.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-12-14 21:45:31 -05:00
Theodore Ts'o 1449032be1 ext4: Turn off multiple page-io submission by default
Jon Nelson has found a test case which causes postgresql to fail with
the error:

psql:t.sql:4: ERROR: invalid page header in block 38269 of relation base/16384/16581

Under memory pressure, it looks like part of a file can end up getting
replaced by zero's.  Until we can figure out the cause, we'll roll
back the change and use block_write_full_page() instead of
ext4_bio_write_page().  The new, more efficient writing function can
be used via the mount option mblk_io_submit, so we can test and fix
the new page I/O code.

To reproduce the problem, install postgres 8.4 or 9.0, and pin enough
memory such that the system just at the end of triggering writeback
before running the following sql script:

begin;
create temporary table foo as select x as a, ARRAY[x] as b FROM
generate_series(1, 10000000 ) AS x;
create index foo_a_idx on foo (a);
create index foo_b_idx on foo USING GIN (b);
rollback;

If the temporary table is created on a hard drive partition which is
encrypted using dm_crypt, then under memory pressure, approximately
30-40% of the time, pgsql will issue the above failure.

This patch should fix this problem, and the problem will come back if
the file system is mounted with the mblk_io_submit mount option.

Reported-by: Jon Nelson <jnelson@jamponi.net>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-12-14 15:27:50 -05:00
Lukas Czerner e681c047e4 ext4: Add EXT4_IOC_TRIM ioctl to handle batched discard
Filesystem independent ioctl was rejected as not common enough to be in
core vfs ioctl. Since we still need to access to this functionality this
commit adds ext4 specific ioctl EXT4_IOC_TRIM to dispatch
ext4_trim_fs().

It takes fstrim_range structure as an argument. fstrim_range is definec in
the include/linux/fs.h and its definition is as follows.

struct fstrim_range {
	__u64 start;
	__u64 len;
	__u64 minlen;
}

start	- first Byte to trim
len	- number of Bytes to trim from start
minlen	- minimum extent length to trim, free extents shorter than this
  number of Bytes will be ignored. This will be rounded up to fs
  block size.

After the FITRIM is done, the number of actually discarded Bytes is stored
in fstrim_range.len to give the user better insight on how much storage
space has been really released for wear-leveling.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-11-19 21:47:07 -05:00
Lukas Czerner 93bb41f4f8 fs: Do not dispatch FITRIM through separate super_operation
There was concern that FITRIM ioctl is not common enough to be included
in core vfs ioctl, as Christoph Hellwig pointed out there's no real point
in dispatching this out to a separate vector instead of just through
->ioctl.

So this commit removes ioctl_fstrim() from vfs ioctl and trim_fs
from super_operation structure.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-11-19 21:18:35 -05:00
Darrick J. Wong 5a9ae68a34 ext4: ext4_fill_super shouldn't return 0 on corruption
At the start of ext4_fill_super, ret is set to -EINVAL, and any failure path
out of that function returns ret.  However, the generic_check_addressable
clause sets ret = 0 (if it passes), which means that a subsequent failure (e.g.
a group checksum error) returns 0 even though the mount should fail.  This
causes vfs_kern_mount in turn to think that the mount succeeded, leading to an
oops.

A simple fix is to avoid using ret for the generic_check_addressable check,
which was last changed in commit 30ca22c70e.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-11-19 09:56:44 -05:00
Dan Carpenter f4c8cc652d ext4: missing unlock in ext4_clear_request_list()
If the the li_request_list was empty then it returned with the lock
held.  Instead of adding a "goto unlock" I just removed that special
case and let it go past the empty list_for_each_safe().

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-11-17 21:46:25 -05:00
Markus Trippelsdorf 08da1193d2 ext4: fix setting random pages PageUptodate
ext4_end_bio calls put_page and kmem_cache_free before calling
SetPageUpdate(). This can result in setting the PageUptodate bit on
random pages and causes the following BUG:

 BUG: Bad page state in process rm  pfn:52e54
 page:ffffea0001222260 count:0 mapcount:0 mapping:          (null) index:0x0
 arch kernel: page flags: 0x4000000000000008(uptodate)

Fix the problem by moving put_io_page() after the SetPageUpdate() call.

Thanks to Hugh Dickins for analyzing this problem.

Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Tested-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Signed-off-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-11-17 21:46:06 -05:00
Wu Fengguang 380cf090f4 ext4: fix redirty_page_for_writepage() typo in comment
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2010-11-15 14:14:52 +01:00
Tejun Heo d4d7762995 block: clean up blkdev_get() wrappers and their users
After recent blkdev_get() modifications, open_by_devnum() and
open_bdev_exclusive() are simple wrappers around blkdev_get().
Replace them with blkdev_get_by_dev() and blkdev_get_by_path().

blkdev_get_by_dev() is identical to open_by_devnum().
blkdev_get_by_path() is slightly different in that it doesn't
automatically add %FMODE_EXCL to @mode.

All users are converted.  Most conversions are mechanical and don't
introduce any behavior difference.  There are several exceptions.

* btrfs now sets FMODE_EXCL in btrfs_device->mode, so there's no
  reason to OR it explicitly on blkdev_put().

* gfs2, nilfs2 and the generic mount_bdev() now set FMODE_EXCL in
  sb->s_mode.

* With the above changes, sb->s_mode now always should contain
  FMODE_EXCL.  WARN_ON_ONCE() added to kill_block_super() to detect
  errors.

The new blkdev_get_*() functions are with proper docbook comments.
While at it, add function description to blkdev_get() too.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Philipp Reisner <philipp.reisner@linbit.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Joern Engel <joern@lazybastard.org>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Jan Kara <jack@suse.cz>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: KONISHI Ryusuke <konishi.ryusuke@lab.ntt.co.jp>
Cc: reiserfs-devel@vger.kernel.org
Cc: xfs-masters@oss.sgi.com
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
2010-11-13 11:55:18 +01:00
Tejun Heo e525fd89d3 block: make blkdev_get/put() handle exclusive access
Over time, block layer has accumulated a set of APIs dealing with bdev
open, close, claim and release.

* blkdev_get/put() are the primary open and close functions.

* bd_claim/release() deal with exclusive open.

* open/close_bdev_exclusive() are combination of open and claim and
  the other way around, respectively.

* bd_link/unlink_disk_holder() to create and remove holder/slave
  symlinks.

* open_by_devnum() wraps bdget() + blkdev_get().

The interface is a bit confusing and the decoupling of open and claim
makes it impossible to properly guarantee exclusive access as
in-kernel open + claim sequence can disturb the existing exclusive
open even before the block layer knows the current open if for another
exclusive access.  Reorganize the interface such that,

* blkdev_get() is extended to include exclusive access management.
  @holder argument is added and, if is @FMODE_EXCL specified, it will
  gain exclusive access atomically w.r.t. other exclusive accesses.

* blkdev_put() is similarly extended.  It now takes @mode argument and
  if @FMODE_EXCL is set, it releases an exclusive access.  Also, when
  the last exclusive claim is released, the holder/slave symlinks are
  removed automatically.

* bd_claim/release() and close_bdev_exclusive() are no longer
  necessary and either made static or removed.

* bd_link_disk_holder() remains the same but bd_unlink_disk_holder()
  is no longer necessary and removed.

* open_bdev_exclusive() becomes a simple wrapper around lookup_bdev()
  and blkdev_get().  It also has an unexpected extra bdev_read_only()
  test which probably should be moved into blkdev_get().

* open_by_devnum() is modified to take @holder argument and pass it to
  blkdev_get().

Most of bdev open/close operations are unified into blkdev_get/put()
and most exclusive accesses are tested atomically at the open time (as
it should).  This cleans up code and removes some, both valid and
invalid, but unnecessary all the same, corner cases.

open_bdev_exclusive() and open_by_devnum() can use further cleanup -
rename to blkdev_get_by_path() and blkdev_get_by_devt() and drop
special features.  Well, let's leave them for another day.

Most conversions are straight-forward.  drbd conversion is a bit more
involved as there was some reordering, but the logic should stay the
same.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Neil Brown <neilb@suse.de>
Acked-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Philipp Reisner <philipp.reisner@linbit.com>
Cc: Peter Osterlund <petero2@telia.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <joel.becker@oracle.com>
Cc: Alex Elder <aelder@sgi.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: dm-devel@redhat.com
Cc: drbd-dev@lists.linbit.com
Cc: Leo Chen <leochen@broadcom.com>
Cc: Scott Branden <sbranden@broadcom.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Cc: Joern Engel <joern@logfs.org>
Cc: reiserfs-devel@vger.kernel.org
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
2010-11-13 11:55:17 +01:00
Linus Torvalds a7bcf21e60 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:
  ext4: Add new ext4 inode tracepoints
  ext4: Don't call sb_issue_discard() in ext4_free_blocks()
  ext4: do not try to grab the s_umount semaphore in ext4_quota_off
  ext4: fix potential race when freeing ext4_io_page structures
  ext4: handle writeback of inodes which are being freed
  ext4: initialize the percpu counters before replaying the journal
  ext4: "ret" may be used uninitialized in ext4_lazyinit_thread()
  ext4: fix lazyinit hang after removing request
2010-11-08 11:54:53 -08:00
Theodore Ts'o 7ff9c073dd ext4: Add new ext4 inode tracepoints
Add ext4_evict_inode, ext4_drop_inode, ext4_mark_inode_dirty, and
ext4_begin_ordered_truncate()

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-11-08 13:51:33 -05:00
Theodore Ts'o b56ff9d397 ext4: Don't call sb_issue_discard() in ext4_free_blocks()
Commit 5c521830cf (ext4: Support discard requests when running in
no-journal mode) attempts to add sb_issue_discard() for data blocks
(in data=writeback mode) and in no-journal mode.  Unfortunately, this
no longer works, because in commit dd3932eddf (block: remove
BLKDEV_IFL_WAIT), sb_issue_discard() only presents a synchronous
interface, and there are times when we call ext4_free_blocks() when we
are are holding a spinlock, or are otherwise in an atomic context.

For now, I've removed the call to sb_issue_discard() to prevent a
deadlock or (if spinlock debugging is enabled) failures like this:

BUG: scheduling while atomic: rc.sysinit/1376/0x00000002
Pid: 1376, comm: rc.sysinit Not tainted 2.6.36-ARCH #1
Call Trace:
[<ffffffff810397ce>] __schedule_bug+0x5e/0x70
[<ffffffff81403110>] schedule+0x950/0xa70
[<ffffffff81060bad>] ? insert_work+0x7d/0x90
[<ffffffff81060fbd>] ? queue_work_on+0x1d/0x30
[<ffffffff81061127>] ? queue_work+0x37/0x60
[<ffffffff8140377d>] schedule_timeout+0x21d/0x360
[<ffffffff812031c3>] ? generic_make_request+0x2c3/0x540
[<ffffffff81402680>] wait_for_common+0xc0/0x150
[<ffffffff81041490>] ? default_wake_function+0x0/0x10
[<ffffffff812034bc>] ? submit_bio+0x7c/0x100
[<ffffffff810680a0>] ? wake_bit_function+0x0/0x40
[<ffffffff814027b8>] wait_for_completion+0x18/0x20
[<ffffffff8120a969>] blkdev_issue_discard+0x1b9/0x210
[<ffffffff811ba03e>] ext4_free_blocks+0x68e/0xb60
[<ffffffff811b1650>] ? __ext4_handle_dirty_metadata+0x110/0x120
[<ffffffff811b098c>] ext4_ext_truncate+0x8cc/0xa70
[<ffffffff810d713e>] ? pagevec_lookup+0x1e/0x30
[<ffffffff81191618>] ext4_truncate+0x178/0x5d0
[<ffffffff810eacbb>] ? unmap_mapping_range+0xab/0x280
[<ffffffff810d8976>] vmtruncate+0x56/0x70
[<ffffffff811925cb>] ext4_setattr+0x14b/0x460
[<ffffffff811319e4>] notify_change+0x194/0x380
[<ffffffff81117f80>] do_truncate+0x60/0x90
[<ffffffff811e08fa>] ? security_inode_permission+0x1a/0x20
[<ffffffff811eaec1>] ? tomoyo_path_truncate+0x11/0x20
[<ffffffff81127539>] do_last+0x5d9/0x770
[<ffffffff811278bd>] do_filp_open+0x1ed/0x680
[<ffffffff8140644f>] ? page_fault+0x1f/0x30
[<ffffffff81132bfc>] ? alloc_fd+0xec/0x140
[<ffffffff81118db1>] do_sys_open+0x61/0x120
[<ffffffff81118e8b>] sys_open+0x1b/0x20
[<ffffffff81002e6b>] system_call_fastpath+0x16/0x1b

https://bugzilla.kernel.org/show_bug.cgi?id=22302

Reported-by: Mathias Burén <mathias.buren@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: jiayingz@google.com
2010-11-08 13:49:33 -05:00
Dmitry Monakhov 87009d86dc ext4: do not try to grab the s_umount semaphore in ext4_quota_off
It's not needed to sync the filesystem, and it fixes a lock_dep complaint.

Signed-off-by: Dmitry Monakhov <dmonakhov@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
2010-11-08 13:47:33 -05:00
Theodore Ts'o 83668e7141 ext4: fix potential race when freeing ext4_io_page structures
Use an atomic_t and make sure we don't free the structure while we
might still be submitting I/O for that page.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-11-08 13:45:33 -05:00
Theodore Ts'o f7ad6d2e92 ext4: handle writeback of inodes which are being freed
The following BUG can occur when an inode which is getting freed when
it still has dirty pages outstanding, and it gets deleted (in this
because it was the target of a rename).  In ordered mode, we need to
make sure the data pages are written just in case we crash before the
rename (or unlink) is committed.  If the inode is being freed then
when we try to igrab the inode, we end up tripping the BUG_ON at
fs/ext4/page-io.c:146.

To solve this problem, we need to keep track of the number of io
callbacks which are pending, and avoid destroying the inode until they
have all been completed.  That way we don't have to bump the inode
count to keep the inode from being destroyed; an approach which
doesn't work because the count could have already been dropped down to
zero before the inode writeback has started (at which point we're not
allowed to bump the count back up to 1, since it's already started
getting freed).

Thanks to Dave Chinner for suggesting this approach, which is also
used by XFS.

  kernel BUG at /scratch_space/linux-2.6/fs/ext4/page-io.c:146!
  Call Trace:
   [<ffffffff811075b1>] ext4_bio_write_page+0x172/0x307
   [<ffffffff811033a7>] mpage_da_submit_io+0x2f9/0x37b
   [<ffffffff811068d7>] mpage_da_map_and_submit+0x2cc/0x2e2
   [<ffffffff811069b3>] mpage_add_bh_to_extent+0xc6/0xd5
   [<ffffffff81106c66>] write_cache_pages_da+0x2a4/0x3ac
   [<ffffffff81107044>] ext4_da_writepages+0x2d6/0x44d
   [<ffffffff81087910>] do_writepages+0x1c/0x25
   [<ffffffff810810a4>] __filemap_fdatawrite_range+0x4b/0x4d
   [<ffffffff810815f5>] filemap_fdatawrite_range+0xe/0x10
   [<ffffffff81122a2e>] jbd2_journal_begin_ordered_truncate+0x7b/0xa2
   [<ffffffff8110615d>] ext4_evict_inode+0x57/0x24c
   [<ffffffff810c14a3>] evict+0x22/0x92
   [<ffffffff810c1a3d>] iput+0x212/0x249
   [<ffffffff810bdf16>] dentry_iput+0xa1/0xb9
   [<ffffffff810bdf6b>] d_kill+0x3d/0x5d
   [<ffffffff810be613>] dput+0x13a/0x147
   [<ffffffff810b990d>] sys_renameat+0x1b5/0x258
   [<ffffffff81145f71>] ? _atomic_dec_and_lock+0x2d/0x4c
   [<ffffffff810b2950>] ? cp_new_stat+0xde/0xea
   [<ffffffff810b29c1>] ? sys_newlstat+0x2d/0x38
   [<ffffffff810b99c6>] sys_rename+0x16/0x18
   [<ffffffff81002a2b>] system_call_fastpath+0x16/0x1b

Reported-by: Nick Bowler <nbowler@elliptictech.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Tested-by: Nick Bowler <nbowler@elliptictech.com>
2010-11-08 13:43:33 -05:00
Theodore Ts'o ce7e010aef ext4: initialize the percpu counters before replaying the journal
We now initialize the percpu counters before replaying the journal,
but after the journal, we recalculate the global counters, to deal
with the possibility of the per-blockgroup counts getting updated by
the journal replay.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-11-03 12:03:21 -04:00
Theodore Ts'o b2c78cd09b ext4: "ret" may be used uninitialized in ext4_lazyinit_thread()
Newer GCC's reported the following build warning:

   fs/ext4/super.c: In function 'ext4_lazyinit_thread':
   fs/ext4/super.c:2702: warning: 'ret' may be used uninitialized in this function

Fix it by removing the need for the ret variable in the first place.

Signed-off-by: "Lukas Czerner" <lczerner@redhat.com>
Reported-by: "Stefan Richter" <stefanr@s5r6.in-berlin.de>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-11-02 14:19:30 -04:00
Lukas Czerner f4245bd4eb ext4: fix lazyinit hang after removing request
When the request has been removed from the list and no other request
has been issued, we will end up with next wakeup scheduled to
MAX_JIFFY_OFFSET which is bad. So check for that.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-11-02 14:07:17 -04:00
Theodore Ts'o eb8abb927a ext4: Remove useless spinlock in ext4_getattr()
Linus noted, and complained to me, that doing while lots of "git diff"'s
of kernel sources, these spinlocks were responsible for 27% of the
spinlock cost on his two-processor system as reported by perf.

Git was doing lots of parallel stats, and this was putting a lot of
pressure on ext4_getattr().  A spinlock to protect a single
memory-to-memory copy is pointless, so remove it.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-11-02 10:38:30 -04:00
Uwe Kleine-König b595076a18 tree-wide: fix comment/printk typos
"gadget", "through", "command", "maintain", "maintain", "controller", "address",
"between", "initiali[zs]e", "instead", "function", "select", "already",
"equal", "access", "management", "hierarchy", "registration", "interest",
"relative", "memory", "offset", "already",

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2010-11-01 15:38:34 -04:00
Al Viro 152a083666 new helper: mount_bdev()
... and switch of the obvious get_sb_bdev() users to ->mount()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-10-29 04:16:13 -04:00
Linus Torvalds 671f837a04 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:
  ext4: BUG_ON fix: check if page has buffers before calling page_buffers()
2010-10-28 15:46:57 -07:00
Theodore Ts'o b1142e8fec ext4: BUG_ON fix: check if page has buffers before calling page_buffers()
We need to make check if a page does not have buffes by checking
page_has_buffers(page) before calling page_buffers(page) in
ext4_writepage().  Otherwise page_buffers() could throw a BUG_ON.

Thanks also to Markus Trippelsdorf and Avinash Kurup who also reported
the problem.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reported-by: Sedat Dilek <sedat.dilek@googlemail.com>
Tested-by: Sedat Dilek <sedat.dilek@googlemail.com>
2010-10-28 17:33:57 -04:00
Ingo Molnar 19ef20143f ext4: fix compile with CONFIG_EXT4_FS_XATTR disabled
Commit 5dabfc78dc ("ext4: rename {exit,init}_ext4_*() to
ext4_{exit,init}_*()") causes

  fs/ext4/super.c:4776: error: implicit declaration of function ‘ext4_init_xattr’

when CONFIG_EXT4_FS_XATTR is disabled.

It renamed init_ext4_xattr to ext4_init_xattr but forgot to update the
dummy definition in fs/ext4/xattr.h.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-10-28 09:29:17 -07:00
Theodore Ts'o a107e5a3a4 Merge branch 'next' into upstream-merge
Conflicts:
	fs/ext4/inode.c
	fs/ext4/mballoc.c
	include/trace/events/ext4.h
2010-10-27 23:44:47 -04:00
Dmitry Monakhov 3d287de3b8 ext4: optimize orphan_list handling for ext4_setattr
Surprisingly chown() on ext4 is not SMP scalable operation. 
Due to unconditional orphan_del(NULL, inode) in ext4_setattr()
result in significant performance overhead because of global orphan
mutex, especially in no-journal mode (where orphan_add() is noop).
It is possible to skip explicit orphan_del if possible.
Results of fchown() micro-benchmark in no-journal mode
while (1) {
   iteration++;
   fchown(fd, uid, gid);
   fchown(fd, uid + 1, gid + 1)
}
measured: iterations per millisecond
| nr_tasks | w/o patch | with patch |
|        1 |       142 |        185 |
|        4 |       109 |        642 |

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 22:08:46 -04:00
Nicolas Kaiser beed5ecbaa ext4: fix unbalanced mutex unlock in error path of ext4_li_request_new
Signed-off-by: Nicolas Kaiser <nikai@nikai.net>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 22:08:42 -04:00
Kazuya Mio a6371b636f ext4: fix compile error in ext4_fallocate()
When I compiled 2.6.36-rc3 kernel with EXT4FS_DEBUG definition, I got
the following compile error.

  CC [M]  fs/ext4/extents.o
fs/ext4/extents.c: In function 'ext4_fallocate':
fs/ext4/extents.c:3772: error: 'block' undeclared (first use in this function)
fs/ext4/extents.c:3772: error: (Each undeclared identifier is reported only once
fs/ext4/extents.c:3772: error: for each function it appears in.)
make[2]: *** [fs/ext4/extents.o] Error 1

The patch fixes this problem.

Signed-off-by: Kazuya Mio <k-mio@sx.jp.nec.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:15 -04:00
Eric Sandeen eee4adc709 ext4: move ext4_mb_{get,put}_buddy_cache_lock and make them static
These functions are only used within fs/ext4/mballoc.c, so move them
so they are used after they are defined, and then make them be static.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:15 -04:00
Theodore Ts'o 61d08673de ext4: rename mark_bitmap_end() to ext4_mark_bitmap_end()
Fix a namespace leak from fs/ext4

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:15 -04:00
Theodore Ts'o 4a873a472b ext4: move flush_completed_IO to fs/ext4/fsync.c and make it static
Fix a namespace leak by moving the function to the file where it is
used and making it static.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:14 -04:00
Theodore Ts'o bf89d16f6e ext4: rename {ext,idx}_pblock and inline small extent functions
Cleanup namespace leaks from fs/ext4 and the inline trivial functions
ext4_{ext,idx}_pblock() and ext4_{ext,idx}_store_pblock() since the
code size actually shrinks when we make these functions inline,
they're so trivial.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:14 -04:00
Theodore Ts'o 1f109d5a17 ext4: make various ext4 functions be static
These functions have no need to be exported beyond file context.

No functions needed to be moved for this commit; just some function
declarations changed to be static and removed from header files.

(A similar patch was submitted by Eric Sandeen, but I wanted to handle
code movement in separate patches to make sure code changes didn't
accidentally get dropped.)

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:14 -04:00
Theodore Ts'o 5dabfc78dc ext4: rename {exit,init}_ext4_*() to ext4_{exit,init}_*()
This is a cleanup to avoid namespace leaks out of fs/ext4

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:14 -04:00
Theodore Ts'o 7f93cff90f ext4: fix kernel oops if the journal superblock has a non-zero j_errno
Commit 84061e0 fixed an accounting bug only to introduce the
possibility of a kernel OOPS if the journal has a non-zero j_errno
field indicating that the file system had detected a fs inconsistency.
After the journal replay, if the journal superblock indicates that the
file system has an error, this indication is transfered to the file
system and then ext4_commit_super() is called to write this to the
disk.

But since the percpu counters are now initialized after the journal
replay, the call to ext4_commit_super() will cause a kernel oops since
it needs to use the percpu counters the ext4 superblock structure.

The fix is to skip setting the ext4 free block and free inode fields
if the percpu counter has not been set.

Thanks to Ken Sumrall for reporting and analyzing the root causes of
this bug.

Addresses-Google-Bug: #3054080

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:13 -04:00
Eric Sandeen 72f84e6560 ext4: update writeback_index based on last page scanned
As pointed out in a prior patch, updating the mapping's
writeback_index based on pages written isn't quite right;
what the writeback index is really supposed to reflect is
the next page which should be scanned for writeback during
periodic flush.

As in write_cache_pages(), write_cache_pages_da() does
this scanning for us as we assemble the mpd for later
writeout.  If we keep track of the next page after the
current scan, we can easily update writeback_index without
worrying about pages written vs. pages skipped, etc.

Without this, an fsync will reset writeback_index to
0 (its starting index) + however many pages it wrote, which
can mess up the progress of periodic flush.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:13 -04:00
Eric Sandeen 5b41d92437 ext4: implement writeback livelock avoidance using page tagging
This is analogous to Jan Kara's commit,
f446daaea9
mm: implement writeback livelock avoidance using page tagging

but since we forked write_cache_pages, we need to reimplement
it there (and in ext4_da_writepages, since range_cyclic handling
was moved to there)

If you start a large buffered IO to a file, and then set
fsync after it, you'll find that fsync does not complete
until the other IO stops.

If you continue re-dirtying the file (say, putting dd
with conv=notrunc in a loop), when fsync finally completes
(after all IO is done), it reports via tracing that
it has written many more pages than the file contains;
in other words it has synced and re-synced pages in
the file multiple times.

This then leads to problems with our writeback_index
update, since it advances it by pages written, and
essentially sets writeback_index off the end of the
file...

With the following patch, we only sync as much as was
dirty at the time of the sync.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:13 -04:00
Eric Sandeen bbd08344e3 ext4: tidy up a void argument in inode.c
This doesn't fix anything at all, it just removes a vestige
of prior use from __mpage_da_writepage()

__mpage_da_writepage() had a *void argument leftover from
its previous life as a callback; make it reflect the actual type.

Fixing this up makes it slightly more obvious to read, and 
enables proper typechecking.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:12 -04:00
Lukas Czerner 27ee40df2b ext4: add batched_discard into ext4 feature list
Should be applied on the top of "lazy inode table initialization"
and "batched discard support" patch-sets.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:12 -04:00
Lukas Czerner 7360d1731e ext4: Add batched discard support for ext4
Walk through allocation groups and trim all free extents. It can be
invoked through FITRIM ioctl on the file system. The main idea is to
provide a way to trim the whole file system if needed, since some SSD's
may suffer from performance loss after the whole device was filled (it
does not mean that fs is full!).

It search for free extents in allocation groups specified by Byte range
start -> start+len. When the free extent is within this range, blocks
are marked as used and then trimmed. Afterwards these blocks are marked
as free in per-group bitmap.

Since fstrim is a long operation it is good to have an ability to
interrupt it by a signal. This was added by Dmitry Monakhov.
Thanks Dimitry.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:12 -04:00
Lukas Czerner 77ca6cdf0a ext4: Use return value from sb_issue_discard()
Use return value from sb_issue_discard() as return value in
ext4_issue_discard(). Since sb_issue_discard() may result in more
serious errors than just -EOPNOTSUPP it is worth to inform user of this
function about them to handle error cases properly.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:11 -04:00
Namhyung Kim 877836905d ext4: Check return value of sb_getblk() and friends
Fail block allocation if sb_getblk() returns NULL. In that case,
sb_find_get_block() also likely to fail so that it should skip
calling ext4_forget().

Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:11 -04:00
Theodore Ts'o bd2d0210cf ext4: use bio layer instead of buffer layer in mpage_da_submit_io
Call the block I/O layer directly instad of going through the buffer
layer.  This should give us much better performance and scalability,
as well as lowering our CPU utilization when doing buffered writeback.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:10 -04:00
Theodore Ts'o 1de3e3df91 ext4: move mpage_put_bnr_to_bhs()'s functionality to mpage_da_submit_io()
This massively simplifies the ext4_da_writepages() code path by
completely removing mpage_put_bnr_bhs(), which is almost 100 lines of
code iterating over a set of pages using pagevec_lookup(), and folds
that functionality into mpage_da_submit_io()'s existing
pagevec_lookup() loop.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:10 -04:00
Theodore Ts'o 3ecdb3a193 ext4: inline walk_page_buffers() into mpage_da_submit_io
Expand the call:

  if (walk_page_buffers(NULL, page_bufs, 0, len, NULL,
                        ext4_bh_delay_or_unwritten))
	goto redirty_page

into mpage_da_submit_io().

This will allow us to merge in mpage_put_bnr_to_bhs() in the next
patch.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:10 -04:00
Theodore Ts'o cb20d51883 ext4: inline ext4_writepage() into mpage_da_submit_io()
As a prepratory step to switching to bio_submit, inline
ext4_writepage() into mpage_da_submit() and then simplify things a
bit.  This makes it clearer what mpage_da_submit needs to do.

Also, move the ClearPageChecked(page) call into
__ext4_journalled_writepage(), as a minor bit of cleanup refactoring.

This also allows us to pull i_size_read() and
ext4_should_journal_data() out of the loop, which should be a very
minor CPU savings.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:09 -04:00
Theodore Ts'o a42afc5f56 ext4: simplify ext4_writepage()
The actual code in ext4_writepage() is unnecessarily convoluted.
Simplify it so it is easier to understand, but otherwise logically
equivalent.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:09 -04:00
Theodore Ts'o 5a87b7a5da ext4: call mpage_da_submit_io() from mpage_da_map_blocks()
Eventually we need to completely reorganize the ext4 writepage
callpath, but for now, we simplify things a little by calling
mpage_da_submit_io() from mpage_da_map_blocks(), since all of the
places where we call mpage_da_map_blocks() it is followed up by a call
to mpage_da_submit_io().

We're also a wee bit better with respect to error handling, but there
are still a number of issues where it's not clear what the right thing
is to do with ext4 functions deep in the writeback codepath fails.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:09 -04:00
Theodore Ts'o 16828088f9 ext4: use KMEM_CACHE instead of kmem_cache_create
Also remove the SLAB_RECLAIM_ACCOUNT flag from the system zone kmem
cache.  This slab tends to be fairly static, so it shouldn't be marked
as likely to have free pages that can be reclaimed.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:09 -04:00
Theodore Ts'o 7845c04975 ext4: use search_dirblock() in ext4_dx_find_entry()
Use the search_dirblock() in ext4_dx_find_entry().  It makes the code
easier to read, and it takes advantage of common code.  It also saves
100 bytes or so of text space.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: Brad Spengler <spender@grsecurity.net>
2010-10-27 21:30:08 -04:00
Theodore Ts'o 8941ec8bb6 ext4: avoid uninitialized memory references in ext3_htree_next_block()
If the first block of htree directory is missing '.' or '..' but is
otherwise a valid directory, and we do a lookup for '.' or '..', it's
possible to dereference an uninitialized memory pointer in
ext4_htree_next_block().

We avoid this by moving the special case from ext4_dx_find_entry() to
ext4_find_entry(); this also means we can optimize ext4_find_entry()
slightly when NFS looks up "..".

Thanks to Brad Spengler for pointing a Clang warning that led me to
look more closely at this code.  The warning was harmless, but it was
useful in pointing out code that was too ugly to live.  This warning was
also reported by Roman Borisov.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: Brad Spengler <spender@grsecurity.net>
2010-10-27 21:30:08 -04:00
Eric Sandeen 640e939656 ext4: remove unused ext4_sb_info members
Not that these take up a lot of room, but the structure is long enough
as it is, and there's no need to confuse people with these various
undocumented & unused structure members...

Signed-off-by: Eric Sandeen <sandeen@redaht.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:08 -04:00
Eric Sandeen c999af2b34 ext4: queue conversion after adding to inode's completed IO list
By queuing the io end on the unwritten workqueue before adding it
to our inode's list of completed IOs, I think we run the risk
of the work getting completed, and the IO freed, before we try
to add it to the inode's i_completed_io_list.

It should be safe to add it to the inode's list of completed
IOs, and -then- queue it for completion, I think.

Thanks to Dave Chinner for pointing out the race.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Jiaying Zhang <jiayingz@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:07 -04:00
Eric Sandeen 3e1e5f5016 ext4: don't use ext4_allocation_contexts for tracing
Many tracepoints were populating an ext4_allocation_context
to pass in, but this requires a slab allocation even when
tracepoints are off.  In fact, 4 of 5 of these allocations
were only for tracing.  In addition, we were only using a
small fraction of the 144 bytes of this structure for this
purpose.

We can do away with all these alloc/frees of the ac and
simply pass in the bits we care about, instead.

I tested this by turning on tracing and running through
xfstests on x86_64.  I did not actually do anything with
the trace output, however.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:07 -04:00
Toshiyuki Okajima 0c9169ccad ext4: fix potential infinite loop in ext4_da_writepages()
On linux-2.6.36-rc2, if we execute the following script, we can hang
the system when the /bin/sync command is executed:

========================================================================
#!/bin/sh

echo -n "HANG UP TEST: "
/bin/dd if=/dev/zero of=/tmp/img bs=1k count=1 seek=1M 2> /dev/null
/sbin/mkfs.ext4 -Fq /tmp/img
/bin/mount -o loop -t ext4 /tmp/img /mnt
/bin/dd if=/dev/zero of=/mnt/file bs=1 count=1 \
seek=$((16*1024*1024*1024*1024-4096)) 2> /dev/null
/bin/sync
/bin/umount /mnt
echo "DONE"
exit 0
========================================================================

We can see the following backtrace if we get the kdump when this
hangup occurs:

======================================================================
kthread()
=> bdi_writeback_thread()
   => wb_do_writeback()
      => wb_writeback()
         => writeback_inodes_wb()
            => writeback_sb_inodes()
               => writeback_single_inode()
                  => ext4_da_writepages()  ---+ 
                                ^ infinite    |
                                |   loop      |
                                +-------------+
======================================================================

The reason why this hangup happens is described as follows:
1) We write the last extent block of the file whose size is the filesystem 
   maximum size.
2) "BH_Delay" flag is set on the buffer_head of its block.
3) - the member, "m_lblk" of struct mpage_da_data is 4294967295 (UINT_MAX)
   - the member, "m_len" of struct mpage_da_data is 1
  mpage_put_bnr_to_bhs() which is called via ext4_da_writepages()
  cannot clear "BH_Delay" flag of the buffer_head because the type of
  m_lblk is ext4_lblk_t and then m_lblk + m_len is overflow.

  Therefore an infinite loop occurs because ext4_da_writepages()
  cannot write the page (which corresponds to the block) since
  "BH_Delay" flag isn't cleared.
----------------------------------------------------------------------
static void mpage_put_bnr_to_bhs(struct mpage_da_data *mpd,
				struct ext4_map_blocks *map)
{
...
	int blocks = map->m_len;
...
		do {
			// cur_logical = 4294967295
			// map->m_lblk = 4294967295
			// blocks = 1
			// *** map->m_lblk + blocks == 0 (OVERFLOW!) ***
			// (cur_logical >= map->m_lblk + blocks) => true
			if (cur_logical >= map->m_lblk + blocks)
				break;
----------------------------------------------------------------------

NOTE: Mounting with the nodelalloc option will avoid this codepath,
and thus, avoid this hang

Signed-off-by: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:07 -04:00
Toshiyuki Okajima e0d10bfa91 ext4: improve llseek error handling for overly large seek offsets
The llseek system call should return EINVAL if passed a seek offset
which results in a write error.  What this maximum offset should be
depends on whether or not the huge_file file system feature is set,
and whether or not the file is extent based or not.


If the file has no "EXT4_EXTENTS_FL" flag, the maximum size which can be 
written (write systemcall) is different from the maximum size which can be 
sought (lseek systemcall).

For example, the following 2 cases demonstrates the differences
between the maximum size which can be written, versus the seek offset
allowed by the llseek system call:

#1: mkfs.ext3 <dev>; mount -t ext4 <dev>
#2: mkfs.ext3 <dev>; tune2fs -Oextent,huge_file <dev>; mount -t ext4 <dev>

Table. the max file size which we can write or seek
       at each filesystem feature tuning and file flag setting
+============+===============================+===============================+
| \ File flag|                               |                               |
|      \     |     !EXT4_EXTENTS_FL          |        EXT4_EXTETNS_FL        |
|case       \|                               |                               |
+------------+-------------------------------+-------------------------------+
| #1         |   write:      2194719883264   | write:       --------------   |
|            |   seek:       2199023251456   | seek:        --------------   |
+------------+-------------------------------+-------------------------------+
| #2         |   write:      4402345721856   | write:       17592186044415   |
|            |   seek:      17592186044415   | seek:        17592186044415   |
+------------+-------------------------------+-------------------------------+

The differences exist because ext4 has 2 maxbytes which are sb->s_maxbytes
(= extent-mapped maxbytes) and EXT4_SB(sb)->s_bitmap_maxbytes (= block-mapped 
maxbytes).  Although generic_file_llseek uses only extent-mapped maxbytes.
(llseek of ext4_file_operations is generic_file_llseek which uses
sb->s_maxbytes.)

Therefore we create ext4 llseek function which uses 2 maxbytes.

The new own function originates from generic_file_llseek().
If the file flag, "EXT4_EXTENTS_FL" is not set, the function alters 
inode->i_sb->s_maxbytes into EXT4_SB(inode->i_sb)->s_bitmap_maxbytes.

Signed-off-by: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
2010-10-27 21:30:06 -04:00
Maciej Żenczykowski c41303ced6 ext4: don't update sb journal_devnum when RO dev
An ext4 filesystem on a read-only device, with an external journal
which is at a different device number then recorded in the superblock
will fail to honor the read-only setting of the device and trigger
a superblock update (write).

For example:
  - ext4 on a software raid which is in read-only mode
  - external journal on a read-write device which has changed device num
  - attempt to mount with -o journal_dev=<new_number>
  - hits BUG_ON(mddev->ro = 1) in md.c

Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Maciej Żenczykowski <zenczykowski@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:06 -04:00
Lukas Czerner 2407518de6 ext4: use sb_issue_zeroout in ext4_ext_zeroout
Change ext4_ext_zeroout to use sb_issue_zeroout instead of its
own approach to zero out extents.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:06 -04:00
Lukas Czerner a31437b85a ext4: use sb_issue_zeroout in setup_new_group_blocks
Use sb_issue_zeroout to zero out inode table and descriptor table
blocks instead of old approach which involves journaling.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:05 -04:00
Lukas Czerner 857ac889cc ext4: add interface to advertise ext4 features in sysfs
User-space should have the opportunity to check what features doest ext4
support in each particular copy. This adds easy interface by creating new
"features" directory in sys/fs/ext4/. In that directory files
advertising feature names can be created.

Add lazy_itable_init to the feature list.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:05 -04:00
Lukas Czerner bfff68738f ext4: add support for lazy inode table initialization
When the lazy_itable_init extended option is passed to mke2fs, it
considerably speeds up filesystem creation because inode tables are
not zeroed out.  The fact that parts of the inode table are
uninitialized is not a problem so long as the block group descriptors,
which contain information regarding how much of the inode table has
been initialized, has not been corrupted However, if the block group
checksums are not valid, e2fsck must scan the entire inode table, and
the the old, uninitialized data could potentially cause e2fsck to
report false problems.

Hence, it is important for the inode tables to be initialized as soon
as possble.  This commit adds this feature so that mke2fs can safely
use the lazy inode table initialization feature to speed up formatting
file systems.

This is done via a new new kernel thread called ext4lazyinit, which is
created on demand and destroyed, when it is no longer needed.  There
is only one thread for all ext4 filesystems in the system. When the
first filesystem with inititable mount option is mounted, ext4lazyinit
thread is created, then the filesystem can register its request in the
request list.

This thread then walks through the list of requests picking up
scheduled requests and invoking ext4_init_inode_table(). Next schedule
time for the request is computed by multiplying the time it took to
zero out last inode table with wait multiplier, which can be set with
the (init_itable=n) mount option (default is 10).  We are doing
this so we do not take the whole I/O bandwidth. When the thread is no
longer necessary (request list is empty) it frees the appropriate
structures and exits (and can be created later later by another
filesystem).

We do not disturb regular inode allocations in any way, it just do not
care whether the inode table is, or is not zeroed. But when zeroing, we
have to skip used inodes, obviously. Also we should prevent new inode
allocations from the group, while zeroing is on the way. For that we
take write alloc_sem lock in ext4_init_inode_table() and read alloc_sem
in the ext4_claim_inode, so when we are unlucky and allocator hits the
group which is currently being zeroed, it just has to wait.

This can be suppresed using the mount option no_init_itable.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:05 -04:00
Sergey Senozhatsky a1c6c5698d ext4: fix NULL pointer dereference in print_daily_error_info()
Fix NULL pointer dereference in print_daily_error_info, when   
called on unmounted fs (EXT4_SB(sb) returns NULL), by removing error 
reporting timer in ext4_put_super.

Google-Bug-Id: 3017663

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:04 -04:00
Lukas Czerner 53fdcf992d ext4: don't hold spinlock while calling ext4_issue_discard()
We can't hold the block group spinlock because we ext4_issue_discard()
calls wait and hence can get rescheduled.

Google-Bug-Id: 3017678

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:04 -04:00
Lukas Czerner 5829870982 ext4: check for negative error code from sb_issue_discard
sb_issue_discard() is returning negative error code, so check for
-EOPNOTSUPP.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:03 -04:00
Eric Sandeen b443e7339a ext4: don't bump up LONG_MAX nr_to_write by a factor of 8
I'm uneasy with lots of stuff going on in ext4_da_writepages(),
but bumping nr_to_write from LLONG_MAX to -8 clearly isn't
making anything better, so avoid the multiplier in that case.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:03 -04:00
Eric Sandeen 659c6009ca ext4: stop looping in ext4_num_dirty_pages when max_pages reached
Today we simply break out of the inner loop when we have accumulated
max_pages; this keeps scanning forwad and doing pagevec_lookup_tag()
in the while (!done) loop, this does potentially a lot of work
with no net effect.

When we have accumulated max_pages, just clean up and return.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:30:03 -04:00
Curt Wohlgemuth fb1813f4a8 ext4: use dedicated slab caches for group_info structures
ext4_group_info structures are currently allocated with kmalloc().
With a typical 4K block size, these are 136 bytes each -- meaning
they'll each consume a 256-byte slab object.  On a system with many
ext4 large partitions, that's a lot of wasted kernel slab space.
(E.g., a single 1TB partition will have about 8000 block groups, using
about 2MB of slab, of which nearly 1MB is wasted.)

This patch creates an array of slab pointers created as needed --
depending on the superblock block size -- and uses these slabs to
allocate the group info objects.

Google-Bug-Id: 2980809

Signed-off-by: Curt Wohlgemuth <curtw@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:29:12 -04:00
Theodore Ts'o 58590b06d7 ext4: fix EOFBLOCKS_FL handling
It turns out we have several problems with how EOFBLOCKS_FL is
handled.  First of all, there was a fencepost error where we were not
clearing the EOFBLOCKS_FL when fill in the last uninitialized block,
but rather when we allocate the next block _after_ the uninitalized
block.  Secondly we were not testing to see if we needed to clear the
EOFBLOCKS_FL when writing to the file O_DIRECT or when were converting
an uninitialized block (which is the most common case).

Google-Bug-Id: 2928259

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-10-27 21:23:12 -04:00
Christoph Hellwig 85fe4025c6 fs: do not assign default i_ino in new_inode
Instead of always assigning an increasing inode number in new_inode
move the call to assign it into those callers that actually need it.
For now callers that need it is estimated conservatively, that is
the call is added to all filesystems that do not assign an i_ino
by themselves.  For a few more filesystems we can avoid assigning
any inode number given that they aren't user visible, and for others
it could be done lazily when an inode number is actually needed,
but that's left for later patches.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-10-25 21:26:11 -04:00
Al Viro 7de9c6ee3e new helper: ihold()
Clones an existing reference to inode; caller must already hold one.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-10-25 21:26:11 -04:00
Christoph Hellwig ebdec241d5 fs: kill block_prepare_write
__block_write_begin and block_prepare_write are identical except for slightly
different calling conventions.  Convert all callers to the __block_write_begin
calling conventions and drop block_prepare_write.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-10-25 21:18:20 -04:00
Linus Torvalds a2887097f2 Merge branch 'for-2.6.37/barrier' of git://git.kernel.dk/linux-2.6-block
* 'for-2.6.37/barrier' of git://git.kernel.dk/linux-2.6-block: (46 commits)
  xen-blkfront: disable barrier/flush write support
  Added blk-lib.c and blk-barrier.c was renamed to blk-flush.c
  block: remove BLKDEV_IFL_WAIT
  aic7xxx_old: removed unused 'req' variable
  block: remove the BH_Eopnotsupp flag
  block: remove the BLKDEV_IFL_BARRIER flag
  block: remove the WRITE_BARRIER flag
  swap: do not send discards as barriers
  fat: do not send discards as barriers
  ext4: do not send discards as barriers
  jbd2: replace barriers with explicit flush / FUA usage
  jbd2: Modify ASYNC_COMMIT code to not rely on queue draining on barrier
  jbd: replace barriers with explicit flush / FUA usage
  nilfs2: replace barriers with explicit flush / FUA usage
  reiserfs: replace barriers with explicit flush / FUA usage
  gfs2: replace barriers with explicit flush / FUA usage
  btrfs: replace barriers with explicit flush / FUA usage
  xfs: replace barriers with explicit flush / FUA usage
  block: pass gfp_mask and flags to sb_issue_discard
  dm: convey that all flushes are processed as empty
  ...
2010-10-22 17:07:18 -07:00
Linus Torvalds 79f14b7c56 Merge branch 'vfs' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/bkl
* 'vfs' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/bkl: (30 commits)
  BKL: remove BKL from freevxfs
  BKL: remove BKL from qnx4
  autofs4: Only declare function when CONFIG_COMPAT is defined
  autofs: Only declare function when CONFIG_COMPAT is defined
  ncpfs: Lock socket in ncpfs while setting its callbacks
  fs/locks.c: prepare for BKL removal
  BKL: Remove BKL from ncpfs
  BKL: Remove BKL from OCFS2
  BKL: Remove BKL from squashfs
  BKL: Remove BKL from jffs2
  BKL: Remove BKL from ecryptfs
  BKL: Remove BKL from afs
  BKL: Remove BKL from USB gadgetfs
  BKL: Remove BKL from autofs4
  BKL: Remove BKL from isofs
  BKL: Remove BKL from fat
  BKL: Remove BKL from ext2 filesystem
  BKL: Remove BKL from do_new_mount()
  BKL: Remove BKL from cgroup
  BKL: Remove BKL from NTFS
  ...
2010-10-22 10:52:01 -07:00
Jan Blunck f2143c4e2e BKL: Remove BKL from ext4 filesystem
The BKL is still used in ext4_put_super(), ext4_fill_super() and
ext4_remount(). All three calles are protected against concurrent calls by
the s_umount rw semaphore of struct super_block.

Therefore the BKL is protecting nothing in this case.

Signed-off-by: Jan Blunck <jblunck@infradead.org>
Acked-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
2010-10-04 21:10:38 +02:00
Jan Blunck db71922217 BKL: Explicitly add BKL around get_sb/fill_super
This patch is a preparation necessary to remove the BKL from do_new_mount().
It explicitly adds calls to lock_kernel()/unlock_kernel() around
get_sb/fill_super operations for filesystems that still uses the BKL.

I've read through all the code formerly covered by the BKL inside
do_kern_mount() and have satisfied myself that it doesn't need the BKL
any more.

do_kern_mount() is already called without the BKL when mounting the rootfs
and in nfsctl. do_kern_mount() calls vfs_kern_mount(), which is called
from various places without BKL: simple_pin_fs(), nfs_do_clone_mount()
through nfs_follow_mountpoint(), afs_mntpt_do_automount() through
afs_mntpt_follow_link(). Both later functions are actually the filesystems
follow_link inode operation. vfs_kern_mount() is calling the specified
get_sb function and lets the filesystem do its job by calling the given
fill_super function.

Therefore I think it is safe to push down the BKL from the VFS to the
low-level filesystems get_sb/fill_super operation.

[arnd: do not add the BKL to those file systems that already
       don't use it elsewhere]

Signed-off-by: Jan Blunck <jblunck@infradead.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Christoph Hellwig <hch@infradead.org>
2010-10-04 21:10:10 +02:00
Christoph Hellwig dd3932eddf block: remove BLKDEV_IFL_WAIT
All the blkdev_issue_* helpers can only sanely be used for synchronous
caller.  To issue cache flushes or barriers asynchronously the caller needs
to set up a bio by itself with a completion callback to move the asynchronous
state machine ahead.  So drop the BLKDEV_IFL_WAIT flag that is always
specified when calling blkdev_issue_* and also remove the now unused flags
argument to blkdev_issue_flush and blkdev_issue_zeroout.  For
blkdev_issue_discard we need to keep it for the secure discard flag, which
gains a more descriptive name and loses the bitops vs flag confusion.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
2010-09-16 20:52:58 +02:00
Patrick J. LoPresti 30ca22c70e ext3/ext4: Factor out disk addressability check
As part of adding support for OCFS2 to mount huge volumes, we need to
check that the sector_t and page cache of the system are capable of
addressing the entire volume.

An identical check already appears in ext3 and ext4.  This patch moves
the addressability check into its own function in fs/libfs.c and
modifies ext3 and ext4 to invoke it.

[Edited to -EINVAL instead of BUG_ON() for bad blocksize_bits -- Joel]

Signed-off-by: Patrick LoPresti <lopresti@gmail.com>
Cc: linux-ext4@vger.kernel.org
Acked-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
2010-09-10 08:41:42 -07:00
Christoph Hellwig 61002f7db3 ext4: do not send discards as barriers
ext4 already uses synchronous discards, no need to add I/O barriers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
2010-09-10 12:35:39 +02:00
Christoph Hellwig 2cf6d26a35 block: pass gfp_mask and flags to sb_issue_discard
We'll need to get rid of the BLKDEV_IFL_BARRIER flag, and to facilitate
that and to make the interface less confusing pass all flags explicitly.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
2010-09-10 12:35:38 +02:00
Linus Torvalds 5f248c9c25 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6: (96 commits)
  no need for list_for_each_entry_safe()/resetting with superblock list
  Fix sget() race with failing mount
  vfs: don't hold s_umount over close_bdev_exclusive() call
  sysv: do not mark superblock dirty on remount
  sysv: do not mark superblock dirty on mount
  btrfs: remove junk sb_dirt change
  BFS: clean up the superblock usage
  AFFS: wait for sb synchronization when needed
  AFFS: clean up dirty flag usage
  cifs: truncate fallout
  mbcache: fix shrinker function return value
  mbcache: Remove unused features
  add f_flags to struct statfs(64)
  pass a struct path to vfs_statfs
  update VFS documentation for method changes.
  All filesystems that need invalidate_inode_buffers() are doing that explicitly
  convert remaining ->clear_inode() to ->evict_inode()
  Make ->drop_inode() just return whether inode needs to be dropped
  fs/inode.c:clear_inode() is gone
  fs/inode.c:evict() doesn't care about delete vs. non-delete paths now
  ...

Fix up trivial conflicts in fs/nilfs2/super.c
2010-08-10 11:26:52 -07:00
Andreas Gruenbacher 2aec7c5232 mbcache: Remove unused features
The mbcache code was written to support a variable number of indexes,
but all the existing users use exactly one index.  Simplify to code to
support only that case.

There are also no users of the cache entry free operation, and none of
the users keep extra data in cache entries.  Remove those features as
well.

Signed-off-by: Andreas Gruenbacher <agruen@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-09 16:48:45 -04:00
Al Viro 0930fcc1ee convert ext4 to ->evict_inode()
pretty much brute-force...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-09 16:48:30 -04:00
Christoph Hellwig 1025774ce4 remove inode_setattr
Replace inode_setattr with opencoded variants of it in all callers.  This
moves the remaining call to vmtruncate into the filesystem methods where it
can be replaced with the proper truncate sequence.

In a few cases it was obvious that we would never end up calling vmtruncate
so it was left out in the opencoded variant:

 spufs: explicitly checks for ATTR_SIZE earlier
 btrfs,hugetlbfs,logfs,dlmfs: explicitly clears ATTR_SIZE earlier
 ufs: contains an opencoded simple_seattr + truncate that sets the filesize just above

In addition to that ncpfs called inode_setattr with handcrafted iattrs,
which allowed to trim down the opencoded variant.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-09 16:47:37 -04:00
Christoph Hellwig 6e1db88d53 introduce __block_write_begin
Split up the block_write_begin implementation - __block_write_begin is a new
trivial wrapper for block_prepare_write that always takes an already
allocated page and can be either called from block_write_begin or filesystem
code that already has a page allocated.  Remove the handling of already
allocated pages from block_write_begin after switching all callers that
do it to __block_write_begin.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-09 16:47:32 -04:00
Christoph Hellwig eafdc7d190 sort out blockdev_direct_IO variants
Move the call to vmtruncate to get rid of accessive blocks to the callers
in prepearation of the new truncate calling sequence.  This was only done
for DIO_LOCKING filesystems, so the __blockdev_direct_IO_newtrunc variant
was not needed anyway.  Get rid of blockdev_direct_IO_no_locking and
its _newtrunc variant while at it as just opencoding the two additional
paramters is shorted than the name suffix.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2010-08-09 16:47:29 -04:00
Linus Torvalds 09dc942c2a Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4
* 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: (40 commits)
  ext4: Adding error check after calling ext4_mb_regular_allocator()
  ext4: Fix dirtying of journalled buffers in data=journal mode
  ext4: re-inline ext4_rec_len_(to|from)_disk functions
  jbd2: Remove t_handle_lock from start_this_handle()
  jbd2: Change j_state_lock to be a rwlock_t
  jbd2: Use atomic variables to avoid taking t_handle_lock in jbd2_journal_stop
  ext4: Add mount options in superblock
  ext4: force block allocation on quota_off
  ext4: fix freeze deadlock under IO
  ext4: drop inode from orphan list if ext4_delete_inode() fails
  ext4: check to make make sure bd_dev is set before dereferencing it
  jbd2: Make barrier messages less scary
  ext4: don't print scary messages for allocation failures post-abort
  ext4: fix EFBIG edge case when writing to large non-extent file
  ext4: fix ext4_get_blocks references
  ext4: Always journal quota file modifications
  ext4: Fix potential memory leak in ext4_fill_super
  ext4: Don't error out the fs if the user tries to make a file too big
  ext4: allocate stripe-multiple IOs on stripe boundaries
  ext4: move aio completion after unwritten extent conversion
  ...

Fix up conflicts in fs/ext4/inode.c as per Ted.

Fix up xfs conflicts as per earlier xfs merge.
2010-08-07 13:03:53 -07:00
Aditya Kali 6c7a120ac6 ext4: Adding error check after calling ext4_mb_regular_allocator()
If the bitmap block on disk is bad, ext4_mb_load_buddy() returns an
error. This error is returned to the caller,
ext4_mb_regular_allocator() and then to ext4_mb_new_blocks().  But
ext4_mb_new_blocks() did not check for the return value of
ext4_mb_regular_allocator() and would repeatedly try to load the
bitmap block. The fix simply catches the return value and exits out of
the 'repeat' loop after cleanup.

We also take the opportunity to clean up the error handling in
ext4_mb_new_blocks().

Google-Bug-Id: 2853530

Signed-off-by: Aditya Kali <adityakali@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-08-05 16:22:24 -04:00
Jan Kara 56d35a4cd1 ext4: Fix dirtying of journalled buffers in data=journal mode
In data=journal mode, we still use block_write_begin() to prepare
page for writing. This function can occasionally mark buffer dirty
which violates journalling assumptions - when a buffer is part of
a transaction, it should be dirty and a buffer can be already part
of a forget list of some transaction when block_write_begin()
gets called. This violation of journalling assumptions then results
in "JBD: Spotted dirty metadata buffer..." warnings.

In fact, temporary dirtying the buffer while the page is still locked
does not really cause problems to the journalling because we won't write
the buffer until the page gets unlocked. So we just have to make sure
to clear dirty bits before unlocking the page.

Signed-off-by: Jan Kara <jack@suse.cz>
2010-08-05 14:41:42 -04:00
Eric Sandeen 0cfc9255a1 ext4: re-inline ext4_rec_len_(to|from)_disk functions
commit 3d0518f4, "ext4: New rec_len encoding for very
large blocksizes" made several changes to this path, but from
a perf perspective, un-inlining ext4_rec_len_from_disk() seems
most significant.  This function is called from ext4_check_dir_entry(),
which on a file-creation workload is called extremely often.

I tested this with bonnie:

# bonnie++ -u root -s 0 -f -x 200 -d /mnt/test -n 32

(this does 200 iterations) and got this for the file creations:

ext4 stock:   Average =  21206.8 files/s
ext4 inlined: Average =  22346.7 files/s  (+5%)

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-08-05 01:46:37 -04:00
Jiri Kosina d790d4d583 Merge branch 'master' into for-next 2010-08-04 15:14:38 +02:00
Uwe Kleine-König 73b2c7165b fix comment typo "choosed" -> "chosen"
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2010-08-04 15:08:39 +02:00
Theodore Ts'o a931da6ac9 jbd2: Change j_state_lock to be a rwlock_t
Lockstat reports have shown that j_state_lock is a major source of
lock contention, especially on systems with more than 4 CPU cores.  So
change it to be a read/write spinlock.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-08-03 21:35:12 -04:00
Theodore Ts'o 8b67f04ab9 ext4: Add mount options in superblock
Allow mount options to be stored in the superblock.  Also add default
mount option bits for nobarrier, block_validity, discard, and nodelalloc.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-08-01 23:14:20 -04:00
Dmitry Monakhov ca0e05e4b1 ext4: force block allocation on quota_off
Perform full sync procedure so that any delayed allocation blocks are
allocated so quota will be consistent.

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-08-01 17:48:36 -04:00
Eric Sandeen 437f88cc03 ext4: fix freeze deadlock under IO
Commit 6b0310fbf0 caused a regression resulting in deadlocks
when freezing a filesystem which had active IO; the vfs_check_frozen
level (SB_FREEZE_WRITE) did not let the freeze-related IO syncing
through.  Duh.

Changing the test to FREEZE_TRANS should let the normal freeze
syncing get through the fs, but still block any transactions from
starting once the fs is completely frozen.

I tested this by running fsstress in the background while periodically
snapshotting the fs and running fsck on the result.  I ran into
occasional deadlocks, but different ones.  I think this is a
fine fix for the problem at hand, and the other deadlocky things
will need more investigation.

Reported-by: Phillip Susi <psusi@cfl.rr.com>
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-08-01 17:33:29 -04:00
Theodore Ts'o 4538821993 ext4: drop inode from orphan list if ext4_delete_inode() fails
There were some error paths in ext4_delete_inode() which was not
dropping the inode from the orphan list.  This could lead to a BUG_ON
on umount when the orphan list is discovered to be non-empty.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-07-29 15:06:10 -04:00
Theodore Ts'o f613dfcb33 ext4: check to make make sure bd_dev is set before dereferencing it
There are some drivers which may not set bdev->bd_dev.  So make sure
it is non-NULL before dereferencing it.

Google-Bug-Id: 1773557

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2010-07-27 11:56:08 -04:00