linux-toradex.git/fs, branch v3.2.55 Linux kernel for Apalis and Colibri modules nilfs2: fix segctor bug that causes file system corruption 2014-02-15T19:20:17+00:00 Andreas Rohner andreas.rohner@gmx.net 2014-01-15T01:56:36+00:00 028d56ae6da361de5e0e36df2623ece176142181 commit 70f2fe3a26248724d8a5019681a869abdaf3e89a upstream. There is a bug in the function nilfs_segctor_collect, which results in active data being written to a segment, that is marked as clean. It is possible, that this segment is selected for a later segment construction, whereby the old data is overwritten. The problem shows itself with the following kernel log message: nilfs_sufile_do_cancel_free: segment 6533 must be clean Usually a few hours later the file system gets corrupted: NILFS: bad btree node (blocknr=8748107): level = 0, flags = 0x0, nchildren = 0 NILFS error (device sdc1): nilfs_bmap_last_key: broken bmap (inode number=114660) The issue can be reproduced with a file system that is nearly full and with the cleaner running, while some IO intensive task is running. Although it is quite hard to reproduce. This is what happens: 1. The cleaner starts the segment construction 2. nilfs_segctor_collect is called 3. sc_stage is on NILFS_ST_SUFILE and segments are freed 4. sc_stage is on NILFS_ST_DAT current segment is full 5. nilfs_segctor_extend_segments is called, which allocates a new segment 6. The new segment is one of the segments freed in step 3 7. nilfs_sufile_cancel_freev is called and produces an error message 8. Loop around and the collection starts again 9. sc_stage is on NILFS_ST_SUFILE and segments are freed including the newly allocated segment, which will contain active data and can be allocated at a later time 10. A few hours later another segment construction allocates the segment and causes file system corruption This can be prevented by simply reordering the statements. If nilfs_sufile_cancel_freev is called before nilfs_segctor_extend_segments the freed segments are marked as dirty and cannot be allocated any more. Signed-off-by: Andreas Rohner <andreas.rohner@gmx.net> Reviewed-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> Tested-by: Andreas Rohner <andreas.rohner@gmx.net> 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> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit 70f2fe3a26248724d8a5019681a869abdaf3e89a upstream.

There is a bug in the function nilfs_segctor_collect, which results in
active data being written to a segment, that is marked as clean.  It is
possible, that this segment is selected for a later segment
construction, whereby the old data is overwritten.

The problem shows itself with the following kernel log message:

  nilfs_sufile_do_cancel_free: segment 6533 must be clean

Usually a few hours later the file system gets corrupted:

  NILFS: bad btree node (blocknr=8748107): level = 0, flags = 0x0, nchildren = 0
  NILFS error (device sdc1): nilfs_bmap_last_key: broken bmap (inode number=114660)

The issue can be reproduced with a file system that is nearly full and
with the cleaner running, while some IO intensive task is running.
Although it is quite hard to reproduce.

This is what happens:

 1. The cleaner starts the segment construction
 2. nilfs_segctor_collect is called
 3. sc_stage is on NILFS_ST_SUFILE and segments are freed
 4. sc_stage is on NILFS_ST_DAT current segment is full
 5. nilfs_segctor_extend_segments is called, which
    allocates a new segment
 6. The new segment is one of the segments freed in step 3
 7. nilfs_sufile_cancel_freev is called and produces an error message
 8. Loop around and the collection starts again
 9. sc_stage is on NILFS_ST_SUFILE and segments are freed
    including the newly allocated segment, which will contain active
    data and can be allocated at a later time
10. A few hours later another segment construction allocates the
    segment and causes file system corruption

This can be prevented by simply reordering the statements.  If
nilfs_sufile_cancel_freev is called before nilfs_segctor_extend_segments
the freed segments are marked as dirty and cannot be allocated any more.

Signed-off-by: Andreas Rohner <andreas.rohner@gmx.net>
Reviewed-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Tested-by: Andreas Rohner <andreas.rohner@gmx.net>
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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
ext4: add explicit casts when masking cluster sizes 2014-02-15T19:20:15+00:00 Theodore Ts'o tytso@mit.edu 2013-12-20T14:29:35+00:00 f3f8d67db827d4206999fc81bca6df60c96c9448 commit f5a44db5d2d677dfbf12deee461f85e9ec633961 upstream. The missing casts can cause the high 64-bits of the physical blocks to be lost. Set up new macros which allows us to make sure the right thing happen, even if at some point we end up supporting larger logical block numbers. Thanks to the Emese Revfy and the PaX security team for reporting this issue. Reported-by: PaX Team <pageexec@freemail.hu> Reported-by: Emese Revfy <re.emese@gmail.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> [bwh: Backported to 3.2: - Adjust context - Drop inapplicable change to ext4_ext_rm_leaf()] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit f5a44db5d2d677dfbf12deee461f85e9ec633961 upstream.

The missing casts can cause the high 64-bits of the physical blocks to
be lost.  Set up new macros which allows us to make sure the right
thing happen, even if at some point we end up supporting larger
logical block numbers.

Thanks to the Emese Revfy and the PaX security team for reporting this
issue.

Reported-by: PaX Team <pageexec@freemail.hu>
Reported-by: Emese Revfy <re.emese@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
[bwh: Backported to 3.2:
 - Adjust context
 - Drop inapplicable change to ext4_ext_rm_leaf()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
ext4: fix del_timer() misuse for ->s_err_report 2014-02-15T19:20:12+00:00 Al Viro viro@ZenIV.linux.org.uk 2013-12-09T01:52:31+00:00 f09946daaea5c088d8dc0883e30c643f5e5684db commit 9105bb149bbbc555d2e11ba5166dfe7a24eae09e upstream. That thing should be del_timer_sync(); consider what happens if ext4_put_super() call of del_timer() happens to come just as it's getting run on another CPU. Since that timer reschedules itself to run next day, you are pretty much guaranteed that you'll end up with kfree'd scheduled timer, with usual fun consequences. AFAICS, that's -stable fodder all way back to 2010... [the second del_timer_sync() is almost certainly not needed, but it doesn't hurt either] Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit 9105bb149bbbc555d2e11ba5166dfe7a24eae09e upstream.

That thing should be del_timer_sync(); consider what happens
if ext4_put_super() call of del_timer() happens to come just as it's
getting run on another CPU.  Since that timer reschedules itself
to run next day, you are pretty much guaranteed that you'll end up
with kfree'd scheduled timer, with usual fun consequences.  AFAICS,
that's -stable fodder all way back to 2010... [the second del_timer_sync()
is almost certainly not needed, but it doesn't hurt either]

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
ext2: Fix oops in ext2_get_block() called from ext2_quota_write() 2014-02-15T19:20:12+00:00 Jan Kara jack@suse.cz 2013-12-03T10:20:06+00:00 f5b4f2e824dec9808d55287576a7b83d80bae937 commit df4e7ac0bb70abc97fbfd9ef09671fc084b3f9db upstream. ext2_quota_write() doesn't properly setup bh it passes to ext2_get_block() and thus we hit assertion BUG_ON(maxblocks == 0) in ext2_get_blocks() (or we could actually ask for mapping arbitrary number of blocks depending on whatever value was on stack). Fix ext2_quota_write() to properly fill in number of blocks to map. Reviewed-by: "Theodore Ts'o" <tytso@mit.edu> Reviewed-by: Christoph Hellwig <hch@lst.de> Reported-by: Christoph Hellwig <hch@infradead.org> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit df4e7ac0bb70abc97fbfd9ef09671fc084b3f9db upstream.

ext2_quota_write() doesn't properly setup bh it passes to
ext2_get_block() and thus we hit assertion BUG_ON(maxblocks == 0) in
ext2_get_blocks() (or we could actually ask for mapping arbitrary number
of blocks depending on whatever value was on stack).

Fix ext2_quota_write() to properly fill in number of blocks to map.

Reviewed-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reported-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
ext4: check for overlapping extents in ext4_valid_extent_entries() 2014-02-15T19:20:12+00:00 Eryu Guan guaneryu@gmail.com 2013-12-04T02:22:21+00:00 4645e4ee32aee01a85bdc03348982a65c65ce216 commit 5946d089379a35dda0e531710b48fca05446a196 upstream. A corrupted ext4 may have out of order leaf extents, i.e. extent: lblk 0--1023, len 1024, pblk 9217, flags: LEAF UNINIT extent: lblk 1000--2047, len 1024, pblk 10241, flags: LEAF UNINIT ^^^^ overlap with previous extent Reading such extent could hit BUG_ON() in ext4_es_cache_extent(). BUG_ON(end < lblk); The problem is that __read_extent_tree_block() tries to cache holes as well but assumes 'lblk' is greater than 'prev' and passes underflowed length to ext4_es_cache_extent(). Fix it by checking for overlapping extents in ext4_valid_extent_entries(). I hit this when fuzz testing ext4, and am able to reproduce it by modifying the on-disk extent by hand. Also add the check for (ee_block + len - 1) in ext4_valid_extent() to make sure the value is not overflow. Ran xfstests on patched ext4 and no regression. Cc: Lukáš Czerner <lczerner@redhat.com> Signed-off-by: Eryu Guan <guaneryu@gmail.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit 5946d089379a35dda0e531710b48fca05446a196 upstream.

A corrupted ext4 may have out of order leaf extents, i.e.

extent: lblk 0--1023, len 1024, pblk 9217, flags: LEAF UNINIT
extent: lblk 1000--2047, len 1024, pblk 10241, flags: LEAF UNINIT
             ^^^^ overlap with previous extent

Reading such extent could hit BUG_ON() in ext4_es_cache_extent().

	BUG_ON(end < lblk);

The problem is that __read_extent_tree_block() tries to cache holes as
well but assumes 'lblk' is greater than 'prev' and passes underflowed
length to ext4_es_cache_extent(). Fix it by checking for overlapping
extents in ext4_valid_extent_entries().

I hit this when fuzz testing ext4, and am able to reproduce it by
modifying the on-disk extent by hand.

Also add the check for (ee_block + len - 1) in ext4_valid_extent() to
make sure the value is not overflow.

Ran xfstests on patched ext4 and no regression.

Cc: Lukáš Czerner <lczerner@redhat.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
ext4: fix use-after-free in ext4_mb_new_blocks 2014-02-15T19:20:12+00:00 Junho Ryu jayr@google.com 2013-12-03T23:10:28+00:00 ec94b7aba9ced72a96cfdf0cdf693b30ff604039 commit 4e8d2139802ce4f41936a687f06c560b12115247 upstream. ext4_mb_put_pa should hold pa->pa_lock before accessing pa->pa_count. While ext4_mb_use_preallocated checks pa->pa_deleted first and then increments pa->count later, ext4_mb_put_pa decrements pa->pa_count before holding pa->pa_lock and then sets pa->pa_deleted. * Free sequence ext4_mb_put_pa (1): atomic_dec_and_test pa->pa_count ext4_mb_put_pa (2): lock pa->pa_lock ext4_mb_put_pa (3): check pa->pa_deleted ext4_mb_put_pa (4): set pa->pa_deleted=1 ext4_mb_put_pa (5): unlock pa->pa_lock ext4_mb_put_pa (6): remove pa from a list ext4_mb_pa_callback: free pa * Use sequence ext4_mb_use_preallocated (1): iterate over preallocation ext4_mb_use_preallocated (2): lock pa->pa_lock ext4_mb_use_preallocated (3): check pa->pa_deleted ext4_mb_use_preallocated (4): increase pa->pa_count ext4_mb_use_preallocated (5): unlock pa->pa_lock ext4_mb_release_context: access pa * Use-after-free sequence [initial status] <pa->pa_deleted = 0, pa_count = 1> ext4_mb_use_preallocated (1): iterate over preallocation ext4_mb_use_preallocated (2): lock pa->pa_lock ext4_mb_use_preallocated (3): check pa->pa_deleted ext4_mb_put_pa (1): atomic_dec_and_test pa->pa_count [pa_count decremented] <pa->pa_deleted = 0, pa_count = 0> ext4_mb_use_preallocated (4): increase pa->pa_count [pa_count incremented] <pa->pa_deleted = 0, pa_count = 1> ext4_mb_use_preallocated (5): unlock pa->pa_lock ext4_mb_put_pa (2): lock pa->pa_lock ext4_mb_put_pa (3): check pa->pa_deleted ext4_mb_put_pa (4): set pa->pa_deleted=1 [race condition!] <pa->pa_deleted = 1, pa_count = 1> ext4_mb_put_pa (5): unlock pa->pa_lock ext4_mb_put_pa (6): remove pa from a list ext4_mb_pa_callback: free pa ext4_mb_release_context: access pa AddressSanitizer has detected use-after-free in ext4_mb_new_blocks Bug report: http://goo.gl/rG1On3 Signed-off-by: Junho Ryu <jayr@google.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit 4e8d2139802ce4f41936a687f06c560b12115247 upstream.

ext4_mb_put_pa should hold pa->pa_lock before accessing pa->pa_count.
While ext4_mb_use_preallocated checks pa->pa_deleted first and then
increments pa->count later, ext4_mb_put_pa decrements pa->pa_count
before holding pa->pa_lock and then sets pa->pa_deleted.

* Free sequence
ext4_mb_put_pa (1):		atomic_dec_and_test pa->pa_count
ext4_mb_put_pa (2):		lock pa->pa_lock
ext4_mb_put_pa (3):			check pa->pa_deleted
ext4_mb_put_pa (4):			set pa->pa_deleted=1
ext4_mb_put_pa (5):		unlock pa->pa_lock
ext4_mb_put_pa (6):		remove pa from a list
ext4_mb_pa_callback:		free pa

* Use sequence
ext4_mb_use_preallocated (1):	iterate over preallocation
ext4_mb_use_preallocated (2):	lock pa->pa_lock
ext4_mb_use_preallocated (3):		check pa->pa_deleted
ext4_mb_use_preallocated (4):		increase pa->pa_count
ext4_mb_use_preallocated (5):	unlock pa->pa_lock
ext4_mb_release_context:	access pa

* Use-after-free sequence
[initial status]		<pa->pa_deleted = 0, pa_count = 1>
ext4_mb_use_preallocated (1):	iterate over preallocation
ext4_mb_use_preallocated (2):	lock pa->pa_lock
ext4_mb_use_preallocated (3):		check pa->pa_deleted
ext4_mb_put_pa (1):		atomic_dec_and_test pa->pa_count
[pa_count decremented]		<pa->pa_deleted = 0, pa_count = 0>
ext4_mb_use_preallocated (4):		increase pa->pa_count
[pa_count incremented]		<pa->pa_deleted = 0, pa_count = 1>
ext4_mb_use_preallocated (5):	unlock pa->pa_lock
ext4_mb_put_pa (2):		lock pa->pa_lock
ext4_mb_put_pa (3):			check pa->pa_deleted
ext4_mb_put_pa (4):			set pa->pa_deleted=1
[race condition!]		<pa->pa_deleted = 1, pa_count = 1>
ext4_mb_put_pa (5):		unlock pa->pa_lock
ext4_mb_put_pa (6):		remove pa from a list
ext4_mb_pa_callback:		free pa
ext4_mb_release_context:	access pa

AddressSanitizer has detected use-after-free in ext4_mb_new_blocks
Bug report: http://goo.gl/rG1On3

Signed-off-by: Junho Ryu <jayr@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
ext4: call ext4_error_inode() if jbd2_journal_dirty_metadata() fails 2014-02-15T19:20:12+00:00 Theodore Ts'o tytso@mit.edu 2013-12-02T14:31:36+00:00 9eb492b82ccf9900c85af95276b60dd1ba1b7d2a commit ae1495b12df1897d4f42842a7aa7276d920f6290 upstream. While it's true that errors can only happen if there is a bug in jbd2_journal_dirty_metadata(), if a bug does happen, we need to halt the kernel or remount the file system read-only in order to avoid further data loss. The ext4_journal_abort_handle() function doesn't do any of this, and while it's likely that this call (since it doesn't adjust refcounts) will likely result in the file system eventually deadlocking since the current transaction will never be able to close, it's much cleaner to call let ext4's error handling system deal with this situation. There's a separate bug here which is that if certain jbd2 errors errors occur and file system is mounted errors=continue, the file system will probably eventually end grind to a halt as described above. But things have been this way in a long time, and usually when we have these sorts of errors it's pretty much a disaster --- and that's why the jbd2 layer aggressively retries memory allocations, which is the most likely cause of these jbd2 errors. Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Reviewed-by: Jan Kara <jack@suse.cz> [bwh: Backported to 3.2: drop logging of missing transaction debug data] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit ae1495b12df1897d4f42842a7aa7276d920f6290 upstream.

While it's true that errors can only happen if there is a bug in
jbd2_journal_dirty_metadata(), if a bug does happen, we need to halt
the kernel or remount the file system read-only in order to avoid
further data loss.  The ext4_journal_abort_handle() function doesn't
do any of this, and while it's likely that this call (since it doesn't
adjust refcounts) will likely result in the file system eventually
deadlocking since the current transaction will never be able to close,
it's much cleaner to call let ext4's error handling system deal with
this situation.

There's a separate bug here which is that if certain jbd2 errors
errors occur and file system is mounted errors=continue, the file
system will probably eventually end grind to a halt as described
above.  But things have been this way in a long time, and usually when
we have these sorts of errors it's pretty much a disaster --- and
that's why the jbd2 layer aggressively retries memory allocations,
which is the most likely cause of these jbd2 errors.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
[bwh: Backported to 3.2: drop logging of missing transaction debug data]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
ceph: wake up 'safe' waiters when unregistering request 2014-02-15T19:20:12+00:00 Yan, Zheng zheng.z.yan@intel.com 2013-10-31T01:10:47+00:00 f4ca736c52df0cff20c52415e313bdf77f5631d0 commit fc55d2c9448b34218ca58733a6f51fbede09575b upstream. We also need to wake up 'safe' waiters if error occurs or request aborted. Otherwise sync(2)/fsync(2) may hang forever. Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com> Signed-off-by: Sage Weil <sage@inktank.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit fc55d2c9448b34218ca58733a6f51fbede09575b upstream.

We also need to wake up 'safe' waiters if error occurs or request
aborted. Otherwise sync(2)/fsync(2) may hang forever.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Sage Weil <sage@inktank.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
ceph: cleanup aborted requests when re-sending requests. 2014-02-15T19:20:11+00:00 Yan, Zheng zheng.z.yan@intel.com 2013-09-26T06:25:36+00:00 b072f9cad8d6d04fea08d3aafc88e4d9e2d95959 commit eb1b8af33c2e42a9a57fc0a7588f4a7b255d2e79 upstream. Aborted requests usually get cleared when the reply is received. If MDS crashes, no reply will be received. So we need to cleanup aborted requests when re-sending requests. Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com> Reviewed-by: Greg Farnum <greg@inktank.com> Signed-off-by: Sage Weil <sage@inktank.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit eb1b8af33c2e42a9a57fc0a7588f4a7b255d2e79 upstream.

Aborted requests usually get cleared when the reply is received.
If MDS crashes, no reply will be received. So we need to cleanup
aborted requests when re-sending requests.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Reviewed-by: Greg Farnum <greg@inktank.com>
Signed-off-by: Sage Weil <sage@inktank.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
hpfs: fix warnings when the filesystem fills up 2014-02-15T19:20:11+00:00 Mikulas Patocka mikulas@artax.karlin.mff.cuni.cz 2013-06-08T23:25:57+00:00 bfefd2a8c3db2a537c7effa34ab84cadbcadbd9e commit bbd465df73f0d8ba41b8a0732766a243d0f5b356 upstream. This patch fixes warnings due to missing lock on write error path. WARNING: at fs/hpfs/hpfs_fn.h:353 hpfs_truncate+0x75/0x80 [hpfs]() Hardware name: empty Pid: 26563, comm: dd Tainted: P O 3.9.4 #12 Call Trace: hpfs_truncate+0x75/0x80 [hpfs] hpfs_write_begin+0x84/0x90 [hpfs] _hpfs_bmap+0x10/0x10 [hpfs] generic_file_buffered_write+0x121/0x2c0 __generic_file_aio_write+0x1c7/0x3f0 generic_file_aio_write+0x7c/0x100 do_sync_write+0x98/0xd0 hpfs_file_write+0xd/0x50 [hpfs] vfs_write+0xa2/0x160 sys_write+0x51/0xa0 page_fault+0x22/0x30 system_call_fastpath+0x1a/0x1f Signed-off-by: Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> [Mikulas Patocka: This is backport of upstream commit bbd465df73f0d8ba41b8a0732766a243d0f5b356, modified for stable kernels 2.6.39 - 3.7.] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> 
commit bbd465df73f0d8ba41b8a0732766a243d0f5b356 upstream.

This patch fixes warnings due to missing lock on write error path.

  WARNING: at fs/hpfs/hpfs_fn.h:353 hpfs_truncate+0x75/0x80 [hpfs]()
  Hardware name: empty
  Pid: 26563, comm: dd Tainted: P           O 3.9.4 #12
  Call Trace:
    hpfs_truncate+0x75/0x80 [hpfs]
    hpfs_write_begin+0x84/0x90 [hpfs]
    _hpfs_bmap+0x10/0x10 [hpfs]
    generic_file_buffered_write+0x121/0x2c0
    __generic_file_aio_write+0x1c7/0x3f0
    generic_file_aio_write+0x7c/0x100
    do_sync_write+0x98/0xd0
    hpfs_file_write+0xd/0x50 [hpfs]
    vfs_write+0xa2/0x160
    sys_write+0x51/0xa0
    page_fault+0x22/0x30
    system_call_fastpath+0x1a/0x1f

Signed-off-by: Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[Mikulas Patocka: This is backport of upstream commit 
 bbd465df73f0d8ba41b8a0732766a243d0f5b356, modified for stable kernels 
 2.6.39 - 3.7.]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>