linux/fs/ext4
Eric Biggers 2f8f5e76c7 ext4: avoid lockdep warning when inheriting encryption context
On a lockdep-enabled kernel, xfstests generic/027 fails due to a lockdep
warning when run on ext4 mounted with -o test_dummy_encryption:

    xfs_io/4594 is trying to acquire lock:
     (jbd2_handle
    ){++++.+}, at:
    [<ffffffff813096ef>] jbd2_log_wait_commit+0x5/0x11b

    but task is already holding lock:
     (jbd2_handle
    ){++++.+}, at:
    [<ffffffff813000de>] start_this_handle+0x354/0x3d8

The abbreviated call stack is:

 [<ffffffff813096ef>] ? jbd2_log_wait_commit+0x5/0x11b
 [<ffffffff8130972a>] jbd2_log_wait_commit+0x40/0x11b
 [<ffffffff813096ef>] ? jbd2_log_wait_commit+0x5/0x11b
 [<ffffffff8130987b>] ? __jbd2_journal_force_commit+0x76/0xa6
 [<ffffffff81309896>] __jbd2_journal_force_commit+0x91/0xa6
 [<ffffffff813098b9>] jbd2_journal_force_commit_nested+0xe/0x18
 [<ffffffff812a6049>] ext4_should_retry_alloc+0x72/0x79
 [<ffffffff812f0c1f>] ext4_xattr_set+0xef/0x11f
 [<ffffffff812cc35b>] ext4_set_context+0x3a/0x16b
 [<ffffffff81258123>] fscrypt_inherit_context+0xe3/0x103
 [<ffffffff812ab611>] __ext4_new_inode+0x12dc/0x153a
 [<ffffffff812bd371>] ext4_create+0xb7/0x161

When a file is created in an encrypted directory, ext4_set_context() is
called to set an encryption context on the new file.  This calls
ext4_xattr_set(), which contains a retry loop where the journal is
forced to commit if an ENOSPC error is encountered.

If the task actually were to wait for the journal to commit in this
case, then it would deadlock because a handle remains open from
__ext4_new_inode(), so the running transaction can't be committed yet.
Fortunately, __jbd2_journal_force_commit() avoids the deadlock by not
allowing the running transaction to be committed while the current task
has it open.  However, the above lockdep warning is still triggered.

This was a false positive which was introduced by: 1eaa566d36: jbd2:
track more dependencies on transaction commit

Fix the problem by passing the handle through the 'fs_data' argument to
ext4_set_context(), then using ext4_xattr_set_handle() instead of
ext4_xattr_set().  And in the case where no journal handle is specified
and ext4_set_context() has to open one, add an ENOSPC retry loop since
in that case it is the outermost transaction.

Signed-off-by: Eric Biggers <ebiggers@google.com>
2016-11-21 11:52:44 -05:00
..
acl.c ext4: use current_time() for inode timestamps 2016-11-14 21:40:10 -05:00
acl.h ext2/3/4: use generic posix ACL infrastructure 2014-01-25 23:58:19 -05:00
balloc.c The major change this cycle is deleting ext4's copy of the file system 2016-07-26 18:35:55 -07:00
bitmap.c ext4: remove unused header files 2015-04-02 23:47:42 -04:00
block_validity.c ext4: add missing KERN_CONT to a few more debugging uses 2016-10-15 09:57:31 -04:00
dir.c ext4: remove unused variable 2016-09-30 02:14:56 -04:00
ext4_extents.h ext4: fix misspellings in comments. 2016-03-09 23:49:05 -05:00
ext4_jbd2.c ext4: fix potential use after free in __ext4_journal_stop 2015-10-17 22:57:06 -04:00
ext4_jbd2.h ext4: optimize ext4_should_retry_alloc() to improve ENOSPC performance 2016-06-26 18:24:01 -04:00
ext4.h ext4: remove unused function ext4_aligned_io() 2016-11-21 11:51:44 -05:00
extents_status.c ext4: remove trailing \n from ext4_warning/ext4_error calls 2016-04-27 01:11:21 -04:00
extents_status.h ext4: move procfs registration code to fs/ext4/sysfs.c 2015-09-23 12:46:17 -04:00
extents.c ext4: use current_time() for inode timestamps 2016-11-14 21:40:10 -05:00
file.c ext4: convert DAX faults to iomap infrastructure 2016-11-20 18:51:24 -05:00
fsync.c ext4: cleanup ext4_sync_parent() 2016-09-05 23:21:43 -04:00
hash.c ext4: remove unused header files 2015-04-02 23:47:42 -04:00
ialloc.c ext4: avoid lockdep warning when inheriting encryption context 2016-11-21 11:52:44 -05:00
indirect.c ext4: refactor direct IO code 2016-05-13 00:44:16 -04:00
inline.c ext4: only set S_DAX if DAX is really supported 2016-11-20 17:32:59 -05:00
inode.c ext4: rip out DAX handling from direct IO path 2016-11-20 18:53:30 -05:00
ioctl.c ext4: use current_time() for inode timestamps 2016-11-14 21:40:10 -05:00
Kconfig ext4 crypto: migrate into vfs's crypto engine 2016-07-10 14:01:03 -04:00
Makefile ext4 crypto: migrate into vfs's crypto engine 2016-07-10 14:01:03 -04:00
mballoc.c ext4: fix stack memory corruption with 64k block size 2016-11-14 21:26:26 -05:00
mballoc.h ext4: add missing KERN_CONT to a few more debugging uses 2016-10-15 09:57:31 -04:00
migrate.c ext4: fix misspellings in comments. 2016-03-09 23:49:05 -05:00
mmp.c fs: have submit_bh users pass in op and flags separately 2016-06-07 13:41:38 -06:00
move_extent.c ext4: enforce online defrag restriction for encrypted files 2016-08-29 15:45:11 -04:00
namei.c ext4: use current_time() for inode timestamps 2016-11-14 21:40:10 -05:00
page-io.c fscrypt: Let fs select encryption index/tweak 2016-11-13 20:18:16 -05:00
readpage.c Merge branch 'akpm' (patches from Andrew) 2016-07-26 19:55:54 -07:00
resize.c ext4: remove trailing \n from ext4_warning/ext4_error calls 2016-04-27 01:11:21 -04:00
super.c ext4: avoid lockdep warning when inheriting encryption context 2016-11-21 11:52:44 -05:00
symlink.c Merge branch 'work.xattr' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-10-10 17:11:50 -07:00
sysfs.c ext4: do not advertise encryption support when disabled 2016-10-12 23:24:51 -04:00
truncate.h ext4: fix races between page faults and hole punching 2015-12-07 14:28:03 -05:00
xattr_security.c switch xattr_handler->set() to passing dentry and inode separately 2016-05-27 15:39:43 -04:00
xattr_trusted.c switch xattr_handler->set() to passing dentry and inode separately 2016-05-27 15:39:43 -04:00
xattr_user.c switch xattr_handler->set() to passing dentry and inode separately 2016-05-27 15:39:43 -04:00
xattr.c ext4: remove parameter from ext4_xattr_ibody_set() 2016-11-14 21:56:48 -05:00
xattr.h ext4: reserve xattr index for the Hurd 2016-07-31 23:38:36 -04:00