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author | OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> | 2016-03-10 07:47:25 +0300 |
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committer | Theodore Ts'o <tytso@mit.edu> | 2016-03-10 07:47:25 +0300 |
commit | c0a2ad9b50dd80eeccd73d9ff962234590d5ec93 (patch) | |
tree | e8b522a30500e6085fca1885cb3fd2df6cdd4499 /fs/ext4/ext4_extents.h | |
parent | 2d90c160e5f1d784e180f1e1458d56eee4d7f4f4 (diff) | |
download | linux-c0a2ad9b50dd80eeccd73d9ff962234590d5ec93.tar.xz |
jbd2: fix FS corruption possibility in jbd2_journal_destroy() on umount path
On umount path, jbd2_journal_destroy() writes latest transaction ID
(->j_tail_sequence) to be used at next mount.
The bug is that ->j_tail_sequence is not holding latest transaction ID
in some cases. So, at next mount, there is chance to conflict with
remaining (not overwritten yet) transactions.
mount (id=10)
write transaction (id=11)
write transaction (id=12)
umount (id=10) <= the bug doesn't write latest ID
mount (id=10)
write transaction (id=11)
crash
mount
[recovery process]
transaction (id=11)
transaction (id=12) <= valid transaction ID, but old commit
must not replay
Like above, this bug become the cause of recovery failure, or FS
corruption.
So why ->j_tail_sequence doesn't point latest ID?
Because if checkpoint transactions was reclaimed by memory pressure
(i.e. bdev_try_to_free_page()), then ->j_tail_sequence is not updated.
(And another case is, __jbd2_journal_clean_checkpoint_list() is called
with empty transaction.)
So in above cases, ->j_tail_sequence is not pointing latest
transaction ID at umount path. Plus, REQ_FLUSH for checkpoint is not
done too.
So, to fix this problem with minimum changes, this patch updates
->j_tail_sequence, and issue REQ_FLUSH. (With more complex changes,
some optimizations would be possible to avoid unnecessary REQ_FLUSH
for example though.)
BTW,
journal->j_tail_sequence =
++journal->j_transaction_sequence;
Increment of ->j_transaction_sequence seems to be unnecessary, but
ext3 does this.
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
Diffstat (limited to 'fs/ext4/ext4_extents.h')
0 files changed, 0 insertions, 0 deletions