[Devel] [PATCH RHEL7 COMMIT] ms/jbd2: clear dirty flag when revoking a buffer from an older transaction
Konstantin Khorenko
khorenko at virtuozzo.com
Thu Aug 22 14:36:32 MSK 2019
The commit is pushed to "branch-rh7-3.10.0-957.27.2.vz7.107.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-957.27.2.vz7.107.5
------>
commit e0e0d13f31f1f86380ae117e5773d82e47454461
Author: zhangyi (F) <yi.zhang at huawei.com>
Date: Thu Aug 22 14:36:30 2019 +0300
ms/jbd2: clear dirty flag when revoking a buffer from an older transaction
Now, we capture a data corruption problem on ext4 while we're truncating
an extent index block. Imaging that if we are revoking a buffer which
has been journaled by the committing transaction, the buffer's jbddirty
flag will not be cleared in jbd2_journal_forget(), so the commit code
will set the buffer dirty flag again after refile the buffer.
fsx kjournald2
jbd2_journal_commit_transaction
jbd2_journal_revoke commit phase 1~5...
jbd2_journal_forget
belongs to older transaction commit phase 6
jbddirty not clear __jbd2_journal_refile_buffer
__jbd2_journal_unfile_buffer
test_clear_buffer_jbddirty
mark_buffer_dirty
Finally, if the freed extent index block was allocated again as data
block by some other files, it may corrupt the file data after writing
cached pages later, such as during unmount time. (In general,
clean_bdev_aliases() related helpers should be invoked after
re-allocation to prevent the above corruption, but unfortunately we
missed it when zeroout the head of extra extent blocks in
ext4_ext_handle_unwritten_extents()).
This patch mark buffer as freed and set j_next_transaction to the new
transaction when it already belongs to the committing transaction in
jbd2_journal_forget(), so that commit code knows it should clear dirty
bits when it is done with the buffer.
This problem can be reproduced by xfstests generic/455 easily with
seeds (3246 3247 3248 3249).
https://jira.sw.ru/browse/PSBM-96719
Signed-off-by: zhangyi (F) <yi.zhang at huawei.com>
Signed-off-by: Theodore Ts'o <tytso at mit.edu>
Reviewed-by: Jan Kara <jack at suse.cz>
Cc: stable at vger.kernel.org
(cherry picked from commit 904cdbd41d749a476863a0ca41f6f396774f26e4)
Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
=====================
Patchset description:
ext4/jbd2: port data corruption fixes from ms
While investigating the data corruption on vzt-ploop-check test, when we
detect one page in file which contains wrong data, we were lucky to have
exact the same pattern in bad page each time. So we've added a small
debug to fail on setting a dirty bit for a page if it contains the
pattern, in the begining of __set_page_dirty and
__set_page_dirty_nobuffers.
We've got a crash, which looks related with the ported patches:
crash> bt
PID: 17855 TASK: ffff8cfb19144000 CPU: 3 COMMAND: "jbd2/ploop45613"
#0 [ffff8cfcb6fdf8a0] machine_kexec at ffffffff9e2643c4
#1 [ffff8cfcb6fdf900] __crash_kexec at ffffffff9e32d672
#2 [ffff8cfcb6fdf9d0] crash_kexec at ffffffff9e32d760
#3 [ffff8cfcb6fdf9e8] oops_end at ffffffff9e99f858
#4 [ffff8cfcb6fdfa10] die at ffffffff9e22f88b
#5 [ffff8cfcb6fdfa40] do_trap at ffffffff9e99eee0
#6 [ffff8cfcb6fdfa90] do_invalid_op at ffffffff9e22c1d4
#7 [ffff8cfcb6fdfb40] invalid_op at ffffffff9e9a928e
[exception RIP: page_check_corruption_pattern+397]
RIP: ffffffff9e3d719d RSP: ffff8cfcb6fdfbf8 RFLAGS: 00010246
RAX: ffff8cfcb6fdffd8 RBX: 00007303b0607000 RCX: 000000010025603b
RDX: 0000000000000190 RSI: 0000000000000000 RDI: 0000000000000206
RBP: ffff8cfcb6fdfc10 R8: ffff8cfbe6c19e00 R9: 0000000000000001
R10: 0000000000000004 R11: 0000000000000005 R12: ffffe079873e7e40
R13: ffff8cfca7bc3ab0 R14: ffff8cfc351d5a90 R15: 0000000000000000
ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018
#8 [ffff8cfcb6fdfbf0] page_check_corruption_pattern at ffffffff9e3d70d6
#9 [ffff8cfcb6fdfc18] __set_page_dirty at ffffffff9e499cb5
#10 [ffff8cfcb6fdfc50] mark_buffer_dirty at ffffffff9e499efa
#11 [ffff8cfcb6fdfc70] __jbd2_journal_temp_unlink_buffer at ffffffffc048893a [jbd2]
#12 [ffff8cfcb6fdfc80] __jbd2_journal_refile_buffer at ffffffffc048ac08 [jbd2]
#13 [ffff8cfcb6fdfca8] jbd2_journal_commit_transaction at ffffffffc048c1e0 [jbd2]
#14 [ffff8cfcb6fdfe48] kjournald2 at ffffffffc0491f79 [jbd2]
#15 [ffff8cfcb6fdfec8] kthread at ffffffff9e2c4661
Before ("jbd2: clear dirty flag when revoking a buffer from an older
transaction") revoken buffer/page can be wrongly marked dirty, and later
be wrongly written to disk. Other patches from the same series might be
also helpful.
https://jira.sw.ru/browse/PSBM-96719
zhangyi (F) (3):
jbd2: clear dirty flag when revoking a buffer from an older
transaction
jbd2: discard dirty data when forgetting an un-journalled buffer
ext4: cleanup clean_bdev_aliases() calls
---
fs/jbd2/transaction.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 9082eae76518..c182906a8bc4 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -1494,14 +1494,21 @@ int jbd2_journal_forget (handle_t *handle, struct buffer_head *bh)
/* However, if the buffer is still owned by a prior
* (committing) transaction, we can't drop it yet... */
JBUFFER_TRACE(jh, "belongs to older transaction");
- /* ... but we CAN drop it from the new transaction if we
- * have also modified it since the original commit. */
+ /* ... but we CAN drop it from the new transaction through
+ * marking the buffer as freed and set j_next_transaction to
+ * the new transaction, so that not only the commit code
+ * knows it should clear dirty bits when it is done with the
+ * buffer, but also the buffer can be checkpointed only
+ * after the new transaction commits. */
- if (jh->b_next_transaction) {
- J_ASSERT(jh->b_next_transaction == transaction);
+ set_buffer_freed(bh);
+
+ if (!jh->b_next_transaction) {
spin_lock(&journal->j_list_lock);
- jh->b_next_transaction = NULL;
+ jh->b_next_transaction = transaction;
spin_unlock(&journal->j_list_lock);
+ } else {
+ J_ASSERT(jh->b_next_transaction == transaction);
/*
* only drop a reference if this transaction modified
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