This is a note to let you know that I've just added the patch titled
jbd2: recheck chechpointing non-dirty buffer
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
jbd2-recheck-chechpointing-non-dirty-buffer.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From c2d6fd9d6f35079f1669f0100f05b46708c74b7f Mon Sep 17 00:00:00 2001
From: Zhang Yi <yi.zhang@xxxxxxxxxx>
Date: Tue, 6 Jun 2023 21:59:23 +0800
Subject: jbd2: recheck chechpointing non-dirty buffer
From: Zhang Yi <yi.zhang@xxxxxxxxxx>
commit c2d6fd9d6f35079f1669f0100f05b46708c74b7f upstream.
There is a long-standing metadata corruption issue that happens from
time to time, but it's very difficult to reproduce and analyse, benefit
from the JBD2_CYCLE_RECORD option, we found out that the problem is the
checkpointing process miss to write out some buffers which are raced by
another do_get_write_access(). Looks below for detail.
jbd2_log_do_checkpoint() //transaction X
//buffer A is dirty and not belones to any transaction
__buffer_relink_io() //move it to the IO list
__flush_batch()
write_dirty_buffer()
do_get_write_access()
clear_buffer_dirty
__jbd2_journal_file_buffer()
//add buffer A to a new transaction Y
lock_buffer(bh)
//doesn't write out
__jbd2_journal_remove_checkpoint()
//finish checkpoint except buffer A
//filesystem corrupt if the new transaction Y isn't fully write out.
Due to the t_checkpoint_list walking loop in jbd2_log_do_checkpoint()
have already handles waiting for buffers under IO and re-added new
transaction to complete commit, and it also removing cleaned buffers,
this makes sure the list will eventually get empty. So it's fine to
leave buffers on the t_checkpoint_list while flushing out and completely
stop using the t_checkpoint_io_list.
Cc: stable@xxxxxxxxxxxxxxx
Suggested-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx>
Tested-by: Zhihao Cheng <chengzhihao1@xxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Link: https://lore.kernel.org/r/20230606135928.434610-2-yi.zhang@xxxxxxxxxxxxxxx
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/jbd2/checkpoint.c | 102 ++++++++++++++-------------------------------------
1 file changed, 29 insertions(+), 73 deletions(-)
--- a/fs/jbd2/checkpoint.c
+++ b/fs/jbd2/checkpoint.c
@@ -58,28 +58,6 @@ static inline void __buffer_unlink(struc
}
/*
- * Move a buffer from the checkpoint list to the checkpoint io list
- *
- * Called with j_list_lock held
- */
-static inline void __buffer_relink_io(struct journal_head *jh)
-{
- transaction_t *transaction = jh->b_cp_transaction;
-
- __buffer_unlink_first(jh);
-
- if (!transaction->t_checkpoint_io_list) {
- jh->b_cpnext = jh->b_cpprev = jh;
- } else {
- jh->b_cpnext = transaction->t_checkpoint_io_list;
- jh->b_cpprev = transaction->t_checkpoint_io_list->b_cpprev;
- jh->b_cpprev->b_cpnext = jh;
- jh->b_cpnext->b_cpprev = jh;
- }
- transaction->t_checkpoint_io_list = jh;
-}
-
-/*
* Check a checkpoint buffer could be release or not.
*
* Requires j_list_lock
@@ -183,6 +161,7 @@ __flush_batch(journal_t *journal, int *b
struct buffer_head *bh = journal->j_chkpt_bhs[i];
BUFFER_TRACE(bh, "brelse");
__brelse(bh);
+ journal->j_chkpt_bhs[i] = NULL;
}
*batch_count = 0;
}
@@ -242,6 +221,11 @@ restart:
jh = transaction->t_checkpoint_list;
bh = jh2bh(jh);
+ /*
+ * The buffer may be writing back, or flushing out in the
+ * last couple of cycles, or re-adding into a new transaction,
+ * need to check it again until it's unlocked.
+ */
if (buffer_locked(bh)) {
get_bh(bh);
spin_unlock(&journal->j_list_lock);
@@ -287,28 +271,32 @@ restart:
}
if (!buffer_dirty(bh)) {
BUFFER_TRACE(bh, "remove from checkpoint");
- if (__jbd2_journal_remove_checkpoint(jh))
- /* The transaction was released; we're done */
+ /*
+ * If the transaction was released or the checkpoint
+ * list was empty, we're done.
+ */
+ if (__jbd2_journal_remove_checkpoint(jh) ||
+ !transaction->t_checkpoint_list)
goto out;
- continue;
+ } else {
+ /*
+ * We are about to write the buffer, it could be
+ * raced by some other transaction shrink or buffer
+ * re-log logic once we release the j_list_lock,
+ * leave it on the checkpoint list and check status
+ * again to make sure it's clean.
+ */
+ BUFFER_TRACE(bh, "queue");
+ get_bh(bh);
+ J_ASSERT_BH(bh, !buffer_jwrite(bh));
+ journal->j_chkpt_bhs[batch_count++] = bh;
+ transaction->t_chp_stats.cs_written++;
+ transaction->t_checkpoint_list = jh->b_cpnext;
}
- /*
- * Important: we are about to write the buffer, and
- * possibly block, while still holding the journal
- * lock. We cannot afford to let the transaction
- * logic start messing around with this buffer before
- * we write it to disk, as that would break
- * recoverability.
- */
- BUFFER_TRACE(bh, "queue");
- get_bh(bh);
- J_ASSERT_BH(bh, !buffer_jwrite(bh));
- journal->j_chkpt_bhs[batch_count++] = bh;
- __buffer_relink_io(jh);
- transaction->t_chp_stats.cs_written++;
+
if ((batch_count == JBD2_NR_BATCH) ||
- need_resched() ||
- spin_needbreak(&journal->j_list_lock))
+ need_resched() || spin_needbreak(&journal->j_list_lock) ||
+ jh2bh(transaction->t_checkpoint_list) == journal->j_chkpt_bhs[0])
goto unlock_and_flush;
}
@@ -322,38 +310,6 @@ restart:
goto restart;
}
- /*
- * Now we issued all of the transaction's buffers, let's deal
- * with the buffers that are out for I/O.
- */
-restart2:
- /* Did somebody clean up the transaction in the meanwhile? */
- if (journal->j_checkpoint_transactions != transaction ||
- transaction->t_tid != this_tid)
- goto out;
-
- while (transaction->t_checkpoint_io_list) {
- jh = transaction->t_checkpoint_io_list;
- bh = jh2bh(jh);
- if (buffer_locked(bh)) {
- get_bh(bh);
- spin_unlock(&journal->j_list_lock);
- wait_on_buffer(bh);
- /* the journal_head may have gone by now */
- BUFFER_TRACE(bh, "brelse");
- __brelse(bh);
- spin_lock(&journal->j_list_lock);
- goto restart2;
- }
-
- /*
- * Now in whatever state the buffer currently is, we
- * know that it has been written out and so we can
- * drop it from the list
- */
- if (__jbd2_journal_remove_checkpoint(jh))
- break;
- }
out:
spin_unlock(&journal->j_list_lock);
result = jbd2_cleanup_journal_tail(journal);
Patches currently in stable-queue which might be from yi.zhang@xxxxxxxxxx are
queue-6.1/jbd2-recheck-chechpointing-non-dirty-buffer.patch
