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acrn-kernel/fs/jbd2
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Zhihao Cheng 45b99c35f8 jbd2: fix data missing when reusing bh which is ready to be checkpointed 
commit e6b9bd7290 upstream.

Following process will make data lost and could lead to a filesystem
corrupted problem:

1. jh(bh) is inserted into T1->t_checkpoint_list, bh is dirty, and
   jh->b_transaction = NULL
2. T1 is added into journal->j_checkpoint_transactions.
3. Get bh prepare to write while doing checkpoing:
           PA				    PB
   do_get_write_access             jbd2_log_do_checkpoint
    spin_lock(&jh->b_state_lock)
     if (buffer_dirty(bh))
      clear_buffer_dirty(bh)   // clear buffer dirty
       set_buffer_jbddirty(bh)
				    transaction =
				    journal->j_checkpoint_transactions
				    jh = transaction->t_checkpoint_list
				    if (!buffer_dirty(bh))
		                      __jbd2_journal_remove_checkpoint(jh)
				      // bh won't be flushed
		                    jbd2_cleanup_journal_tail
    __jbd2_journal_file_buffer(jh, transaction, BJ_Reserved)
4. Aborting journal/Power-cut before writing latest bh on journal area.

In this way we get a corrupted filesystem with bh's data lost.

Fix it by moving the clearing of buffer_dirty bit just before the call
to __jbd2_journal_file_buffer(), both bit clearing and jh->b_transaction
assignment are under journal->j_list_lock locked, so that
jbd2_log_do_checkpoint() will wait until jh's new transaction fininshed
even bh is currently not dirty. And journal_shrink_one_cp_list() won't
remove jh from checkpoint list if the buffer head is reused in
do_get_write_access().

Fetch a reproducer in [Link].

Link: https://bugzilla.kernel.org/show_bug.cgi?id=216898
Cc: <stable@kernel.org>
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: zhanchengbin <zhanchengbin1@huawei.com>
Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230110015327.1181863-1-chengzhihao1@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2023-03-10 09:34:20 +01:00
..
Kconfig
…
Makefile
…
checkpoint.c jbd2: rename jbd_debug() to jbd2_debug() 2022-08-02 23:52:19 -04:00
commit.c jbd2: wake up journal waiters in FIFO order, not LIFO 2022-09-30 23:46:52 -04:00
journal.c - Yu Zhao's Multi-Gen LRU patches are here. They've been under test in 2022-10-10 17:53:04 -07:00
recovery.c - Yu Zhao's Multi-Gen LRU patches are here. They've been under test in 2022-10-10 17:53:04 -07:00
revoke.c jbd2: rename jbd_debug() to jbd2_debug() 2022-08-02 23:52:19 -04:00
transaction.c jbd2: fix data missing when reusing bh which is ready to be checkpointed 2023-03-10 09:34:20 +01:00