iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

jbd2: fix data missing when reusing bh which is ready to be checkpointed

Browse Source 
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>
This commit is contained in:
Zhihao Cheng 2023-01-10 09:53:27 +08:00 committed by Theodore Ts'o
parent 3039d8b869
commit e6b9bd7290
1 changed files with 29 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

50
fs/jbd2/transaction.c
View File

@ -1010,36 +1010,28 @@ repeat:
* ie. locked but not dirty) or tune2fs (which may actually have
* the buffer dirtied, ugh.) */
if (buffer_dirty(bh)) {
if (buffer_dirty(bh) && jh->b_transaction) {
warn_dirty_buffer(bh);
/*
* First question: is this buffer already part of the current
* transaction or the existing committing transaction?
*/
if (jh->b_transaction) {
J_ASSERT_JH(jh,
jh->b_transaction == transaction ||
jh->b_transaction ==
journal->j_committing_transaction);
if (jh->b_next_transaction)
J_ASSERT_JH(jh, jh->b_next_transaction ==
transaction);
warn_dirty_buffer(bh);
}
/*
* In any case we need to clean the dirty flag and we must
* do it under the buffer lock to be sure we don't race
* with running write-out.
* We need to clean the dirty flag and we must do it under the
* buffer lock to be sure we don't race with running write-out.
*/
JBUFFER_TRACE(jh, "Journalling dirty buffer");
clear_buffer_dirty(bh);
/*
* The buffer is going to be added to BJ_Reserved list now and
* nothing guarantees jbd2_journal_dirty_metadata() will be
* ever called for it. So we need to set jbddirty bit here to
* make sure the buffer is dirtied and written out when the
* journaling machinery is done with it.
*/
set_buffer_jbddirty(bh);
}
unlock_buffer(bh);
error = -EROFS;
if (is_handle_aborted(handle)) {
spin_unlock(&jh->b_state_lock);
unlock_buffer(bh);
goto out;
}
error = 0;
@ -1049,8 +1041,10 @@ repeat:
* b_next_transaction points to it
*/
if (jh->b_transaction == transaction ||
jh->b_next_transaction == transaction)
jh->b_next_transaction == transaction) {
unlock_buffer(bh);
goto done;
}
/*
* this is the first time this transaction is touching this buffer,
@ -1074,10 +1068,24 @@ repeat:
*/
smp_wmb();
spin_lock(&journal->j_list_lock);
if (test_clear_buffer_dirty(bh)) {
/*
* Execute buffer dirty clearing and jh->b_transaction
* assignment under journal->j_list_lock locked to
* prevent bh being removed from checkpoint list if
* the buffer is in an intermediate state (not dirty
* and jh->b_transaction is NULL).
*/
JBUFFER_TRACE(jh, "Journalling dirty buffer");
set_buffer_jbddirty(bh);
}
__jbd2_journal_file_buffer(jh, transaction, BJ_Reserved);
spin_unlock(&journal->j_list_lock);
unlock_buffer(bh);
goto done;
}
unlock_buffer(bh);
/*
* If there is already a copy-out version of this buffer, then we don't
* need to make another one