On Thu, Jul 11 2024, wangjianjian (C) wrote:
> On 2024/7/11 16:35, Luis Henriques (SUSE) wrote:
>> When a full journal commit is on-going, any fast commit has to be enqueued
>> into a different queue: FC_Q_STAGING instead of FC_Q_MAIN. This enqueueing
>> is done only once, i.e. if an inode is already queued in a previous fast
>> commit entry it won't be enqueued again. However, if a full commit starts
>> _after_ the inode is enqueued into FC_Q_MAIN, the next fast commit needs to
>> be done into FC_Q_STAGING. And this is not being done in function
>> ext4_fc_track_template().
>> This patch fixes the issue by re-enqueuing an inode into the STAGING queue
>> during the fast commit clean-up callback if it has a tid (i_sync_tid)
>> greater than the one being handled. The STAGING queue will then be spliced
>> back into MAIN.
>> This bug was found using fstest generic/047. This test creates several 32k
>> bytes files, sync'ing each of them after it's creation, and then shutting
>> down the filesystem. Some data may be loss in this operation; for example a
>> file may have it's size truncated to zero.
>> Signed-off-by: Luis Henriques (SUSE) <luis.henriques@xxxxxxxxx>
>> ---
>> Hi!
>> v4 of this patch enqueues the inode into STAGING *only* if the current tid
>> is non-zero. It will be zero when doing an fc commit, and this would mean
>> to always re-enqueue the inode. This fixes the regressions caught by Ted
>> in v3 with fstests generic/472 generic/496 generic/643.
>> Also, since 2nd patch of v3 has already been merged, I've rebased this patch
>> to be applied on top of it.
>> fs/ext4/fast_commit.c | 10 ++++++++++
>> 1 file changed, 10 insertions(+)
>> diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c
>> index 3926a05eceee..facbc8dbbaa2 100644
>> --- a/fs/ext4/fast_commit.c
>> +++ b/fs/ext4/fast_commit.c
>> @@ -1290,6 +1290,16 @@ static void ext4_fc_cleanup(journal_t *journal, int full, tid_t tid)
>> EXT4_STATE_FC_COMMITTING);
>> if (tid_geq(tid, iter->i_sync_tid))
>> ext4_fc_reset_inode(&iter->vfs_inode);
>> + } else if (tid) {
>> + /*
>> + * If the tid is valid (i.e. non-zero) re-enqueue the
> one quick question about tid, if one disk is using long time and its tid get
> wrapped to 0, is it a valid seq? I don't find code handling this situation.
Hmm... OK. So, to answer to your question, the 'tid' is expected to wrap.
That's why we use:
if (tid_geq(tid, iter->i_sync_tid))
instead of:
if (tid >= iter->i_sync_tid)
(The second patch in v3 actually fixed a few places where the tid_*()
helpers weren't being used.)
But your question shows me that my patch is wrong as '0' may actually be a
valid 'tid' value.
Cheers,
--
Luís
>> + * inode into STAGING, which will then be splice back
>> + * into MAIN
>> + */
>> + list_add_tail(&EXT4_I(&iter->vfs_inode)->i_fc_list,
>> + &sbi->s_fc_q[FC_Q_STAGING]);
>> + }
>> +
>> /* Make sure EXT4_STATE_FC_COMMITTING bit is clear */
>> smp_mb();
>> #if (BITS_PER_LONG < 64)
>>
> --
> Regards
>
