Hi Jan, >> >> >> If all the write operations were journaled, then this patch would not allow >> ext4 filesystem to have any dirty data after its frozen. >> (as journal_start() would block). >> >> I think the only one candidate that creates dirty data without calling >> ext4_journal_start() is mmapped? > No, the problem is in any write path. The problem is with operations > that happen during the phase when s_frozen == SB_FREEZE_WRITE. These > operations dirty the filesystem but running sync may easily miss them. > During this phase journal is not frozen so that does not help you in any > way. > > Honza Ok! No new transaction can really start after the journal is frozen. But we can have dirty data after SB_FREEZE_WRITE and before SB_FREEZE_TRANS. I agree with you. However, can this be fixed by adding a sync_filesystem() in freeze_super() after the sb->s_op->freeze_fs() is over? So then essentially, when freeze_super() returns, the page cache is clean? I do definitely agree that the fix is to add a lock for mutual exclusion between freeze filesystem and writes to a frozen filesystem. Thanks! Regards, Surbhi. -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
