On Thu, Feb 25, 2016 at 08:28:27PM +0900, OGAWA Hirofumi wrote: > On umount path, jbd2_journal_destroy() writes latest transaction ID > (->j_tail_sequence) to be used at next mount. > > The bug is that ->j_tail_sequence is not holding latest transaction ID > in some cases. So, at next mount, there is chance to conflict with > remaining (not overwritten yet) transactions. > > mount (id=10) > write transaction (id=11) > write transaction (id=12) > umount (id=10) <= the bug doesn't write latest ID > > mount (id=10) > write transaction (id=11) > crash > > recovery > transaction (id=11) > transaction (id=12) <= valid transaction ID, but old commit > must not replay > > Like above, this bug become the cause of recovery failure, or FS > corruption. > > So why ->j_tail_sequence doesn't point latest ID? > > Because if checkpoint transactions was reclaimed by memory pressure > (i.e. bdev_try_to_free_page()), then ->j_tail_sequence is not updated. > (And another case is, __jbd2_journal_clean_checkpoint_list() is called > with empty transaction.) > > So in above cases, ->j_tail_sequence is not pointing latest > transaction ID at umount path. Plus, REQ_FLUSH for checkpoint is not > done too. > > So, to fix this problem with minimum changes, this patch updates > ->j_tail_sequence, and issue REQ_FLUSH. (With more complex changes, > some optimizations would be possible to avoid unnecessary REQ_FLUSH > for example though.) > > BTW, > > journal->j_tail_sequence = > ++journal->j_transaction_sequence; > > Increment of ->j_transaction_sequence seems to be unnecessary, but > ext3 does this. > > Signed-off-by: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx> Thanks, applied. - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
