Dmitry Monakhov wrote: > Jan Kara <jack@xxxxxxx> writes: > >>> The fact is that I've been able to reproduce the problem on LVM block >>> devices, and sd* block devices so it's definitely not a loop device >>> specific problem. >>> >>> By the way, I tried several other things other than "echo s >>>> /proc/sysrq_trigger" I tried multiple sync followed with a one minute >>> "sleep", >>> >>> "echo 3 >/proc/sys/vm/drop_caches" seems to lower the chances of "hash >>> changes" but doesn't stops them. >> Strange. When I use sync(1) in your script and use /dev/sda5 instead of a >> /dev/loop0, I cannot reproduce the problem (was running the script for >> something like an hour). > Theoretically some pages may exist after rw=>ro remount > because of generic race between write/sync, And they will be written > in by writepage if page already has buffers. This not happen in ext4 > because. Each time it try to perform writepages it try to start_journal > and this result in EROFS. > The race bug will be closed some day but new one may appear again. > > Let's be honest and change ext3 writepage like follows: > - check ROFS flag inside write page > - dump writepage's errors. > > sounds like the wrong approach to me, we really need to fix the root cause and make remount,ro finish the job, I think. Throwing away writes which an application already thinks are completed just because remount,ro didn't keep up sounds like a bad idea. I think I would much rather have the write complete shortly after the readonly transition, if I had to choose... I haven't looked at these paths at all but just hand-wavily, remount,ro should follow pretty much the same path as freeze, I think. And if freeze isn't getting everything on-disk we have an even bigger problem. -Eric -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
