Hello, On Wed 03-08-11 22:25:48, Toshiyuki Okajima wrote: > On Wed, 3 Aug 2011 11:57:54 +0200 > Jan Kara <jack@xxxxxxx> wrote: > > On Wed 03-08-11 11:42:03, Toshiyuki Okajima wrote: > > > >(2011/08/01 18:57), Jan Kara wrote: > > > >>On Mon 01-08-11 18:45:58, Toshiyuki Okajima wrote: > > > >>>(2011/08/01 17:45), Jan Kara wrote: > > > >>>>On Mon 01-08-11 13:54:51, Toshiyuki Okajima wrote: > > > >>>>>If there are some inodes in orphan list while a filesystem is being > > > >>>>>read-only mounted, we should recommend that pepole umount and then > > > >>>>>mount it when they try to remount with read-write. But the current > > > >>>>>message/comment recommends that they umount and then remount it. > > > <SNIP> > > > >>>>the most... BTW, I guess you didn't really see this message in practice, did > > > >>>>you? > > > >>>No. > > > >>>I have seen this message in practice while quotacheck command was repeatedly > > > >>>executed per an hour. > > > >>Interesting. Are you able to reproduce this? Quotacheck does remount > > > >>read-only + remount read-write but you cannot really remount the filesystem > > > >>read-only when it has orphan inodes and so you should not see those when > > > >>you remount read-write again. Possibly there's race between remounting and > > > >>unlinking... > > > >Yes. I can reproduce it. However, it is not frequently reproduced > > > >by using the original procedure (qutacheck per an hour). So, I made a > > > >reproducer. > > > To tell the truth, I think the race creates the message: > > > ----------------------------------------------------------------------- > > > EXT3-fs: <dev>: couldn't remount RDWR because of > > > unprocessed orphan inode list. Please umount/remount instead. > > > ----------------------------------------------------------------------- > > > which hides a serious problem. > > I've inquired about this at linux-fsdevel (I think you were in CC unless > > I forgot). It's a race in VFS remount code as you properly analyzed below. > > People are working on fixing it but it's not trivial. Filesystem is really > > a wrong place to fix such problem. If there is a trivial fix for ext3 to > > workaround the issue, I can take it but I'm not willing to push anything > > complex - effort should better be spent working on a generic fix. > I also think read-only remount race in VFS layer should be fixed. > However, I think this race depends on ext3/ext4 filesystem > implementation. (Orphan inode list) > So, we should modify ext3/ext4(jbd/jbd2) to fix it. Umm, I don't understand here. If VFS makes sure that there are no files open for writing, no unfinished operations changing the filesystem (e.g. unlink), and no open-but-unlinked files, what remains for ext3 to check? Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- 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
