(CCed Jan, the author of freeze code) On 08/14/2012 10:12 PM, Marco Stornelli wrote: > Il 14/08/2012 15:53, Liu Bo ha scritto: >> On 08/14/2012 08:59 PM, Marco Stornelli wrote: >>> Il 14/08/2012 07:01, liub.liubo@xxxxxxxxx ha scritto: >>>> From: Liu Bo <bo.li.liu@xxxxxxxxxx> >>>> >>>> I found this while testing xfstests 068, the story is >>>> >>>> t1 t2 >>>> sys_sync thaw_super >>>> iterate_supers >>>> down_read(sb->s_umount) down_write(sb->s_umount) --->wait for t1 >>>> sync_fs (with wait mode) >>>> start_transaction >>>> sb_start_intwrite --------------------> wait for t2 to set s_writers.frozen to SB_UNFROZEN >>>> >>>> In this patch, I add an helper sb_start_intwrite_trylock() and use it before we >>>> start_transaction in sync_fs() with wait mode so that we won't hit the deadlock. >>>> >>> >>> IMHO, we should avoid to call the sync operation on a frozen fs. The freeze operation, indeed, already include a sync operation. >>> According to man page, no other operation should modify the fs after the freeze. >>> So for me the modification is inside sync_filesystem (and sync_one_sb). >> >> Do you mean that we should add the trylock check in sync_filesystem? >> >> But it seems to be useless because we already run into down_read(sb->s_umount) before starting sync_one_sb(). >> >> thanks, >> liubo >> > > I meant that we should check if there are in a "complete" freeze state (according to the "states" of a freeze transaction) and simply skip the sync operation. > I'm ok with it. What do you think about it, Jan? Any comments? thanks, liubo > Marco -- 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
