Messages in this thread | | | Date | Wed, 3 Aug 2011 19:29:22 +0200 | From | Pavel Machek <> | Subject | Re: [RFC][PATCH] PM / Freezer: Freeze filesystems along with freezing processes (was: Re: PM / hibernate xfs lock up / xfs_reclaim_inodes_ag) |
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Hi!
> Freeze all filesystems during the freezing of tasks by calling > freeze_bdev() for each of them and thaw them during the thawing > of tasks with the help of thaw_bdev(). > > This is needed by hibernation, because some filesystems (e.g. XFS) > deadlock with the preallocation of memory used by it if the memory > pressure caused by it is too heavy. > > The additional benefit of this change is that, if something goes > wrong after filesystems have been frozen, they will stay in a > consistent state and journal replays won't be necessary (e.g. after > a failing suspend or resume). In particular, this should help to > solve a long-standing issue that in some cases during resume from > hibernation the boot loader causes the journal to be replied for the > filesystem containing the kernel image and initrd causing it to > become inconsistent with the information stored in the hibernation > image.
> +/** > + * freeze_filesystems - Force all filesystems into a consistent state. > + */ > +void freeze_filesystems(void) > +{ > + struct super_block *sb; > + > + lockdep_off();
Ouch. So... why do we need to silence this?
> + /* > + * Freeze in reverse order so filesystems dependant upon others are > + * frozen in the right order (eg. loopback on ext3). > + */ > + list_for_each_entry_reverse(sb, &super_blocks, s_list) { > + if (!sb->s_root || !sb->s_bdev || > + (sb->s_frozen == SB_FREEZE_TRANS) || > + (sb->s_flags & MS_RDONLY) || > + (sb->s_flags & MS_FROZEN)) > + continue;
Should we stop NFS from modifying remote server, too?
Plus... ext3 writes to read-only filesystems on mount; not sure if it does it later. But RDONLY means 'user cant write to it' not 'bdev will not be modified'. Should we freeze all?
How can 'already frozen' happen?
> + list_for_each_entry(sb, &super_blocks, s_list) > + if (sb->s_flags & MS_FROZEN) { > + sb->s_flags &= ~MS_FROZEN; > + thaw_bdev(sb->s_bdev, sb); > + }
...because we'll unfreeze it even if we did not freeze it...
Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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