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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