On Sat 28-01-12 14:45:49, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rjw@xxxxxxx>
>
> Freeze all filesystems during system suspend and (kernel-driven)
> hibernation by calling freeze_supers() for all superblocks and thaw
> them during the subsequent resume with the help of thaw_supers().
>
> This makes filesystems stay in a consistent state in case something
> goes wrong between system suspend (or hibernation) and the subsequent
> resume (e.g. journal replays won't be necessary in those cases). 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/or initrd causing it to become inconsistent with the information
> stored in the hibernation image.
>
> The user-space-driven hibernation (s2disk) is not covered by this
> change, because the freezing of filesystems prevents s2disk from
> accessing device special files it needs to do its job.
>
> This change is based on earlier work by Nigel Cunningham.
>
> Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
> ---
> fs/super.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/fs.h | 3 +
> kernel/power/hibernate.c | 11 +++++--
> kernel/power/power.h | 23 --------------
> kernel/power/suspend.c | 42 +++++++++++++++++++++++++++
> 5 files changed, 128 insertions(+), 24 deletions(-)
>
> Index: linux/fs/super.c
> ===================================================================
> --- linux.orig/fs/super.c
> +++ linux/fs/super.c
> @@ -594,6 +594,79 @@ void iterate_supers_type(struct file_sys
> EXPORT_SYMBOL(iterate_supers_type);
>
> /**
> + * thaw_supers - call thaw_super() for all superblocks
> + */
> +void thaw_supers(void)
> +{
> + struct super_block *sb, *p = NULL;
> +
> + spin_lock(&sb_lock);
> + list_for_each_entry(sb, &super_blocks, s_list) {
> + if (list_empty(&sb->s_instances))
> + continue;
> + sb->s_count++;
> + spin_unlock(&sb_lock);
> +
> + if (sb->s_flags & MS_FROZEN) {
> + thaw_super(sb);
> + sb->s_flags &= ~MS_FROZEN;
> + }
> +
> + spin_lock(&sb_lock);
> + if (p)
> + __put_super(p);
> + p = sb;
> + }
> + if (p)
> + __put_super(p);
> + spin_unlock(&sb_lock);
> +}
At least for thawing you can use iterate_supers() helper.
> +/**
> + * freeze_supers - call freeze_super() for all superblocks
> + */
> +int freeze_supers(void)
> +{
> + struct super_block *sb, *p = NULL;
> + int error = 0;
> +
> + spin_lock(&sb_lock);
> + /*
> + * Freeze in reverse order so filesystems depending on others are
> + * frozen in the right order (eg. loopback on ext3).
> + */
Ho, hum, are you sure the order in super_blocks list is the one you need?
Maybe it is but I'm not sure you are guaranteed it is. I've added Al to CC,
he'll likely have opinion on this...
> + list_for_each_entry_reverse(sb, &super_blocks, s_list) {
> + if (list_empty(&sb->s_instances))
> + continue;
> + sb->s_count++;
> + spin_unlock(&sb_lock);
> +
> + if (sb->s_root && sb->s_frozen != SB_FREEZE_TRANS
> + && !(sb->s_flags & MS_RDONLY)) {
> + error = freeze_super(sb);
> + if (!error)
> + sb->s_flags |= MS_FROZEN;
> + }
> +
> + spin_lock(&sb_lock);
> + if (error)
> + break;
> + if (p)
> + __put_super(p);
> + p = sb;
> + }
> + if (p)
> + __put_super(p);
> + spin_unlock(&sb_lock);
> +
> + if (error)
> + thaw_supers();
> +
> + return error;
> +}
> +
> +
> +/**
> * get_super - get the superblock of a device
> * @bdev: device to get the superblock for
> *
Honza
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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