On Mon 20-07-15 19:01:06, Oleg Nesterov wrote:
> Move the "fool the lockdep" code from sb_wait_write() into the new
> simple helper, sb_lockdep_release(), called once before return from
> freeze_super().
>
> This is preparation, but imo this makes sense in any case. This way
> we do not hide from lockdep the "write" locks we hold when we call
> s_op->freeze_fs(sb).
>
> Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Good. You can add:
Reviewed-by: Jan Kara <jack@xxxxxxxx>
Honza
> ---
> fs/super.c | 16 ++++++++++------
> 1 files changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/fs/super.c b/fs/super.c
> index d0fdd49..e7ea9f1 100644
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -1236,16 +1236,10 @@ static void sb_wait_write(struct super_block *sb, int level)
> {
> s64 writers;
>
> - /*
> - * We just cycle-through lockdep here so that it does not complain
> - * about returning with lock to userspace
> - */
> rwsem_acquire(&sb->s_writers.lock_map[level-1], 0, 0, _THIS_IP_);
> - rwsem_release(&sb->s_writers.lock_map[level-1], 1, _THIS_IP_);
>
> do {
> DEFINE_WAIT(wait);
> -
> /*
> * We use a barrier in prepare_to_wait() to separate setting
> * of frozen and checking of the counter
> @@ -1261,6 +1255,14 @@ static void sb_wait_write(struct super_block *sb, int level)
> } while (writers);
> }
>
> +static void sb_freeze_release(struct super_block *sb)
> +{
> + int level;
> + /* Avoid the warning from lockdep_sys_exit() */
> + for (level = 0; level < SB_FREEZE_LEVELS; ++level)
> + rwsem_release(sb->s_writers.lock_map + level, 1, _THIS_IP_);
> +}
> +
> /**
> * freeze_super - lock the filesystem and force it into a consistent state
> * @sb: the super to lock
> @@ -1349,6 +1351,7 @@ int freeze_super(struct super_block *sb)
> sb->s_writers.frozen = SB_UNFROZEN;
> smp_wmb();
> wake_up(&sb->s_writers.wait_unfrozen);
> + sb_freeze_release(sb);
> deactivate_locked_super(sb);
> return ret;
> }
> @@ -1358,6 +1361,7 @@ int freeze_super(struct super_block *sb)
> * sees write activity when frozen is set to SB_FREEZE_COMPLETE.
> */
> sb->s_writers.frozen = SB_FREEZE_COMPLETE;
> + sb_freeze_release(sb);
> up_write(&sb->s_umount);
> return 0;
> }
> --
> 1.5.5.1
>
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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