Re: [PATCH 3/3] vfs: fix filesystem_sync vs write race on rw=>ro remount v2

[Jan Kara <jack@suse.cz>]

On Sat 27-02-10 03:25:49, Dmitry Monakhov wrote:
> +/**
> + * Check whenever is it possible to remount given sb to readonly.
> + * @sb : super block in question
> + *
> + * Caller is responsible to set ST_REMOUNT_RO state before the call.
> + */
> +int fs_may_remount_ro(struct super_block *sb)
> +{
> +	struct vfsmount *mnt;
> +	int ret = 1;
> +	spin_lock(&vfsmount_lock);
> +	list_for_each_entry(mnt, &sb->s_vfsmount, mnt_sb_list) {
> +		ret = !mnt_check_writers(mnt, 0);
> +		if (ret)
> +			break;
> +	}
> +	spin_unlock(&vfsmount_lock);
> +	/*
> +	 * If new writer appears after we have checked all vfsmounts.
> +	 * Then ST_REMOUNT_RO bit will be cleared.
> +	 */
> +	if (!test_bit(ST_REMOUNT_RO, &sb->s_state))
> +		ret = 0;
> +	return ret;
> +}
  This misses the case when the superblock as unlinked-but-open files.
In such case we have to fail remount RO as well. The original
fs_may_remount_ro checks for that..

								Honza
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR