On Sat, Mar 29, 2025 at 09:42:14AM +0100, Christian Brauner wrote:
> The locking guarantees that the superblock is alive and sb->s_root is
> still set. Remove the pointless check.
>
> Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
> ---
> fs/super.c | 19 ++++++-------------
> 1 file changed, 6 insertions(+), 13 deletions(-)
>
> diff --git a/fs/super.c b/fs/super.c
> index 97a17f9d9023..dc14f4bf73a6 100644
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -930,8 +930,7 @@ void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
>
> locked = super_lock_shared(sb);
> if (locked) {
> - if (sb->s_root)
> - f(sb, arg);
> + f(sb, arg);
> super_unlock_shared(sb);
> }
>
> @@ -967,11 +966,8 @@ void iterate_supers_type(struct file_system_type *type,
> spin_unlock(&sb_lock);
>
> locked = super_lock_shared(sb);
> - if (locked) {
> - if (sb->s_root)
> - f(sb, arg);
> - super_unlock_shared(sb);
> - }
> + if (locked)
> + f(sb, arg);
Hey Christian,
I might be trying to be the second(?) user of iterate_supers_type[1]. :)
This change removes the call to super_unlock_shared, which means that
iterate_supers_type returns with the super_lock(s) still held. I'm
guessing that this is a bug and not an intentional change to require the
callback to call super_unlock_shared, right?
--D
[1] https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/commit/?h=health-monitoring&id=3ae9b1d43dcdeaa38e93dc400d1871872ba0e27f
>
> spin_lock(&sb_lock);
> if (p)
> @@ -991,18 +987,15 @@ struct super_block *user_get_super(dev_t dev, bool excl)
>
> spin_lock(&sb_lock);
> list_for_each_entry(sb, &super_blocks, s_list) {
> - if (sb->s_dev == dev) {
> + if (sb->s_dev == dev) {
> bool locked;
>
> sb->s_count++;
> spin_unlock(&sb_lock);
> /* still alive? */
> locked = super_lock(sb, excl);
> - if (locked) {
> - if (sb->s_root)
> - return sb;
> - super_unlock(sb, excl);
> - }
> + if (locked)
> + return sb; /* caller will drop */
> /* nope, got unmounted */
> spin_lock(&sb_lock);
> __put_super(sb);
>
> --
> 2.47.2
>
>
