On Wed, May 31, 2023 at 09:57:37AM +0000, Qi Zheng wrote:
> From: Kirill Tkhai <tkhai@xxxxx>
>
> The patch makes s_dentry_lru and s_inode_lru be destroyed
> later from the workqueue. This is preparation to split
> unregister_shrinker(super_block::s_shrink) in two stages,
> and to call finalize stage from destroy_super_work().
>
> Note, that generic filesystem shrinker unregistration
> is safe to be split in two stages right after this
> patch, since super_cache_count() and super_cache_scan()
> have a deal with s_dentry_lru and s_inode_lru only.
>
> But there are two exceptions: XFS and SHMEM, which
> define .nr_cached_objects() and .free_cached_objects()
> callbacks. These two do not allow us to do the splitting
> right after this patch. They touch fs-specific data,
> which is destroyed earlier, than destroy_super_work().
> So, we can't call unregister_shrinker_delayed_finalize()
> from destroy_super_work() because of them, and next
> patches make preparations to make this possible.
>
> Signed-off-by: Kirill Tkhai <tkhai@xxxxx>
> Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
> ---
> fs/super.c | 17 +++++------------
> 1 file changed, 5 insertions(+), 12 deletions(-)
>
> diff --git a/fs/super.c b/fs/super.c
> index 8d8d68799b34..2ce4c72720f3 100644
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -159,6 +159,11 @@ static void destroy_super_work(struct work_struct *work)
> destroy_work);
> int i;
>
> + WARN_ON(list_lru_count(&s->s_dentry_lru));
> + WARN_ON(list_lru_count(&s->s_inode_lru));
> + list_lru_destroy(&s->s_dentry_lru);
> + list_lru_destroy(&s->s_inode_lru);
> +
> for (i = 0; i < SB_FREEZE_LEVELS; i++)
> percpu_free_rwsem(&s->s_writers.rw_sem[i]);
> kfree(s);
> @@ -177,8 +182,6 @@ static void destroy_unused_super(struct super_block *s)
> if (!s)
> return;
> up_write(&s->s_umount);
> - list_lru_destroy(&s->s_dentry_lru);
> - list_lru_destroy(&s->s_inode_lru);
> security_sb_free(s);
> put_user_ns(s->s_user_ns);
> kfree(s->s_subtype);
> @@ -287,8 +290,6 @@ static void __put_super(struct super_block *s)
> {
> if (!--s->s_count) {
> list_del_init(&s->s_list);
> - WARN_ON(s->s_dentry_lru.node);
> - WARN_ON(s->s_inode_lru.node);
Why are you removing the wanrings from here? Regardless of where
we tear down the lru lists, they *must* be empty here otherwise we
have a memory leak. Hence I don't think these warnings should be
moved at all.
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
