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Howlett" , Usama Arif , Kiryl Shutsemau , Dave Chinner , Roman Gushchin , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 1/7] mm: list_lru: lock_list_lru_of_memcg() cannot return NULL if !skip_empty Message-ID: <375b41d1-6fcb-4b79-889e-20e4b4fbcf02@lucifer.local> References: <20260318200352.1039011-1-hannes@cmpxchg.org> <20260318200352.1039011-2-hannes@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260318200352.1039011-2-hannes@cmpxchg.org> X-Rspam-User: X-Stat-Signature: 5kfna4nwz8k4wu95pfkfyof8cx9pgj4f X-Rspamd-Queue-Id: B112940008 X-Rspamd-Server: rspam09 X-HE-Tag: 1774351846-643499 X-HE-Meta: U2FsdGVkX1/Icn18ASNXhnH/uB0iJasszZKIsjHzbJestAAi9JxRx3b/0wE8tJe9d3jWJFQWolB4Q5s03U7SCku4zcjsjfTGqqrIVMiSeVnDuV/WHWL8xSeyLK9+lWuNNgzxX9iqC+Ycm5AlgcRSNuE3p67FQ+lv6KdJO9EsG6+QeQgkU/4ejZWFDguwzW/4rFDKMXKKbopD6eybg6SHZfih2kjhMsr07t/4DVeDkCUomZxLoUzYTOAEyaCRTdVyw9KQiwImGefnjW+6sVlC9XfUr/2cEU0KNDyPxz2ZEAXMcSt0WH0jaKb01VenIKYb3oiWWSQOLtO2EEF3jYngvE5Pnl5Ggc8i6XC8VRMpBSrh2/r8Nb6cMSw024q/lms4N9fhmoBP7HSTsd054LBQvGLQt5eDmus7Hs9R2spxMVY8Csa3wlRWdxmw4ywWrPI5SF1pDwCWbsZUwwh9JPRyeum+137jKMlAbzVjJfff9alL1UsJTzWyLJ0yvBDjSf6b8sPM8xz+oURQt06HsfCKihyCXfO7acjGbJ5p2LT8KVgnmFWZ4BgmVDu45mRbKC2Kn1KKqRI7iambqRwGfxgkTqN8lzLLOCOpiufwVVywz7GSjG/zgVcNEnGO9z2FPuLKGiWyg3RZPRmmPLetzHI8fPXZTBs4VEfiVo9tgPfFIX6Q0CinMzVPJBSKe4eM5v2i55cy/9CC1C0BKgPxua3YBRmOJr1EOF/4jsFlk/PTU7UsY4mTfR89dWRnJpN3jnM5cbxAQ/2MXg1j/ANgfBoHDVp8cvIiPwrB2CHXpZ3Z6SiEbMI0dSzzevK0FGJYbKpDHnGscHeivFSbW+GXf9WjTPWXcJ2feNM8O6FSAnqSWenYR028/dd6nj1NQ2x2PeexDWtlxGHEHPphXhefo1EfMYsEx4MlUHN+w3PhIk5nZYiCPgSYd7W0FYqVikp0YopzWJtIYr5ZqIAxYt2J0bU f2IZ5FZk Q4yA8+nPs/TCbRkLzBb/k7KidlBoXuxME9GDyq5FQOvbIgwFl7SSOecDDoHLev67pvfc3lWs4nYGFlIdmdcDSbvMryOB2hcs9Pizl+NnKmtiL1Fw8XvZiryM4m4q8r/pIm02ZLwxCJ6cz/g4IsUoq9yM4A7n5wPCH7xAjhl0YhuPmn6OompBt70MZGKj7SbZU9iZ2zx1LDdcbeUakoZcJjmjlMwmh/INpJLMOiv5RmeuAg6PG/h3jLLBztYtL/igbuNQjWgBNUzCwRUQQL4uzx6nXGxF9SVugIRlsh++2qp1lZxdVQ1RZOOtkiyEw43vDii6qHlHAke59p2MHnSLMyGI9hZ35G5Nv7+E+WMY6gEmNpLFUVTeiqnBHTtAcp0Z6UeSm Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Mar 18, 2026 at 03:53:19PM -0400, Johannes Weiner wrote: > skip_empty is only for the shrinker to abort and skip a list that's > empty or whose cgroup is being deleted. > > For list additions and deletions, the cgroup hierarchy is walked > upwards until a valid list_lru head is found, or it will fall back to > the node list. Acquiring the lock won't fail. Remove the NULL checks > in those callers. > > Reviewed-by: David Hildenbrand (Arm) > Signed-off-by: Johannes Weiner LGTM, as !skip_empty and so that just isn't possible, so: Reviewed-by: Lorenzo Stoakes (Oracle) > --- > mm/list_lru.c | 5 +---- > 1 file changed, 1 insertion(+), 4 deletions(-) > > diff --git a/mm/list_lru.c b/mm/list_lru.c > index 26463ae29c64..d96fd50fc9af 100644 > --- a/mm/list_lru.c > +++ b/mm/list_lru.c > @@ -165,8 +165,6 @@ bool list_lru_add(struct list_lru *lru, struct list_head *item, int nid, > struct list_lru_one *l; > > l = lock_list_lru_of_memcg(lru, nid, memcg, false, false); > - if (!l) > - return false; > if (list_empty(item)) { > list_add_tail(item, &l->list); > /* Set shrinker bit if the first element was added */ > @@ -203,9 +201,8 @@ bool list_lru_del(struct list_lru *lru, struct list_head *item, int nid, > { > struct list_lru_node *nlru = &lru->node[nid]; > struct list_lru_one *l; > + > l = lock_list_lru_of_memcg(lru, nid, memcg, false, false); > - if (!l) > - return false; > if (!list_empty(item)) { > list_del_init(item); > l->nr_items--; > -- > 2.53.0 > Cheers, Lorenzo