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b=bljgESA/jqmLYPOioHWBwsF8jHKWn4DOAoZBVAKxkywX+5Bf74eaadpUyEuoLLVkm hQv/E4KkGHbO4sbCaR99hIFpwTRlnzKda066KDq0Nh8iAaj1shfHlwZ9CVBUcW3n54 6j/O1/6JpQzHWQymZxABYN1ZbyjRN4/VFkCC0HAKgevx9KZGkW1X5ehAndML9xQI4D Rf8ilzwltkI07ufLvxxW2v5nJRZtKg1/Uqsh3iaP4YDVkD+Uj5TQMFklq5JlgEdG4o Co1XBUCYvgDD2R42QFMsvEbBrs7WpuJDU7uT7Qg5flrB49iW5znSMcxKoLfVXwdWTT 2WEoJz5Ces8zw== From: "Vlastimil Babka (SUSE)" Date: Tue, 09 Jun 2026 11:17:49 +0200 Subject: [PATCH RFC 04/15] mm/slab: introduce alloc_flags and SLAB_ALLOC_TRYLOCK MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260609-slab_alloc_flags-v1-4-2bf4a4b9b526@kernel.org> References: <20260609-slab_alloc_flags-v1-0-2bf4a4b9b526@kernel.org> In-Reply-To: <20260609-slab_alloc_flags-v1-0-2bf4a4b9b526@kernel.org> To: Harry Yoo Cc: Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , Suren Baghdasaryan , Alexei Starovoitov , Andrew Morton , Johannes Weiner , Michal Hocko , Shakeel Butt , Alexander Potapenko , Marco Elver , Dmitry Vyukov , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, "Vlastimil Babka (SUSE)" X-Mailer: b4 0.15.2 X-Rspamd-Server: rspam10 X-Rspam-User: X-Stat-Signature: f99wybutcxk67spdeux3wiob4m84qn6j X-Rspamd-Queue-Id: 2CFD34000D X-HE-Tag: 1780996691-917500 X-HE-Meta: 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 JdN8zai8 /Y9BUQNZbK0MMaYyl+BM4lDrOQbMuCJG3CCKQZD033yKlY1L12mXeyCVmFJP5ITeskzVOL2GExvJVesTT08DDvoGGbyUb+h1gI2Hd5Gj0jTlMikO26qbr7E5gP9wHmMfsXvQdZNRJcaiOS31biheAuC8SAxupeN0/khnzBpXttZLwQLkhSbjlNs/3gUFHBlOTvGfyM5NSAE1ZRD5rXsLUPMbnD/fekNpo72LBEwFZ184qAn2KSH9rrvxexmZoghEYGvUgAtI3v6xmYmZ45vviR9ipoaLaW6AVXO1o Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Similarly to the page allocators, introduce slab-allocator specific alloc flags that internally control allocation behavior in addition to gfp_flags, without occupying the limited gfp flags space. Introduce the first flag SLAB_ALLOC_TRYLOCK that behaves similarly to page allocator's ALLOC_TRYLOCK and will be used to reimplement kmalloc_nolock()'s "!allow_spin" behavior. That currently relies on gfpflags_allow_spinning() and thus the lack of both __GFP_RECLAIM flags, importantly __GFP_KSWAPD_RECLAIM. This can give false-positive results e.g. in early boot with a restricted gfp_allowed_mask. Also introduce alloc_flags_allow_spinning() to replace the usage of gfpflags_allow_spinning(). Start using alloc_flags and the new check first in alloc_from_pcs() and __pcs_replace_empty_main(). This means some slab allocations that were falsely treated as kmalloc_nolock() due to their gfp flags will now have higher chances of succeed, and this will further increase with followup changes. Remove a WARN_ON_ONCE() from refill_objects() as it's now legitimate to reach it from a slab allocation that's not _nolock() and yet lacks __GFP_KSWAPD_RECLAIM for other reasons. Signed-off-by: Vlastimil Babka (SUSE) --- mm/slab.h | 9 +++++++++ mm/slub.c | 17 ++++++++--------- 2 files changed, 17 insertions(+), 9 deletions(-) diff --git a/mm/slab.h b/mm/slab.h index 1bf9c3021ae3..3e75182ee144 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -16,6 +16,15 @@ * Internal slab definitions */ +/* slab's alloc_flags definitions */ +#define SLAB_ALLOC_DEFAULT 0x00 +#define SLAB_ALLOC_TRYLOCK 0x01 + +static inline bool alloc_flags_allow_spinning(const unsigned int alloc_flags) +{ + return !(alloc_flags & SLAB_ALLOC_TRYLOCK); +} + #ifdef CONFIG_64BIT # ifdef system_has_cmpxchg128 # define system_has_freelist_aba() system_has_cmpxchg128() diff --git a/mm/slub.c b/mm/slub.c index 06fc1656080f..278d8cbcc7ee 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -4622,7 +4622,8 @@ bool slab_post_alloc_hook(struct kmem_cache *s, struct list_lru *lru, * unlocked. */ static struct slub_percpu_sheaves * -__pcs_replace_empty_main(struct kmem_cache *s, struct slub_percpu_sheaves *pcs, gfp_t gfp) +__pcs_replace_empty_main(struct kmem_cache *s, struct slub_percpu_sheaves *pcs, + gfp_t gfp, unsigned int alloc_flags) { struct slab_sheaf *empty = NULL; struct slab_sheaf *full; @@ -4648,7 +4649,7 @@ __pcs_replace_empty_main(struct kmem_cache *s, struct slub_percpu_sheaves *pcs, return NULL; } - allow_spin = gfpflags_allow_spinning(gfp); + allow_spin = alloc_flags_allow_spinning(alloc_flags); full = barn_replace_empty_sheaf(barn, pcs->main, allow_spin); @@ -4734,7 +4735,7 @@ __pcs_replace_empty_main(struct kmem_cache *s, struct slub_percpu_sheaves *pcs, } static __fastpath_inline -void *alloc_from_pcs(struct kmem_cache *s, gfp_t gfp, int node) +void *alloc_from_pcs(struct kmem_cache *s, gfp_t gfp, unsigned int alloc_flags, int node) { struct slub_percpu_sheaves *pcs; bool node_requested; @@ -4779,7 +4780,7 @@ void *alloc_from_pcs(struct kmem_cache *s, gfp_t gfp, int node) pcs = this_cpu_ptr(s->cpu_sheaves); if (unlikely(pcs->main->size == 0)) { - pcs = __pcs_replace_empty_main(s, pcs, gfp); + pcs = __pcs_replace_empty_main(s, pcs, gfp, alloc_flags); if (unlikely(!pcs)) return NULL; } @@ -4912,7 +4913,7 @@ static __fastpath_inline void *slab_alloc_node(struct kmem_cache *s, struct list if (unlikely(object)) goto out; - object = alloc_from_pcs(s, gfpflags, node); + object = alloc_from_pcs(s, gfpflags, SLAB_ALLOC_DEFAULT, node); if (unlikely(!object)) { struct slab_alloc_context ac = { @@ -5343,6 +5344,7 @@ void *_kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_flags, in { gfp_t alloc_gfp = __GFP_NOWARN | __GFP_NOMEMALLOC | gfp_flags; size_t orig_size = size; + unsigned int alloc_flags = SLAB_ALLOC_TRYLOCK; struct kmem_cache *s; bool can_retry = true; void *ret; @@ -5381,7 +5383,7 @@ void *_kmalloc_nolock_noprof(DECL_TOKEN_PARAMS(size, token), gfp_t gfp_flags, in */ return NULL; - ret = alloc_from_pcs(s, alloc_gfp, node); + ret = alloc_from_pcs(s, alloc_gfp, alloc_flags, node); if (ret) goto success; @@ -7200,9 +7202,6 @@ refill_objects(struct kmem_cache *s, void **p, gfp_t gfp, unsigned int min, unsigned int refilled; struct slab *slab; - if (WARN_ON_ONCE(!gfpflags_allow_spinning(gfp))) - return 0; - refilled = __refill_objects_node(s, p, gfp, min, max, get_node(s, local_node), /* allow_spin = */ true); -- 2.54.0