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b=D/rUgR+Qfo2Hp9IBWwVLfW6pbvEMQr5eKPyun8iieLmRUWw5YzvSDwFIioOlE0kJk 4Lf7aYcvfU3DbpO1FnLGiWMYRyrLJ/MK66S8PLV7Zm8N7gxJMKto9kwHo5vdQVX44g ryoYZkZDjKteFeAxAHeWclPYntpwGa8iaaIxtp5bAG7y5AsSgJGXvTOgv680C06v0Z MMnne6t30X5rSajz4OdH/W9B10wcOQn2HCBXhfIla/wQMTobskOBi/0CaJ9XTwVoOL fVWlBNnYs76OgUCOf1RE9xd51TtfTEGa1+ZWG6FpqbmaG/v9bxbw27NKYWQEXOsQSQ gzJKDmve8vaqg== From: "Vlastimil Babka (SUSE)" Date: Tue, 09 Jun 2026 11:17:58 +0200 Subject: [PATCH RFC 13/15] mm/slab: remove __GFP_NO_OBJ_EXT usage from alloc_slab_obj_exts() MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260609-slab_alloc_flags-v1-13-2bf4a4b9b526@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: rspam07 X-Rspam-User: X-Stat-Signature: 8eawbhd8i3stf6i5r1ne6rdtr4ai685e X-Rspamd-Queue-Id: 6D6B5100004 X-HE-Tag: 1780996726-326066 X-HE-Meta: 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 g6j4/m7y S3f0Syxo1Z/PwwRg8VUEnbwGhlkfo7R+8rP1bwiM7hSdooqB4SsTbq93Gyyil21FokVp7a3MbPrMMMr8csi1TvVjGxjA8RxLy6OWqi/vfg400u2TvuApwQTWFHIh5VlvK6uE+57ZACVudx2M99lqZBP2+faY8gUWW5ahuZa9yDsBKAu2+4gBgL+jIEuLSYyjmw0MvA2eKuDNEXu+vjnuX9xUGsC9LPQ5pYVH1UMZC0QpgtXx+xyvgjNxheJYH+d7MZ8Sd3kfwulx9RyV0a4NHxG5TjPvNvlCLHHKt Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: __GFP_NO_OBJ_EXT has limited scope within the slab allocator itself and gfp flags are a scarce resource, unlike slab's alloc_flags. Introduce SLAB_ALLOC_NO_RECURSE alloc flag that has the same intent as __GFP_NO_OBJ_EXT but a more generic name, meaning that a kmalloc() family function should not recurse into another kmalloc*() for the purposes of allocating auxiliary structures (obj_ext arrays or sheaves). First, replace the __GFP_NO_OBJ_EXT for allocating obj_ext arrays in alloc_slab_obj_exts(). Make use of the newly added kmalloc_flags() function, where we can pass alloc_flags with SLAB_ALLOC_NO_RECURSE added. This will also pass through SLAB_ALLOC_TRYLOCK so we don't need to special case kmalloc_nolock() anymore. Note that until now the kmalloc_nolock() ignored the incoming gfp flags and hardcoded __GFP_ZERO | __GFP_NO_OBJ_EXT. But it's correct to pass on the incoming gfp flags (only augmented with __GFP_ZERO), because if alloc_flags contain SLAB_ALLOC_TRYLOCK, the incoming gfp flags have to be also compatible with it. Signed-off-by: Vlastimil Babka (SUSE) --- mm/slab.h | 1 + mm/slub.c | 13 +++++-------- 2 files changed, 6 insertions(+), 8 deletions(-) diff --git a/mm/slab.h b/mm/slab.h index 13517abcad21..e5bd800d831e 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -20,6 +20,7 @@ #define SLAB_ALLOC_DEFAULT 0x00 #define SLAB_ALLOC_TRYLOCK 0x01 #define SLAB_ALLOC_NEW_SLAB 0x02 /* a flag for alloc_slab_obj_exts() */ +#define SLAB_ALLOC_NO_RECURSE 0x04 /* prevent kmalloc() recursion */ static inline bool alloc_flags_allow_spinning(const unsigned int alloc_flags) { diff --git a/mm/slub.c b/mm/slub.c index 86691eb14002..8a655636dee6 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2167,15 +2167,12 @@ int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s, gfp &= ~OBJCGS_CLEAR_MASK; /* Prevent recursive extension vector allocation */ - gfp |= __GFP_NO_OBJ_EXT; + alloc_flags |= SLAB_ALLOC_NO_RECURSE; sz = obj_exts_alloc_size(s, slab, gfp); - if (unlikely(!allow_spin)) - vec = kmalloc_nolock(sz, __GFP_ZERO | __GFP_NO_OBJ_EXT, - slab_nid(slab)); - else - vec = kmalloc_node(sz, gfp | __GFP_ZERO, slab_nid(slab)); + /* This will use kmalloc_nolock() if alloc_flags say so */ + vec = kmalloc_flags(sz, gfp | __GFP_ZERO, alloc_flags, slab_nid(slab)); if (!vec) { /* @@ -2251,7 +2248,7 @@ static inline void free_slab_obj_exts(struct slab *slab, bool allow_spin) } /* - * obj_exts was created with __GFP_NO_OBJ_EXT flag, therefore its + * obj_exts was created with SLAB_ALLOC_NO_RECURSE flag, therefore its * corresponding extension will be NULL. alloc_tag_sub() will throw a * warning if slab has extensions but the extension of an object is * NULL, therefore replace NULL with CODETAG_EMPTY to indicate that @@ -2374,7 +2371,7 @@ __alloc_tagging_slab_alloc_hook(struct kmem_cache *s, void *object, gfp_t flags, if (s->flags & (SLAB_NO_OBJ_EXT | SLAB_NOLEAKTRACE)) return; - if (flags & __GFP_NO_OBJ_EXT) + if (alloc_flags & SLAB_ALLOC_NO_RECURSE) return; slab = virt_to_slab(object); -- 2.54.0