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b=GEd6pmnWoUybWjiSrGOgz3MjARHxwYF1EkDs3P05KxdPrviAgZnvZrs3E+6sqnGyV /Xc1+8914FhjyocqKuioJa8fozQXsDwux14jBP19Ecyuqba2Gn0k6k1BAwHWsCnjOp O6ShU/N7791wlISrpDXJKvtNRIMG84z/WSudl9weD0K38WwRwUur2BfDVDpIHF23il u1tmFh2iyChexe2PkTC0Q3knY09QmGQM+D0OofLrzHtoccqpHWYtKPCKS9guSiGc/u AlzpHYv/fqwCHFnUxkz4yseJ1+E9O7lY6wFjATckkfEJFXS0VjQFd6TfrgQ/YAn0y5 EetBTmqF7i+jg== From: "Vlastimil Babka (SUSE)" Date: Wed, 10 Jun 2026 17:40:17 +0200 Subject: [PATCH v2 15/16] 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: <20260610-slab_alloc_flags-v2-15-7190909db118@kernel.org> References: <20260610-slab_alloc_flags-v2-0-7190909db118@kernel.org> In-Reply-To: <20260610-slab_alloc_flags-v2-0-7190909db118@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-Queue-Id: 77C0A12000C X-Stat-Signature: sscem9xtawny3ieg7f975s6mignej5nh X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1781106132-398441 X-HE-Meta: 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 h9cT8Gm7 k/3H9vAdaUcY3/MJydpx8vGgnXVLcFeoC/9X79RRdKSxe6imFt/COS34hWGiqx7CrEHxzxOVfIKD1SoEKRjlkOeww53oDAdL8AbzKv9uQQ8GXyyyaT0Bs6VegyQizGNcZHklPxWVphfObGgHKnbw7/sGF3kwPNHzYzC/L4Z/KXW/+rpFHjQr/dzNw/DtR22pPDQg5LYjhKXN5qWebPnK3X1ueNODt6K8tFplg3akuQs3duT+RXx9xiWFQ+egWs6D94YNj/uKp2sEvrcjhr2B8bUkVLeuL8sS62P9L 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 45bfcfb35a9c..509f330654b8 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -21,6 +21,7 @@ #define SLAB_ALLOC_DEFAULT 0x00 /* no flags */ #define SLAB_ALLOC_TRYLOCK 0x01 /* a kmalloc_nolock() allocation */ #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 cbb38bd01e46..7dfbd0251aa2 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