From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3628F38553F; Tue, 9 Jun 2026 09:17:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780996676; cv=none; b=u8zfEXBQnAieL1TMabV4vuChDQfGNC9MCpsHnoLqOXVKoVw9oAg5MdqqhvasQ+UUjtu9WBAhNrW1Uzo8wKvU+fhfaobIWp7k7AScm/CmRKxvSI8oCgk1C6NeuddImccVGOtVG98rVvOggneKfMAKKqyZcOCXJ5YY6f5O8iTkO3I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780996676; c=relaxed/simple; bh=edk1gWq6wJegftSJ6gxR54wjWbnVE8DBfhA2Ljpkr30=; h=From:Subject:Date:Message-Id:MIME-Version:Content-Type:To:Cc; b=O+AL+i8mLbyP9tvf2ZSw2ssbv2ONEz6iSj2CvOGW7IMEl4j/Nmtj8sLpyoTThOuESWgminHqD7K/FaHwibk/Vy9n9dK4nL6dX9veNS4qudJyPL2fUc9eb4d3OJaqVC/6LzABw8n3EXxUdunPbPvfYpO2unESiOrD209vJCGYGFg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=InpuJTdi; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="InpuJTdi" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 428AB1F00893; Tue, 9 Jun 2026 09:17:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780996674; bh=JklGHxBs/e7WoHWY8zy6xxkN2IXkLn5LKgi5O76JqdY=; h=From:Subject:Date:To:Cc; b=InpuJTdixIWUvPPcFY6VIL8TLmanaDGHTbitvz3Ypi3itXf5Wqncv9tnKBpDPSicn wokRauUzVrN38x7gCY9XFJFFNcFtk3EGI+QotA50dpBp2jrGsZSLaqPe9hkaj4lHgc QVQpfUUWcFqM6IVplaSZMt6Y4tNd9lw9RktAlsS2UzgLTZMHBVYF0Vi5PLYiytcfy3 rNXaaeWM4zj3ct4b4kxLDzM52lMrq4N3oSIIZDPH2lnEDWhWspSrtHndryL1y64PKG dqyA/Mto7LbJZuiHUeWCVSR/AAxYjocA7zmzTsDBcaUg2o6+3L7ZeKfdPw8rHqDGZm 0HFWmqQQXoFtw== From: "Vlastimil Babka (SUSE)" Subject: [PATCH RFC 00/15] mm/slab: introduce alloc_flags and slab_alloc_context Date: Tue, 09 Jun 2026 11:17:45 +0200 Message-Id: <20260609-slab_alloc_flags-v1-0-2bf4a4b9b526@kernel.org> Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-B4-Tracking: v=1; b=H4sIADnaJ2oC/6tWKk4tykwtVrJSqFYqSi3LLM7MzwNyDHUUlJIzE vPSU3UzU4B8JSMDIzMDMwND3eKcxKT4xJyc/OT4tJzE9GJdI9NkcwujJINkU/NkJaC2gqLUtMw KsJHRSkFuzkqxEMHi0qSs1OQSkGFKtbUAms3VdHkAAAA= X-Change-ID: 20260601-slab_alloc_flags-25c782b0c57c 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 This series is based on slab/for-next. If all goes well, it would hopefully go to slab/for-next soon after the 7.2 merge window, so any other work can be based on it to avoid conflicts, as it touches a lot parts of slab. Git: https://git.kernel.org/pub/scm/linux/kernel/git/vbabka/linux.git/log/?h=b4/slab_alloc_flags The slab implementation currently relies on gfp flags to convey some context information internally: - The absence of both __GFP_RECLAIM flags is interpreted as "cannot spin on locks", and intended to be used by kmalloc_nolock(). But false positives are possible e.g. during early boot where gfp_allowed_mask clears __GFP_RECLAIM from all allocations. This leads to unnecessary allocation failures and workarounds such as fd3634312a04 ("debugobject: Make it work with deferred page initialization - again"). - __GFP_NO_OBJ_EXT exists and takes up valuable bit in the gfp flags space, only to prevent recursive kmalloc() allocations for obj_ext arrays and sheaves. The page allocator uses its internal alloc_flags to convey various context information, including ALLOC_TRYLOCK (meaning "cannot spin"). This series copies that concept for the slab allocator, with its own slab-specific internal flags: - SLAB_ALLOC_DEFAULT - no extra flags (the value is 0), but explicit - SLAB_ALLOC_TRYLOCK - do not spin on locks (used by kmalloc_nolock()) - SLAB_ALLOC_NEW_SLAB - replacing existing 'bool new_slab' parameter for allocating obj_ext arrays - SLAB_ALLOC_NO_RECURSE - replacing usage of __GFP_NO_OBJ_EXT To reduce the amount of parameters in various internal functions, we additionally introduce slab_alloc_context (also inspired by page allocator's alloc_context) for passing a number of existing arguments and the new alloc_flags: /* Structure holding extra parameters for slab allocations */ struct slab_alloc_context { unsigned long caller_addr; unsigned long orig_size; unsigned int alloc_flags; struct list_lru *lru; }; This also replaces the existing struct partial_context. The last necessary piece is kmalloc_flags() which can take the alloc_flags in addition to gfp flags and is intended for the recursive allocations of sheaves and obj_ext arrays, so that both SLAB_ALLOC_TRYLOCK and SLAB_ALLOC_NO_RECURSE can be communicated. Internally it decides between kmalloc_nolock() and normal kmalloc() depending SLAB_ALLOC_TRYLOCK. The rest of the series is gradually expanding the usage of both alloc_flags and slab_alloc_context as necessary, with bits of refactoring. Then, __GFP_NO_OBJ_EXT is removed completely. Note that some usage of gfpflags_allow_spinning() relying on absence of __GFP_RECLAIM remains outside of slab (and page allocator) in memcg, page_owner and stackdepot code. These can thus yield false-positive decisions that spinning is not allowed, but should not result in important allocations failing anymore. Signed-off-by: Vlastimil Babka (SUSE) --- Vlastimil Babka (SUSE) (15): mm/slab: always zero only requested size on alloc mm/slab: stop inlining __slab_alloc_node() mm/slab: introduce slab_alloc_context mm/slab: introduce alloc_flags and SLAB_ALLOC_TRYLOCK mm/slab: add alloc_flags to slab_alloc_context mm/slab: replace struct partial_context with slab_alloc_context mm/slab: pass alloc_flags to new slab allocation mm/slab: pass alloc_flags through slab_post_alloc_hook() chain mm/slab: replace slab_alloc_node() parameters with slab_alloc_context mm/slab: allow kmem_cache_alloc_bulk() with any gfp flags mm/slab: pass slab_alloc_context to __do_kmalloc_node() mm/slab: introduce kmalloc_flags() mm/slab: remove __GFP_NO_OBJ_EXT usage from alloc_slab_obj_exts() mm/slab: replace __GFP_NO_OBJ_EXT with SLAB_ALLOC_NO_RECURSE for sheaves mm: remove the __GFP_NO_OBJ_EXT flag include/linux/gfp_types.h | 7 - include/linux/slab.h | 14 +- include/trace/events/mmflags.h | 10 +- lib/alloc_tag.c | 2 +- mm/kfence/core.c | 6 +- mm/memcontrol.c | 5 +- mm/slab.h | 16 +- mm/slub.c | 423 ++++++++++++++++++++++++---------------- tools/include/linux/gfp_types.h | 7 - 9 files changed, 288 insertions(+), 202 deletions(-) --- base-commit: 500b2c9755301742bdbb61249511ac11a4665dae change-id: 20260601-slab_alloc_flags-25c782b0c57c Best regards, -- Vlastimil Babka (SUSE)