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 BCA383F888F; Wed, 10 Jun 2026 15:40:20 +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=1781106021; cv=none; b=jrmLBQU0FFe6G6+uqAC2MgNrw9fFGFNyXY2BDMUDphFE93fnFA189RgahVoXjccwDpYfv/Il8MyR1MfnN3OOaR+eXoInl9ZSFarM4qKc2gM5Y1cdMrVwogYi0VRgcWAwePj9DWOTdLmhn6nEabzct41JccLFcg8dPJf3YxafJZU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781106021; c=relaxed/simple; bh=xte04xdEje1GOGQhHnKnSLer2ZCrbbfb6ar17VBuod0=; h=From:Subject:Date:Message-Id:MIME-Version:Content-Type:To:Cc; b=r6iv2mS02abovp5v7D8AXJRth2wRpM1GrNrabaMFfJ62WiVpuhwRSvqKmza6IUw3ozUN2mo7ezloxRiqXagYy5VFGidxemHgbUMkihAhm2dliV+h/QpLL2ExS/NkgFh7Lik2pE3EVbTM6cHfTb0xXjC7XSkF08/3QLu8CFuQzqE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Q5gNJkTh; 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="Q5gNJkTh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 417291F00898; Wed, 10 Jun 2026 15:40:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781106020; bh=rh6k92Y5yfUvQ1Ydl5es3+m24euL6hyzwkyjlD+xQ1I=; h=From:Subject:Date:To:Cc; b=Q5gNJkThO/m2qp1lkXJFqQaBB8SIHT6CIi8Qj5jPW5jfIX8YyEvV7VIB4Nn4+aG2X hLuXcz3sIQz6ljVMErk3JkZNmqUGJpd2nSXULBASDJbfQF5YyUFx3bu0s+n0YlzFRl Jxu3ly32wNL/+kRr0G5N+6zH/jHTURY85x5I2ayOpOHtaCvhx7fD9wMxkCNN7g/1ms iebecj6TSgrh6xha2dzaTCfpgDOd9SpX4z20D3I7Vg3lybrTtVH1gwCufq0LG8iwhs kPPP6tZsPBPtvswVFKD/1ULSU7THWCJy5ZKvm+o6quJzm6rTOzK94drCj8PZFtqXlD iTW114BWt6elA== From: "Vlastimil Babka (SUSE)" Subject: [PATCH v2 00/16] mm/slab: introduce alloc_flags and slab_alloc_context Date: Wed, 10 Jun 2026 17:40:02 +0200 Message-Id: <20260610-slab_alloc_flags-v2-0-7190909db118@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=H4sIAFKFKWoC/2WNyw6CMBBFf4XM2poy4SGu+A9DSFsHqDat6SDRE P5dwLhyeZJzz52BKVpiOCczRJos2+BXwEMCZlC+J2GvKwNKLGQhU8FO6VY5F0zbOdWzwNyUJ9T S5KWBdfaI1NnXnrw0X+anvpEZt85mDJbHEN/755Ru3i9f/eenVEiBustUpiudY1HfKXpyxxB7a JZl+QAQBFkpwwAAAA== 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)" , stable@vger.kernel.org X-Mailer: b4 0.15.2 This series is based on slab/for-next. As suggested by Alexei I will try to put it there ASAP (hence the early respin) and see if it looks stable enough to be send in the second 7.2 merge window week. 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) --- Changes in v2: - Due to Sashiko review, drop the idea of zeroing orig_size unconditionally, as it can break krealloc(). Thanks to that found a pre-existing bug fixed by the new Patch 1. The kfence zeroing related cleanup is implemented differently in Patch 2. - Prevent nested kmalloc_nolock warnings due to added gfp flags (Sashiko) - Fix a pre-existing issue with opportunistic slab allocation from the target node only effectively dropping __GFP_NOMEMALLOC and __GFP_RECLAIM. (Sashiko) - Move kmalloc_flags() definitions to mm/slab.h (per Harry). - Link to v1: https://patch.msgid.link/20260609-slab_alloc_flags-v1-0-2bf4a4b9b526@kernel.org --- Vlastimil Babka (SUSE) (16): mm/slab: do not limit zeroing to orig_size when only red zoning is enabled mm/slab: do not init any kfence objects on allocation 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: allow __GFP_NOMEMALLOC and __GFP_NOWARN for kmalloc_nolock() 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 include/linux/slab.h | 5 +- mm/kfence/core.c | 2 +- mm/memcontrol.c | 5 +- mm/slab.h | 29 +++- mm/slub.c | 439 +++++++++++++++++++++++++++++++-------------------- 5 files changed, 304 insertions(+), 176 deletions(-) --- base-commit: 500b2c9755301742bdbb61249511ac11a4665dae change-id: 20260601-slab_alloc_flags-25c782b0c57c Best regards, -- Vlastimil Babka (SUSE)