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 7AB9F416D1D; Wed, 10 Jun 2026 15:40:57 +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=1781106058; cv=none; b=YK8DoxNz36LcyZvOsHHlpaoZwWz9K3QKOIbmxgUwAjoerbRRM0xuZpnFXdWl/nAJsNCyEVuDyORszj3qSX60uNTQS1mS+ydSNQ2Q/NRv/H598x+1I2K6jA/EAtR8yHCACE8PvetISoms3UwTHRPBI+lC1ibpIZ+utd5CxQSyuFA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781106058; c=relaxed/simple; bh=e+XV3AZqAoAC7RIKgePG4YKkJSPPEI10nmOB2NUI12c=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=c4xFqkGGQtfEEO9jDCoHsuQiWbu4Z4H2MGZMMj0GbsYUawj8paEQlloZMETjBNIjCBk4ckxzdE60hBbVFYf8fERSyBbm+zdJV49F3KwqBAwqpIyYmdoB6YeXUBP5GdBRQvoFbalG99j8KMlACWjeKMnxQfcketAjcPeV/ht9aec= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=aCXPhkm8; 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="aCXPhkm8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C19E11F00898; Wed, 10 Jun 2026 15:40:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781106057; bh=uzrQqVr+7rwNnJX12Vdm6hcXiPQHxl3cGwRGRVjeEkE=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=aCXPhkm8nAkdUVhcPCJUTOjkUtEJISo7BfGZrCD7i28tiCbagbHjNon8sAPgrzyYc 2RkRNiVBG+fSPgFQixWt62WNno7HDDOpVLkxlbVAOff0N2BRYxkY26fOCMQgqnxIQg Vo6/+wKzhCMrPVUUkdYBvEko/zuKCyMmAc5ejtIHc93n94xPW9QfEejrYaYkqazkc0 TZ+dRNAy1COnYajg+g3r+nMP1/8JHCUZ3ShqlSynY7NQKWfgT6lUPu/5jED69sEsyf rTxnFxgtwHqzh6qGp2iD7D9WVL1dU3WYdmEvzAnc8FubCtBIY8M6+XDQ9jNguIIFzo OR6jq3M1atcFA== From: "Vlastimil Babka (SUSE)" Date: Wed, 10 Jun 2026 17:40:07 +0200 Subject: [PATCH v2 05/16] mm/slab: introduce alloc_flags and SLAB_ALLOC_TRYLOCK 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 Message-Id: <20260610-slab_alloc_flags-v2-5-7190909db118@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 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..96f65b625600 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 /* no flags */ +#define SLAB_ALLOC_TRYLOCK 0x01 /* a kmalloc_nolock() allocation */ + +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 a3cac7281cc6..e79fbca11bc0 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -4638,7 +4638,8 @@ 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; @@ -4664,7 +4665,7 @@ __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); @@ -4750,7 +4751,7 @@ __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; @@ -4795,7 +4796,7 @@ 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; } @@ -4928,7 +4929,7 @@ 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 = { @@ -5359,6 +5360,7 @@ 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; @@ -5397,7 +5399,7 @@ 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; @@ -7216,9 +7218,6 @@ 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