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 966383E3D89; Mon, 15 Jun 2026 11:55:00 +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=1781524501; cv=none; b=JgAnSI70bGvtCf3ADAmO3sgXeotODF6PEYRLG9DSl4SUC9dsoldBu3oxUVIc9YB4vuGSejWhaQpQ89iVeATquRaWuWImr5jX86HPB+Xh21la71jjmdBKM2phQpjl4uSr2MLOOMNoMdhg9sZMN4V3E/de+DuAHMVRI3heWI3AozM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781524501; c=relaxed/simple; bh=EHSxUcTa9peC1o1CDsf5F2rsI6T9qgfjOE1EoGX5B24=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=mAS8XSuyAeUn3y2YxJL0etX5Htr/ttMrHF9a11Oi2O2W1zRsB17hlSd3tgoysBxpzJDyi45k5h19K0uMR9nk9SBz0uV0yz14kT7j6jigPGtyBd/Ytg6zko2a4qjLWqImZZUOf9/rqWW2l/S+NYZDG/0ZX+XsbCBMnbKtXovLTLA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=E//gYDDW; 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="E//gYDDW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C51A51F000E9; Mon, 15 Jun 2026 11:54:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781524500; bh=glc3QEqPnlGb8w7UmY4poSPBjS3UXiolMpPhxF92RJo=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=E//gYDDWQdOcb5vH3L6tFTUI9pZsx8ZrNEH0l8RXCgxzkf/cXKHMKNwLC9ZZEgDes JgwGJ7F1TvYbR6dXtfBIcAMm8d9b8ctTBeLB0t5TO6Wbyh7WTp7NWA3SmqVySwgjOx L0RV6WXLu+nPKn3BNXoFI/sMWJEc1QKOmv+LAZWmzawkXHHhzBp8tPyb4dsJS/ByR7 bFylYFJphbfSHbY7oDaavJuSk7LEEP3xC3sU6Ioseff5HNljL80Q/5kFUNHKQCevES pW55GNJ+T2zyYs5Z3JwqR2kW7W/EeeKxx5Fen47XvbnGcOU5W4ygRYWedJeO0aR/RH wgloQ17asotIQ== From: "Vlastimil Babka (SUSE)" Date: Mon, 15 Jun 2026 13:54:37 +0200 Subject: [PATCH v3 04/15] mm/slab: introduce alloc_flags and SLAB_ALLOC_NOLOCK 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: <20260615-slab_alloc_flags-v3-4-ce1146d140fb@kernel.org> References: <20260615-slab_alloc_flags-v3-0-ce1146d140fb@kernel.org> In-Reply-To: <20260615-slab_alloc_flags-v3-0-ce1146d140fb@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_NOLOCK 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 success, 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. Link: https://patch.msgid.link/20260610-slab_alloc_flags-v2-5-7190909db118@kernel.org Reviewed-by: Harry Yoo (Oracle) Reviewed-by: Hao Li Reviewed-by: Suren Baghdasaryan 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..f1246f0c9f74 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_NOLOCK 0x01 /* a kmalloc_nolock() allocation */ + +static inline bool alloc_flags_allow_spinning(const unsigned int alloc_flags) +{ + return !(alloc_flags & SLAB_ALLOC_NOLOCK); +} + #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 8a0c5553876e..c53592baa027 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -4641,7 +4641,8 @@ 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; @@ -4667,7 +4668,7 @@ __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); @@ -4753,7 +4754,7 @@ __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; @@ -4798,7 +4799,7 @@ 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; } @@ -4931,7 +4932,7 @@ 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)) { const struct slab_alloc_context ac = { @@ -5362,6 +5363,7 @@ 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_NOLOCK; struct kmem_cache *s; bool can_retry = true; void *ret; @@ -5404,7 +5406,7 @@ 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; @@ -7218,9 +7220,6 @@ 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