From nobody Mon Feb 9 04:30:11 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id A8BC03126A3 for ; Mon, 12 Jan 2026 15:46:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768232811; cv=none; b=ngvOpyNvVc2wc/0uDq8wyhiespY25sxhijmaXPBX6+jL+nb6kdPGuenirrx5SHTIkAhbt30rPAZAHo5ICooi1CSZ2LdEwrWxhph9xu0cLpu+pRik9Uab4zVyVk4n+EQkyv5wW1oDsWJ7DQJ0AthQDWmxyAZv4cPmPiLfQiOUtqk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768232811; c=relaxed/simple; bh=th2YzedDg+I+Z++h/5UVgR6l3o0jgXTasXPuIBPLus0=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=SWTAOTG1DU1A23vZHFvbknUZtK5qOnDLO8QpgdMjhQjv6zLz1+mApehidH6otp1v5Wmq/wpffV4s8CTpjEyjfPg4eXisntFpr0H3BXgnqLKZ/0EIGRNqeOL8YwkRSU7d4D7z3siamX8Yh9rL+zl1WZ0uvSWNTEiVAtqo4igmVK8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 43C981516; Mon, 12 Jan 2026 07:46:42 -0800 (PST) Received: from 010265703453.arm.com (unknown [10.57.48.115]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 8CA563F694; Mon, 12 Jan 2026 07:46:46 -0800 (PST) From: Robin Murphy To: m.szyprowski@samsung.com, akpm@linux-foundation.org, vbabka@suse.cz, david@kernel.org Cc: bhe@redhat.com, iommu@lists.linux-foundation.org, linux-mm@kvack.org, vladimir.kondratiev@mobileye.com, s-adivi@ti.com, linux-kernel@vger.kernel.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, rppt@kernel.org, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com Subject: [PATCH 1/3] dma/pool: Improve pool lookup Date: Mon, 12 Jan 2026 15:46:36 +0000 Message-Id: X-Mailer: git-send-email 2.34.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" If CONFIG_ZONE_DMA32 is enabled, but we have not allocated the corresponding atomic_pool_dma32, dma_guess_pool() may return the NULL value of that and fail a GFP_DMA32 allocation without trying to fall back to other pools which may exist. Furthermore, if no GFP_DMA pool exists, it is preferable to try GFP_DMA32 rather than immediately fall back to GFP_KERNEL with even less chance of success. Improve matters by encoding an explicit order of pool preference for each flag. Signed-off-by: Robin Murphy Reviewed-by: Baoquan He --- kernel/dma/pool.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c index 26392badc36b..2645cfb5718b 100644 --- a/kernel/dma/pool.c +++ b/kernel/dma/pool.c @@ -224,10 +224,10 @@ postcore_initcall(dma_atomic_pool_init); static inline struct gen_pool *dma_guess_pool(struct gen_pool *prev, gfp_t= gfp) { if (prev =3D=3D NULL) { - if (IS_ENABLED(CONFIG_ZONE_DMA32) && (gfp & GFP_DMA32)) - return atomic_pool_dma32; - if (atomic_pool_dma && (gfp & GFP_DMA)) - return atomic_pool_dma; + if (gfp & GFP_DMA) + return atomic_pool_dma ?: atomic_pool_dma32 ?: atomic_pool_kernel; + if (gfp & GFP_DMA32) + return atomic_pool_dma32 ?: atomic_pool_dma ?: atomic_pool_kernel; return atomic_pool_kernel; } if (prev =3D=3D atomic_pool_kernel) --=20 2.34.1 From nobody Mon Feb 9 04:30:11 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 364BC346AE6 for ; Mon, 12 Jan 2026 15:46:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768232813; cv=none; b=alTSMiXC5YIl1NURgGih9sLQTjZQgoaAgHpRrRwfm+A+bO8VdoMF3c6MXi44xmXanUU4tU8FBNuEai9nz18+tE9jiDSqdSMzbM3wWzDQxxJIVrqEdlidxaGNK3Qo/lrveCzDVjgMMI4pH1Yl9FojZTjvMl+pdihGR9H6sREZGgA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768232813; c=relaxed/simple; bh=nOMWBIq8JKQYsN92Dk6QiYobQyynbnmDDEryxHer4N0=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=NjAvXPBRGyvD4ygFD9WiwrHEALF5h4nB7ccn1aFFE2t1UbutfXTLXfBJzVjbVQls2dQgBwluzQoSa8zn47QDZBOmvb8rDpyxWbS7ag0RQApIOTCHKNrr5H194n0GhxjJAyi4Za9F2hcdnzwslESZ8FvevFUTI5HDOvNzCJA/+qU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 0768C153B; Mon, 12 Jan 2026 07:46:45 -0800 (PST) Received: from 010265703453.arm.com (unknown [10.57.48.115]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 508153F694; Mon, 12 Jan 2026 07:46:49 -0800 (PST) From: Robin Murphy To: m.szyprowski@samsung.com, akpm@linux-foundation.org, vbabka@suse.cz, david@kernel.org Cc: bhe@redhat.com, iommu@lists.linux-foundation.org, linux-mm@kvack.org, vladimir.kondratiev@mobileye.com, s-adivi@ti.com, linux-kernel@vger.kernel.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, rppt@kernel.org, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com Subject: [PATCH 2/3] mm_zone: Generalise has_managed_dma() Date: Mon, 12 Jan 2026 15:46:37 +0000 Message-Id: X-Mailer: git-send-email 2.34.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" It would be useful to be able to check for potential DMA pages beyond just ZONE_DMA - generalise the existing has_managed_dma() function to allow checking other zones too. Signed-off-by: Robin Murphy Acked-by: David Hildenbrand (Red Hat) Acked-by: Mike Rapoport (Microsoft) Reviewed-by: Baoquan He --- include/linux/mmzone.h | 9 +++++---- mm/page_alloc.c | 8 ++------ 2 files changed, 7 insertions(+), 10 deletions(-) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 75ef7c9f9307..fc5d6c88d2f0 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -1648,14 +1648,15 @@ static inline int is_highmem(const struct zone *zon= e) return is_highmem_idx(zone_idx(zone)); } =20 -#ifdef CONFIG_ZONE_DMA -bool has_managed_dma(void); -#else +bool has_managed_zone(enum zone_type zone); static inline bool has_managed_dma(void) { +#ifdef CONFIG_ZONE_DMA + return has_managed_zone(ZONE_DMA); +#else return false; -} #endif +} =20 =20 #ifndef CONFIG_NUMA diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 822e05f1a964..36ccc85c5073 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7418,20 +7418,16 @@ bool put_page_back_buddy(struct page *page) } #endif =20 -#ifdef CONFIG_ZONE_DMA -bool has_managed_dma(void) +bool has_managed_zone(enum zone_type zone) { struct pglist_data *pgdat; =20 for_each_online_pgdat(pgdat) { - struct zone *zone =3D &pgdat->node_zones[ZONE_DMA]; - - if (managed_zone(zone)) + if (managed_zone(&pgdat->node_zones[zone])) return true; } return false; } -#endif /* CONFIG_ZONE_DMA */ =20 #ifdef CONFIG_UNACCEPTED_MEMORY =20 --=20 2.34.1 From nobody Mon Feb 9 04:30:11 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 0F8F83644BC for ; Mon, 12 Jan 2026 15:46:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768232816; cv=none; b=Zp7R+ESkaIG34u6Le7l9uXrh0ZGBLI+imr1nmVEIh2KJDp1FmdsEiil2wAsu8bgiLaByR6p1jycfJ8rIZev40ek6FUatKYN59FhD3cskTLgAXnSnNHG1m8agwRgADjPzv6f4G/cXThESg9kqEG9WvZpJDfDq78wBKb9svMkBHTA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768232816; c=relaxed/simple; bh=9BCgbGEN6YvO8PtqQjF4kxhcZB2A1GWo4Tq7+Q1XqJI=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=asn6R2YkYdEKiKTge+qVn+sRBzHTLjPn5eosvJMxITsAkSEZfZL45WI7blB0IjAcf3w782ztwqPSVwjJni3iBhDSs5+dJeimfFGUgkhjRWotpaFgLAVM7+ruO58S1GYdk3Sg9PfWRzMj/yzLfCkD0EDUaBdPr1kY2PjlnQ8Ww+8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BE5DE1596; Mon, 12 Jan 2026 07:46:47 -0800 (PST) Received: from 010265703453.arm.com (unknown [10.57.48.115]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 1267C3F694; Mon, 12 Jan 2026 07:46:51 -0800 (PST) From: Robin Murphy To: m.szyprowski@samsung.com, akpm@linux-foundation.org, vbabka@suse.cz, david@kernel.org Cc: bhe@redhat.com, iommu@lists.linux-foundation.org, linux-mm@kvack.org, vladimir.kondratiev@mobileye.com, s-adivi@ti.com, linux-kernel@vger.kernel.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, rppt@kernel.org, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com Subject: [PATCH 3/3] dma/pool: Avoid allocating redundant pools Date: Mon, 12 Jan 2026 15:46:38 +0000 Message-Id: <8ab8d8a620dee0109f33f5cb63d6bfeed35aac37.1768230104.git.robin.murphy@arm.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" On smaller systems, e.g. embedded arm64, it is common for all memory to end up in ZONE_DMA32 or even ZONE_DMA. In such cases it is redundant to allocate a nominal pool for an empty higher zone that just ends up coming from a lower zone that should already have its own pool anyway. We already have logic to skip allocating a ZONE_DMA pool when that is empty, so generalise that to save memory in the case of other zones too. Signed-off-by: Robin Murphy Reviewed-by: Baoquan He --- kernel/dma/pool.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c index 2645cfb5718b..c5da29ad010c 100644 --- a/kernel/dma/pool.c +++ b/kernel/dma/pool.c @@ -184,6 +184,12 @@ static __init struct gen_pool *__dma_atomic_pool_init(= size_t pool_size, return pool; } =20 +#ifdef CONFIG_ZONE_DMA32 +#define has_managed_dma32 has_managed_zone(ZONE_DMA32) +#else +#define has_managed_dma32 false +#endif + static int __init dma_atomic_pool_init(void) { int ret =3D 0; @@ -199,17 +205,20 @@ static int __init dma_atomic_pool_init(void) } INIT_WORK(&atomic_pool_work, atomic_pool_work_fn); =20 - atomic_pool_kernel =3D __dma_atomic_pool_init(atomic_pool_size, + /* All memory might be in the DMA zone(s) to begin with */ + if (has_managed_zone(ZONE_NORMAL)) { + atomic_pool_kernel =3D __dma_atomic_pool_init(atomic_pool_size, GFP_KERNEL); - if (!atomic_pool_kernel) - ret =3D -ENOMEM; + if (!atomic_pool_kernel) + ret =3D -ENOMEM; + } if (has_managed_dma()) { atomic_pool_dma =3D __dma_atomic_pool_init(atomic_pool_size, GFP_KERNEL | GFP_DMA); if (!atomic_pool_dma) ret =3D -ENOMEM; } - if (IS_ENABLED(CONFIG_ZONE_DMA32)) { + if (has_managed_dma32) { atomic_pool_dma32 =3D __dma_atomic_pool_init(atomic_pool_size, GFP_KERNEL | GFP_DMA32); if (!atomic_pool_dma32) @@ -228,7 +237,7 @@ static inline struct gen_pool *dma_guess_pool(struct ge= n_pool *prev, gfp_t gfp) return atomic_pool_dma ?: atomic_pool_dma32 ?: atomic_pool_kernel; if (gfp & GFP_DMA32) return atomic_pool_dma32 ?: atomic_pool_dma ?: atomic_pool_kernel; - return atomic_pool_kernel; + return atomic_pool_kernel ?: atomic_pool_dma32 ?: atomic_pool_dma; } if (prev =3D=3D atomic_pool_kernel) return atomic_pool_dma32 ? atomic_pool_dma32 : atomic_pool_dma; --=20 2.34.1