From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-189.mta0.migadu.com (out-189.mta0.migadu.com [91.218.175.189]) (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 1C64A3603C2 for ; Fri, 12 Jun 2026 02:27:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.189 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781231261; cv=none; b=okuklcL5rLr+P7uihkefJ5i4v5okJqRq/DW5uMX36GgICVaT9AfXo90h6LmtuHElMAX3pv7fGrLg2dRu7OtfIh6Aw6yaPtFI1VujfMR7zmGT8utFjWaGyf6lfi2yDv9usnqbO7fdjyBKKj77MOdYieIYFpo23nKBCsuwuuA+u0s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781231261; c=relaxed/simple; bh=G9NAY/DcosKetWJ9OoSbtvH2y7gHpA8If9b/1e06p3c=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=eSHar1NwlWFCxkqKpnrrYkNezSitPyMaPidpZmkgzJrCVKO9Ri7xpGLxXljBjd2HomXYtgvOllv/t6ZviwOGN2pECYzVOdpcRc05xRDU6XWiUWuPlvVI/ttzhby6OaNjS8oi6qf0tQb3XagsySTwFfKm4FHNVfWhd2qf8c891oA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=H7OlTz3G; arc=none smtp.client-ip=91.218.175.189 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="H7OlTz3G" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1781231258; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=6rnxGR0B6+PGyTAZIojjMa7xppAB2J31XJIy8wkmbfs=; b=H7OlTz3GZdT+97dlSASQyZ/Coe5wEFEuw/D1Ow7sM+Emlkjgy9l4JjSPAcN/08GmGpSBFi fMDsllyGBS1KRg96K8bcg1V9b6tbZLaPiVechr3Pvw1IQY222uITqvjVaAodqgm/+LOeGd uwracgj0MSDAgVrlueq5VPJif5wZunI= From: Kaitao Cheng To: Andrew Morton , Uladzislau Rezki , Dennis Zhou , Tejun Heo , Christoph Lameter Cc: Vlastimil Babka , Michal Hocko , muchun.song@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Kaitao Cheng Subject: [PATCH v3 1/3] mm/vmalloc: honor GFP constraints in pcpu_get_vm_areas() Date: Fri, 12 Jun 2026 10:26:46 +0800 Message-ID: <20260612022648.13008-2-kaitao.cheng@linux.dev> In-Reply-To: <20260612022648.13008-1-kaitao.cheng@linux.dev> References: <20260612022648.13008-1-kaitao.cheng@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT From: Kaitao Cheng pcpu_alloc_noprof() derives pcpu_gfp from the caller supplied GFP mask and passes it down to the backing percpu allocator. However, when the percpu vmalloc allocator has to create a new chunk, pcpu_create_chunk() calls pcpu_get_vm_areas() to allocate the corresponding vmalloc areas. pcpu_get_vm_areas() currently performs its internal allocations with GFP_KERNEL, including vmap area metadata, vm_struct metadata and KASAN vmalloc shadow population. This means that a caller which deliberately uses GFP_NOFS or GFP_NOIO can still enter FS or IO reclaim while creating the vmalloc areas for a new percpu chunk. One possible case is blk-cgroup after commit 5d726c4dbeed ("blk-cgroup: fix possible deadlock while configuring policy"). blkg_conf_prep() now serializes against blkcg_deactivate_policy() with q->blkcg_mutex, and blkg_alloc() was changed to GFP_NOIO for that reason: CPU0: blkg_conf_prep() mutex_lock(q->blkcg_mutex) blkg_alloc(..., GFP_NOIO) alloc_percpu_gfp(..., GFP_NOIO) pcpu_alloc_noprof(..., GFP_NOIO) pcpu_create_chunk(GFP_NOIO) pcpu_get_vm_areas() -> if percpu chunks are exhausted, chunk create may do internal GFP_KERNEL allocations -> direct reclaim / writeback can issue IO to this queue -> IO waits because the queue is frozen CPU1: blkcg_deactivate_policy() blk_mq_freeze_queue(q) mutex_lock(q->blkcg_mutex) -> waits for CPU0 ... unfreeze only happens after q->blkcg_mutex is acquired/released So the concern is that the caller deliberately uses GFP_NOIO because it may hold a lock which can be acquired after queue freeze, but the percpu slow path can temporarily lose that allocation context. Pass the caller supplied GFP mask from pcpu_create_chunk() to pcpu_get_vm_areas(), and use it for the internal vmalloc metadata and KASAN shadow allocations. Fixes: 9a5b183941b5 ("mm, percpu: do not consider sleepable allocations atomic") Signed-off-by: Kaitao Cheng Reviewed-by: Uladzislau Rezki (Sony) --- include/linux/vmalloc.h | 4 ++-- mm/percpu-vm.c | 2 +- mm/vmalloc.c | 23 ++++++++++++----------- 3 files changed, 15 insertions(+), 14 deletions(-) diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h index d87dc7f77f4e..e4d8d0a9f30f 100644 --- a/include/linux/vmalloc.h +++ b/include/linux/vmalloc.h @@ -310,14 +310,14 @@ static inline void set_vm_flush_reset_perms(void *addr) {} #if defined(CONFIG_MMU) && defined(CONFIG_SMP) struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets, const size_t *sizes, int nr_vms, - size_t align); + size_t align, gfp_t gfp); void pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms); # else static inline struct vm_struct ** pcpu_get_vm_areas(const unsigned long *offsets, const size_t *sizes, int nr_vms, - size_t align) + size_t align, gfp_t gfp) { return NULL; } diff --git a/mm/percpu-vm.c b/mm/percpu-vm.c index 4f5937090590..69b00741dc68 100644 --- a/mm/percpu-vm.c +++ b/mm/percpu-vm.c @@ -340,7 +340,7 @@ static struct pcpu_chunk *pcpu_create_chunk(gfp_t gfp) return NULL; vms = pcpu_get_vm_areas(pcpu_group_offsets, pcpu_group_sizes, - pcpu_nr_groups, pcpu_atom_size); + pcpu_nr_groups, pcpu_atom_size, gfp); if (!vms) { pcpu_free_chunk(chunk); return NULL; diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 1afca3568b9b..08f468135e4d 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -4946,16 +4946,17 @@ pvm_determine_end_from_reverse(struct vmap_area **va, unsigned long align) * @sizes: array containing size of each area * @nr_vms: the number of areas to allocate * @align: alignment, all entries in @offsets and @sizes must be aligned to this + * @gfp: allocation flags passed to the underlying memory allocator * * Returns: kmalloc'd vm_struct pointer array pointing to allocated * vm_structs on success, %NULL on failure * * Percpu allocator wants to use congruent vm areas so that it can * maintain the offsets among percpu areas. This function allocates - * congruent vmalloc areas for it with GFP_KERNEL. These areas tend to - * be scattered pretty far, distance between two areas easily going up - * to gigabytes. To avoid interacting with regular vmallocs, these - * areas are allocated from top. + * congruent vmalloc areas for it. These areas tend to be scattered + * pretty far, distance between two areas easily going up to gigabytes. + * To avoid interacting with regular vmallocs, these areas are allocated + * from top. * * Despite its complicated look, this allocator is rather simple. It * does everything top-down and scans free blocks from the end looking @@ -4966,7 +4967,7 @@ pvm_determine_end_from_reverse(struct vmap_area **va, unsigned long align) */ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets, const size_t *sizes, int nr_vms, - size_t align) + size_t align, gfp_t gfp) { const unsigned long vmalloc_start = ALIGN(VMALLOC_START, align); const unsigned long vmalloc_end = VMALLOC_END & ~(align - 1); @@ -5004,14 +5005,14 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets, return NULL; } - vms = kzalloc_objs(vms[0], nr_vms); - vas = kzalloc_objs(vas[0], nr_vms); + vms = kzalloc_objs(vms[0], nr_vms, gfp); + vas = kzalloc_objs(vas[0], nr_vms, gfp); if (!vas || !vms) goto err_free2; for (area = 0; area < nr_vms; area++) { - vas[area] = kmem_cache_zalloc(vmap_area_cachep, GFP_KERNEL); - vms[area] = kzalloc_obj(struct vm_struct); + vas[area] = kmem_cache_zalloc(vmap_area_cachep, gfp); + vms[area] = kzalloc_obj(struct vm_struct, gfp); if (!vas[area] || !vms[area]) goto err_free; } @@ -5101,7 +5102,7 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets, /* populate the kasan shadow space */ for (area = 0; area < nr_vms; area++) { - if (kasan_populate_vmalloc(vas[area]->va_start, sizes[area], GFP_KERNEL)) + if (kasan_populate_vmalloc(vas[area]->va_start, sizes[area], gfp)) goto err_free_shadow; } @@ -5158,7 +5159,7 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets, continue; vas[area] = kmem_cache_zalloc( - vmap_area_cachep, GFP_KERNEL); + vmap_area_cachep, gfp); if (!vas[area]) goto err_free; } -- 2.43.0