From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id CD5B0CD6E4A for ; Thu, 4 Jun 2026 11:32:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 131026B0088; Thu, 4 Jun 2026 07:32:00 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 108C16B008A; Thu, 4 Jun 2026 07:32:00 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 01EAE6B008C; Thu, 4 Jun 2026 07:31:59 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id EAD816B0088 for ; Thu, 4 Jun 2026 07:31:59 -0400 (EDT) Received: from smtpin13.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 5615CC1DDD for ; Thu, 4 Jun 2026 11:31:59 +0000 (UTC) X-FDA: 84842015958.13.8CA781D Received: from out-183.mta0.migadu.com (out-183.mta0.migadu.com [91.218.175.183]) by imf29.hostedemail.com (Postfix) with ESMTP id 3991C120009 for ; Thu, 4 Jun 2026 11:31:57 +0000 (UTC) Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=CYZ9U8Kh; spf=pass (imf29.hostedemail.com: domain of kaitao.cheng@linux.dev designates 91.218.175.183 as permitted sender) smtp.mailfrom=kaitao.cheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1780572717; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=7UgAkBaY/d/7ezqgbIeADZSgUpEbmYU0w3siNBffvvc=; b=tpr2ATqvmARL8iDpuzgiGoAedUTXprTe9JWL1cVYk9I/6avmevxhpUzJbcnT6PORKXtHCu vSQXdHtoH1PwJja9MHJFYgGrObZcoFY9ZlwqPm8jvvi0ZDgxszevjHIwsEoCzyt3sxbuJO MwVwmWMECd3GvORJJ/4tCTP43A438B8= ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=CYZ9U8Kh; spf=pass (imf29.hostedemail.com: domain of kaitao.cheng@linux.dev designates 91.218.175.183 as permitted sender) smtp.mailfrom=kaitao.cheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1780572717; b=L3QpPG522AmeQbPFVjYXOJZ7ohtRW1ojZ8wK8KYLpLfNEwdg6wZ7bzLgipZdIKKKT8cAjv Kl7sAWg1k4Es55R/t5PSkat/n+m5CELfKxKz7oMdi6VQBkEzB+2rDHLRhAofxbXFZPqt73 JZh2SzkZhBs08QqFSriHvSdkbzCLhus= 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=1780572716; 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=7UgAkBaY/d/7ezqgbIeADZSgUpEbmYU0w3siNBffvvc=; b=CYZ9U8Khray64pOp693cftUUp4vB3ZgNwkX1LXln+EDnb+eFbn6FJAM0Lljh/cImZvHzri wz1iNunqsUXPuoRf7OpPGiYDvWQTtObS+MYyknGp74jBvX8CokpefVlwqpQHm34CweoTWx 5mcDoV3VGQVc26v0kCEl5Ejq+l1Ta78= From: Kaitao Cheng To: Andrew Morton , Dennis Zhou , Tejun Heo , Christoph Lameter , Uladzislau Rezki , Pedro Falcato , Vlastimil Babka , Michal Hocko Cc: muchun.song@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Kaitao Cheng Subject: [PATCH v2 1/3] mm/vmalloc: honor GFP constraints in pcpu_get_vm_areas() Date: Thu, 4 Jun 2026 19:30:59 +0800 Message-ID: <20260604113101.89510-2-kaitao.cheng@linux.dev> In-Reply-To: <20260604113101.89510-1-kaitao.cheng@linux.dev> References: <20260604113101.89510-1-kaitao.cheng@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 3991C120009 X-Stat-Signature: nexdx4mn14kdupit3ex97btkfjppam7b X-Rspam-User: X-HE-Tag: 1780572717-802273 X-HE-Meta: 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 btgZ9ABY j8a1Ft9KW4hSswvLezr9oy1dNCeC1V42i8Ry8zZM+S0AJRvdXQyOyjYxWA38yCc7NB+xGQHM8MK6Cs7AcnlFAkuTH6pJrKgVKhauDsWQ5BjYpd4HJDbNCYzNYHVSug0JOdTAQhUEw5dEBuZI7cSlcprwhT+nrhLpDVDd6ZbX/8d93ZCJPxWBvNU+ofp8gwhJ+vHXDKZjRWKvCsw5gSPRimoXKz6lk0V+Bmq/Uocc5FBmRWRnbNUMFWHoSOA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 --- 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 3b02c0c6b371..9601e06624c8 100644 --- a/include/linux/vmalloc.h +++ b/include/linux/vmalloc.h @@ -308,14 +308,14 @@ 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