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[209.85.220.65]) by mx.google.com with SMTPS id i13sor6624559pgr.87.2019.07.13.12.39.19 for (Google Transport Security); Sat, 13 Jul 2019 12:39:19 -0700 (PDT) Received-SPF: pass (google.com: domain of rientjes@google.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=n0KFTozv; spf=pass (google.com: domain of rientjes@google.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=rientjes@google.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:in-reply-to:message-id:references :user-agent:mime-version; bh=4rwRS7GM+nAGTGCY3bn6psvJVMqQf5Gz5RaBpQRnLL8=; b=n0KFTozv9CtnAVuGyX9D6NNG61GDCR6T64sYf9upTmnmAdBFsnDEUe1t04Bu/LT2D+ bqBxtGoXwlL1gRCO7WG9Ry/284/rMlUsnYIrhM2DGa+J+n8e/x6f6zHA4id9QtkHa0lh yUECAj3rN/6p1EB2mV2pFisblC3mqlEQjqMnDIujn/DWYMn1r1/cFrH44limBhWtA471 7Ivil9qXvMi9HM/BXy38rCzLWP4HvU3WnGlPrgV9sfbyNU5xKXnzdknElbXLdolGGYg7 PDlDb+DUR0wgpZ8zpQE63IgFYMKyfyV09ZDJLsq+hVRQu169Lp9V4242fwagSZfrMEY1 Paow== X-Google-Smtp-Source: APXvYqxOrGaeCkdz67qh5Pd8o/OBYvz4gK7V7SeQ+uf99qRLAi4vYDlYPDSLlTDG/ZmBLF3HPE9yUQ== X-Received: by 2002:a63:6686:: with SMTP id a128mr11260150pgc.361.1563046758563; Sat, 13 Jul 2019 12:39:18 -0700 (PDT) Received: from [2620:15c:17:3:3a5:23a7:5e32:4598] ([2620:15c:17:3:3a5:23a7:5e32:4598]) by smtp.gmail.com with ESMTPSA id k6sm11697073pfi.12.2019.07.13.12.39.17 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Sat, 13 Jul 2019 12:39:17 -0700 (PDT) Date: Sat, 13 Jul 2019 12:39:16 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Yang Shi cc: mhocko@suse.com, dvyukov@google.com, catalin.marinas@arm.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: page_alloc: document kmemleak's non-blockable __GFP_NOFAIL case In-Reply-To: <1562964544-59519-1-git-send-email-yang.shi@linux.alibaba.com> Message-ID: References: <1562964544-59519-1-git-send-email-yang.shi@linux.alibaba.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sat, 13 Jul 2019, Yang Shi wrote: > When running ltp's oom test with kmemleak enabled, the below warning was > triggerred since kernel detects __GFP_NOFAIL & ~__GFP_DIRECT_RECLAIM is > passed in: > > WARNING: CPU: 105 PID: 2138 at mm/page_alloc.c:4608 __alloc_pages_nodemask+0x1c31/0x1d50 > Modules linked in: loop dax_pmem dax_pmem_core > ip_tables x_tables xfs virtio_net net_failover virtio_blk failover > ata_generic virtio_pci virtio_ring virtio libata > CPU: 105 PID: 2138 Comm: oom01 Not tainted 5.2.0-next-20190710+ #7 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.10.2-0-g5f4c7b1-prebuilt.qemu-project.org 04/01/2014 > RIP: 0010:__alloc_pages_nodemask+0x1c31/0x1d50 > ... > kmemleak_alloc+0x4e/0xb0 > kmem_cache_alloc+0x2a7/0x3e0 > ? __kmalloc+0x1d6/0x470 > ? ___might_sleep+0x9c/0x170 > ? mempool_alloc+0x2b0/0x2b0 > mempool_alloc_slab+0x2d/0x40 > mempool_alloc+0x118/0x2b0 > ? __kasan_check_read+0x11/0x20 > ? mempool_resize+0x390/0x390 > ? lock_downgrade+0x3c0/0x3c0 > bio_alloc_bioset+0x19d/0x350 > ? __swap_duplicate+0x161/0x240 > ? bvec_alloc+0x1b0/0x1b0 > ? do_raw_spin_unlock+0xa8/0x140 > ? _raw_spin_unlock+0x27/0x40 > get_swap_bio+0x80/0x230 > ? __x64_sys_madvise+0x50/0x50 > ? end_swap_bio_read+0x310/0x310 > ? __kasan_check_read+0x11/0x20 > ? check_chain_key+0x24e/0x300 > ? bdev_write_page+0x55/0x130 > __swap_writepage+0x5ff/0xb20 > > The mempool_alloc_slab() clears __GFP_DIRECT_RECLAIM, kmemleak has > __GFP_NOFAIL set all the time due to commit > d9570ee3bd1d4f20ce63485f5ef05663866fe6c0 ("kmemleak: allow to coexist > with fault injection"). > It only clears __GFP_DIRECT_RECLAIM provisionally to see if the allocation would immediately succeed before falling back to the elements in the mempool. If that fails, and the mempool is empty, mempool_alloc() attempts the allocation with __GFP_DIRECT_RECLAIM. So for the problem described here, I think what we really want is this: diff --git a/mm/mempool.c b/mm/mempool.c --- a/mm/mempool.c +++ b/mm/mempool.c @@ -386,7 +386,7 @@ void *mempool_alloc(mempool_t *pool, gfp_t gfp_mask) gfp_mask |= __GFP_NORETRY; /* don't loop in __alloc_pages */ gfp_mask |= __GFP_NOWARN; /* failures are OK */ - gfp_temp = gfp_mask & ~(__GFP_DIRECT_RECLAIM|__GFP_IO); + gfp_temp = gfp_mask & ~(__GFP_DIRECT_RECLAIM|__GFP_IO|__GFP_NOFAIL); repeat_alloc: But bio_alloc_bioset() plays with gfp_mask itself: are we sure that it isn't the one clearing __GFP_DIRECT_RECLAIM itself before falling back to saved_gfp? In other words do we also want this? diff --git a/block/bio.c b/block/bio.c --- a/block/bio.c +++ b/block/bio.c @@ -462,16 +462,16 @@ struct bio *bio_alloc_bioset(gfp_t gfp_mask, unsigned int nr_iovecs, * We solve this, and guarantee forward progress, with a rescuer * workqueue per bio_set. If we go to allocate and there are * bios on current->bio_list, we first try the allocation - * without __GFP_DIRECT_RECLAIM; if that fails, we punt those - * bios we would be blocking to the rescuer workqueue before - * we retry with the original gfp_flags. + * without __GFP_DIRECT_RECLAIM or __GFP_NOFAIL; if that fails, + * we punt those bios we would be blocking to the rescuer + * workqueue before we retry with the original gfp_flags. */ - if (current->bio_list && (!bio_list_empty(¤t->bio_list[0]) || !bio_list_empty(¤t->bio_list[1])) && bs->rescue_workqueue) - gfp_mask &= ~__GFP_DIRECT_RECLAIM; + gfp_mask &= ~(__GFP_DIRECT_RECLAIM | + __GFP_NOFAIL); p = mempool_alloc(&bs->bio_pool, gfp_mask); if (!p && gfp_mask != saved_gfp) {