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Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.8.0 From: Pankaj Raghav Subject: Re: [LSF/MM/BPF TOPIC] Cloud storage optimizations To: Keith Busch , Luis Chamberlain CC: Matthew Wilcox , Theodore Ts'o , Daniel Gomez , =?UTF-8?Q?Javier_Gonz=c3=a1lez?= , , , , , Dave Chinner , "Christoph Hellwig" Content-Language: en-US In-Reply-To: <367c04f8-f5f6-a628-c4a9-7534fa83eb88@samsung.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [106.210.248.172] X-ClientProxiedBy: CAMSVWEXC01.scsc.local (2002:6a01:e347::6a01:e347) To CAMSVWEXC02.scsc.local (2002:6a01:e348::6a01:e348) X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFtrGKsWRmVeSWpSXmKPExsWy7djP87oilsIpBq/2K1psOXaP0WLl6qNM FpMOXWO02HtL22LP3pMsFvfW/Ge12Pd6L7PFjQlPGS1ae36yW/z+MYfNgcvj1CIJj80rtDw2 repk89j0aRK7x+Qbyxk9dt9sYPNoOnOU2ePzJrkAjigum5TUnMyy1CJ9uwSujN3XNrAUTOKu uPGvqIHxOkcXIyeHhICJxNNdH1m7GLk4hARWMEqcu7cZyvnCKHFgZwMLSJWQwGdGiZ3Xw2E6 eh4fhIovZ5RoOlkHVzNrVw1E825GieN/vjKDJHgF7CS27T/ODmKzCKhKHP11gwUiLihxcuYT IJuDQ1QgSuLF6zIQk01AS6KxE6xaWMBaYtOsPYwgYREBT4n/x1VBpjMLfGaSeDfrKBNIDbOA uMStJ/PBbE4Be4kd3x5AxTUlWrf/Zoew5SW2v53DDHG+ssSc1zug7FqJU1tuMYEMlRBYzSnx 4ek/NoiEi8SGWcegbGGJV8e3sEPYMhL/d0IskxColnh64zczRHMLo0T/zvVsIJdKAF3ddyYH osZRYt/1PiaIMJ/EjbeCEPfwSUzaNp15AqPqLKSAmIXknVlIXpiF5IUFjCyrGMVTS4tz01OL jfJSy/WKE3OLS/PS9ZLzczcxApPW6X/Hv+xgXP7qo94hRiYOxkOMEhzMSiK84SwCKUK8KYmV ValF+fFFpTmpxYcYpTlYlMR5tW1PJgsJpCeWpGanphakFsFkmTg4pRqYxK4aqZh0l8RKvXv/ ofFpQsGko8Lan7bVC8+d1DH911HvhEVn8v9vWZCXxNVSkFc2USHtSPTBSst1HQZPpz17/VHj +LEZ25Z1cZoU3Sy8mpW15cxWMdMjaVtrDDukKl/y8s6+GXY2/ZjgqTDHrMqulq3sLXdCT4v1 rv8TnaVqf0mcW3+jvYp45MtL9vP3MQduKmm9oTntyAazayWT/G5qL2JrTl5+YaruyQIV0x11 cmU7RC56Bp1wMrxlGHrf90b2CY7Dsyutfl0J/VGjEqe8WKmS30/Laf45S6vgrz//fXzNucKl ckOF1K8X7F5P63IOi/1fr36wzcebZ6pJoLLI0YC/n+vdMwSmR97vS/FXYinOSDTUYi4qTgQA mOV1fckDAAA= X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFnrHIsWRmVeSWpSXmKPExsVy+t/xu7oilsIpBu+nMFlsOXaP0WLl6qNM FpMOXWO02HtL22LP3pMsFvfW/Ge12Pd6L7PFjQlPGS1ae36yW/z+MYfNgcvj1CIJj80rtDw2 repk89j0aRK7x+Qbyxk9dt9sYPNoOnOU2ePzJrkAjig9m6L80pJUhYz84hJbpWhDCyM9Q0sL PSMTSz1DY/NYKyNTJX07m5TUnMyy1CJ9uwS9jN3XNrAUTOKuuPGvqIHxOkcXIyeHhICJRM/j gyxdjFwcQgJLGSW2NRxghEjISHy68pEdwhaW+HOtiw2i6COjxLMJ+1hBEkICuxklTp32A7F5 Bewktu0/DtbAIqAqcfTXDRaIuKDEyZlPwGxRgSiJp3cOMXcxcnCwCWhJNHaClQsLWEtsmrWH ESQsIuAp8f+4KsgqZoHPTBJ9e6cyQ+y9wCwxuX0h2F5mAXGJW0/mM4HYnAL2Eju+PWCCiGtK tG7/zQ5hy0tsfzuHGeIBZYk5r3dA2bUSn/8+Y5zAKDoLyXmzkIydhWTULCSjFjCyrGIUSS0t zk3PLTbUK07MLS7NS9dLzs/dxAiM+G3Hfm7ewTjv1Ue9Q4xMHIyHGCU4mJVEeMNZBFKEeFMS K6tSi/Lji0pzUosPMZoCw2gis5Rocj4w5eSVxBuaGZgamphZGphamhkrifN6FnQkCgmkJ5ak ZqemFqQWwfQxcXBKNTBpu2cmfo8Wm50Z+XT9iStMu2qrq8NV/XhfezJZ/1rortb4d128tXHY tt3uiw98qC5VCUr527p74eliAdvXdfwBf3QLw2/8nT9bO/iwx+yYZf6fko6++m0R+liTOzg1 6sXWtXVL9p98EPVGVuZX40qBZ7c9KvJzcv1Nl7y/t8eN+e+0vWFWH/2+cM5ffUR06WXX266v Tk59e2h/eH+d34fmn//ChDIvffbP33OXPewaY4/YnsKNZwXe9cYvWl7S0pW78EnS3l6mPwrT On3aFGwuNAgH6KwRmMP+Ve7MLuZnQos/S11IVdjR/5Bhpv2UL6cPXSvy9bgRvZfrUMealAeH 59+z4br7McDUcT/nD645SizFGYmGWsxFxYkAaQaBGYEDAAA= X-CMS-MailID: 20230316154316eucas1p203d1cb0da33c72fa8972d10c04714826 X-Msg-Generator: CA X-RootMTR: 20230303223216eucas1p2517850ab1c4f98dc4e09d83673525983 X-EPHeader: CA CMS-TYPE: 201P X-CMS-RootMailID: 20230303223216eucas1p2517850ab1c4f98dc4e09d83673525983 References: <367c04f8-f5f6-a628-c4a9-7534fa83eb88@samsung.com> Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 2023-03-16 16:29, Pankaj Raghav wrote: > Hi Keith, > > On 2023-03-03 23:32, Keith Busch wrote: >>> Yes, clearly it says *yet* so that begs the question what would be >>> required? >> >> Oh, gotcha. I'll work on a list of places it currently crashes. >> > I started looking into this to see why it crashes when we increase the LBA > size of a block device greater than the page size. These are my primary > findings: > > - Block device aops (address_space_operations) are all based on buffer > head, which limits us to work on only PAGE_SIZE chunks. > > For a 8k LBA size, the stack trace you posted ultimately fails inside > alloc_page_buffers as the size will be > PAGE_SIZE. > > struct buffer_head *alloc_page_buffers(struct page *page, unsigned long > size, bool retry) > Aghh. Sorry for the ugly formatting: struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, bool retry) { struct buffer_head *bh, *head; gfp_t gfp = GFP_NOFS | __GFP_ACCOUNT; long offset; struct mem_cgroup *memcg, *old_memcg; if (retry) gfp |= __GFP_NOFAIL; /* The page lock pins the memcg */ memcg = page_memcg(page); old_memcg = set_active_memcg(memcg); head = NULL; offset = PAGE_SIZE; while ((offset -= size) >= 0) { // we will not go into this loop as offset will be negative ... ... } ... return head; // we return NULL for LBA size > 4k }