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b=DacyOXAs9CcEdnJCARgCEQOxk7HC/wim6+i7PLYp5ybh12vCgnXGJQnOw0UyI5ERTt ccz9M2KbbUMiOBri4VOcJ5ejFEPnJW+oY3OWgBhfyTCje2m79ib+jrDyLGC7gGBliHDS ciU0D0JJfEI3M/KE7sAfuuu1mwXkY5lMUP/nhx4b/tmNdj2vpTH371sBvzp0KiI4AMGf ze5G3lGn/BFGoljK+30QzRMd6srAs4NZNPPQ/11kN4pVGaudbhwJva7jFn0vEVjRSDKF wy9THL7dSjA4TDILFEsZw8JYlbGIJqiGa6SWYfOHY52EIvVHYfkHWBn57qLTIyoBNpXb uS5A== X-Gm-Message-State: AOJu0YxmoMhR4Kr6/dvr5lVdojKQ3jSQscCTngdUKS4HsR4wNfZ00WoF AwR3WuUQrxin+caTP05LB4owjP4lZH5qgL/FD74zxERj2ajKx6FOA6U= X-Google-Smtp-Source: AGHT+IH5RHc6E6gGJ5fTOVow2UXuKlTH5TSJinTQzKV/yi/t/o1D2iGvhxrP+vtIWp2/THtyZMwOjw/pgdmzUCKSCRc= X-Received: by 2002:a2e:9214:0:b0:2b6:9ed5:bf15 with SMTP id k20-20020a2e9214000000b002b69ed5bf15mr338347ljg.23.1691711186833; Thu, 10 Aug 2023 16:46:26 -0700 (PDT) MIME-Version: 1.0 References: <20230810095652.3905184-1-fengwei.yin@intel.com> <26949c92-95a0-414f-918a-8b8cc11e3e9c@intel.com> <3732dd16-148d-4ac6-8295-86a12f89365b@intel.com> In-Reply-To: From: Yosry Ahmed Date: Thu, 10 Aug 2023 16:45:50 -0700 Message-ID: Subject: Re: [PATCH] zswap: don't warn if none swapcache folio is passed to zswap_load To: Yu Zhao Cc: "Yin, Fengwei" , linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, willy@infradead.org, hannes@cmpxchg.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: CBABA100004 X-Stat-Signature: wfo4o7puz7sf8fe5i1ci9sdhnqx3kaky X-HE-Tag: 1691711188-556116 X-HE-Meta: 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 ca17QdR6 5ieImBqP/uOSHNkeKxnn2Kdf0VXekbqgRFCuI/9M9mUViY8Yl3NdxeWfEXsx/YB+zaFqCsjzyzMbtU9N7tLr9sXWfRgyc8HkB+PAx25D2R48zyA0i2BUGDxjMTzZjrFaIV9JEslct44usm8d40sP2bumZbMFVKHrYNvedfmDneth75MGokvxsFjHEgpFQFiOEBkiy0vD+7nswWVMGsFJZRrd2UAoZbdue6gmortMYugHqQlix+BWoONeyMg9IcDgXbwA9LELl0kcbRGPpgkllo4fEmuasRCLYIY5x20sv0UlXZHVFRj2EpJQYJLxQ7Y9cXGP8 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 Thu, Aug 10, 2023 at 4:44=E2=80=AFPM Yu Zhao wrote: > > On Thu, Aug 10, 2023 at 5:31=E2=80=AFPM Yin, Fengwei wrote: > > > > > > > > On 8/11/2023 7:15 AM, Yosry Ahmed wrote: > > > On Thu, Aug 10, 2023 at 4:09=E2=80=AFPM Yin, Fengwei wrote: > > >> > > >> > > >> > > >> On 8/11/2023 2:44 AM, Yu Zhao wrote: > > >>> On Thu, Aug 10, 2023 at 3:58=E2=80=AFAM Yin Fengwei wrote: > > >>>> > > >>>> With mm-unstable branch, if trigger swap activity and it's possibl= e > > >>>> see following warning: > > >>>> [ 178.093511][ T651] WARNING: CPU: 2 PID: 651 at mm/zswap.c:1387= zswap_load+0x67/0x570 > > >>>> [ 178.095155][ T651] Modules linked in: > > >>>> [ 178.096103][ T651] CPU: 2 PID: 651 Comm: gmain Not tainted 6.5= .0-rc4-00492-gad3232df3e41 #148 > > >>>> [ 178.098372][ T651] Hardware name: QEMU Standard PC (i440FX + P= IIX,1996), BIOS 1.14.0-2 04/01/2014 > > >>>> [ 178.101114][ T651] RIP: 0010:zswap_load+0x67/0x570 > > >>>> [ 178.102359][ T651] Code: a0 78 4b 85 e8 ea db ff ff 48 8b 00 a= 8 01 0f 84 84 04 00 00 48 89 df e8 d7 db ff ff 48 8b 00 a9 00 00 08 00 0f 8= 5 c4 > > >>>> [ 178.106376][ T651] RSP: 0018:ffffc900011b3760 EFLAGS: 00010246 > > >>>> [ 178.107675][ T651] RAX: 0017ffffc0080001 RBX: ffffea0004a991c0= RCX:ffffc900011b37dc > > >>>> [ 178.109242][ T651] RDX: 0000000000000000 RSI: 0000000000000001= RDI:ffffea0004a991c0 > > >>>> [ 178.110916][ T651] RBP: ffffea0004a991c0 R08: 0000000000000243= R09:00000000c9a1aafc > > >>>> [ 178.112377][ T651] R10: 00000000c9657db3 R11: 000000003c9657db= R12:0000000000014b9c > > >>>> [ 178.113698][ T651] R13: ffff88813501e710 R14: ffff88810d591000= R15:0000000000000000 > > >>>> [ 178.115008][ T651] FS: 00007fb21a9ff700(0000) GS:ffff88813bc8= 0000(0000) knlGS:0000000000000000 > > >>>> [ 178.116423][ T651] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080= 050033 > > >>>> [ 178.117421][ T651] CR2: 00005632cbfc81f6 CR3: 0000000131450002= CR4:0000000000370ee0 > > >>>> [ 178.118683][ T651] DR0: 0000000000000000 DR1: 0000000000000000= DR2:0000000000000000 > > >>>> [ 178.119894][ T651] DR3: 0000000000000000 DR6: 00000000fffe0ff0= DR7:0000000000000400 > > >>>> [ 178.121087][ T651] Call Trace: > > >>>> [ 178.121654][ T651] > > >>>> [ 178.122109][ T651] ? zswap_load+0x67/0x570 > > >>>> [ 178.122658][ T651] ? __warn+0x81/0x170 > > >>>> [ 178.123119][ T651] ? zswap_load+0x67/0x570 > > >>>> [ 178.123608][ T651] ? report_bug+0x167/0x190 > > >>>> [ 178.124150][ T651] ? handle_bug+0x3c/0x70 > > >>>> [ 178.124615][ T651] ? exc_invalid_op+0x13/0x60 > > >>>> [ 178.125192][ T651] ? asm_exc_invalid_op+0x16/0x20 > > >>>> [ 178.125753][ T651] ? zswap_load+0x67/0x570 > > >>>> [ 178.126231][ T651] ? lock_acquire+0xbb/0x290 > > >>>> [ 178.126745][ T651] ? folio_add_lru+0x40/0x1c0 > > >>>> [ 178.127261][ T651] ? find_held_lock+0x2b/0x80 > > >>>> [ 178.127776][ T651] swap_readpage+0xc7/0x5c0 > > >>>> [ 178.128273][ T651] do_swap_page+0x86d/0xf50 > > >>>> [ 178.128770][ T651] ? __pte_offset_map+0x3e/0x290 > > >>>> [ 178.129321][ T651] ? __pte_offset_map+0x1c4/0x290 > > >>>> [ 178.129883][ T651] __handle_mm_fault+0x6ad/0xca0 > > >>>> [ 178.130419][ T651] handle_mm_fault+0x18b/0x410 > > >>>> [ 178.130992][ T651] do_user_addr_fault+0x1f1/0x820 > > >>>> [ 178.132076][ T651] exc_page_fault+0x63/0x1a0 > > >>>> [ 178.132599][ T651] asm_exc_page_fault+0x22/0x30 > > >>>> > > >>>> It's possible that swap_readpage() is called with none swapcache f= olio > > >>>> in do_swap_page() and trigger this warning. So we shouldn't assume > > >>>> zswap_load() always takes swapcache folio. > > >>> > > >>> Did you use a bdev with QUEUE_FLAG_SYNCHRONOUS? Otherwise it sounds > > >>> like a bug to me. > > >> I hit this warning with zram which has QUEUE_FLAG_SYNCHRONOUS set. T= hanks. > > > > > > Does it make sense to keep the warning and instead change it to check > > > SWP_SYNCHRONOUS_IO as well? Something like: > > > > > > VM_WARN_ON_ONCE(!folio_test_swapcache(folio) && > > > !swap_type_to_swap_info(type)->flags && SWP_SYNCHRONOUS_IO); > > > > > > Of course this is too ugly, so perhaps we want a helper to check if a > > > swapfile is synchronous. > > My understanding was that the WARN here is zswap_load() doesn't expect > > a folio not in swapcache. With zram, swap_readpage() must accept the > > folio not in swapcache. So this warn should not be there. > > > > But your comment make more sense to me. I will update the patch not > > to remove this WARN. Thanks. > > That can cause another warning. > > Please don't overegineer. How so? Using zswap with zram is a weird combination, if anything I would prefer leaving the warning as-is than removing it to be honest.