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AJvYcCUFe/oKwywLTKp6JQzKEX2CM5beikAX0FAP2NSsTwyyqNawLRkRa9gLctz43Uu5AN5jkaBFp7opVg==@kvack.org X-Gm-Message-State: AOJu0YwhNmnbZneuCPGpYtR+2pYMyMOebnxs0NwDrAP5ZGEwyt2TVnv0 a09IV/pzHfY8m8smsmz4KPdJv+1QdbIqN8aEF7RUDM5CuNwgJxxlvHXPo566Gifr42uFRZ7pBVz OCNdK3Bl7z6iyMikfL04OBUr++OzBLUw= X-Gm-Gg: ASbGncuxXuIMCd13Rs75wQ8etgG6srf3NrZtnCH89YVChyEtVXm/UhRmbIeFA2NkuK8 8UA0EgqQ+kFDG98rEljK6ZHLukA9Fxm6HTdKFYJONE8HRwVzjE3Z16rFhzNDqLaI7ijVoTNY5IH Nn/e5yD5DVTZpLVJLtD0xOMAZk91qbcJL/HOgtycpIayT1oWsZ/xS0KFVK39fzxvBPgM5PvJCmh QYd5ooc32lTkQWDqlXJRpMZZ1ilV9rdBpYPI90AzGbQXrEcEhqUUQKeKdPA+m5L5Qb9Gg== X-Google-Smtp-Source: AGHT+IG3fjIllf1M6OCTBTd4dSunSkyg52cMugpNYk6tQ4JIDEp/Anl2MiBIRm+2Hyasb11VlNQQzK6UXmCqQNXT5qw= X-Received: by 2002:a05:622a:554:b0:4ee:2bfb:1658 with SMTP id d75a77b69052e-4f017655416mr83408181cf.45.1764871612155; Thu, 04 Dec 2025 10:06:52 -0800 (PST) MIME-Version: 1.0 References: <20251120184211.2379439-1-joannelkoong@gmail.com> <20251120184211.2379439-3-joannelkoong@gmail.com> <5c1630ac-d304-4854-9ba6-5c9cc1f78be5@kernel.org> <504d100d-b8f3-475b-b575-3adfd17627b5@kernel.org> In-Reply-To: From: Joanne Koong Date: Thu, 4 Dec 2025 10:06:40 -0800 X-Gm-Features: AWmQ_bkfmaBxtqNiCodT9gGB1wJnTwkgc9tefeZRB6rVjqiHpy8rJCyBAd9v5hc Message-ID: Subject: Re: [PATCH v1 2/2] fs/writeback: skip inodes with potential writeback hang in wait_sb_inodes() To: Miklos Szeredi Cc: "David Hildenbrand (Red Hat)" , akpm@linux-foundation.org, linux-mm@kvack.org, shakeel.butt@linux.dev, athul.krishna.kr@protonmail.com, stable@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 2BCE140018 X-Stat-Signature: jxsobqegn94uy6ddp1dcnc7qzwbzttxi X-Rspam-User: X-HE-Tag: 1764871613-870468 X-HE-Meta: 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 kkJbNw+H Q5poXPKi2fFIUFCpg9EP2mu4Nb+PwSQHpniZOGAlWZz6prqczIdefEJGcCiwnMNusw6XmeglCWyc0Ei60Z4tReeMmJH5XMvoBKh12gdBfQnAUUJq6NmBQHhQYHNdeoPNvYXXCjdkjH38t0/P1FW6GdZWHqY12bk8ROOsSByylSKDbjvPFvoS4S5oQT/44GyruveBe2WC8Z95NLBQNMPmhMqMce+qh1M6jReY78E7z90Lhdpl/rYN1v8kurAFs6y0a9GRVFVZAgfqX+hbzCl11cFueC6cadBO3ftCY5EMHSjnG2w/BV+uQEQ1ms8y9X57YA+nSrXPqQhB+7asr5gB4Hmvrvy+wrvrYlVUOzDHFpD8cTiYGaUlQB7qMJZl483JZ51NKC7gEP8yJWSAmdaAsxvU+PDAPKHG9S+pYWsX+xr/y04t5ZBjz7wHRhRHAW+wHui0b 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: List-Subscribe: List-Unsubscribe: On Wed, Dec 3, 2025 at 1:28=E2=80=AFAM Miklos Szeredi w= rote: > > On Wed, 26 Nov 2025 at 18:58, Joanne Koong wrote= : > > > > On Wed, Nov 26, 2025 at 2:55=E2=80=AFAM David Hildenbrand (Red Hat) > > wrote: > > > > > > > >> having a flag that states something like that that > > > >> "AS_NO_WRITEBACK_WAIT_ON_DATA_SYNC" would probable be what we woul= d want > > > >> to add to avoid waiting for writeback with clear semantics why it = is ok > > > >> in that specific scenario. > > > > > > > > Having a separate AS_NO_WRITEBACK_WAIT_ON_DATA_SYNC mapping flag > > > > sounds reasonable to me and I agree is more clearer semantically. > > > > > > Good. Then it's clear that we are not waiting because writeback is > > > shaky, but because even if it would be working, because we don't have= to > > > because there are no such guarantees. > > > > > > Maybe > > > > > > AS_NO_DATA_INTEGRITY > > > > > > or similar would be cleaner, I'll have to leave that to you and Miklo= s > > > to decide what exactly the semantics are that fuse currently doesn't > > > provide. > > > > After reading Miklos's reply, I must have misunderstood this then - my > > understanding was that the reason we couldn't guarantee data integrity > > in fuse was because of the temp pages design where checking the > > writeback flag on the real folio doesn't reflect writeback state, but > > that removing the temp pages and using the real folio now does > > guarantee this. But it seems like it's not as simple as that and > > there's no data integrity guarantees for other reasons. > > > > Changing this to AS_NO_DATA_INTEGRITY sounds good to me, if that > > sounds good to Miklos as well. Or do you have another preference, > > Miklos? > > Sure, sounds good. > > (Sorry about the delay, missed this.) Is the reason we can't guarantee data integrity because the server ultimately controls disk persistence whereby it can claim to have written data even if it didn't? If so, it seems like NFS / the other network-based filesystems would also have to set that AS_NO_DATA_INTEGRITY mapping flag too to be consistent? Or is there some other reason? Thanks, Joanne > > Thanks, > Miklos