From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 72B612E716C for ; Tue, 12 Aug 2025 11:58:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754999899; cv=none; b=fkwmwLquGHBnFesYkACiYagBn6E9KC6CpwA7KBtVVO3te6Nahyk1Pp7SwC3fbqjpzt7tNL1ScS2XiuJwUWrALs3hgEDajZj0+24Q5i0VG9h0sO/BNh6EZAr/2anoakis3s1WxnvOFBhj7i4qxEs2rV2mtr4vh3/CIFl42LxAMkc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754999899; c=relaxed/simple; bh=2K/lMwtMsS20M57UJp77Ng6BYJn+IrOPRs0xGcgyeWg=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=sNVYSIsjUteYJcUsuFpniTI/ddVD/iwvE+qzbX7OK9xZPB9Wq/SZAgDJwngNPahbEA+cmKJjEkUY2AwnbsBhL2h2nMSnDpIiB/IeSzj5kp9UvYny5EBddnR61H6LcJOEAPNbBaODkpHaz7EkP0eBfn0r2GqDfkzQXEGwyMEQcrs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=C+UJx8Ez; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="C+UJx8Ez" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D4D4FC4CEF4; Tue, 12 Aug 2025 11:58:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1754999899; bh=2K/lMwtMsS20M57UJp77Ng6BYJn+IrOPRs0xGcgyeWg=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=C+UJx8Ez68YCqS2fH38BwLywCrIwiE41wrCnvCohimlJIID8TUOqWNv/0ke86Dlh8 JH3X6bcJbSvaTq0qbDQFC8rX/y+tla4smMkjko2eUs8HsxqL8/Tq37JadIOe6j8BcE 5XvwK1jTyRewvHqdj49ZOF2XI0um7IAQp+kIfciMETWJRezXKZmrMIcRJDDlFobPHg 4ol7/0TCD3ImMSAyUJ/EFcG+fv7tFn8RuKbTMMQRrPSByGvI5sizYnXZULjBKI5/aW 57g6OEXboiu4w9X7pyt4G3h7/pNYx3wp2GonRTZqCP2EIoEjVZzlfcvt/i70VPsJ3O WdsFYbmlc+2jA== Message-ID: Subject: Re: parts of pages on NFS being replaced by swaths of NULs From: Jeff Layton To: Trond Myklebust , Anna Schumaker Cc: Chuck Lever , linux-nfs@vger.kernel.org Date: Tue, 12 Aug 2025 07:58:17 -0400 In-Reply-To: <752db17aff35a92b79e4c7bd3003ed890fe91403.camel@kernel.org> References: <1c42a7fd9677ad1aa9a3a53eda738b3a6da3728e.camel@kernel.org> <752db17aff35a92b79e4c7bd3003ed890fe91403.camel@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 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10:52 -0400, Jeff Layton wrote: > > We've been seeing a rather nasty bit of data corruption with NFS in > > our > > environment. The clients in this env run a patched v6.9 kernel > > (mostly > > due to GPU driver requirements). Most of the patches are NFS > > containerization fixes. > >=20 > > The workload is python scripts writing JSONL files sequentially using > > bog-standard buffered write() calls. We're fairly certain that > > userland > > is not seeking so there should be no gaps in the data written. > >=20 > > The problem is that we see ranges of written files being replaced by > > NULs. The length of the file seemingly doesn't change from what it > > should be, but a chunk of it will be zeroed-out. Looking at the > > offsets > > of the zeroed out ranges, the front part of one page is fine, but the > > data from some random offset in the page to the end of the page is > > zeroes. > >=20 > > We have a reproducer but we have to run it in a heavily parallel > > configuration to make it happen, so it's evidently a tight race of > > some > > sort. > >=20 > > We've turned up some tracepoints and reproduced this twice. What we > > see > > in both cases is that the client just doesn't write some section of > > the > > file. > >=20 > > In the first trace, there was is a gap of 2201 bytes between these > > two > > writes on the wire: > >=20 > > =C2=A0kworker/u1038:1-2597138 [106] ..... 46138.516795: > > nfs_initiate_write: fileid=3D00:aa:10056165185 fhandle=3D0x6bd94d55 > > offset=3D53248 count=3D1895 stable=3DUNSTABLE > > =C2=A0oil-localfs-252-2605046 [163] ..... 46138.551459: > > nfs_initiate_write: fileid=3D00:aa:10056165185 fhandle=3D0x6bd94d55 > > offset=3D57344 count=3D443956 stable=3DFILE_SYNC > >=20 > > The zeroed-out range is from 55143-57344. At the same time that the > > file is growing from 53248 to 55143 (due to sequential write() > > activity), the client is kicking off writeback for the range up to > > 55143. It's issuing 2 writes, one for 0-53248 and one for 53248-55143 > > (note that I've filtered out all but one of the DS filehandles for > > brevity): > >=20 > > =C2=A0oil-localfs-252-2605046 [162] ..... 46138.516414: nfs_size_grow: > > fileid=3D00:aa:10056165185 fhandle=3D0x8bfc64c9 > > version=3D1753485366409158129 cursize=3D49152 newsize=3D50130 > > =C2=A0oil-localfs-252-2605046 [162] ..... 46138.516593: nfs_size_grow: > > fileid=3D00:aa:10056165185 fhandle=3D0x8bfc64c9 > > version=3D1753485366409158129 cursize=3D50130 newsize=3D53248 > > =C2=A0kworker/u1038:1-2597138 [106] ..... 46138.516740: > > nfs_initiate_write: fileid=3D00:aa:10056165185 fhandle=3D0x6bd94d55 > > offset=3D0 count=3D53248 stable=3DUNSTABLE > > =C2=A0oil-localfs-252-2605046 [162] ..... 46138.516753: nfs_size_grow: > > fileid=3D00:aa:10056165185 fhandle=3D0x8bfc64c9 > > version=3D1753485366409158129 cursize=3D53248 newsize=3D55143 > > =C2=A0kworker/u1038:1-2597138 [106] ..... 46138.516795: > > nfs_initiate_write: fileid=3D00:aa:10056165185 fhandle=3D0x6bd94d55 > > offset=3D53248 count=3D1895 stable=3DUNSTABLE > > =C2=A0kworker/u1037:2-2871862 [097] ..... 46138.517659: nfs4_pnfs_write= : > > error=3D0 (OK) fileid=3D00:aa:10056165185 fhandle=3D0x6bd94d55 offset= =3D0 > > count=3D53248 res=3D53248 stateid=3D1:0x79a9c471 layoutstateid=3D1:0xcb= d8aaad > > =C2=A0kworker/u1037:2-2871862 [097] ..... 46138.517662: > > nfs_writeback_done: error=3D53248 fileid=3D00:aa:10056165185 > > fhandle=3D0x6bd94d55 offset=3D0 count=3D53248 res=3D53248 stable=3DUNST= ABLE > > verifier=3D5199cdae2816c899 > > =C2=A0kworker/u1037:5-2593935 [226] ..... 46138.517669: nfs4_pnfs_write= : > > error=3D0 (OK) fileid=3D00:aa:10056165185 fhandle=3D0x6bd94d55 offset= =3D53248 > > count=3D1895 res=3D1895 stateid=3D1:0x79a9c471 layoutstateid=3D1:0xcbd8= aaad > > =C2=A0kworker/u1037:5-2593935 [226] ..... 46138.517672: > > nfs_writeback_done: error=3D1895 fileid=3D00:aa:10056165185 > > fhandle=3D0x6bd94d55 offset=3D53248 count=3D1895 res=3D1895 stable=3DUN= STABLE > > verifier=3D5199cdae2816c899 > > =C2=A0oil-localfs-252-2605046 [162] ..... 46138.518360: nfs_size_grow: > > fileid=3D00:aa:10056165185 fhandle=3D0x8bfc64c9 > > version=3D1753485366409158129 cursize=3D55143 newsize=3D57344 > > =C2=A0oil-localfs-252-2605046 [162] ..... 46138.518556: nfs_size_grow: > > fileid=3D00:aa:10056165185 fhandle=3D0x8bfc64c9 > > version=3D1753485366409158129 cursize=3D57344 newsize=3D60156 > >=20 > > ...and just after writeback completes, we see the file size grow from > > 55143 to the end of the page (57344). > >=20 > > The second trace has similar symptoms. There is a lot more (smaller) > > write activity (due to memory pressure?). There is a gap of 3791 > > bytes > > between these on-the-wire writes, however: > >=20 > > =C2=A0kworker/u1036:0-2339252 [217] ..... 479572.054622: > > nfs_initiate_write: fileid=3D00:96:10067193438 fhandle=3D0xc9992232 > > offset=3D221184 count=3D4401 stable=3DUNSTABLE > > =C2=A0kworker/u1030:1-2297876 [042] ..... 479572.074194: > > nfs_initiate_write: fileid=3D00:96:10067193438 fhandle=3D0xc9992232 > > offset=3D229376 count=3D261898 stable=3DUNSTABLE > >=20 > > Same situation -- the at page at offset 53248 has 305 bytes on it, > > and > > the remaining is zeroed. This trace shows similar racing write() and > > writeback activity as in Friday's trace. At around the same time as > > the > > client was growing the file over the affected range, writeback was > > kicking off for everything up to the affected range (this has some > > other wb related calls filtered for brevity): > >=20 > > =C2=A0 oil-localfs-86-727850=C2=A0 [215] ..... 479572.053987: nfs_size_= grow: > > fileid=3D00:96:10067193438 fhandle=3D0x14c40498 > > version=3D1753823598774309300 cursize=3D217088 > > newsize=3D220572=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=20 > > =C2=A0kworker/u1036:8-2339326 [088] ..... 479572.054008: > > nfs_initiate_write: fileid=3D00:96:10067193438 fhandle=3D0xc9992232 > > offset=3D217088 count=3D3484 > > stable=3DUNSTABLE=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=20 > > =C2=A0 oil-localfs-86-727850=C2=A0 [215] ..... 479572.054405: nfs_size_= grow: > > fileid=3D00:96:10067193438 fhandle=3D0x14c40498 > > version=3D1753823598774309300 cursize=3D220572 > > newsize=3D221184=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=20 > > =C2=A0kworker/u1036:1-2297875 [217] ..... 479572.054418: > > nfs_initiate_write: fileid=3D00:96:10067193438 fhandle=3D0xc9992232 > > offset=3D220572 count=3D612 > > stable=3DUNSTABLE=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=20 > > =C2=A0 oil-localfs-86-727850=C2=A0 [215] ..... 479572.054581: nfs_size_= grow: > > fileid=3D00:96:10067193438 fhandle=3D0x14c40498 > > version=3D1753823598774309300 cursize=3D221184 > > newsize=3D225280=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=20 > > =C2=A0 oil-localfs-86-727850=C2=A0 [215] ..... 479572.054584: nfs_size_= grow: > > fileid=3D00:96:10067193438 fhandle=3D0x14c40498 > > version=3D1753823598774309300 cursize=3D225280 > > newsize=3D225585=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=20 > > =C2=A0kworker/u1036:0-2339252 [217] ..... 479572.054622: > > nfs_initiate_write: fileid=3D00:96:10067193438 fhandle=3D0xc9992232 > > offset=3D221184 count=3D4401 > > stable=3DUNSTABLE=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=20 > > =C2=A0 oil-localfs-86-727850=C2=A0 [215] ..... 479572.054997: nfs_size_= grow: > > fileid=3D00:96:10067193438 fhandle=3D0x14c40498 > > version=3D1753823598774309300 cursize=3D225585 > > newsize=3D229376=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=20 > > =C2=A0 oil-localfs-86-727850=C2=A0 [215] ..... 479572.055190: nfs_size_= grow: > > fileid=3D00:96:10067193438 fhandle=3D0x14c40498 > > version=3D1753823598774309300 cursize=3D229376 > > newsize=3D230598=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=20 > >=20 > > Could this be a race between extending an existing dirty page, and > > writeback kicking off for the pre-extension range on the page? Maybe > > the client is clearing the dirty bit, thinking that the write covers > > the dirty range, but it has an outdated idea about what that range is > > or doesn't properly check? > >=20 > > Traces for both events, filtered on the relevant fileid are attached. > > I've rolled patches for some new tracepoints that I'm going to > > attempt > > to turn up next, but I thought that this was a good point to solicit > > ideas. > >=20 > > Happy to entertain other thoughts or patches! >=20 > So... The fact that we are seeing a nfs_size_grow() for the hole at > offset 55143 means that either an existing request was updated, or a > new one was created in order to cover that hole, and it must have been > marked as dirty. >=20 > I'm not seeing anything in the NFS code that can lose that request > without triggering either the nfs_write_error tracepoint, the > nfs_commit_error tracepoint, the nfs_invalidate_folio tracepoint or > else completing the write. >=20 > The only other way I can see this data being lost is if something is > corrupting folio->private, or if the page cache is somehow managing to > throw away a dirty folio. > Of the two, there was for a while a netfs bug which would corrupt > folio->private, but I assume you're not using cachefs? After staring at this code a lot, I have a theory. But, it seems like we'd be seeing this a lot more if it were correct, so I must be overlooking something. Here's the scenario: --------------8<-------------- Userland has written some of a file and the last folio is not full. Writeback has kicked off for the inode and is successful. nfs_write_completion() calls nfs_page_end_writeback(). That will unlock the nfs_page (clear PG_BUSY) and leave it attached to the folio, and on the commit list. Next a write from userland comes in to extend the file to the end of the page (and beyond). nfs_try_to_update_request() merges the write into the original request and re-marks the page dirty. Later the commit runs successfully and the write verifier matches. nfs_commit_release_pages() runs and nfs_inode_remove_request() is called which detaches the nfs_page from the folio. Eventually, writeback starts up again and the folio is picked up and submitted by nfs_writepages(), but folio->private is now NULL, and it's ignored. But...like I said I feel like we'd hit this all the time if it were possible, even though I don't see what prevents it. If this is a possibility, then the patch may be as simple as something like this? diff --git a/fs/nfs/write.c b/fs/nfs/write.c index bb0e78644ffb..72402208fa33 100644 --- a/fs/nfs/write.c +++ b/fs/nfs/write.c @@ -1867,7 +1867,7 @@ static void nfs_commit_release_pages(struct nfs_commit_data *data) * returned by the server against all stored verfs. */ if (nfs_write_match_verf(verf, req)) { /* We have a match */ - if (folio) + if (folio && !folio_test_dirty(folio)) nfs_inode_remove_request(req); dprintk_cont(" OK\n"); goto next;