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 9C0C27FBAC for ; Tue, 19 Aug 2025 21:50:02 +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=1755640203; cv=none; b=sdBwQAe8dTv+Z88ZaJ6hV0Lt9mwCE2repIwreA6lnfQRGLIT2FuQKChwGlzHvqjo0tS3ZloO0bZKwcjNWrYxiB4d5qv/jdlKIhspH/PrnKVrJaLVy05EQ5jVA51JBSXVlcTxBDEVmGcoAAkBq166++o0bZS58C/R9N7mPa+jUs0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755640203; c=relaxed/simple; bh=Z+gi1PDqcCWlvfjh83bX8r8Qby5mcaZwFMZi5z75ac0=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=UOmpTEiD75lU51b0q6ICoJcJydTmahBzMU97lYGRt0jFLoRW4lnjEN54AP3DTswcTi3dK0RmwcaFN5uq7U/SIQ6Sh1TUsyCKtUoAU02cPheX29Zz2Q0fsGFd2CfQgNzSlBOkBll9rT/Qyu4+WNRqfVH5jdt4nv5ucpWLuZs6gNM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=iNSXIrhE; 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="iNSXIrhE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4BB6BC4CEF1; Tue, 19 Aug 2025 21:50:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1755640202; bh=Z+gi1PDqcCWlvfjh83bX8r8Qby5mcaZwFMZi5z75ac0=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=iNSXIrhEGq+efwnvJ8hZhRHtgmi6nL6B4VY55rIsmQSAZskKyl8Ib7H6Jq8ISsivb EKhpeNU9MRR7hmh5uRptZJPaeDrrz4CB0MaiW7D1ayb/uOn9fwQKkYWUficas2UkZ2 k22JCxqdmMGHGSfUGRuBDcYQo+Z879Kfd7OrwbwBFB4hoGyrIEXruFkhg6TEhXhPjV xfTQVYcFg4CeIIXIX6je547W/DmToICIdHWjHWmB9tuKhWYXyNGwvTfizAxUbVd6xl gf8ns9MTIfoZEZCNAcaZ3gAIUXgNpsCX+RzgsGPfUg/lnJlj3CVqx9sFX52L6qa2Y8 ed0pDBkaFte5w== Message-ID: <666a5c90fa13775a15e53c67bf38f0db60b8f6f9.camel@kernel.org> Subject: Re: seeing CRC mismatch with NFS DIRECT WRITE when localio_O_DIRECT_align_misaligned_IO=Y From: Jeff Layton To: Mike Snitzer Cc: Trond Myklebust , Anna Schumaker , Chuck Lever , linux-nfs@vger.kernel.org, jonathan.flynn@hammerspace.com Date: Tue, 19 Aug 2025 17:50:01 -0400 In-Reply-To: References: <1c42a7fd9677ad1aa9a3a53eda738b3a6da3728e.camel@kernel.org> <752db17aff35a92b79e4c7bd3003ed890fe91403.camel@kernel.org> <972c7790fa69cc64a591b71fcc7a40b2cd477beb.camel@kernel.org> <06e0e537326414677386eab40a27d5cf1b3ea3c1.camel@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv 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linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Tue, 2025-08-19 at 17:38 -0400, Mike Snitzer wrote: > On Tue, Aug 19, 2025 at 04:13:16PM -0400, Jeff Layton wrote: > > On Tue, 2025-08-19 at 14:38 -0400, Mike Snitzer wrote: > > > On Sat, Aug 16, 2025 at 05:25:28PM -0400, Mike Snitzer wrote: > > > > On Sat, Aug 16, 2025 at 07:51:17AM -0700, Trond Myklebust wrote: > > > > >=20 > > > > > That's not sufficient AFAICS. Does the following patch work? > > > > >=20 > > > > > 8<------------------------------------------------------------ > > > > > From fc9690dda01f001c6cd11665701394da8ebba1ab Mon Sep 17 00:00:00= 2001 > > > > > Message-ID: > > > > > From: Trond Myklebust > > > > > Date: Sat, 16 Aug 2025 07:25:20 -0700 > > > > > Subject: [PATCH] NFS: Fix a race when updating an existing write > > > > >=20 > > > > > After nfs_lock_and_join_requests() tests for whether the request = is > > > > > still attached to the mapping, nothing prevents a call to > > > > > nfs_inode_remove_request() from succeeding until we actually lock= the > > > > > page group. > > > > > The reason is that whoever called nfs_inode_remove_request() does= n't > > > > > necessarily have a lock on the page group head. > > > > >=20 > > > > > So in order to avoid races, let's take the page group lock earlie= r in > > > > > nfs_lock_and_join_requests(), and hold it across the removal of t= he > > > > > request in nfs_inode_remove_request(). > > > > >=20 > > > > > Reported-by: Jeff Layton > > > > > Fixes: c3f2235782c3 ("nfs: fold nfs_folio_find_and_lock_request i= nto nfs_lock_and_join_requests") > > > > > Signed-off-by: Trond Myklebust > > > > > --- > > > > > fs/nfs/pagelist.c | 9 +++++---- > > > > > fs/nfs/write.c | 29 ++++++++++------------------- > > > > > include/linux/nfs_page.h | 1 + > > > > > 3 files changed, 16 insertions(+), 23 deletions(-) > > > > >=20 > > > > > diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c > > > > > index 11968dcb7243..6e69ce43a13f 100644 > > > > > --- a/fs/nfs/pagelist.c > > > > > +++ b/fs/nfs/pagelist.c > > > > > @@ -253,13 +253,14 @@ nfs_page_group_unlock(struct nfs_page *req) > > > > > nfs_page_clear_headlock(req); > > > > > } > > > > > =20 > > > > > -/* > > > > > - * nfs_page_group_sync_on_bit_locked > > > > > +/** > > > > > + * nfs_page_group_sync_on_bit_locked - Test if all requests have= @bit set > > > > > + * @req: request in page group > > > > > + * @bit: PG_* bit that is used to sync page group > > > > > * > > > > > * must be called with page group lock held > > > > > */ > > > > > -static bool > > > > > -nfs_page_group_sync_on_bit_locked(struct nfs_page *req, unsigned= int bit) > > > > > +bool nfs_page_group_sync_on_bit_locked(struct nfs_page *req, uns= igned int bit) > > > > > { > > > > > struct nfs_page *head =3D req->wb_head; > > > > > struct nfs_page *tmp; > > > > > diff --git a/fs/nfs/write.c b/fs/nfs/write.c > > > > > index fa5c41d0989a..8b7c04737967 100644 > > > > > --- a/fs/nfs/write.c > > > > > +++ b/fs/nfs/write.c > > > > > @@ -153,20 +153,10 @@ nfs_page_set_inode_ref(struct nfs_page *req= , struct inode *inode) > > > > > } > > > > > } > > > > > =20 > > > > > -static int > > > > > -nfs_cancel_remove_inode(struct nfs_page *req, struct inode *inod= e) > > > > > +static void nfs_cancel_remove_inode(struct nfs_page *req, struct= inode *inode) > > > > > { > > > > > - int ret; > > > > > - > > > > > - if (!test_bit(PG_REMOVE, &req->wb_flags)) > > > > > - return 0; > > > > > - ret =3D nfs_page_group_lock(req); > > > > > - if (ret) > > > > > - return ret; > > > > > if (test_and_clear_bit(PG_REMOVE, &req->wb_flags)) > > > > > nfs_page_set_inode_ref(req, inode); > > > > > - nfs_page_group_unlock(req); > > > > > - return 0; > > > > > } > > > > > =20 > > > > > /** > > > > > @@ -585,19 +575,18 @@ static struct nfs_page *nfs_lock_and_join_r= equests(struct folio *folio) > > > > > } > > > > > } > > > > > =20 > > > > > + ret =3D nfs_page_group_lock(head); > > > > > + if (ret < 0) > > > > > + goto out_unlock; > > > > > + > > > > > /* Ensure that nobody removed the request before we locked it *= / > > > > > if (head !=3D folio->private) { > > > > > + nfs_page_group_unlock(head); > > > > > nfs_unlock_and_release_request(head); > > > > > goto retry; > > > > > } > > > > > =20 > > > > > - ret =3D nfs_cancel_remove_inode(head, inode); > > > > > - if (ret < 0) > > > > > - goto out_unlock; > > > > > - > > > > > - ret =3D nfs_page_group_lock(head); > > > > > - if (ret < 0) > > > > > - goto out_unlock; > > > > > + nfs_cancel_remove_inode(head, inode); > > > > > =20 > > > > > /* lock each request in the page group */ > > > > > for (subreq =3D head->wb_this_page; > > > > > @@ -786,7 +775,8 @@ static void nfs_inode_remove_request(struct n= fs_page *req) > > > > > { > > > > > struct nfs_inode *nfsi =3D NFS_I(nfs_page_to_inode(req)); > > > > > =20 > > > > > - if (nfs_page_group_sync_on_bit(req, PG_REMOVE)) { > > > > > + nfs_page_group_lock(req); > > > > > + if (nfs_page_group_sync_on_bit_locked(req, PG_REMOVE)) { > > > > > struct folio *folio =3D nfs_page_to_folio(req->wb_head); > > > > > struct address_space *mapping =3D folio->mapping; > > > > > =20 > > > > > @@ -798,6 +788,7 @@ static void nfs_inode_remove_request(struct n= fs_page *req) > > > > > } > > > > > spin_unlock(&mapping->i_private_lock); > > > > > } > > > > > + nfs_page_group_unlock(req); > > > > > =20 > > > > > if (test_and_clear_bit(PG_INODE_REF, &req->wb_flags)) { > > > > > atomic_long_dec(&nfsi->nrequests); > > > > > diff --git a/include/linux/nfs_page.h b/include/linux/nfs_page.h > > > > > index 169b4ae30ff4..9aed39abc94b 100644 > > > > > --- a/include/linux/nfs_page.h > > > > > +++ b/include/linux/nfs_page.h > > > > > @@ -160,6 +160,7 @@ extern void nfs_join_page_group(struct nfs_pa= ge *head, > > > > > extern int nfs_page_group_lock(struct nfs_page *); > > > > > extern void nfs_page_group_unlock(struct nfs_page *); > > > > > extern bool nfs_page_group_sync_on_bit(struct nfs_page *, unsign= ed int); > > > > > +extern bool nfs_page_group_sync_on_bit_locked(struct nfs_page *,= unsigned int); > > > > > extern int nfs_page_set_headlock(struct nfs_page *req); > > > > > extern void nfs_page_clear_headlock(struct nfs_page *req); > > > > > extern bool nfs_async_iocounter_wait(struct rpc_task *, struct n= fs_lock_context *); > > > > > --=20 > > > > > 2.50.1 > > > > >=20 > > > > >=20 > > > >=20 > > > >=20 > > > > Trond, > > > >=20 > > > > You're the best! ;) > > > >=20 > > > > Your patch fixes corruption I've been chasing for the past week > > > > relative to NFS DIRECT, specifically with: > > > > echo Y > /sys/module/nfs/parameters/localio_O_DIRECT_align_misalign= ed_IO > > > >=20 > > > > So you need my latest NFS DIRECT patchset: > > > > https://lore.kernel.org/linux-nfs/20250815233003.55071-1-snitzer@ke= rnel.org/ > > > >=20 > > > > With it, writes would be corrupted when using the attached reproduc= er > > > > (from Jon Flynn, with the assistance of ChatGPT) that pulls out the > > > > subset of MLperf unet3d test (when ran in buffered IO mode, so > > > > entirely misaligned relative to DIO-alignment requirements) that we= 've > > > > seen npz CRC compare failure with. > > > >=20 > > > > I tested my patchset with your patch applied and it all "just works= ". > > > >=20 > > > > Ship it all! > > > >=20 > > > > Thanks, > > > > Mike > > > >=20 > > > > ps. running the attached reproducer is as simple as: > > > > ./mlperf_npz_tool.py --npz-path /mnt/share1/sample_a.npz > > >=20 > > > So even with this patch there is something still causing data > > > corruption on much faster systems. This mlperf_npz_tool.py reproduce= r > > > works fine on a slower VMware based testbed, but once I load the same > > > kernel (with Trond's fix applied) on a very fast baremetal system I > > > still see CRC mismatch due to write corruption if > > > localio_O_DIRECT_align_misaligned_IO=3DY (from my NFS DIRECT patchset= ). > > >=20 > > > Again, both of my latest NFSD DIRECT and NFS DIRECT patchsets are > > > applied: > > > https://lore.kernel.org/linux-nfs/20250815144607.50967-1-snitzer@kern= el.org/ > > > https://lore.kernel.org/linux-nfs/20250815233003.55071-1-snitzer@kern= el.org/ > > >=20 > > > And I'm hacking nfs4 to impose O_DIRECT on buffered IO (reproducer > > > doesn't open its files with O_DIRECT but NFS client acts like it did)= . > > > I can dig out the patch to achieve that if others are interested. > > >=20 > > > Mike > >=20 > > Can you compare a corrupt file with the expected output? That might > > give us a clue about the nature of this bug. >=20 > While it _is_ interesting that "speed kills" my particular lithmus > test: I've changed the $SUBJECT because this issue could easily be > unique to my new NFS DIRECT code or the test itself. So best to > divorce my issue from the original issue you reported that was the > catalyst for Trond's fix (that did seem to help my testcase). >=20 > To be clear, this may well be some bug in the python application (that > happens to be part of the MLperf "industry benchmark")... >=20 > Using other tools to verify data integrity have all passed. In > particular, dt isn't able to see any issues (but dt is more of an open > secret in the utility belt of companies like NetApp, Red Hat, now > Hammerspace, etc): https://github.com/RobinTMiller/dt.git > This patch header in the NFSD DIRECT series shows how dt proved very > useful: > https://lore.kernel.org/linux-nfs/20250815144607.50967-6-snitzer@kernel.o= rg/ >=20 > But back to the mlperf_npz_tool.py, I can easily generate good vs bad > files, any words of wisdom for useful tools to analyze the > differences? ChatGPT? Other AIs? > > hexdump isn't showing useful or approachable differences, basically > the entire good vs bad file is different: >=20 > # hexdump /tmp/good.npz > /root/analyze_this/good.hd > # hexdump /tmp/bad.npz > /root/analyze_this/bad.hd > # diff -Naur /root/analyze_this/good.hd /root/analyze_this/bad.hd > hd.di= ff >=20 > # ls -alh > total 1.7G > drwxr-xr-x 2 root root 50 Aug 19 20:53 . > dr-xr-x---. 25 root root 4.0K Aug 19 20:56 .. > -rw-r--r-- 1 root root 421M Aug 19 20:52 bad.hd > -rw-r--r-- 1 root root 421M Aug 19 20:51 good.hd > -rw-r--r-- 1 root root 803M Aug 19 20:54 hd.diff >=20 > # less hd.diff > --- /root/analyze_this/good.hd 2025-08-19 20:51:55.797022245 +0000 > +++ /root/analyze_this/bad.hd 2025-08-19 20:52:14.868669416 +0000 > @@ -254,983046 +254,983046 @@ > 0000fd0 a73d eae0 f2b0 df27 6098 16be b990 f5b0 > 0000fe0 e2d1 857f 1843 6b2f 079b f319 5386 b6f7 > 0000ff0 e5ac ec09 29cd 17e9 1341 8a18 e54b 5057 > -0001000 7711 ef46 982e fe27 a0b5 0d2f 0f05 0130 > -0001010 d6e2 4a4c 74be f4cc a1ed cd98 fe09 0ba0 > -0001020 65b5 05a1 426f 7658 c9d9 0381 8ed5 b4ad > ... > +0001000 2325 8099 b007 9fd9 8596 01fe ae93 d384 > +0001010 422e 7685 abab 0d9b 0a05 b4e9 b774 f619 > +0001020 10fc 37d0 9e72 795c 82cd c9c8 9cac 4665 > ... > 8b01000 ce50 6a33 b82d f7ce 0699 5948 1a7e 4e33 > 8b01010 ed0c f087 853e 952b 77c4 6e51 2790 26af > 8b01020 d588 4bc7 313e d729 c20f 4412 8844 8fa6 >=20 2 interesting things there: 1/ the corruption doesn't appear to be zeroes, so this is definitely a different bug than the one we saw before. 2/ It looks like the corruption starts on a page boundary. How far does it extend? If it's all page aligned, then that's probably an important clue. --=20 Jeff Layton