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 6997130C35E for ; Tue, 19 Aug 2025 20:13:18 +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=1755634400; cv=none; b=qMcNJBko4eofBtIsSBzTcUd/ml9TajnqyyVazj/M453vZX6fruzf+POiVoDD7kZoR2MSIm9osQEZ/72h4FumwCt4z8uUu3S5Xd3uMUUy+PegWrXQ7KSCjy7qR7WahqHsYwgZx7N5eraoFGY2MU0rc0+RJErqWRD2CC8v8ybsZvY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755634400; c=relaxed/simple; bh=pAnpXN2pBh9ikmjRiAfF5u6MMzL5VU41MYDOZ48gZPs=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=BROB/YCIW950qWx5+tkvb705p2mfP+s0TAO7U5773d5IDGO7c5/knn+IIwhWDHRfbJanY69aTpggq4q7BZGNvt98khULvLtJmYxdxjiE4yS24qlPcBffnjg025Hnh6T14GVhfKFreuVVwHuGdxXymFj/wTlCPoi5b3bpkFL01Kc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lTwMaYh+; 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="lTwMaYh+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5BF8EC113D0; Tue, 19 Aug 2025 20:13:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1755634397; bh=pAnpXN2pBh9ikmjRiAfF5u6MMzL5VU41MYDOZ48gZPs=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=lTwMaYh+STP75E7RfV7ghD3nmpWeyNO3VjQRSjXDigVk4G62L9oMVnXB6MwnGtOb5 SDT10R9rHkS6wVf2j5/n6dC+jhchaaQJk8qLK8CuHkV7RhIGYoLKU9t5q5ggfUPaTb CG7upSAXDy/JmgIDHaTVoNUnjVuxj6H3NHA7ScWmDHg0Pt0cJivDBnlkxR9m/azR2d GFC/ikemz4mkL6K3LHneOsPkdmJQY6ggw+t1AymXMIsbHTxep2V0JXGbZ7pwYud9cj xNN7eIqc8eGbdoxRir0LYMLx8kQTjD93mVkOtzY8nFBpg6o5vWKdPlHVSNKACN2uu/ HVb89Pp8wJTNA== Message-ID: <06e0e537326414677386eab40a27d5cf1b3ea3c1.camel@kernel.org> Subject: Re: parts of pages on NFS being replaced by swaths of NULs From: Jeff Layton To: Mike Snitzer , Trond Myklebust Cc: Anna Schumaker , Chuck Lever , linux-nfs@vger.kernel.org, jonathan.flynn@hammerspace.com Date: Tue, 19 Aug 2025 16:13:16 -0400 In-Reply-To: References: <1c42a7fd9677ad1aa9a3a53eda738b3a6da3728e.camel@kernel.org> <752db17aff35a92b79e4c7bd3003ed890fe91403.camel@kernel.org> <972c7790fa69cc64a591b71fcc7a40b2cd477beb.camel@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV 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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 00:00:00 200= 1 > > > 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() doesn't > > > necessarily have a lock on the page group head. > > >=20 > > > So in order to avoid races, let's take the page group lock earlier in > > > nfs_lock_and_join_requests(), and hold it across the removal of the > > > request in nfs_inode_remove_request(). > > >=20 > > > Reported-by: Jeff Layton > > > Fixes: c3f2235782c3 ("nfs: fold nfs_folio_find_and_lock_request into = 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 @bi= t 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, unsigne= d 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, st= ruct inode *inode) > > > } > > > } > > > =20 > > > -static int > > > -nfs_cancel_remove_inode(struct nfs_page *req, struct inode *inode) > > > +static void nfs_cancel_remove_inode(struct nfs_page *req, struct ino= de *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_reque= sts(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 nfs_p= age *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 nfs_p= age *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_page *= 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 *, unsigned i= nt); > > > +extern bool nfs_page_group_sync_on_bit_locked(struct nfs_page *, uns= igned 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 nfs_l= ock_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_misaligned_I= O > >=20 > > So you need my latest NFS DIRECT patchset: > > https://lore.kernel.org/linux-nfs/20250815233003.55071-1-snitzer@kernel= .org/ > >=20 > > With it, writes would be corrupted when using the attached reproducer > > (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 reproducer > 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@kernel.o= rg/ > https://lore.kernel.org/linux-nfs/20250815233003.55071-1-snitzer@kernel.o= rg/ >=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 Can you compare a corrupt file with the expected output? That might give us a clue about the nature of this bug. --=20 Jeff Layton