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Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: To: Michael Mulqueen Cc: dhowells@redhat.com, ericvh@kernel.org, lucho@ionkov.net, asmadeus@codewreck.org, pc@manguebit.org, linux_oss@crudebyte.com, v9fs@lists.linux.dev, netfs@lists.linux.dev, linux-fsdevel@vger.kernel.org, regressions@lists.linux.dev Subject: Re: PROBLEM: [REGRESSION 7.1-rc4 -> 7.1-rc5] 9p: silent NUL corruption of file data on cache modes with CACHE_WRITEBACK Precedence: bulk X-Mailing-List: v9fs@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Date: Fri, 11 Sep 2026 10:25:04 +0100 Message-ID: <2226525.1789118704@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 X-Mimecast-MFC-PROC-ID: lJayanXEoVr0QPLGv3m-3_tREwOhUqEL6nzFEhLw8i8_1789118711 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="us-ascii" Content-ID: <2226524.1789118704.1@warthog.procyon.org.uk> Content-Transfer-Encoding: quoted-printable Does the attached work for you? With it I see: cache=3Dnone read 0/20 write 0/20 [cache=3D0x0] cache=3Dreadahead read 0/20 write 0/20 [cache=3D0x1] cache=3Dmmap read 0/20 write 0/20 [cache=3D0x5] cache=3Dloose read 0/20 write 0/20 [cache=3D0xf] cache=3Dfscache read 0/20 write 0/20 [cache=3D0x8f] David --- commit a7f0af2e23c3ab191c08c1041dc67afd971a8c49 Author: David Howells Date: Fri Sep 11 10:15:43 2026 +0100 9p: Fix v9fs_issue_write() to update i_size and remote_i_size =20 Fix v9fs_issue_write() to update i_size and remote_i_size to the new si= ze of the server file if we made it larger, using the start fpos and the c= ount returned by p9_client_write() to calculate the new minimum file size. =20 This assumes that if the 9P server makes a short write (say it hits ENOSPC), a reduced count is returned. =20 Fixes: 5fb70e7275a6 ("netfs, 9p: Implement helpers for new write code") Reported-by: Michael Mulqueen Closes: https://lore.kernel.org/r/fbb9e395-1e07-4212-8f70-23f3cd498074@= method-b.uk/ Signed-off-by: David Howells cc: Eric Van Hensbergen cc: Latchesar Ionkov cc: Dominique Martinet cc: Christian Schoenebeck cc: Paulo Alcantara cc: v9fs@lists.linux.dev cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org diff --git a/fs/9p/vfs_addr.c b/fs/9p/vfs_addr.c index 1ac0b3dcc077..13cf87a5f90c 100644 --- a/fs/9p/vfs_addr.c +++ b/fs/9p/vfs_addr.c @@ -54,11 +54,37 @@ static void v9fs_begin_writeback(struct netfs_io_reques= t *wreq) static void v9fs_issue_write(struct netfs_io_subrequest *subreq) { =09struct p9_fid *fid =3D subreq->rreq->netfs_priv; +=09struct inode *inode =3D subreq->rreq->inode; +=09struct netfs_inode *ictx =3D netfs_inode(inode); =09int err, len; =20 =09len =3D p9_client_write(fid, subreq->start, &subreq->io_iter, &err); -=09if (len > 0) +=09if (len > 0) { +=09=09uoff_t end =3D subreq->start + len, i_size, remote, zp; +=09=09bool set =3D false; + +=09=09spin_lock(&inode->i_lock); + +=09=09/* We can read the sizes directly as we hold i_lock. */ +=09=09i_size =3D inode->i_size; +=09=09remote =3D ictx->_remote_i_size; +=09=09zp =3D ictx->_zero_point; + +=09=09if (end > i_size) { +=09=09=09i_size =3D end; +=09=09=09set =3D true; +=09=09} +=09=09if (end > remote) { +=09=09=09remote =3D end; +=09=09=09set =3D true; +=09=09} + +=09=09if (set) +=09=09=09netfs_write_sizes(inode, i_size, remote, zp); +=09=09spin_unlock(&inode->i_lock); + =09=09__set_bit(NETFS_SREQ_MADE_PROGRESS, &subreq->flags); +=09} =09netfs_write_subrequest_terminated(subreq, len ?: err); } =20