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 202CD341069; Tue, 16 Dec 2025 11:22:43 +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=1765884163; cv=none; b=PPMMUxsQgahGSWNHeJ6n7JJrYxSF0HbeA5PiWwYFde8FZd6lGx+PHbWCFVXYPaSNJpk8x0ZUh5euh/r8hwCS2LMN9Zx0SPSsIVTZ7/UfpQJm8xQP2IpcnYlXV1pe2n/iVqUmdPA2/7JC4FNDmEAZqjKlCrm5BYN06hooTmdQ66k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765884163; c=relaxed/simple; bh=HV1IKTN2kp9cvZMZWlqjS59mZBdt2t6iD/LIeIkAcHo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=kgtosshWgq4XXwMpPulLlDh4Q+IS70Vahfzs461zIbiq2MLB804BUi9rEpBxejzzFEcoByfScbS7QJaIFwhkB5ZODeZPTY1ozE0qD5CAw0S3+nnhM7xyz5QUVdzTr5iEwkTPuD9RpDnMDTMr6Y1FBed5B9N8QYKLJzo8rEDT5NY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=rGjJpX/o; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="rGjJpX/o" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 98746C4CEF1; Tue, 16 Dec 2025 11:22:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1765884163; bh=HV1IKTN2kp9cvZMZWlqjS59mZBdt2t6iD/LIeIkAcHo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=rGjJpX/oMYF54w3uQqKPCBi0dUUodNLIcDpPfIsXlUubdgQph5BgFamtgZMawKVuA 5PDlWohy10B3GM4wVCULDZayGTt4AOFHGhpeGCdDjPvNu6BisTf62ATqf37bYXPilz e09i6GP9/HsZa7vgbLtfzvExAO5n27WOdokdmAPI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Tingmao Wang , Dominique Martinet , Sasha Levin Subject: [PATCH 6.12 111/354] fs/9p: Dont open remote file with APPEND mode when writeback cache is used Date: Tue, 16 Dec 2025 12:11:18 +0100 Message-ID: <20251216111324.944560058@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20251216111320.896758933@linuxfoundation.org> References: <20251216111320.896758933@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Tingmao Wang [ Upstream commit a63dd8fd137933551bfd9aeeeaa942f04c7aad65 ] When page cache is used, writebacks are done on a page granularity, and it is expected that the underlying filesystem (such as v9fs) should respect the write position. However, currently v9fs will passthrough O_APPEND to the server even on cached mode. This causes data corruption if a sync or fstat gets between two writes to the same file. This patch removes the APPEND flag from the open request we send to the server when writeback caching is involved. I believe keeping server-side APPEND is probably fine for uncached mode (even if two fds are opened, one without O_APPEND and one with it, this should still be fine since they would use separate fid for the writes). Signed-off-by: Tingmao Wang Fixes: 4eb3117888a9 ("fs/9p: Rework cache modes and add new options to Documentation") Message-ID: <20251102235631.8724-1-m@maowtm.org> Signed-off-by: Dominique Martinet Signed-off-by: Sasha Levin --- fs/9p/vfs_file.c | 11 ++++++++--- fs/9p/vfs_inode.c | 3 +-- fs/9p/vfs_inode_dotl.c | 2 +- 3 files changed, 10 insertions(+), 6 deletions(-) diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c index 348cc90bf9c56..de0d1f74de46c 100644 --- a/fs/9p/vfs_file.c +++ b/fs/9p/vfs_file.c @@ -43,14 +43,18 @@ int v9fs_file_open(struct inode *inode, struct file *file) struct v9fs_session_info *v9ses; struct p9_fid *fid; int omode; + int o_append; p9_debug(P9_DEBUG_VFS, "inode: %p file: %p\n", inode, file); v9ses = v9fs_inode2v9ses(inode); - if (v9fs_proto_dotl(v9ses)) + if (v9fs_proto_dotl(v9ses)) { omode = v9fs_open_to_dotl_flags(file->f_flags); - else + o_append = P9_DOTL_APPEND; + } else { omode = v9fs_uflags2omode(file->f_flags, v9fs_proto_dotu(v9ses)); + o_append = P9_OAPPEND; + } fid = file->private_data; if (!fid) { fid = v9fs_fid_clone(file_dentry(file)); @@ -58,9 +62,10 @@ int v9fs_file_open(struct inode *inode, struct file *file) return PTR_ERR(fid); if ((v9ses->cache & CACHE_WRITEBACK) && (omode & P9_OWRITE)) { - int writeback_omode = (omode & ~P9_OWRITE) | P9_ORDWR; + int writeback_omode = (omode & ~(P9_OWRITE | o_append)) | P9_ORDWR; p9_debug(P9_DEBUG_CACHE, "write-only file with writeback enabled, try opening O_RDWR\n"); + err = p9_client_open(fid, writeback_omode); if (err < 0) { p9_debug(P9_DEBUG_CACHE, "could not open O_RDWR, disabling caches\n"); diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c index 3e68521f4e2f9..1723a37d1846e 100644 --- a/fs/9p/vfs_inode.c +++ b/fs/9p/vfs_inode.c @@ -791,7 +791,7 @@ v9fs_vfs_atomic_open(struct inode *dir, struct dentry *dentry, p9_omode = v9fs_uflags2omode(flags, v9fs_proto_dotu(v9ses)); if ((v9ses->cache & CACHE_WRITEBACK) && (p9_omode & P9_OWRITE)) { - p9_omode = (p9_omode & ~P9_OWRITE) | P9_ORDWR; + p9_omode = (p9_omode & ~(P9_OWRITE | P9_OAPPEND)) | P9_ORDWR; p9_debug(P9_DEBUG_CACHE, "write-only file with writeback enabled, creating w/ O_RDWR\n"); } @@ -1404,4 +1404,3 @@ static const struct inode_operations v9fs_symlink_inode_operations = { .getattr = v9fs_vfs_getattr, .setattr = v9fs_vfs_setattr, }; - diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c index 3397939fd2d5a..40a4fc65a5441 100644 --- a/fs/9p/vfs_inode_dotl.c +++ b/fs/9p/vfs_inode_dotl.c @@ -286,7 +286,7 @@ v9fs_vfs_atomic_open_dotl(struct inode *dir, struct dentry *dentry, } if ((v9ses->cache & CACHE_WRITEBACK) && (p9_omode & P9_OWRITE)) { - p9_omode = (p9_omode & ~P9_OWRITE) | P9_ORDWR; + p9_omode = (p9_omode & ~(P9_OWRITE | P9_DOTL_APPEND)) | P9_ORDWR; p9_debug(P9_DEBUG_CACHE, "write-only file with writeback enabled, creating w/ O_RDWR\n"); } -- 2.51.0