6.12-stable review patch. If anyone has any objections, please let me know.
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From: Tingmao Wang m@maowtm.org
[ 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 m@maowtm.org 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 asmadeus@codewreck.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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"); }