Add FOPEN_FETCH_ATTR flag to indicate that attributes should be
fetched from the server after an open.
For fuse servers that are backed by network filesystems, this is
needed to ensure that file attributes are up to date between
consecutive open calls.
For example, if there is a file that is opened on two fuse mounts,
in the following scenario:
on mount A, open file.txt w/ O_APPEND, write "hi", close file
on mount B, open file.txt w/ O_APPEND, write "world", close file
on mount A, open file.txt w/ O_APPEND, write "123", close file
when the file is reopened on mount A, the file inode contains the old
size and the last append will overwrite the data that was written when
the file was opened/written on mount B.
(This corruption can be reproduced on the example libfuse passthrough_hp
server with writeback caching disabled and nopassthrough)
Having this flag as an option enables parity with NFS's close-to-open
consistency.
Signed-off-by: Joanne Koong <joannelkoong@xxxxxxxxx>
---
fs/fuse/file.c | 7 ++++++-
include/uapi/linux/fuse.h | 7 ++++++-
2 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index f39456c65ed7..437487ce413d 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -264,7 +264,12 @@ static int fuse_open(struct inode *inode, struct file *file)
err = fuse_do_open(fm, get_node_id(inode), file, false);
if (!err) {
ff = file->private_data;
- err = fuse_finish_open(inode, file);
+ if (ff->open_flags & FOPEN_FETCH_ATTR) {
+ fuse_invalidate_attr(inode);
+ err = fuse_update_attributes(inode, file, STATX_BASIC_STATS);
+ }
+ if (!err)
+ err = fuse_finish_open(inode, file);
if (err)
fuse_sync_release(fi, ff, file->f_flags);
else if (is_truncate)
diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
index d08b99d60f6f..f5d1af6fe352 100644
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -217,6 +217,9 @@
* - add backing_id to fuse_open_out, add FOPEN_PASSTHROUGH open flag
* - add FUSE_NO_EXPORT_SUPPORT init flag
* - add FUSE_NOTIFY_RESEND, add FUSE_HAS_RESEND init flag
+ *
+ * 7.41
+ * - add FOPEN_FETCH_ATTR
*/
#ifndef _LINUX_FUSE_H
@@ -252,7 +255,7 @@
#define FUSE_KERNEL_VERSION 7
/** Minor version number of this interface */
-#define FUSE_KERNEL_MINOR_VERSION 40
+#define FUSE_KERNEL_MINOR_VERSION 41
/** The node ID of the root inode */
#define FUSE_ROOT_ID 1
@@ -360,6 +363,7 @@ struct fuse_file_lock {
* FOPEN_NOFLUSH: don't flush data cache on close (unless FUSE_WRITEBACK_CACHE)
* FOPEN_PARALLEL_DIRECT_WRITES: Allow concurrent direct writes on the same inode
* FOPEN_PASSTHROUGH: passthrough read/write io for this open file
+ * FOPEN_FETCH_ATTR: attributes are fetched after file is opened
*/
#define FOPEN_DIRECT_IO (1 << 0)
#define FOPEN_KEEP_CACHE (1 << 1)
@@ -369,6 +373,7 @@ struct fuse_file_lock {
#define FOPEN_NOFLUSH (1 << 5)
#define FOPEN_PARALLEL_DIRECT_WRITES (1 << 6)
#define FOPEN_PASSTHROUGH (1 << 7)
+#define FOPEN_FETCH_ATTR (1 << 8)
/**
* INIT request/reply flags
--
2.43.5
