fuse: add feature flag for expire-only

Add an init flag idicating whether the FUSE_EXPIRE_ONLY flag of
FUSE_NOTIFY_INVAL_ENTRY is effective.

This is needed for backports of this feature, otherwise the server could
just check the protocol version.

Fixes: 4f8d370 ("fuse: add "expire only" mode to FUSE_NOTIFY_INVAL_ENTRY")
Cc: <[email protected]> # v6.2
Signed-off-by: Miklos Szeredi <[email protected]>

Author: Miklos Szeredi

fs/fuse/inode.c

@@ -1254,7 +1254,8 @@ void fuse_send_init(struct fuse_mount *fm)
 		FUSE_ABORT_ERROR | FUSE_MAX_PAGES | FUSE_CACHE_SYMLINKS |
 		FUSE_NO_OPENDIR_SUPPORT | FUSE_EXPLICIT_INVAL_DATA |
 		FUSE_HANDLE_KILLPRIV_V2 | FUSE_SETXATTR_EXT | FUSE_INIT_EXT |
-		FUSE_SECURITY_CTX | FUSE_CREATE_SUPP_GROUP;
+		FUSE_SECURITY_CTX | FUSE_CREATE_SUPP_GROUP |
+		FUSE_HAS_EXPIRE_ONLY;
 #ifdef CONFIG_FUSE_DAX
 	if (fm->fc->dax)
 		flags |= FUSE_MAP_ALIGNMENT;

include/uapi/linux/fuse.h

@@ -206,6 +206,7 @@
  *  - add extension header
  *  - add FUSE_EXT_GROUPS
  *  - add FUSE_CREATE_SUPP_GROUP
+ *  - add FUSE_HAS_EXPIRE_ONLY
  */
 
 #ifndef _LINUX_FUSE_H
@@ -369,6 +370,7 @@ struct fuse_file_lock {
  * FUSE_HAS_INODE_DAX:  use per inode DAX
  * FUSE_CREATE_SUPP_GROUP: add supplementary group info to create, mkdir,
  *			symlink and mknod (single group that matches parent)
+ * FUSE_HAS_EXPIRE_ONLY: kernel supports expiry-only entry invalidation
  */
 #define FUSE_ASYNC_READ		(1 << 0)
 #define FUSE_POSIX_LOCKS	(1 << 1)
@@ -406,6 +408,7 @@ struct fuse_file_lock {
 #define FUSE_SECURITY_CTX	(1ULL << 32)
 #define FUSE_HAS_INODE_DAX	(1ULL << 33)
 #define FUSE_CREATE_SUPP_GROUP	(1ULL << 34)
+#define FUSE_HAS_EXPIRE_ONLY	(1ULL << 35)
 
 /**
  * CUSE INIT request/reply flags