fuse: don't need GETATTR after every READ

If 'auto_inval_data' mode is active, then fuse_file_read_iter() will call
fuse_update_attributes(), which will check the attribute validity and send
a GETATTR request if some of the attributes are no longer valid.  The page
cache is then invalidated if the size or mtime have changed.

Then, if a READ request was sent and reply received (which is the case if
the data wasn't cached yet, or if the file is opened for O_DIRECT), the
atime attribute is invalidated.

This will result in the next read() also triggering a GETATTR, ...

This can be fixed by only sending GETATTR if the mode or size are invalid,
we don't need to do a refresh if only atime is invalid.

More generally, none of the callers of fuse_update_attributes() need an
up-to-date atime value, so for now just remove STATX_ATIME from the request
mask when attributes are updated for internal use.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/fuse/dir.c

@@ -952,7 +952,9 @@ static int fuse_update_get_attr(struct inode *inode, struct file *file,
 
 int fuse_update_attributes(struct inode *inode, struct file *file)
 {
-	return fuse_update_get_attr(inode, file, NULL, STATX_BASIC_STATS, 0);
+	/* Do *not* need to get atime for internal purposes */
+	return fuse_update_get_attr(inode, file, NULL,
+				    STATX_BASIC_STATS & ~STATX_ATIME, 0);
 }
 
 int fuse_reverse_inval_entry(struct super_block *sb, u64 parent_nodeid,