smb: enable reuse of deferred file handles for write operations

Previously, deferred file handles were reused only for read
operations, this commit extends to reusing deferred handles
for write operations. By reusing these handles we can reduce
the need for open/close operations over the wire.

Signed-off-by: Bharath SM <[email protected]>
Signed-off-by: Steve French <[email protected]>

Author: bharathsm-ms

fs/smb/client/file.c

@@ -990,7 +990,11 @@ int cifs_open(struct inode *inode, struct file *file)
 	}
 
 	/* Get the cached handle as SMB2 close is deferred */
-	rc = cifs_get_readable_path(tcon, full_path, &cfile);
+	if (OPEN_FMODE(file->f_flags) & FMODE_WRITE) {
+		rc = cifs_get_writable_path(tcon, full_path, FIND_WR_FSUID_ONLY, &cfile);
+	} else {
+		rc = cifs_get_readable_path(tcon, full_path, &cfile);
+	}
 	if (rc == 0) {
 		if (file->f_flags == cfile->f_flags) {
 			file->private_data = cfile;