cifs: Fix non-availability of dedup breaking generic/304

Deduplication isn't supported on cifs, but cifs doesn't reject it, instead
treating it as extent duplication/cloning.  This can cause generic/304 to go
silly and run for hours on end.

Fix cifs to indicate EOPNOTSUPP if REMAP_FILE_DEDUP is set in
->remap_file_range().

Note that it's unclear whether or not commit b073a08 is meant to cause
cifs to return an error if REMAP_FILE_DEDUP.

Fixes: b073a08 ("cifs: fix that return -EINVAL when do dedupe operation")
Cc: [email protected]
Suggested-by: Dave Chinner <[email protected]>
cc: Xiaoli Feng <[email protected]>
cc: Shyam Prasad N <[email protected]>
cc: Rohith Surabattula <[email protected]>
cc: Jeff Layton <[email protected]>
cc: Darrick Wong <[email protected]>
cc: [email protected]
cc: [email protected]
cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]/
Signed-off-by: David Howells <[email protected]>
Signed-off-by: Steve French <[email protected]>

Author: dhowells

fs/smb/client/cifsfs.c

@@ -1277,7 +1277,9 @@ static loff_t cifs_remap_file_range(struct file *src_file, loff_t off,
 	unsigned int xid;
 	int rc;
 
-	if (remap_flags & ~(REMAP_FILE_DEDUP | REMAP_FILE_ADVISORY))
+	if (remap_flags & REMAP_FILE_DEDUP)
+		return -EOPNOTSUPP;
+	if (remap_flags & ~REMAP_FILE_ADVISORY)
 		return -EINVAL;
 
 	cifs_dbg(FYI, "clone range\n");