vfs: no fallback for ->copy_file_range

Now that we have generic_copy_file_range(), remove it as a fallback
case when offloads fail. This puts the responsibility for executing
fallbacks on the filesystems that implement ->copy_file_range and
allows us to add operational validity checks to
generic_copy_file_range().

Rework vfs_copy_file_range() to call a new do_copy_file_range()
helper to execute the copying callout, and move calls to
generic_file_copy_range() into filesystem methods where they
currently return failures.

[Amir] overlayfs is not responsible of executing the fallback.
It is the responsibility of the underlying filesystem.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index f5fcd6360056..c65823270313 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -1148,6 +1148,10 @@ static ssize_t cifs_copy_file_range(struct file *src_file, loff_t off,
 	rc = cifs_file_copychunk_range(xid, src_file, off, dst_file, destoff,
 					len, flags);
 	free_xid(xid);
+
+	if (rc == -EOPNOTSUPP)
+		rc = generic_copy_file_range(src_file, off, dst_file,
+					     destoff, len, flags);
 	return rc;
 }