vfs: make remap_file_range functions take and return bytes completed

Change the remap_file_range functions to take a number of bytes to
operate upon and return the number of bytes they operated on.  This is a
requirement for allowing fs implementations to return short clone/dedupe
results to the user, which will enable us to obey resource limits in a
graceful manner.

A subsequent patch will enable copy_file_range to signal to the
->clone_file_range implementation that it can handle a short length,
which will be returned in the function's return value.  For now the
short return is not implemented anywhere so the behavior won't change --
either copy_file_range manages to clone the entire range or it tries an
alternative.

Neither clone ioctl can take advantage of this, alas.

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

1 files changed, 8 insertions, 8 deletions

diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index 9809b0e5746f..fbaeafe44b5f 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -2527,18 +2527,18 @@ out:
 	return offset;
 }
 
-static int ocfs2_remap_file_range(struct file *file_in,
-				  loff_t pos_in,
-				  struct file *file_out,
-				  loff_t pos_out,
-				  u64 len,
-				  unsigned int remap_flags)
+static loff_t ocfs2_remap_file_range(struct file *file_in, loff_t pos_in,
+				     struct file *file_out, loff_t pos_out,
+				     loff_t len, unsigned int remap_flags)
 {
+	int ret;
+
 	if (remap_flags & ~(REMAP_FILE_DEDUP | REMAP_FILE_ADVISORY))
 		return -EINVAL;
 
-	return ocfs2_reflink_remap_range(file_in, pos_in, file_out, pos_out,
-					 len, remap_flags);
+	ret = ocfs2_reflink_remap_range(file_in, pos_in, file_out, pos_out,
+					len, remap_flags);
+	return ret < 0 ? ret : len;
 }
 
 const struct inode_operations ocfs2_file_iops = {