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>

2 files changed, 9 insertions, 9 deletions

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 1cc797a08a5b..8750b7235516 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -125,6 +125,7 @@ static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
 	struct file *new_file;
 	loff_t old_pos = 0;
 	loff_t new_pos = 0;
+	loff_t cloned;
 	int error = 0;
 
 	if (len == 0)
@@ -141,11 +142,10 @@ static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
 	}
 
 	/* Try to use clone_file_range to clone up within the same fs */
-	error = do_clone_file_range(old_file, 0, new_file, 0, len);
-	if (!error)
+	cloned = do_clone_file_range(old_file, 0, new_file, 0, len);
+	if (cloned == len)
 		goto out;
 	/* Couldn't clone, so now we try to copy the data */
-	error = 0;
 
 	/* FIXME: copy up sparse files efficiently */
 	while (len) {
diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index fffb36fd5920..6c3fec6168e9 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -434,14 +434,14 @@ enum ovl_copyop {
 	OVL_DEDUPE,
 };
 
-static ssize_t ovl_copyfile(struct file *file_in, loff_t pos_in,
+static loff_t ovl_copyfile(struct file *file_in, loff_t pos_in,
 			    struct file *file_out, loff_t pos_out,
-			    u64 len, unsigned int flags, enum ovl_copyop op)
+			    loff_t len, unsigned int flags, enum ovl_copyop op)
 {
 	struct inode *inode_out = file_inode(file_out);
 	struct fd real_in, real_out;
 	const struct cred *old_cred;
-	ssize_t ret;
+	loff_t ret;
 
 	ret = ovl_real_fdget(file_out, &real_out);
 	if (ret)
@@ -489,9 +489,9 @@ static ssize_t ovl_copy_file_range(struct file *file_in, loff_t pos_in,
 			    OVL_COPY);
 }
 
-static int ovl_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 ovl_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)
 {
 	enum ovl_copyop op;