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, 15 insertions, 12 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index c5435ca81132..c72d8c3c065a 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1777,9 +1777,9 @@ struct file_operations {
 #endif
         ssize_t (*copy_file_range)(struct file *, loff_t, struct file *,
                         loff_t, size_t, unsigned int);
-        int (*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);
+        loff_t (*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 (*fadvise)(struct file *, loff_t, loff_t, int);
 } __randomize_layout;
 
@@ -1844,19 +1844,22 @@ extern ssize_t vfs_copy_file_range(struct file *, loff_t , struct file *,
                                    loff_t, size_t, unsigned int);
 extern int generic_remap_file_range_prep(struct file *file_in, loff_t pos_in,
                                          struct file *file_out, loff_t pos_out,
-                                         u64 *count, unsigned int remap_flags);
-extern int do_clone_file_range(struct file *file_in, loff_t pos_in,
-                               struct file *file_out, loff_t pos_out, u64 len);
-extern int vfs_clone_file_range(struct file *file_in, loff_t pos_in,
-                                struct file *file_out, loff_t pos_out, u64 len);
+                                         loff_t *count,
+                                         unsigned int remap_flags);
+extern loff_t do_clone_file_range(struct file *file_in, loff_t pos_in,
+                                  struct file *file_out, loff_t pos_out,
+                                  loff_t len);
+extern loff_t vfs_clone_file_range(struct file *file_in, loff_t pos_in,
+                                   struct file *file_out, loff_t pos_out,
+                                   loff_t len);
 extern int vfs_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
                                          struct inode *dest, loff_t destoff,
                                          loff_t len, bool *is_same);
 extern int vfs_dedupe_file_range(struct file *file,
                                  struct file_dedupe_range *same);
-extern int vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos,
-                                     struct file *dst_file, loff_t dst_pos,
-                                     u64 len);
+extern loff_t vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos,
+                                        struct file *dst_file, loff_t dst_pos,
+                                        loff_t len);
 
 
 struct super_operations {
@@ -2986,7 +2989,7 @@ extern int generic_file_readonly_mmap(struct file *, struct vm_area_struct *);
 extern ssize_t generic_write_checks(struct kiocb *, struct iov_iter *);
 extern int generic_remap_checks(struct file *file_in, loff_t pos_in,
                                 struct file *file_out, loff_t pos_out,
-                                uint64_t *count, unsigned int remap_flags);
+                                loff_t *count, unsigned int remap_flags);
 extern ssize_t generic_file_read_iter(struct kiocb *, struct iov_iter *);
 extern ssize_t __generic_file_write_iter(struct kiocb *, struct iov_iter *);
 extern ssize_t generic_file_write_iter(struct kiocb *, struct iov_iter *);