ovl: use vfs_clone_file_range() for copy up if possible

When copying up within the same fs, try to use vfs_clone_file_range().
This is very efficient when lower and upper are on the same fs
with file reflink support. If vfs_clone_file_range() fails for any
reason, copy up falls back to the regular data copy code.

Tested correct behavior when lower and upper are on:
1. same ext4 (copy)
2. same xfs + reflink patches + mkfs.xfs (copy)
3. same xfs + reflink patches + mkfs.xfs -m reflink=1 (reflink)
4. different xfs + reflink patches + mkfs.xfs -m reflink=1 (copy)

For comparison, on my laptop, xfstest overlay/001 (copy up of large
sparse files) takes less than 1 second in the xfs reflink setup vs.
25 seconds on the rest of the setups.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 36795ee..f18c1a6 100644 (file)
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -153,6 +153,13 @@ static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
                goto out_fput;
        }
 
+       /* Try to use clone_file_range to clone up within the same fs */
+       error = vfs_clone_file_range(old_file, 0, new_file, 0, len);
+       if (!error)
+               goto out;
+       /* Couldn't clone, so now we try to copy the data */
+       error = 0;
+
        /* FIXME: copy up sparse files efficiently */
        while (len) {
                size_t this_len = OVL_COPY_UP_CHUNK_SIZE;
@@ -177,7 +184,7 @@ static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
 
                len -= bytes;
        }
-
+out:
        if (!error)
                error = vfs_fsync(new_file, 0);
        fput(new_file);