Commit 2ea98466 authored Sep 23, 2016 by Amir Goldstein Committed by Miklos Szeredi Dec 16, 2016

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>

parent 31c3a706

fs/overlayfs/copy_up.c

+8 −1

Original line number	Diff line number	Diff line
		@@ -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);