For performance reason, leave data at the start of disk, is preferable
while deduping
It's might sense for the reasons:
1. Spinning rust - start of the disk is much faster
2. Btrfs can deallocate empty data chunk from the end of fs - ie it's compact fs
Signed-off-by: Timofey Titovets <nefelim...@gmail.com>
---
fs/btrfs/ioctl.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 3e3e613..3eb77c0 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3074,8 +3074,13 @@ static int btrfs_extent_same(struct inode *src,
u64 loff, u64 olen,
/* pass original length for comparison so we stay within i_size */
ret = btrfs_cmp_data(src, loff, dst, dst_loff, olen, &cmp);
- if (ret == 0)
- ret = btrfs_clone(src, dst, loff, olen, len, dst_loff, 1);
+ if (ret == 0) {
+ /* prefer inode with lowest offset as source for clone*/
+ if (loff > dest_loff)
+ ret = btrfs_clone(dst, src, dst_loff, olen, len, loff, 1);
+ else
+ ret = btrfs_clone(src, dst, loff, olen, len, dst_loff, 1);
+ }
if (same_inode)
unlock_extent(&BTRFS_I(src)->io_tree, same_lock_start,
--
2.6.1
From 5ed3822bc308c726d91a837fbd97ebacaa51e58d Mon Sep 17 00:00:00 2001
From: Timofey Titovets <nefelim...@gmail.com>
Date: Tue, 20 Oct 2015 15:53:20 +0300
Subject: [RFC PATCH] btrfs/ioctl.c: Prefer inode with lowest offset as source for
clone
For performance reason, leave data at the start of disk, is preferable
Signed-off-by: Timofey Titovets <nefelim...@gmail.com>
---
fs/btrfs/ioctl.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 3e3e613..3eb77c0 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3074,8 +3074,13 @@ static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,
/* pass original length for comparison so we stay within i_size */
ret = btrfs_cmp_data(src, loff, dst, dst_loff, olen, &cmp);
- if (ret == 0)
- ret = btrfs_clone(src, dst, loff, olen, len, dst_loff, 1);
+ if (ret == 0) {
+ /* prefer inode with lowest offset as source for clone*/
+ if (loff > dest_loff)
+ ret = btrfs_clone(dst, src, dst_loff, olen, len, loff, 1);
+ else
+ ret = btrfs_clone(src, dst, loff, olen, len, dst_loff, 1);
+ }
if (same_inode)
unlock_extent(&BTRFS_I(src)->io_tree, same_lock_start,
--
2.6.1
