From ed5d5f37e653b606c93b2d5f1cdd155be6fefce0 Mon Sep 17 00:00:00 2001
From: Liu Bo <bo.li.liu@oracle.com>
Date: Tue, 27 Feb 2018 18:10:58 -0700
Subject: [PATCH] Btrfs: dev-replace: skip prealloc extents when copy nocow
 pages

It doens't make sense to process prealloc extents as pages will be
filled with zero when reading prealloc extents.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/scrub.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index beb441d0c5c6..9fb7d09842e6 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -4480,7 +4480,8 @@ static int check_extent_to_block(struct btrfs_inode *inode, u64 start, u64 len,
 	 * move on to the next inode.
 	 */
 	if (em->block_start > logical ||
-	    em->block_start + em->block_len < logical + len) {
+	    em->block_start + em->block_len < logical + len ||
+	    test_bit(EXTENT_FLAG_PREALLOC, &em->flags)) {
 		free_extent_map(em);
 		ret = 1;
 		goto out_unlock;