Merge branch 'for-chris-4.9' of git://git.kernel.org/pub/scm/linux/kernel/git/fdmanana/linux into for-linus-4.9

1 files changed, 58 insertions, 0 deletions

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 978796865bfc..0b4628999b77 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -5805,6 +5805,64 @@ static int changed_extent(struct send_ctx *sctx,
 	int ret = 0;
 
 	if (sctx->cur_ino != sctx->cmp_key->objectid) {
+
+		if (result == BTRFS_COMPARE_TREE_CHANGED) {
+			struct extent_buffer *leaf_l;
+			struct extent_buffer *leaf_r;
+			struct btrfs_file_extent_item *ei_l;
+			struct btrfs_file_extent_item *ei_r;
+
+			leaf_l = sctx->left_path->nodes[0];
+			leaf_r = sctx->right_path->nodes[0];
+			ei_l = btrfs_item_ptr(leaf_l,
+					      sctx->left_path->slots[0],
+					      struct btrfs_file_extent_item);
+			ei_r = btrfs_item_ptr(leaf_r,
+					      sctx->right_path->slots[0],
+					      struct btrfs_file_extent_item);
+
+			/*
+			 * We may have found an extent item that has changed
+			 * only its disk_bytenr field and the corresponding
+			 * inode item was not updated. This case happens due to
+			 * very specific timings during relocation when a leaf
+			 * that contains file extent items is COWed while
+			 * relocation is ongoing and its in the stage where it
+			 * updates data pointers. So when this happens we can
+			 * safely ignore it since we know it's the same extent,
+			 * but just at different logical and physical locations
+			 * (when an extent is fully replaced with a new one, we
+			 * know the generation number must have changed too,
+			 * since snapshot creation implies committing the current
+			 * transaction, and the inode item must have been updated
+			 * as well).
+			 * This replacement of the disk_bytenr happens at
+			 * relocation.c:replace_file_extents() through
+			 * relocation.c:btrfs_reloc_cow_block().
+			 */
+			if (btrfs_file_extent_generation(leaf_l, ei_l) ==
+			    btrfs_file_extent_generation(leaf_r, ei_r) &&
+			    btrfs_file_extent_ram_bytes(leaf_l, ei_l) ==
+			    btrfs_file_extent_ram_bytes(leaf_r, ei_r) &&
+			    btrfs_file_extent_compression(leaf_l, ei_l) ==
+			    btrfs_file_extent_compression(leaf_r, ei_r) &&
+			    btrfs_file_extent_encryption(leaf_l, ei_l) ==
+			    btrfs_file_extent_encryption(leaf_r, ei_r) &&
+			    btrfs_file_extent_other_encoding(leaf_l, ei_l) ==
+			    btrfs_file_extent_other_encoding(leaf_r, ei_r) &&
+			    btrfs_file_extent_type(leaf_l, ei_l) ==
+			    btrfs_file_extent_type(leaf_r, ei_r) &&
+			    btrfs_file_extent_disk_bytenr(leaf_l, ei_l) !=
+			    btrfs_file_extent_disk_bytenr(leaf_r, ei_r) &&
+			    btrfs_file_extent_disk_num_bytes(leaf_l, ei_l) ==
+			    btrfs_file_extent_disk_num_bytes(leaf_r, ei_r) &&
+			    btrfs_file_extent_offset(leaf_l, ei_l) ==
+			    btrfs_file_extent_offset(leaf_r, ei_r) &&
+			    btrfs_file_extent_num_bytes(leaf_l, ei_l) ==
+			    btrfs_file_extent_num_bytes(leaf_r, ei_r))
+				return 0;
+		}
+
 		inconsistent_snapshot_error(sctx, result, "extent");
 		return -EIO;
 	}