[PATCH 1/2] V2 Avoid sending disknr==0 extents when possible

[Alex Lyakas <alex.btrfs@xxxxxxxxxxxxxxxxx>]

In the following cases we do not send disknr==0 extents:
1) full send 2) new inode in a diff-send 3) when disknr==0 extents are
added to the end of an inode

Original-version-by: Chen Yang <chenyang.fnst@xxxxxxxxxxxxxx>
Signed-off-by: Alex Lyakas <alex.btrfs@xxxxxxxxxxxxxxxxx>
---
 fs/btrfs/send.c |   30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 321b7fb..e23f5cf 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -3846,7 +3846,8 @@ static int is_extent_unchanged(struct send_ctx *sctx,
        btrfs_item_key_to_cpu(eb, &found_key, slot);
        if (found_key.objectid != key.objectid ||
            found_key.type != key.type) {
-               ret = 0;
+               /* No need to send a no-data extent it in this case */
+               ret = (left_disknr == 0) ? 1 : 0;
                goto out;
        }

@@ -3872,7 +3873,8 @@ static int is_extent_unchanged(struct send_ctx *sctx,
                 * This may only happen on the first iteration.
                 */
                if (found_key.offset + right_len <= ekey->offset) {
-                       ret = 0;
+                       /* No need to send a no-data extent it in this case */
+                       ret = (left_disknr == 0) ? 1 : 0;
                        goto out;
                }

@@ -3953,6 +3955,30 @@ static int process_extent(struct send_ctx *sctx,
                        ret = 0;
                        goto out;
                }
+       } else {
+               struct extent_buffer *eb;
+               struct btrfs_file_extent_item *ei;
+               u8 extent_type;
+               u64 extent_disknr;
+
+               eb = path->nodes[0];
+               ei = btrfs_item_ptr(eb, path->slots[0],
+                               struct btrfs_file_extent_item);
+
+               extent_type = btrfs_file_extent_type(eb, ei);
+               extent_disknr = btrfs_file_extent_disk_bytenr(eb, ei);
+               if (extent_type == BTRFS_FILE_EXTENT_REG &&
+                       extent_disknr == 0) {
+                       /*
+                        * This is disknr=0 extent in a full-send or a
+                        * new inode in a diff-send. Since we will
+                        * send truncate command in finish_inode_if_needed
+                        * anyways, the inode size will be correct,
+                        * and we don't have to send all-zero data.
+                        */
+                       ret = 0;
+                       goto out;
+               }
        }

        ret = find_extent_clone(sctx, path, key->objectid, key->offset,
--
1.7.9.5
--
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