Btrfs: make send's file extent item search more efficient

Instead of looking for a file extent item, process it, release the path
and do a btree search for the next file extent item, just process all
file extent items in a leaf without intermediate btree searches. This way
we save cpu and we're not blocking other tasks or affecting concurrency on
the btree, because send's paths use the commit root and skip btree node/leaf
locking.

Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index c96e879bcb160254d5268a688f8c97c48c5e9003..4d31f72bdf41cb02a37317c4c7348ce9116f0846 100644 (file)
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -4573,17 +4573,25 @@ static int process_all_extents(struct send_ctx *sctx)
        key.objectid = sctx->cmp_key->objectid;
        key.type = BTRFS_EXTENT_DATA_KEY;
        key.offset = 0;
-       while (1) {
-               ret = btrfs_search_slot_for_read(root, &key, path, 1, 0);
-               if (ret < 0)
-                       goto out;
-               if (ret) {
-                       ret = 0;
-                       goto out;
-               }
+       ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+       if (ret < 0)
+               goto out;
 
+       while (1) {
                eb = path->nodes[0];
                slot = path->slots[0];
+
+               if (slot >= btrfs_header_nritems(eb)) {
+                       ret = btrfs_next_leaf(root, path);
+                       if (ret < 0) {
+                               goto out;
+                       } else if (ret > 0) {
+                               ret = 0;
+                               break;
+                       }
+                       continue;
+               }
+
                btrfs_item_key_to_cpu(eb, &found_key, slot);
 
                if (found_key.objectid != key.objectid ||
@@ -4596,8 +4604,7 @@ static int process_all_extents(struct send_ctx *sctx)
                if (ret < 0)
                        goto out;
 
-               btrfs_release_path(path);
-               key.offset = found_key.offset + 1;
+               path->slots[0]++;
        }
 
 out: