Btrfs: Hash in the offset and owner for file extent backref keys

This makes searches for backrefs and backref insertion much more efficient
when there are many backrefs for a single extent

Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 0fc8dfd..8761aec 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -397,13 +397,12 @@ static u64 hash_extent_ref(u64 root_objectid, u64 ref_generation,
        high_crc = crc32c(high_crc, &lenum, sizeof(lenum));
        lenum = cpu_to_le64(ref_generation);
        low_crc = crc32c(low_crc, &lenum, sizeof(lenum));
-
-#if 0
-       lenum = cpu_to_le64(owner);
-       low_crc = crc32c(low_crc, &lenum, sizeof(lenum));
-       lenum = cpu_to_le64(owner_offset);
-       low_crc = crc32c(low_crc, &lenum, sizeof(lenum));
-#endif
+       if (owner >= BTRFS_FIRST_FREE_OBJECTID) {
+               lenum = cpu_to_le64(owner);
+               low_crc = crc32c(low_crc, &lenum, sizeof(lenum));
+               lenum = cpu_to_le64(owner_offset);
+               low_crc = crc32c(low_crc, &lenum, sizeof(lenum));
+       }
        return ((u64)high_crc << 32) | (u64)low_crc;
 }