Btrfs: optimize read_block_for_search

This patch does two things, first it only does one call to
btrfs_buffer_uptodate() with the gen specified instead of once with 0 and then
again with gen specified.  The other thing is to call btrfs_read_buffer() on the
buffer we've found instead of dropping it and then calling read_tree_block().
This will keep us from doing yet another radix tree lookup for a buffer we've
already found.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 1c9dc71089ce5244be2554476f203f0ae09728ed..c85cde7612485c208f4e878da0e883f5c414aad8 100644 (file)
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -2359,35 +2359,28 @@ read_block_for_search(struct btrfs_trans_handle *trans,
        tmp = btrfs_find_tree_block(root, blocknr, blocksize);
        if (tmp) {
                /* first we do an atomic uptodate check */
-               if (btrfs_buffer_uptodate(tmp, 0, 1) > 0) {
-                       if (btrfs_buffer_uptodate(tmp, gen, 1) > 0) {
-                               /*
-                                * we found an up to date block without
-                                * sleeping, return
-                                * right away
-                                */
-                               *eb_ret = tmp;
-                               return 0;
-                       }
-                       /* the pages were up to date, but we failed
-                        * the generation number check.  Do a full
-                        * read for the generation number that is correct.
-                        * We must do this without dropping locks so
-                        * we can trust our generation number
-                        */
-                       free_extent_buffer(tmp);
-                       btrfs_set_path_blocking(p);
+               if (btrfs_buffer_uptodate(tmp, gen, 1) > 0) {
+                       *eb_ret = tmp;
+                       return 0;
+               }
 
-                       /* now we're allowed to do a blocking uptodate check */
-                       tmp = read_tree_block(root, blocknr, blocksize, gen);
-                       if (tmp && btrfs_buffer_uptodate(tmp, gen, 0) > 0) {
-                               *eb_ret = tmp;
-                               return 0;
-                       }
-                       free_extent_buffer(tmp);
-                       btrfs_release_path(p);
-                       return -EIO;
+               /* the pages were up to date, but we failed
+                * the generation number check.  Do a full
+                * read for the generation number that is correct.
+                * We must do this without dropping locks so
+                * we can trust our generation number
+                */
+               btrfs_set_path_blocking(p);
+
+               /* now we're allowed to do a blocking uptodate check */
+               ret = btrfs_read_buffer(tmp, gen);
+               if (!ret) {
+                       *eb_ret = tmp;
+                       return 0;
                }
+               free_extent_buffer(tmp);
+               btrfs_release_path(p);
+               return -EIO;
        }
 
        /*