Btrfs: don't loop forever on bad btree blocks

When btrfs discovers the generation number in a btree block is
incorrect, it can loop forever without forcing the RAID
code to try a valid mirror, and without returning EIO.

This changes things to properly kick out the EIO.

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

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index c3df14ce2cc2c00d232028d1238121ff9c37e35c..6921231e0efb8e279da15a0d6ff73469e2b9f886 100644 (file)
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -1577,13 +1577,33 @@ read_block_for_search(struct btrfs_trans_handle *trans,
        blocksize = btrfs_level_size(root, level - 1);
 
        tmp = btrfs_find_tree_block(root, blocknr, blocksize);
-       if (tmp && btrfs_buffer_uptodate(tmp, gen)) {
-               /*
-                * we found an up to date block without sleeping, return
-                * right away
-                */
-               *eb_ret = tmp;
-               return 0;
+       if (tmp) {
+               if (btrfs_buffer_uptodate(tmp, 0)) {
+                       if (btrfs_buffer_uptodate(tmp, gen)) {
+                               /*
+                                * 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);
+                       tmp = read_tree_block(root, blocknr, blocksize, gen);
+                       if (tmp && btrfs_buffer_uptodate(tmp, gen)) {
+                               *eb_ret = tmp;
+                               return 0;
+                       }
+                       free_extent_buffer(tmp);
+                       btrfs_release_path(NULL, p);
+                       return -EIO;
+               }
        }
 
        /*
@@ -1596,8 +1616,7 @@ read_block_for_search(struct btrfs_trans_handle *trans,
        btrfs_unlock_up_safe(p, level + 1);
        btrfs_set_path_blocking(p);
 
-       if (tmp)
-               free_extent_buffer(tmp);
+       free_extent_buffer(tmp);
        if (p->reada)
                reada_for_search(root, p, level, slot, key->objectid);