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>

1 files changed, 28 insertions, 9 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index c3df14ce2cc2..6921231e0efb 100644
--- 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);