On 09/14/2016 11:51 AM, Liu Bo wrote:
When relocating tree blocks, we firstly get block information from
back references in the extent tree, we then search fs tree to try to
find all parents of a block.

However, if fs tree is corrupted, eg. if there're some missing
items, we could come across these WARN_ONs and BUG_ONs.

This makes us print some error messages and return gracefully
from balance.

Signed-off-by: Liu Bo <[email protected]>
---
 fs/btrfs/relocation.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index c0c13dc..680e234 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -923,9 +923,16 @@ again:
                        path2->slots[level]--;

                eb = path2->nodes[level];
-               WARN_ON(btrfs_node_blockptr(eb, path2->slots[level]) !=
-                       cur->bytenr);
-
+               if (btrfs_node_blockptr(eb, path2->slots[level]) !=
+                   cur->bytenr) {
+                       btrfs_err(root->fs_info,
+       "couldn't find block (%llu) (level %d) in tree (%llu) with key (%llu %u 
%llu)",
+                                 cur->bytenr, level - 1, root->objectid,
+                                 node_key->objectid, node_key->type,
+                                 node_key->offset);
+                       err = -ENOENT;
+                       goto out;
+               }
                lower = cur;
                need_check = true;
                for (; level < BTRFS_MAX_LEVEL; level++) {
@@ -2686,11 +2693,15 @@ static int do_relocation(struct btrfs_trans_handle 
*trans,

                if (!upper->eb) {
                        ret = btrfs_search_slot(trans, root, key, path, 0, 1);
-                       if (ret < 0) {
-                               err = ret;
+                       if (ret) {
+                               if (ret < 0)
+                                       err = ret;
+                               else
+                                       err = -ENOENT;
+
+                               btrfs_release_path(path);
                                break;
                        }
-                       BUG_ON(ret > 0);

                        if (!upper->eb) {
                                upper->eb = path->nodes[upper->level];


Reviewed-by: Josef Bacik <[email protected]>

Thanks,

Josef
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