Btrfs: Fix more false enospc errors and an oops from empty clustering

In comes cases the empty cluster was added twice to the total number of
bytes the allocator was trying to find.

With empty clustering on, the hint byte was sometimes outside of the
block group.  Add an extra goto to find the correct block group.

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

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 0d73a53c67633e38f2805c29f838e4ee40090df5..b92e92c29e3b6c66205208e5d42d54dfbc4b3324 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2152,11 +2152,13 @@ static int noinline find_free_extent(struct btrfs_trans_handle *trans,
        }
        search_start = max(search_start, first_logical_byte(root, 0));
        search_start = max(search_start, hint_byte);
-       total_needed += empty_size;
 
-       if (search_start != last_wanted)
+       if (last_wanted && search_start != last_wanted) {
                last_wanted = 0;
+               empty_size += empty_cluster;
+       }
 
+       total_needed += empty_size;
        block_group = btrfs_lookup_block_group(root->fs_info, search_start);
        if (!block_group)
                block_group = btrfs_lookup_first_block_group(root->fs_info,
@@ -2171,7 +2173,9 @@ static int noinline find_free_extent(struct btrfs_trans_handle *trans,
                 * group thats not of the proper type, while looping this
                 * should never happen
                 */
-               WARN_ON(!block_group);
+               if (!block_group)
+                       goto new_group_no_lock;
+
                mutex_lock(&block_group->alloc_mutex);
                if (unlikely(!block_group_bits(block_group, data)))
                        goto new_group;
@@ -2248,12 +2252,13 @@ static int noinline find_free_extent(struct btrfs_trans_handle *trans,
                        break;
                }
 new_group:
+               mutex_unlock(&block_group->alloc_mutex);
+new_group_no_lock:
                last_wanted = 0;
-               if (loop > 0) {
+               if (!allowed_chunk_alloc && loop > 0) {
                        total_needed -= empty_cluster;
                        empty_cluster = 0;
                }
-               mutex_unlock(&block_group->alloc_mutex);
                /*
                 * Here's how this works.
                 * loop == 0: we were searching a block group via a hint
@@ -2271,6 +2276,10 @@ new_group:
                        cur = head->next;
                        loop++;
                } else if (loop == 1 && cur == head) {
+
+                       total_needed -= empty_cluster;
+                       empty_cluster = 0;
+
                        if (allowed_chunk_alloc && !chunk_alloc_done) {
                                up_read(&space_info->groups_sem);
                                ret = do_chunk_alloc(trans, root, num_bytes +