Btrfs: check for empty bitmap list in setup_cluster_bitmaps

[cascardo/linux.git] / fs / btrfs / free-space-cache.c

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 0948d34..e6fc7d9 100644 (file)
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -2972,7 +2972,7 @@ setup_cluster_bitmap(struct btrfs_block_group_cache *block_group,
                     u64 cont1_bytes, u64 min_bytes)
 {
        struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
-       struct btrfs_free_space *entry;
+       struct btrfs_free_space *entry = NULL;
        int ret = -ENOSPC;
        u64 bitmap_offset = offset_to_bitmap(ctl, offset);
 
@@ -2983,8 +2983,10 @@ setup_cluster_bitmap(struct btrfs_block_group_cache *block_group,
         * The bitmap that covers offset won't be in the list unless offset
         * is just its start offset.
         */
-       entry = list_first_entry(bitmaps, struct btrfs_free_space, list);
-       if (entry->offset != bitmap_offset) {
+       if (!list_empty(bitmaps))
+               entry = list_first_entry(bitmaps, struct btrfs_free_space, list);
+
+       if (!entry || entry->offset != bitmap_offset) {
                entry = tree_search_offset(ctl, bitmap_offset, 1, 0);
                if (entry && list_empty(&entry->list))
                        list_add(&entry->list, bitmaps);