In find_free_extent() under checks: tag, we have the following code

------
                search_start = ALIGN(offset, fs_info->stripesize);
                /* move on to the next group */
                if (search_start + num_bytes >
                    block_group->key.objectid + block_group->key.offset) {
                        btrfs_add_free_space(block_group, offset, num_bytes);
                        goto loop;
                }
                if (offset < search_start)
                        btrfs_add_free_space(block_group, offset,
                                             search_start - offset);
                BUG_ON(offset > search_start);
------

However ALIGN() is rounding up, thus @search_start >= @offset and that
BUG_ON() will never be triggered.

Signed-off-by: Qu Wenruo <w...@suse.com>
---
changelog:
v2:
  Fix my stupid error on judging whether ALIGN() is rounding up or down.
---
 fs/btrfs/extent-tree.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index f18e86177067..de4a85dfb98e 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -7754,7 +7754,7 @@ static noinline int find_free_extent(struct btrfs_fs_info 
*fs_info,
                        goto loop;
                }
 checks:
-               search_start = ALIGN(offset, fs_info->stripesize);
+               search_start = round_up(offset, fs_info->stripesize);
 
                /* move on to the next group */
                if (search_start + num_bytes >
@@ -7766,7 +7766,6 @@ static noinline int find_free_extent(struct btrfs_fs_info 
*fs_info,
                if (offset < search_start)
                        btrfs_add_free_space(block_group, offset,
                                             search_start - offset);
-               BUG_ON(offset > search_start);
 
                ret = btrfs_add_reserved_bytes(block_group, ram_bytes,
                                num_bytes, delalloc);
-- 
2.18.0

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