[PATCH] btrfs: add missing ASSERT for system space_info in reserve_chunk_space

[Jiasheng Jiang <jiashengjiangcool@gmail.com>]

In reserve_chunk_space(), btrfs_find_space_info() is called to retrieve
the space_info for the SYSTEM block group. However, the returned pointer
is immediately dereferenced by spin_lock(&info->lock) without validation.

While the SYSTEM space_info is expected to be present during normal
operations, direct dereference without checking creates a risk of a
null pointer dereference. This deviates from the coding pattern seen
in peer functions like btrfs_chunk_alloc() where such returns are
validated with an ASSERT.

Add an ASSERT() to ensure the pointer is valid before access, improving
code robustness and consistency with the rest of the block-group logic.

Signed-off-by: Jiasheng Jiang <jiashengjiangcool@gmail.com>
---
 fs/btrfs/block-group.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index 08b14449fabe..f4229ee4f573 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -4313,6 +4313,7 @@ static void reserve_chunk_space(struct btrfs_trans_handle *trans,
 	lockdep_assert_held(&fs_info->chunk_mutex);
 
 	info = btrfs_find_space_info(fs_info, BTRFS_BLOCK_GROUP_SYSTEM);
+	ASSERT(info);
 	spin_lock(&info->lock);
 	left = info->total_bytes - btrfs_space_info_used(info, true);
 	spin_unlock(&info->lock);
-- 
2.25.1