ext4: Add BUG_ON debugging checks to noalloc_get_block_write()

Enforce that noalloc_get_block_write() is only called to map one block
at a time, and that it always is successful in finding a mapping for
given an inode's logical block block number if it is called with
create == 1.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index fd5f27a9b81b..e6113c3a126f 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2433,11 +2433,14 @@ static int noalloc_get_block_write(struct inode *inode, sector_t iblock,
         int ret = 0;
         unsigned max_blocks = bh_result->b_size >> inode->i_blkbits;
 
+        BUG_ON(bh_result->b_size != inode->i_sb->s_blocksize);
+
         /*
          * we don't want to do block allocation in writepage
          * so call get_block_wrap with create = 0
          */
         ret = ext4_get_blocks(NULL, inode, iblock, max_blocks, bh_result, 0);
+        BUG_ON(create && ret == 0);
         if (ret > 0) {
                 bh_result->b_size = (ret << inode->i_blkbits);
                 ret = 0;