f2fs: describe orphan block layout dynamically

An on-disk orphan block contains a variable-length array of 32-bit
inode numbers followed by a fixed footer at the end of the block. A
compile-time whole-block structure cannot represent the footer position
when the block size varies at runtime.

Remove struct f2fs_orphan_block, introduce
struct f2fs_orphan_block_footer, and compute sbi->orphans_per_block
dynamically in init_sb_info(). Add helpers to access the inode entry array
and footer from a block buffer.

Update orphan inode recovery, checkpointing, and mount paths to use the
parameterized helpers. This preserves the on-disk format while decoupling
orphan handling from compile-time constants.

Signed-off-by: Kelvin Zhang <zhangxp1998@gmail.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

1 files changed, 14 insertions, 6 deletions

diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
index 061f906a7b94..bdb8c63ac0c6 100644
--- a/include/linux/f2fs_fs.h
+++ b/include/linux/f2fs_fs.h
@@ -220,14 +220,22 @@ struct f2fs_checkpoint {
 
 /*
  * For orphan inode management
+ *
+ * The number of inode entries in an orphan block depends on the filesystem
+ * block size. Its exact on-disk layout is:
+ *
+ * 0                           blocksize - 16             blocksize
+ * +--------------------------+--------------------------+
+ * | ino[0] ... ino[n - 1]    | struct f2fs_orphan_footer |
+ * +--------------------------+--------------------------+
+ *
+ * n = (blocksize - sizeof(struct f2fs_orphan_footer)) / sizeof(__le32)
  */
-#define F2FS_ORPHANS_PER_BLOCK	((F2FS_BLKSIZE - 4 * sizeof(__le32)) / sizeof(__le32))
-
-#define GET_ORPHAN_BLOCKS(n)	(((n) + F2FS_ORPHANS_PER_BLOCK - 1) / \
-					F2FS_ORPHANS_PER_BLOCK)
-
 struct f2fs_orphan_block {
-	__le32 ino[F2FS_ORPHANS_PER_BLOCK];	/* inode numbers */
+	DECLARE_FLEX_ARRAY(__le32, ino);
+} __packed;
+
+struct f2fs_orphan_footer {
 	__le32 reserved;	/* reserved */
 	__le16 blk_addr;	/* block index in current CP */
 	__le16 blk_count;	/* Number of orphan inode blocks in CP */