libext2fs: fix orphan file size > kernel limit with large blocksize

Kernel commit 0a6ce20c1564 ("ext4: verify orphan file size is not too big")
limits the maximum supported orphan file size to 8 << 20.

However, in e2fsprogs, the orphan file size is set to 32–512 filesystem
blocks when creating a filesystem.

With 64k block size, formatting an ext4 fs >32G gives an orphan file bigger
than the kernel allows, so mount prints an error and fails:

    EXT4-fs (vdb): orphan file too big: 8650752
    EXT4-fs (vdb): mount failed

Therefore, synchronize the kernel change to e2fsprogs to avoid creating
orphan files larger than the kernel limit.

Signed-off-by: Baokun Li <libaokun1@huawei.com>
Message-ID: <20251112122157.1990595-1-libaokun@huaweicloud.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Author: LiBaokun96

lib/ext2fs/ext2fs.h

@@ -1819,6 +1819,8 @@ errcode_t ext2fs_set_data_io(ext2_filsys fs, io_channel new_io);
 errcode_t ext2fs_rewrite_to_io(ext2_filsys fs, io_channel new_io);
 
 /* orphan.c */
+#define EXT4_MAX_ORPHAN_FILE_SIZE	8 << 20
+#define EXT4_DEFAULT_ORPHAN_FILE_SIZE	2 << 20
 extern errcode_t ext2fs_create_orphan_file(ext2_filsys fs, blk_t num_blocks);
 extern errcode_t ext2fs_truncate_orphan_file(ext2_filsys fs);
 extern e2_blkcnt_t ext2fs_default_orphan_file_blocks(ext2_filsys fs);

lib/ext2fs/orphan.c

@@ -164,6 +164,8 @@ errcode_t ext2fs_create_orphan_file(ext2_filsys fs, blk_t num_blocks)
 	memset(zerobuf, 0, fs->blocksize);
 	ob_tail = ext2fs_orphan_block_tail(fs, buf);
 	ob_tail->ob_magic = ext2fs_cpu_to_le32(EXT4_ORPHAN_BLOCK_MAGIC);
+	if (num_blocks * fs->blocksize > EXT4_MAX_ORPHAN_FILE_SIZE)
+		num_blocks = EXT4_MAX_ORPHAN_FILE_SIZE / fs->blocksize;
 	oi.num_blocks = num_blocks;
 	oi.alloc_blocks = 0;
 	oi.last_blk = 0;
@@ -216,18 +218,18 @@ errcode_t ext2fs_create_orphan_file(ext2_filsys fs, blk_t num_blocks)
 
 /*
  * Find reasonable size for orphan file. We choose orphan file size to be
- * between 32 and 512 filesystem blocks and not more than 1/4096 of the
- * filesystem unless it is really small.
+ * between 32 filesystem blocks and EXT4_DEFAULT_ORPHAN_FILE_SIZE, and not
+ * more than 1/fs->blocksize of the filesystem unless it is really small.
  */
 e2_blkcnt_t ext2fs_default_orphan_file_blocks(ext2_filsys fs)
 {
 	__u64 num_blocks = ext2fs_blocks_count(fs->super);
-	e2_blkcnt_t blks = 512;
+	e2_blkcnt_t blks = EXT4_DEFAULT_ORPHAN_FILE_SIZE / fs->blocksize;
 
 	if (num_blocks < 128 * 1024)
 		blks = 32;
-	else if (num_blocks < 2 * 1024 * 1024)
-		blks = num_blocks / 4096;
+	else if (num_blocks < EXT4_DEFAULT_ORPHAN_FILE_SIZE)
+		blks = num_blocks / fs->blocksize;
 	return (blks + EXT2FS_CLUSTER_MASK(fs)) & ~EXT2FS_CLUSTER_MASK(fs);
 }