libext2fs: fix alloc_allocate_group_table() if the flexbg_offset wraps

If the previous block group's inode table ends at the very end of file
system, wrap around to the beginning of the flex_bg.

This fixes a bug was tickled by:

mke2fs.conf:
	frontload = {
		features = extent,huge_file,flex_bg,uninit_bg,dir_nlink,extra_isize,^resize_inode,sparse_super2
		hash_alg = half_md4
		num_backup_sb = 0
		packed_meta_blocks = 1
		inode_ratio = 4194304
		flex_bg_size = 262144
	}

mke2fs -T frontload /tmp/foo.img 2T
resize2fs -M /tmp/foo.img
resize2fs -M /tmp/foo.img

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

diff --git a/lib/ext2fs/alloc_tables.c b/lib/ext2fs/alloc_tables.c
index fec9003..bc99943 100644 (file)
--- a/lib/ext2fs/alloc_tables.c
+++ b/lib/ext2fs/alloc_tables.c
@@ -54,8 +54,8 @@ static blk64_t flexbg_offset(ext2_filsys fs, dgrp_t group, blk64_t start_blk,
         * Don't do a long search if the previous block
         * search is still valid.
         */
-       if (start_blk && ext2fs_test_block_bitmap_range2(bmap, start_blk,
-                                                        elem_size))
+       if (start_blk && start_blk < ext2fs_blocks_count(fs->super) &&
+           ext2fs_test_block_bitmap_range2(bmap, start_blk, elem_size))
                return start_blk;
 
        start_blk = ext2fs_group_first_block2(fs, flexbg_size * flexbg);