From a0ade1deb86d2325aecc36272bb4505a6eec9235 Mon Sep 17 00:00:00 2001 From: Lukas Czerner Date: Mon, 20 Feb 2012 23:02:06 -0500 Subject: [PATCH] ext4: fix resize when resizing within single group When resizing file system in the way that the new size of the file system is still in the same group (no new groups are added), then we can hit a BUG_ON in ext4_alloc_group_tables() BUG_ON(flex_gd->count == 0 || group_data == NULL); because flex_gd->count is zero. The reason is the missing check for such case, so the code always extend the last group fully and then attempt to add more groups, but at that time n_blocks_count is actually smaller than o_blocks_count. It can be easily reproduced like this: mkfs.ext4 -b 4096 /dev/sda 30M mount /dev/sda /mnt/test resize2fs /dev/sda 50M Fix this by checking whether the resize happens within the singe group and only add that many blocks into the last group to satisfy user request. Then o_blocks_count == n_blocks_count and the resize will exit successfully without and attempt to add more groups into the fs. Also fix mixing together block number and blocks count which might be confusing and can easily lead to off-by-one errors (but it is actually not the case here since the two occurrence of this mix-up will cancel each other). Signed-off-by: Lukas Czerner Reported-by: Milan Broz Reviewed-by: Eric Sandeen Signed-off-by: "Theodore Ts'o" --- fs/ext4/resize.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c index f9d948f0eb86..3fed79da0d2c 100644 --- a/fs/ext4/resize.c +++ b/fs/ext4/resize.c @@ -1582,7 +1582,7 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count) ext4_fsblk_t o_blocks_count; ext4_group_t o_group; ext4_group_t n_group; - ext4_grpblk_t offset; + ext4_grpblk_t offset, add; unsigned long n_desc_blocks; unsigned long o_desc_blocks; unsigned long desc_blocks; @@ -1605,7 +1605,7 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count) return 0; ext4_get_group_no_and_offset(sb, n_blocks_count - 1, &n_group, &offset); - ext4_get_group_no_and_offset(sb, o_blocks_count, &o_group, &offset); + ext4_get_group_no_and_offset(sb, o_blocks_count - 1, &o_group, &offset); n_desc_blocks = (n_group + EXT4_DESC_PER_BLOCK(sb)) / EXT4_DESC_PER_BLOCK(sb); @@ -1634,10 +1634,12 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count) } brelse(bh); - if (offset != 0) { - /* extend the last group */ - ext4_grpblk_t add; - add = EXT4_BLOCKS_PER_GROUP(sb) - offset; + /* extend the last group */ + if (n_group == o_group) + add = n_blocks_count - o_blocks_count; + else + add = EXT4_BLOCKS_PER_GROUP(sb) - (offset + 1); + if (add > 0) { err = ext4_group_extend_no_check(sb, o_blocks_count, add); if (err) goto out; -- 2.20.1