ext4: fix corruption when online resizing a 1K bigalloc fs

stable inclusion
from stable-v5.10.163
commit f06c980287f165d4e8e0628de0cdcda87ffa022f
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I7PJ9N

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f06c980287f165d4e8e0628de0cdcda87ffa022f



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commit 0aeaa255 upstream.

When a backup superblock is updated in update_backups(), the primary
superblock's offset in the group (that is, sbi->s_sbh->b_blocknr) is used
as the backup superblock's offset in its group. However, when the block
size is 1K and bigalloc is enabled, the two offsets are not equal. This
causes the backup group descriptors to be overwritten by the superblock
in update_backups(). Moreover, if meta_bg is enabled, the file system will
be corrupted because this feature uses backup group descriptors.

To solve this issue, we use a more accurate ext4_group_first_block_no() as
the offset of the backup superblock in its group.

Fixes: d77147ff ("ext4: add support for online resizing with bigalloc")
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: stable@kernel.org
Link: https://lore.kernel.org/r/20221117040341.1380702-4-libaokun1@huawei.com


Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: zhaoxiaoqiang11 <zhaoxiaoqiang11@jd.com>