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ext4: fix online resize's handling of a too-small final block group

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Avoid growing the file system to an extent so that the last block
group is too small to hold all of the metadata that must be stored in
the block group.

This problem can be triggered with the following reproducer:

umount /mnt
mke2fs -F -m0 -b 4096 -t ext4 -O resize_inode,^has_journal \
	-E resize=1073741824 /tmp/foo.img 128M
mount /tmp/foo.img /mnt
truncate --size 1708M /tmp/foo.img
resize2fs /dev/loop0 295400
umount /mnt
e2fsck -fy /tmp/foo.img

Reported-by: Torsten Hilbrich <torsten.hilbrich@secunet.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
This commit is contained in:
Theodore Ts'o 2018-09-03 22:19:43 -04:00
parent 4274f516d4
commit f0a459dec5
1 changed files with 20 additions and 0 deletions
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20
fs/ext4/resize.c
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@ -1986,6 +1986,26 @@ retry:
}
}
/*
* Make sure the last group has enough space so that it's
* guaranteed to have enough space for all metadata blocks
* that it might need to hold. (We might not need to store
* the inode table blocks in the last block group, but there
* will be cases where this might be needed.)
*/
if ((ext4_group_first_block_no(sb, n_group) +
ext4_group_overhead_blocks(sb, n_group) + 2 +
sbi->s_itb_per_group + sbi->s_cluster_ratio) >= n_blocks_count) {
n_blocks_count = ext4_group_first_block_no(sb, n_group);
n_group--;
n_blocks_count_retry = 0;
if (resize_inode) {
iput(resize_inode);
resize_inode = NULL;
}
goto retry;
}
/* extend the last group */
if (n_group == o_group)
add = n_blocks_count - o_blocks_count;