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btrfs: don't use btrfs_chunk::sub_stripes from disk 

[BUG]
There are two reports (the earliest one from LKP, a more recent one from
kernel bugzilla) that we can have some chunks with 0 as sub_stripes.

This will cause divide-by-zero errors at btrfs_rmap_block, which is
introduced by a recent kernel patch ac0677348f ("btrfs: merge
calculations for simple striped profiles in btrfs_rmap_block"):

		if (map->type & (BTRFS_BLOCK_GROUP_RAID0 |
				 BTRFS_BLOCK_GROUP_RAID10)) {
			stripe_nr = stripe_nr * map->num_stripes + i;
			stripe_nr = div_u64(stripe_nr, map->sub_stripes); <<<
		}

[CAUSE]
From the more recent report, it has been proven that we have some chunks
with 0 as sub_stripes, mostly caused by older mkfs.

It turns out that the mkfs.btrfs fix is only introduced in 6718ab4d33aa
("btrfs-progs: Initialize sub_stripes to 1 in btrfs_alloc_data_chunk")
which is included in v5.4 btrfs-progs release.

So there would be quite some old filesystems with such 0 sub_stripes.

[FIX]
Just don't trust the sub_stripes values from disk.

We have a trusted btrfs_raid_array[] to fetch the correct sub_stripes
numbers for each profile and that are fixed.

By this, we can keep the compatibility with older filesystems while
still avoid divide-by-zero bugs.

Reported-by: kernel test robot <oliver.sang@intel.com>
Reported-by: Viktor Kuzmin <kvaster@gmail.com>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=216559
Fixes: ac0677348f ("btrfs: merge calculations for simple striped profiles in btrfs_rmap_block")
CC: stable@vger.kernel.org # 6.0
Reviewed-by: Su Yue <glass@fydeos.io>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo 2022-10-21 08:43:45 +08:00 committed by David Sterba
parent 2398091f9c
commit 76a66ba101
1 changed files with 11 additions and 1 deletions
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12
fs/btrfs/volumes.c
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@ -7142,6 +7142,7 @@ static int read_one_chunk(struct btrfs_key *key, struct extent_buffer *leaf,
u64 devid;
u64 type;
u8 uuid[BTRFS_UUID_SIZE];
int index;
int num_stripes;
int ret;
int i;
@ -7149,6 +7150,7 @@ static int read_one_chunk(struct btrfs_key *key, struct extent_buffer *leaf,
logical = key->offset;
length = btrfs_chunk_length(leaf, chunk);
type = btrfs_chunk_type(leaf, chunk);
index = btrfs_bg_flags_to_raid_index(type);
num_stripes = btrfs_chunk_num_stripes(leaf, chunk);
#if BITS_PER_LONG == 32
@ -7202,7 +7204,15 @@ static int read_one_chunk(struct btrfs_key *key, struct extent_buffer *leaf,
map->io_align = btrfs_chunk_io_align(leaf, chunk);
map->stripe_len = btrfs_chunk_stripe_len(leaf, chunk);
map->type = type;
map->sub_stripes = btrfs_chunk_sub_stripes(leaf, chunk);
/*
* We can't use the sub_stripes value, as for profiles other than
* RAID10, they may have 0 as sub_stripes for filesystems created by
* older mkfs (<v5.4).
* In that case, it can cause divide-by-zero errors later.
* Since currently sub_stripes is fixed for each profile, let's
* use the trusted value instead.
*/
map->sub_stripes = btrfs_raid_array[index].sub_stripes;
map->verified_stripes = 0;
em->orig_block_len = btrfs_calc_stripe_length(em);
for (i = 0; i < num_stripes; i++) {