From: Qu Wenruo <wqu@xxxxxxxx>
commit 76a66ba101329316a5d7f4275070be22eb85fdf2 upstream.
[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 ac0677348f3c ("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@xxxxxxxxx>
Reported-by: Viktor Kuzmin <kvaster@xxxxxxxxx>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=216559
Fixes: ac0677348f3c ("btrfs: merge calculations for simple striped profiles in btrfs_rmap_block")
CC: stable@xxxxxxxxxxxxxxx # 6.0
Reviewed-by: Su Yue <glass@xxxxxxxxx>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/btrfs/volumes.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -7029,6 +7029,7 @@ static int read_one_chunk(struct btrfs_k
u64 devid;
u64 type;
u8 uuid[BTRFS_UUID_SIZE];
+ int index;
int num_stripes;
int ret;
int i;
@@ -7036,6 +7037,7 @@ static int read_one_chunk(struct btrfs_k
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
@@ -7089,7 +7091,15 @@ static int read_one_chunk(struct btrfs_k
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++) {
