Hi， > -----Original Message----- > From: Nikolay Borisov [mailto:nborisov@xxxxxxxx] > Sent: Tuesday, October 17, 2017 9:36 PM > To: Gu, Jinxiang/顾 金香 <gujx@xxxxxxxxxxxxxx>; linux-btrfs@xxxxxxxxxxxxxxx; hch@xxxxxx > Subject: Re: [PATCH] btrfs: Fix bug for misused dev_t when lookup in dev state hash table. > > > > On 17.10.2017 14:34, Gu Jinxiang wrote: > > From: Gu JinXiang <gujx@xxxxxxxxxxxxxx> > > > > Fix bug of commit 74d46992e0d9 > > ("block: replace bi_bdev with a gendisk pointer and partitions index"). > > > > In this modify, use bio_dev(bio) to find dev state in function > > __btrfsic_submit_bio. But when dev_state added to hashtable, it is > > using dev_t of block_device. > > This is rather incomprehensible. So bio_dev(bio) actually returns the dev_t of the device to which this bio is submitted > and the same dev_t should be used when btrfsic_dev_state_hashtable_add is called? What am I missing in here? > bio_dev(bio) returns a dev_t of part0 which is different from dev_t in block_device(bd_dev). bd_dev in block_device represents the exact partition. block_device.bd_dev = bio->bi_partno (same as block_device.bd_partno) + bio_dev(bio). When add a dev_state into hashtable it is using the exact partition's dev_t. So when lookup it, it should also use the exact partition's dev_t. > > > > > Reproduce of this bug: > > Use MOUNT_OPTIONS="-o check_int" when run btrfs/001 in xfstest. > > Then there will be WARNING like below. > > WARNING: > > btrfs: attempt to write superblock which references block M @29523968 (sda7 /1111654400/2) which is never written! > > > > Signed-off-by: Gu JinXiang <gujx@xxxxxxxxxxxxxx> > > --- > > fs/btrfs/check-integrity.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/fs/btrfs/check-integrity.c b/fs/btrfs/check-integrity.c > > index fb07e3c22b9a..02f9eb83173f 100644 > > --- a/fs/btrfs/check-integrity.c > > +++ b/fs/btrfs/check-integrity.c > > @@ -2803,7 +2803,7 @@ static void __btrfsic_submit_bio(struct bio *bio) > > mutex_lock(&btrfsic_mutex); > > /* since btrfsic_submit_bio() is also called before > > * btrfsic_mount(), this might return NULL */ > > - dev_state = btrfsic_dev_state_lookup(bio_dev(bio)); > > + dev_state = btrfsic_dev_state_lookup(bio_dev(bio) + bio->bi_partno); > > So this function looks up in btrfsic_dev_state_hashtable. And stuff in this hashtable ias added via > btrfsic_dev_state_hashtable_add function which seems to be only using the dev_t (after your other patch is applied): > > static void btrfsic_dev_state_hashtable_add( > > struct btrfsic_dev_state *ds, > > struct btrfsic_dev_state_hashtable *h) > > { > > const unsigned int hashval = > > (((unsigned int)((uintptr_t)ds->bdev->bd_dev)) & > > (BTRFSIC_DEV2STATE_HASHTABLE_SIZE - 1)); > > > > list_add(&ds->collision_resolving_node, h->table + hashval); > > } > > > So how come your change is correct since you are passing the dev_t + partition number? > > > if (NULL != dev_state && > > (bio_op(bio) == REQ_OP_WRITE) && bio_has_data(bio)) { > > unsigned int i = 0; > > > ��.n��������+%������w��{.n�����{����n�r������&��z�ޗ�zf���h���~����������_��+v���)ߣ�
