On 18.10.2017 06:43, Gu, Jinxiang wrote: > 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. Right, ok. Can you please put this explanation into the changelog of the patch and resend > >> >>> >>> 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; >>> >> > > > -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
