Re: [PATCH v2] btrfs: not a disk error if the bio_add_page fails

[Anand Jain <anand.jain@oracle.com>]

On 01/05/2018 02:50 AM, Liu Bo wrote:
> On Thu, Jan 04, 2018 at 09:47:56AM -0800, Liu Bo wrote:
>> On Wed, Jan 03, 2018 at 09:52:43PM +0800, Anand Jain wrote:
>>> bio_add_page() can fail for logical reasons as from the bio_add_page()
>>> comments:- 'This will only fail if either
>>> bio->bi_vcnt == bio->bi_max_vecs or it's a cloned bio.' Don't inc the
>>> write error statistics for this. And set -EINVAL instead of -EIO.
>>>
>>
>> It's correct to skip increasing counter, but why -EINVAL?
>> (its caller only cares about if it's non-zero.)
> 
> Well...there is no chance that bio_add_page() could return
> non-PAGE_SIZE as this bio has been just created, we can remove the
> error handling after bio_add_page().

  Ah. right, bio_add_page() can't fail in this thread, its not
  a bio clone, and its the first call to bio_add_page(). Will
  remove error handling part.

Thanks, Anand

> thanks,
> -liubo
>>
>> thanks,
>>
>> -liubo
>>> Signed-off-by: Anand Jain <anand.jain@oracle.com>
>>> ---
>>> v1->v2: Add missing bio_put(). Thanks Filipe.
>>>
>>>   fs/btrfs/scrub.c | 9 +++++----
>>>   1 file changed, 5 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
>>> index ecfe3118d9dd..57ac39a3f046 100644
>>> --- a/fs/btrfs/scrub.c
>>> +++ b/fs/btrfs/scrub.c
>>> @@ -4617,15 +4617,16 @@ static int write_page_nocow(struct scrub_ctx *sctx,
>>>   	bio->bi_opf = REQ_OP_WRITE | REQ_SYNC;
>>>   	ret = bio_add_page(bio, page, PAGE_SIZE, 0);
>>>   	if (ret != PAGE_SIZE) {
>>> -leave_with_eio:
>>> +		bio_put(bio);
>>> +		return -EINVAL;
>>> +	}
>>> +
>>> +	if (btrfsic_submit_bio_wait(bio)) {
>>>   		bio_put(bio);
>>>   		btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_WRITE_ERRS);
>>>   		return -EIO;
>>>   	}
>>>   
>>> -	if (btrfsic_submit_bio_wait(bio))
>>> -		goto leave_with_eio;
>>> -
>>>   	bio_put(bio);
>>>   	return 0;
>>>   }
>>> -- 
>>> 2.15.0
>>>
>>> --
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