On Fri, Oct 6, 2017 at 2:31 PM, Ilya Dryomov <idryomov@xxxxxxxxx> wrote:
> On Fri, Oct 6, 2017 at 2:05 PM, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
>> On Thu, Oct 05, 2017 at 09:32:33PM +0200, Ilya Dryomov wrote:
>>> This is to avoid returning -EREMOTEIO in the following case: device
>>> doesn't support WRITE SAME but scsi_disk::max_ws_blocks != 0, zeroout
>>> is called with BLKDEV_ZERO_NOFALLBACK. Enter blkdev_issue_zeroout(),
>>> bdev_write_zeroes_sectors() != 0, so we issue WRITE ZEROES. The
>>> request fails with ILLEGAL REQUEST, sd_done() sets ->no_write_same and
>>> updates queue_limits, ILLEGAL REQUEST is translated into -EREMOTEIO,
>>> which is returned from submit_bio_wait(). Manual zeroing is not
>>> allowed, so we must return an error, but it shouldn't be -EREMOTEIO if
>>> queue_limits just got updated because of ILLEGAL REQUEST. Without this
>>> conditional, we'd get
>>
>> Hmm. I think we'd better off to just do the before the retry loop:
>>
>> if (ret && try_write_zeroes) {
>> if (!(flags & BLKDEV_ZERO_NOFALLBACK))
>> try_write_zeroes = false;
>> goto retry;
>> }
>> ret = -EOPNOTSUPP;
>> }
>
> This would unconditionally overwrite any WRITE ZEROS error. If we get
> e.g. -EIO, and manual zeroing is not allowed, I don't think we want to
> return -EOPNOTSUPP?
>
> Returning -EOPNOTSUPP to mean "can't zero using either method" doesn't
> make sense to me, because manual zeroing is always supported, just not
> always allowed.
Ping...
Thanks,
Ilya
