From: Damien Le Moal <Damien.LeMoal@wdc.com>
To: Kanchan Joshi <joshi.k@samsung.com>
Cc: "axboe@kernel.dk" <axboe@kernel.dk>,
"kbusch@kernel.org" <kbusch@kernel.org>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"hch@lst.de" <hch@lst.de>,
Selvakumar S <selvakuma.s1@samsung.com>,
Nitesh Shetty <nj.shetty@samsung.com>,
Javier Gonzalez <javier.gonz@samsung.com>
Subject: Re: [PATCH 2/2] block: enable zone-append for iov_iter of bvec type
Date: Fri, 3 Jul 2020 08:07:38 +0000 [thread overview]
Message-ID: <CY4PR04MB375124BE75E2E824F543EA11E76A0@CY4PR04MB3751.namprd04.prod.outlook.com> (raw)
In-Reply-To: 20200703065311.GB26058@test-zns
On 2020/07/03 15:56, Kanchan Joshi wrote:
> On Fri, Jul 03, 2020 at 05:32:56AM +0000, Damien Le Moal wrote:
>> On 2020/07/03 0:42, Kanchan Joshi wrote:
>>> zone-append with bvec iov_iter gives WARN_ON, and returns -EINVAL.
>>> Add new helper to process such iov_iter and add pages in bio honoring
>>> zone-append specific constraints.
>>>
>>> Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
>>> Signed-off-by: Selvakumar S <selvakuma.s1@samsung.com>
>>> Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
>>> Signed-off-by: Javier Gonzalez <javier.gonz@samsung.com>
>>> ---
>>> block/bio.c | 31 ++++++++++++++++++++++++++++---
>>> 1 file changed, 28 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/block/bio.c b/block/bio.c
>>> index 0cecdbc..ade9da7 100644
>>> --- a/block/bio.c
>>> +++ b/block/bio.c
>>> @@ -975,6 +975,30 @@ static int __bio_iov_bvec_add_pages(struct bio *bio, struct iov_iter *iter)
>>> iov_iter_advance(iter, size);
>>> return 0;
>>> }
>>> +static int __bio_iov_bvec_append_add_pages(struct bio *bio, struct iov_iter *iter)
>>> +{
>>> + const struct bio_vec *bv = iter->bvec;
>>> + unsigned int len;
>>> + size_t size;
>>> + struct request_queue *q = bio->bi_disk->queue;
>>> + unsigned int max_append_sectors = queue_max_zone_append_sectors(q);
>>> + bool same_page = false;
>>> +
>>> + if (WARN_ON_ONCE(!max_append_sectors))
>>> + return -EINVAL;
>>> +
>>> + if (WARN_ON_ONCE(iter->iov_offset > bv->bv_len))
>>> + return -EINVAL;
>>> +
>>> + len = min_t(size_t, bv->bv_len - iter->iov_offset, iter->count);
>>> + size = bio_add_hw_page(q, bio, bv->bv_page, len,
>>> + bv->bv_offset + iter->iov_offset,
>>> + max_append_sectors, &same_page);
>>> + if (unlikely(size != len))
>>> + return -EINVAL;
>>> + iov_iter_advance(iter, size);
>>> + return 0;
>>> +}
>>>
>>> #define PAGE_PTRS_PER_BVEC (sizeof(struct bio_vec) / sizeof(struct page *))
>>>
>>> @@ -1105,9 +1129,10 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
>>>
>>> do {
>>> if (bio_op(bio) == REQ_OP_ZONE_APPEND) {
>>> - if (WARN_ON_ONCE(is_bvec))
>>> - return -EINVAL;
>>> - ret = __bio_iov_append_get_pages(bio, iter);
>>> + if (is_bvec)
>>> + ret = __bio_iov_bvec_append_add_pages(bio, iter);
>>> + else
>>> + ret = __bio_iov_append_get_pages(bio, iter);
>>> } else {
>>> if (is_bvec)
>>> ret = __bio_iov_bvec_add_pages(bio, iter);
>>>
>>
>> The only user of this function that issues zone append requests is zonefs. The
>> issued requests are not using bvec iter but a user direct IO buffer iter. So
>> this change would have no user at all as far as I can see. Am I missing
>> something ? What IO path makes this change necessary ?
>
> Yes, zonefs does not use bvec iter. But while enabling io-uring path for
> zone-append, I hit into this condition returning -EINVAL.
>
> Reference (from user zone-append series cover letter):
> "Append using io_uring fixed-buffer --->
> This is flagged as not-supported at the moment. Reason being, for fixed-buffer
> io-uring sends iov_iter of bvec type. But current append-infra in block-layer
> does not support such iov_iter."
>
> And zone-append doesn't have a problem in using bvec iter as well, so
> thought that this may make infra more complete/future-proof?
As long as there is no possible user for this change, I do not see the point in
adding it.
--
Damien Le Moal
Western Digital Research
next prev parent reply other threads:[~2020-07-03 8:07 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20200702154204epcas5p15106774a3d556b77050710722da89922@epcas5p1.samsung.com>
2020-07-02 15:38 ` [PATCH 0/2] fix/extend zone-append in block-layer Kanchan Joshi
[not found] ` <CGME20200702154208epcas5p39fe202f642a9d5c8dde9b911645c594c@epcas5p3.samsung.com>
2020-07-02 15:38 ` [PATCH 1/2] block: fix error code for zone-append Kanchan Joshi
2020-07-03 5:29 ` Damien Le Moal
2020-07-03 6:20 ` Kanchan Joshi
[not found] ` <CGME20200702154213epcas5p4e8d42861cb5ae91ddeccf1ed73107304@epcas5p4.samsung.com>
2020-07-02 15:38 ` [PATCH 2/2] block: enable zone-append for iov_iter of bvec type Kanchan Joshi
2020-07-03 5:32 ` Damien Le Moal
2020-07-03 6:53 ` Kanchan Joshi
2020-07-03 8:07 ` Damien Le Moal [this message]
2020-07-03 13:02 ` Johannes Thumshirn
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