public inbox for [email protected]
 help / color / mirror / Atom feed
From: "[email protected]" <[email protected]>
To: Jens Axboe <[email protected]>
Cc: Pavel Begunkov <[email protected]>,
	Damien Le Moal <[email protected]>,
	Kanchan Joshi <[email protected]>,
	"[email protected]" <[email protected]>,
	"[email protected]" <[email protected]>,
	"[email protected]" <[email protected]>,
	"[email protected]" <[email protected]>,
	"[email protected]" <[email protected]>,
	"[email protected]" <[email protected]>,
	"[email protected]" <[email protected]>,
	"[email protected]" <[email protected]>,
	"[email protected]" <[email protected]>
Subject: Re: [PATCH 3/3] io_uring: add support for zone-append
Date: Sun, 21 Jun 2020 20:52:07 +0200	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 19.06.2020 09:02, Jens Axboe wrote:
>On 6/19/20 8:59 AM, Pavel Begunkov wrote:
>> On 19/06/2020 17:15, Jens Axboe wrote:
>>> On 6/19/20 3:41 AM, [email protected] wrote:
>>>> Jens,
>>>>
>>>> Would you have time to answer a question below in this thread?
>>>>
>>>> On 18.06.2020 11:11, [email protected] wrote:
>>>>> On 18.06.2020 08:47, Damien Le Moal wrote:
>>>>>> On 2020/06/18 17:35, [email protected] wrote:
>>>>>>> On 18.06.2020 07:39, Damien Le Moal wrote:
>>>>>>>> On 2020/06/18 2:27, Kanchan Joshi wrote:
>>>>>>>>> From: Selvakumar S <[email protected]>
>>>>>>>>>
>>>>>>>>> Introduce three new opcodes for zone-append -
>>>>>>>>>
>>>>>>>>>   IORING_OP_ZONE_APPEND     : non-vectord, similiar to IORING_OP_WRITE
>>>>>>>>>   IORING_OP_ZONE_APPENDV    : vectored, similar to IORING_OP_WRITEV
>>>>>>>>>   IORING_OP_ZONE_APPEND_FIXED : append using fixed-buffers
>>>>>>>>>
>>>>>>>>> Repurpose cqe->flags to return zone-relative offset.
>>>>>>>>>
>>>>>>>>> Signed-off-by: SelvaKumar S <[email protected]>
>>>>>>>>> Signed-off-by: Kanchan Joshi <[email protected]>
>>>>>>>>> Signed-off-by: Nitesh Shetty <[email protected]>
>>>>>>>>> Signed-off-by: Javier Gonzalez <[email protected]>
>>>>>>>>> ---
>>>>>>>>> fs/io_uring.c                 | 72 +++++++++++++++++++++++++++++++++++++++++--
>>>>>>>>> include/uapi/linux/io_uring.h |  8 ++++-
>>>>>>>>> 2 files changed, 77 insertions(+), 3 deletions(-)
>>>>>>>>>
>>>>>>>>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>>>>>>>>> index 155f3d8..c14c873 100644
>>>>>>>>> --- a/fs/io_uring.c
>>>>>>>>> +++ b/fs/io_uring.c
>>>>>>>>> @@ -649,6 +649,10 @@ struct io_kiocb {
>>>>>>>>> 	unsigned long		fsize;
>>>>>>>>> 	u64			user_data;
>>>>>>>>> 	u32			result;
>>>>>>>>> +#ifdef CONFIG_BLK_DEV_ZONED
>>>>>>>>> +	/* zone-relative offset for append, in bytes */
>>>>>>>>> +	u32			append_offset;
>>>>>>>>
>>>>>>>> this can overflow. u64 is needed.
>>>>>>>
>>>>>>> We chose to do it this way to start with because struct io_uring_cqe
>>>>>>> only has space for u32 when we reuse the flags.
>>>>>>>
>>>>>>> We can of course create a new cqe structure, but that will come with
>>>>>>> larger changes to io_uring for supporting append.
>>>>>>>
>>>>>>> Do you believe this is a better approach?
>>>>>>
>>>>>> The problem is that zone size are 32 bits in the kernel, as a number
>>>>>> of sectors.  So any device that has a zone size smaller or equal to
>>>>>> 2^31 512B sectors can be accepted. Using a zone relative offset in
>>>>>> bytes for returning zone append result is OK-ish, but to match the
>>>>>> kernel supported range of possible zone size, you need 31+9 bits...
>>>>>> 32 does not cut it.
>>>>>
>>>>> Agree. Our initial assumption was that u32 would cover current zone size
>>>>> requirements, but if this is a no-go, we will take the longer path.
>>>>
>>>> Converting to u64 will require a new version of io_uring_cqe, where we
>>>> extend at least 32 bits. I believe this will need a whole new allocation
>>>> and probably ioctl().
>>>>
>>>> Is this an acceptable change for you? We will of course add support for
>>>> liburing when we agree on the right way to do this.
>>>
>>> If you need 64-bit of return value, then it's not going to work. Even
>>> with the existing patches, reusing cqe->flags isn't going to fly, as
>>> it would conflict with eg doing zone append writes with automatic
>>> buffer selection.
>>
>> Buffer selection is for reads/recv kind of requests, but appends
>> are writes. In theory they can co-exist using cqe->flags.
>
>Yeah good point, since it's just writes, doesn't matter. But the other
>point still stands, it could potentially conflict with other flags, but
>I guess only to the extent where both flags would need extra storage in
>->flags. So not a huge concern imho.

Very good point Pavel!

If co-existing with the current flags is an option, I'll explore this
for the next version.

Thanks Jens and Pavel for the time and ideas!

Javier

  reply	other threads:[~2020-06-21 18:52 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20200617172653epcas5p488de50090415eb802e62acc0e23d8812@epcas5p4.samsung.com>
2020-06-17 17:23 ` [PATCH 0/3] zone-append support in aio and io-uring Kanchan Joshi
     [not found]   ` <CGME20200617172702epcas5p4dbf4729d31d9a85ab1d261d04f238e61@epcas5p4.samsung.com>
2020-06-17 17:23     ` [PATCH 1/3] fs,block: Introduce IOCB_ZONE_APPEND and direct-io handling Kanchan Joshi
2020-06-17 19:02       ` Pavel Begunkov
2020-06-18  7:16       ` Damien Le Moal
2020-06-18 18:35         ` Kanchan Joshi
     [not found]   ` <CGME20200617172706epcas5p4dcbc164063f58bad95b211b9d6dfbfa9@epcas5p4.samsung.com>
2020-06-17 17:23     ` [PATCH 2/3] aio: add support for zone-append Kanchan Joshi
2020-06-18  7:33       ` Damien Le Moal
     [not found]   ` <CGME20200617172713epcas5p352f2907a12bd4ee3c97be1c7d8e1569e@epcas5p3.samsung.com>
2020-06-17 17:23     ` [PATCH 3/3] io_uring: " Kanchan Joshi
2020-06-17 18:55       ` Pavel Begunkov
2020-06-18  7:39       ` Damien Le Moal
2020-06-18  8:35         ` [email protected]
2020-06-18  8:47           ` Damien Le Moal
2020-06-18  9:11             ` [email protected]
2020-06-19  9:41               ` [email protected]
2020-06-19 11:15                 ` Matias Bjørling
2020-06-19 14:18                   ` Jens Axboe
2020-06-19 15:14                     ` Matias Bjørling
2020-06-19 15:20                       ` Jens Axboe
2020-06-19 15:40                         ` Matias Bjørling
2020-06-19 15:44                           ` Jens Axboe
2020-06-21 18:55                             ` [email protected]
2020-06-19 14:15                 ` Jens Axboe
2020-06-19 14:59                   ` Pavel Begunkov
2020-06-19 15:02                     ` Jens Axboe
2020-06-21 18:52                       ` [email protected] [this message]
2020-06-17 17:42   ` [PATCH 0/3] zone-append support in aio and io-uring Matthew Wilcox
2020-06-18  6:56   ` Christoph Hellwig
2020-06-18  8:29     ` Javier González
2020-06-18 17:52     ` Kanchan Joshi
2020-06-19  3:08       ` Damien Le Moal
2020-06-19  7:56       ` Christoph Hellwig
2020-06-18  8:04   ` Matias Bjørling
2020-06-18  8:27     ` Javier González
2020-06-18  8:32       ` Matias Bjørling
2020-06-18  8:39         ` Javier González
2020-06-18  8:46           ` Matias Bjørling
2020-06-18 14:16     ` Christoph Hellwig
2020-06-18 19:21     ` Kanchan Joshi
2020-06-18 20:04       ` Matias Bjørling
2020-06-19  1:03         ` Damien Le Moal

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200621185207.m7535hzpm4ubrk4i@MacBook-Pro.localdomain \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox