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From: Kanchan Joshi <[email protected]>
To: Damien Le Moal <[email protected]>
Cc: "[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]" <[email protected]>,
	"[email protected]" <[email protected]>,
	"[email protected]" <[email protected]>,
	"[email protected]" <[email protected]>,
	"[email protected]" <[email protected]>,
	Arnav Dawn <[email protected]>
Subject: Re: [PATCH v2 1/2] fs,block: Introduce RWF_ZONE_APPEND and handling in direct IO path
Date: Tue, 30 Jun 2020 13:46:48 +0530	[thread overview]
Message-ID: <20200630081648.GB5701@test-zns> (raw)
In-Reply-To: <CY4PR04MB375162ABFFA5BB660869C57DE76F0@CY4PR04MB3751.namprd04.prod.outlook.com>

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On Tue, Jun 30, 2020 at 07:56:46AM +0000, Damien Le Moal wrote:
>On 2020/06/30 16:53, Damien Le Moal wrote:
>> On 2020/06/30 16:43, Kanchan Joshi wrote:
>>> On Tue, Jun 30, 2020 at 12:37:07AM +0000, Damien Le Moal wrote:
>>>> On 2020/06/30 3:35, Kanchan Joshi wrote:
>>>>> On Fri, Jun 26, 2020 at 02:50:20AM +0000, Damien Le Moal wrote:
>>>>>> On 2020/06/26 2:18, Kanchan Joshi wrote:
>>>>>>> Introduce RWF_ZONE_APPEND flag to represent zone-append. User-space
>>>>>>> sends this with write. Add IOCB_ZONE_APPEND which is set in
>>>>>>> kiocb->ki_flags on receiving RWF_ZONE_APPEND.
>>>>>>> Make direct IO submission path use IOCB_ZONE_APPEND to send bio with
>>>>>>> append op. Direct IO completion returns zone-relative offset, in sector
>>>>>>> unit, to upper layer using kiocb->ki_complete interface.
>>>>>>> Report error if zone-append is requested on regular file or on sync
>>>>>>> kiocb (i.e. one without ki_complete).
>>>>>>>
>>>>>>> Signed-off-by: Kanchan Joshi <[email protected]>
>>>>>>> Signed-off-by: SelvaKumar S <[email protected]>
>>>>>>> Signed-off-by: Arnav Dawn <[email protected]>
>>>>>>> Signed-off-by: Nitesh Shetty <[email protected]>
>>>>>>> Signed-off-by: Javier Gonzalez <[email protected]>
>>>>>>> ---
>>>>>>>  fs/block_dev.c          | 28 ++++++++++++++++++++++++----
>>>>>>>  include/linux/fs.h      |  9 +++++++++
>>>>>>>  include/uapi/linux/fs.h |  5 ++++-
>>>>>>>  3 files changed, 37 insertions(+), 5 deletions(-)
>>>>>>>
>>>>>>> diff --git a/fs/block_dev.c b/fs/block_dev.c
>>>>>>> index 47860e5..5180268 100644
>>>>>>> --- a/fs/block_dev.c
>>>>>>> +++ b/fs/block_dev.c
>>>>>>> @@ -185,6 +185,10 @@ static unsigned int dio_bio_write_op(struct kiocb *iocb)
>>>>>>>  	/* avoid the need for a I/O completion work item */
>>>>>>>  	if (iocb->ki_flags & IOCB_DSYNC)
>>>>>>>  		op |= REQ_FUA;
>>>>>>> +
>>>>>>> +	if (iocb->ki_flags & IOCB_ZONE_APPEND)
>>>>>>> +		op |= REQ_OP_ZONE_APPEND;
>>>>>>
>>>>>> This is wrong. REQ_OP_WRITE is already set in the declaration of "op". How can
>>>>>> this work ?
>>>>> REQ_OP_ZONE_APPEND will override the REQ_WRITE op, while previously set op
>>>>> flags (REQ_FUA etc.) will be retained. But yes, this can be made to look
>>>>> cleaner.
>>>>> V3 will include the other changes you pointed out. Thanks for the review.
>>>>>
>>>>
>>>> REQ_OP_WRITE and REQ_OP_ZONE_APPEND are different bits, so there is no
>>>> "override". A well formed BIO bi_opf is one op+flags. Specifying multiple OP
>>>> codes does not make sense.
>>>
>>> one op+flags behavior is retained here. OP is not about bits (op flags are).
>>> Had it been, REQ_OP_WRITE (value 1) can not be differentiated from
>>> REQ_OP_ZONE_APPEND (value 13).
>>> We do not do "bio_op(bio) & REQ_OP_WRITE", rather we look at the
>>> absolute value "bio_op(bio) == REQ_OP_WRITE".
>>
>> Sure, the ops are not bits like the flags, but (excluding the flags) doing:
>>
>> op |= REQ_OP_ZONE_APPEND;
>>
>> will give you op == (REQ_OP_WRITE | REQ_OP_ZONE_APPEND). That's not what you want...
>
>And yes, REQ_OP_WRITE | REQ_OP_ZONE_APPEND == REQ_OP_ZONE_APPEND... But still
>not a reason for not setting the op correctly :)
Right, this is what op override was about, and intent was to minimize
the changes in the existing function. As said before, completely agree about
changing, code should not draw suspicion. 

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  reply	other threads:[~2020-06-30  8:19 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20200625171829epcas5p268486a0780571edb4999fc7b3caab602@epcas5p2.samsung.com>
2020-06-25 17:15 ` [PATCH v2 0/2] zone-append support in io-uring and aio Kanchan Joshi
     [not found]   ` <CGME20200625171834epcas5p226a24dfcb84cfa83fe29a2bd17795d85@epcas5p2.samsung.com>
2020-06-25 17:15     ` [PATCH v2 1/2] fs,block: Introduce RWF_ZONE_APPEND and handling in direct IO path Kanchan Joshi
2020-06-26  2:50       ` Damien Le Moal
2020-06-29 18:32         ` Kanchan Joshi
2020-06-30  0:37           ` Damien Le Moal
2020-06-30  7:40             ` Kanchan Joshi
2020-06-30  7:52               ` Damien Le Moal
2020-06-30  7:56                 ` Damien Le Moal
2020-06-30  8:16                   ` Kanchan Joshi [this message]
2020-06-26  8:58       ` Christoph Hellwig
2020-06-26 21:15         ` Kanchan Joshi
2020-06-27  6:51           ` Christoph Hellwig
     [not found]   ` <CGME20200625171838epcas5p449183e12770187142d8d55a9bf422a8d@epcas5p4.samsung.com>
2020-06-25 17:15     ` [PATCH v2 2/2] io_uring: add support for zone-append Kanchan Joshi
2020-06-25 19:40       ` Pavel Begunkov
2020-06-26  3:11   ` [PATCH v2 0/2] zone-append support in io-uring and aio Damien Le Moal
2020-06-26  6:37     ` javier.gonz
2020-06-26  6:56       ` Damien Le Moal
2020-06-26  7:03         ` [email protected]
2020-06-26 22:15     ` Kanchan Joshi
2020-06-30 12:46   ` Matthew Wilcox

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