linux-kernel - Re: [PATCH 3/6] direct-io: add support for write stream IDs

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Date:	Fri, 10 Apr 2015 16:50:05 -0700
From:	Ming Lin <mlin@...nel.org>
To:	Jens Axboe <axboe@...nel.dk>
Cc:	Dave Chinner <david@...morbit.com>, Jens Axboe <axboe@...com>,
	lkml <linux-kernel@...r.kernel.org>,
	linux-fsdevel@...r.kernel.org, ming.l@....samsung.com
Subject: Re: [PATCH 3/6] direct-io: add support for write stream IDs

On Wed, Mar 25, 2015 at 7:26 AM, Jens Axboe <axboe@...nel.dk> wrote:
> On 03/24/2015 08:43 PM, Dave Chinner wrote:
>>
>> On Tue, Mar 24, 2015 at 09:27:00AM -0600, Jens Axboe wrote:
>>>
>>> Get the streamid from the file, if any, and set it on the bio.
>>>
>>> Signed-off-by: Jens Axboe <axboe@...com>
>>> ---
>>>   fs/direct-io.c | 4 ++++
>>>   1 file changed, 4 insertions(+)
>>>
>>> diff --git a/fs/direct-io.c b/fs/direct-io.c
>>> index e181b6b2e297..5d2750346451 100644
>>> --- a/fs/direct-io.c
>>> +++ b/fs/direct-io.c
>>> @@ -77,6 +77,7 @@ struct dio_submit {
>>>         int reap_counter;               /* rate limit reaping */
>>>         sector_t final_block_in_request;/* doesn't change */
>>>         int boundary;                   /* prev block is at a boundary */
>>> +       int streamid;                   /* Write stream ID */
>>>         get_block_t *get_block;         /* block mapping function */
>>>         dio_submit_t *submit_io;        /* IO submition function */
>>>
>>> @@ -372,6 +373,8 @@ dio_bio_alloc(struct dio *dio, struct dio_submit
>>> *sdio,
>>>
>>>         sdio->bio = bio;
>>>         sdio->logical_offset_in_bio = sdio->cur_page_fs_offset;
>>> +
>>> +       bio_set_streamid(bio, sdio->streamid);
>>>   }
>>>
>>>   /*
>>> @@ -1205,6 +1208,7 @@ do_blockdev_direct_IO(int rw, struct kiocb *iocb,
>>> struct inode *inode,
>>>         sdio.blkbits = blkbits;
>>>         sdio.blkfactor = i_blkbits - blkbits;
>>>         sdio.block_in_file = offset >> blkbits;
>>> +       sdio.streamid = iocb->ki_filp->f_streamid;
>>
>>
>> If iocb->ki_filp->f_streamid is not set, then it should fall back to
>> whatever is set on the inode->i_streamid.

Why should do the fall back?

>
>
> Good point, agree. Will make that change.

Hi Jens,

That change causes problem for direct IO, for example

process 1:
fd = open("/dev/nvme0n1", O_DIRECT...);
//set stream_id 1
fadvise(fd, 1, 0, POSIX_FADV_STREAMID);
pwrite(fd, ....);

process 2:
fd = open("/dev/nvme0n1", O_DIRECT...);
//should be legacy stream_id 0
pwrite(fd, ....);

But now process 2 also see stream_id 1, which is wrong.

Thanks,
Ming

>
>
> --
> Jens Axboe
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