From: Jens Axboe <axboe@fb.com>
To: Ming Lin <mlin@kernel.org>, Jens Axboe <axboe@kernel.dk>
Cc: Dave Chinner <david@fromorbit.com>,
lkml <linux-kernel@vger.kernel.org>,
<linux-fsdevel@vger.kernel.org>, <ming.l@ssi.samsung.com>
Subject: Re: [PATCH 3/6] direct-io: add support for write stream IDs
Date: Fri, 17 Apr 2015 09:17:09 -0600 [thread overview]
Message-ID: <553123F5.8040909@fb.com> (raw)
In-Reply-To: <CAF1ivSb_TwuYY9RJcfkJxRmSFeaCVuzXuksS4uEsd4ahPLDPEA@mail.gmail.com>
On 04/10/2015 05:50 PM, Ming Lin wrote:
> On Wed, Mar 25, 2015 at 7:26 AM, Jens Axboe <axboe@kernel.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@fb.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?
Because the assumption is that, in general, the specific file is a good
indication of the data lifetime, if someone has already set that. It's a
better guess than writing without any stream attached.
> 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.
I guess for that case, it is a problem. Basically the fallback breaks
down for full block devices, or huge files that are used as a general
backing store (like a vm image, for instance). Hmm, not sure what the
right solution would be here, or if there really is one. It's probably
best NOT to do the fallback after all.
--
Jens Axboe
next prev parent reply other threads:[~2015-04-17 15:18 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-24 15:26 [PATCH RFC] Support for write stream IDs Jens Axboe
2015-03-24 15:26 ` [PATCH 1/6] block: add support for carrying a stream ID in a bio Jens Axboe
2015-03-24 17:11 ` Matias Bjørling
2015-03-24 17:26 ` Jens Axboe
2015-03-24 17:26 ` Jens Axboe
2015-03-24 22:07 ` Ming Lin-SSI
2015-03-25 1:42 ` Jens Axboe
2015-03-25 1:42 ` Jens Axboe
2015-03-25 8:11 ` Matias Bjørling
2015-03-25 18:36 ` Ming Lin-SSI
2015-03-25 2:30 ` Dave Chinner
2015-04-12 10:42 ` Dmitry Monakhov
2015-03-24 15:26 ` [PATCH 2/6] Add support for per-file stream ID Jens Axboe
2015-03-24 15:27 ` [PATCH 3/6] direct-io: add support for write stream IDs Jens Axboe
2015-03-25 2:43 ` Dave Chinner
2015-03-25 14:26 ` Jens Axboe
2015-04-10 23:50 ` Ming Lin
2015-04-11 0:06 ` Ming Lin
2015-04-11 11:59 ` Dave Chinner
2015-04-17 6:20 ` Ming Lin
2015-04-17 23:06 ` Dave Chinner
2015-04-17 23:11 ` Jens Axboe
2015-04-17 23:51 ` Dave Chinner
2015-04-18 2:00 ` Jens Axboe
2015-04-17 15:17 ` Jens Axboe [this message]
2015-03-24 15:27 ` [PATCH 4/6] Add stream ID support for buffered writeback Jens Axboe
2015-03-25 2:40 ` Dave Chinner
2015-03-25 14:17 ` Jens Axboe
2015-03-24 15:27 ` [PATCH 5/6] btrfs: add support for buffered writeback stream ID Jens Axboe
2015-03-24 15:27 ` [PATCH 6/6] xfs: " Jens Axboe
2015-03-25 2:41 ` Dave Chinner
2015-03-24 17:03 ` [PATCH RFC] Support for write stream IDs Jeff Moyer
2015-03-24 17:08 ` Jens Axboe
2015-03-24 21:46 ` Ming Lin-SSI
2015-03-24 21:48 ` Jens Axboe
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