From: Bart Van Assche <bvanassche@acm.org>
To: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>
Cc: martin.petersen@oracle.com, linux-scsi@vger.kernel.org,
linux-block@vger.kernel.org,
Daejun Park <daejun7.park@samsung.com>,
Jaegeuk Kim <jaegeuk@kernel.org>
Subject: Re: please revert the UFS HPB support
Date: Thu, 21 Oct 2021 09:22:46 -0700 [thread overview]
Message-ID: <2cba13c3-bcd5-2a47-e4cb-54fa1ca088f3@acm.org> (raw)
In-Reply-To: <20211021151728.GA31600@lst.de>
On 10/21/21 8:17 AM, Christoph Hellwig wrote:
> On Thu, Oct 21, 2021 at 05:15:20PM +0200, Christoph Hellwig wrote:
>>>> I just noticed the UFS HPB support landed in 5.15, and just as
>>>> before it is completely broken by allocating another request on
>>>> the same device and then reinserting it in the queue. It is bad
>>>> enough that we have to live with blk_insert_cloned_request for
>>>> dm-mpath, but this is too big of an API abuse to make it into
>>>> a release. We need to drop this code ASAP, and I can prepare
>>>> a patch for that.
>>>
>>> That sounds awful, do you have a link to the offending commit(s)?
>>
>> I'll need to look for it, busy in calls right now, but just grep for
>> blk_insert_cloned_request.
>
> Might as well finish the git blame:
>
> commit 41d8a9333cc96f5ad4dd7a52786585338257d9f1
> Author: Daejun Park <daejun7.park@samsung.com>
> Date: Mon Jul 12 18:00:25 2021 +0900
>
> scsi: ufs: ufshpb: Add HPB 2.0 support
>
> Version 2.0 of HBP supports reads of varying sizes from 4KB to 1MB.
>
> A read operation <= 32KB is supported as single HPB read. A read between
> 36KB and 1MB is supported by a combination of write buffer command and HPB
> read command to deliver more PPN. The write buffer commands may not be
> issued immediately due to busy tags. To use HPB read more aggressively, the
> driver can requeue the write buffer command. The requeue threshold is
> implemented as timeout and can be modified with requeue_timeout_ms entry in
> sysfs.
(+Daejun)
Daejun, can the HPB code be reworked such that it does not use
blk_insert_cloned_request()? I'm concerned that if the HPB code is not
reworked that it will be removed from the upstream kernel.
Thanks,
Bart.
next prev parent reply other threads:[~2021-10-21 16:22 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-21 14:42 please revert the UFS HPB support Christoph Hellwig
2021-10-21 15:13 ` Jens Axboe
2021-10-21 15:15 ` Christoph Hellwig
2021-10-21 15:17 ` Christoph Hellwig
2021-10-21 16:22 ` Bart Van Assche [this message]
2021-10-23 15:43 ` James Bottomley
[not found] ` <CGME20211023154316epcas2p208f95cf1e4a87a4b61d2daf1a2b3c725@epcms2p3>
2021-10-25 5:16 ` Daejun Park
2021-10-25 7:07 ` Christoph Hellwig
2021-10-25 11:39 ` James Bottomley
2021-10-23 1:54 ` Martin K. Petersen
2021-10-23 4:40 ` Christoph Hellwig
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