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From: Ming Lei <ming.lei@redhat.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Thierry Reding <thierry.reding@gmail.com>,
	Jens Axboe <axboe@kernel.dk>,
	Ulf Hansson <ulf.hansson@linaro.org>,
	Adrian Hunter <adrian.hunter@intel.com>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
	Simon Horman <horms+renesas@verge.net.au>,
	Jon Hunter <jonathanh@nvidia.com>,
	linux-block@vger.kernel.org, linux-mmc@vger.kernel.org,
	linux-tegra@vger.kernel.org
Subject: Re: [PATCH 1/3] block: Respect the device's maximum segment size
Date: Thu, 12 Sep 2019 08:57:29 +0800	[thread overview]
Message-ID: <20190912005728.GA2731@ming.t460p> (raw)
In-Reply-To: <20190909161331.GA19650@lst.de>

On Mon, Sep 09, 2019 at 06:13:31PM +0200, Christoph Hellwig wrote:
> On Mon, Sep 09, 2019 at 02:56:56PM +0200, Thierry Reding wrote:
> > From: Thierry Reding <treding@nvidia.com>
> > 
> > When enabling the DMA map merging capability for a queue, ensure that
> > the maximum segment size does not exceed the device's limit.
> 
> We can't do that unfortunately.  If we use the virt_boundary setting
> we do aggressive merges that there is no accounting for.  So we can't
> limit the segment size.

Could you explain a bit why we can't do that?

The segment size limit is basically removed since the following commit
200a9aff7b02 ("block: remove the segment size check in bio_will_gap").

Before that commit, the max segment size limit worked.


Thanks,
Ming

  parent reply	other threads:[~2019-09-12  0:57 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-09 12:56 [PATCH 0/3] mmc: Fix scatter/gather on SDHCI Thierry Reding
2019-09-09 12:56 ` [PATCH 1/3] block: Respect the device's maximum segment size Thierry Reding
2019-09-09 16:13   ` Christoph Hellwig
2019-09-09 19:19     ` Thierry Reding
2019-09-10  2:03       ` Yoshihiro Shimoda
2019-09-10  6:13         ` Christoph Hellwig
2019-09-10  7:37           ` Thierry Reding
2019-09-11 10:36             ` Christoph Hellwig
2019-09-10  7:30         ` Thierry Reding
2019-09-11  7:23           ` Yoshihiro Shimoda
2019-09-11 10:37         ` Christoph Hellwig
2019-09-12  0:57     ` Ming Lei [this message]
2019-09-12  8:19       ` Christoph Hellwig
2019-09-09 12:56 ` [PATCH 2/3] mmc: core: Respect MMC host's " Thierry Reding
2019-09-09 12:56 ` [PATCH 3/3] mmc: sdhci: Set DMA maximum segment size to 64 KiB Thierry Reding

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