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To:     Christoph Hellwig <hch@infradead.org>
Cc:     Hannes Reinecke <hare@suse.de>, Arnd Bergmann <arnd@arndb.de>,
        "\(Exiting\) Baolin Wang" <baolin.wang@linaro.org>,
        Baolin Wang <baolin.wang7@gmail.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Ulf Hansson <ulf.hansson@linaro.org>, asutoshd@codeaurora.org,
        Orson Zhai <orsonzhai@gmail.com>,
        Lyra Zhang <zhang.lyra@gmail.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        linux-mmc <linux-mmc@vger.kernel.org>,
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        Hannes Reinecke <hare@suse.com>,
        linux-block <linux-block@vger.kernel.org>,
        Paolo Valente <paolo.valente@linaro.org>
Subject: Re: [PATCH v6 0/4] Add MMC software queue support
From:   "Martin K. Petersen" <martin.petersen@oracle.com>
Organization: Oracle Corporation
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Date:   Thu, 28 Nov 2019 07:15:09 -0500
In-Reply-To: <20191127090023.GA23040@infradead.org> (Christoph Hellwig's
        message of "Wed, 27 Nov 2019 01:00:23 -0800")
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Christoph,

> equivalent to SCSI logical units and nvme namespace, just with a
> pretty idiotic design decision that only allows I/O to one of them at
> a time.  The block layer way to deal with them is to use a shared
> tagset for multiple request queues, which doesn't use up a whole lot
> of resources.  The only hard part is the draining when switching
> between partitions, and there is no really nice way to deal with that.
> If requests are batched enough we could just drain and switch every
> time an other partition access comes in.

This mirrors single_lun in SCSI closely. I was hoping we could
eventually get rid of that travesty but if MMC needs something similar,
maybe it would be good to move that plumbing to block?

-- 
Martin K. Petersen	Oracle Linux Engineering