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From: Christoph Hellwig <hch@lst.de>
To: Richard Weinberger <richard.weinberger@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>,
	Richard Weinberger <richard@nod.at>, Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, linux-um@lists.infradead.org,
	"linux-mtd @ lists . infradead . org"
	<linux-mtd@lists.infradead.org>
Subject: Re: [PATCH, RFC] ubd: remove use of blk_rq_map_sg
Date: Wed, 17 Oct 2018 08:14:18 +0200	[thread overview]
Message-ID: <20181017061418.GA21790@lst.de> (raw)
In-Reply-To: <CAFLxGvwx4TPTHRY91LMBdd7h4pgCjw2zY7Q67r3CRHTqfzSB1w@mail.gmail.com>

On Wed, Oct 17, 2018 at 12:43:14AM +0200, Richard Weinberger wrote:
> On Mon, Oct 15, 2018 at 8:56 AM Christoph Hellwig <hch@lst.de> wrote:
> >
> > There is no good reason to create a scatterlist in the ubd driver,
> > it can just iterate the request directly.
> 
> BTW: Does it make sense to drop blk_rq_map_sq from()
> drivers/mtd/ubi/block.c too?
> If so we have to allocate a temporary structure for the worker thread
> for each segment, just like
> UBD does already. I'm not sure if that is cheaper than blk_rq_map_sq().

UBI should not need a new per-thread structure, mostly because there
are no threads involved.  The scatterlist support in UBI only seems
to exists for ubiblock, but it goes down a few layers.  In the end
all that could switch to a iov_iter-like setup and clean things up
a lot, but it would be a fair amount of work.

WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Richard Weinberger <richard.weinberger@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>, Richard Weinberger <richard@nod.at>,
	linux-um@lists.infradead.org, linux-block@vger.kernel.org,
	"linux-mtd @ lists . infradead . org"
	<linux-mtd@lists.infradead.org>, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH, RFC] ubd: remove use of blk_rq_map_sg
Date: Wed, 17 Oct 2018 08:14:18 +0200	[thread overview]
Message-ID: <20181017061418.GA21790@lst.de> (raw)
In-Reply-To: <CAFLxGvwx4TPTHRY91LMBdd7h4pgCjw2zY7Q67r3CRHTqfzSB1w@mail.gmail.com>

On Wed, Oct 17, 2018 at 12:43:14AM +0200, Richard Weinberger wrote:
> On Mon, Oct 15, 2018 at 8:56 AM Christoph Hellwig <hch@lst.de> wrote:
> >
> > There is no good reason to create a scatterlist in the ubd driver,
> > it can just iterate the request directly.
> 
> BTW: Does it make sense to drop blk_rq_map_sq from()
> drivers/mtd/ubi/block.c too?
> If so we have to allocate a temporary structure for the worker thread
> for each segment, just like
> UBD does already. I'm not sure if that is cheaper than blk_rq_map_sq().

UBI should not need a new per-thread structure, mostly because there
are no threads involved.  The scatterlist support in UBI only seems
to exists for ubiblock, but it goes down a few layers.  In the end
all that could switch to a iov_iter-like setup and clean things up
a lot, but it would be a fair amount of work.

______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/


  reply	other threads:[~2018-10-17  6:14 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-15  6:56 [PATCH, RFC] ubd: remove use of blk_rq_map_sg Christoph Hellwig
2018-10-15  6:56 ` Christoph Hellwig
2018-10-15  8:40 ` Richard Weinberger
2018-10-15  8:40   ` Richard Weinberger
2018-10-15  8:45   ` Christoph Hellwig
2018-10-15  8:45     ` Christoph Hellwig
2018-10-15 19:17     ` Richard Weinberger
2018-10-15 19:17       ` Richard Weinberger
2018-10-15 20:42       ` Richard Weinberger
2018-10-15 20:42         ` Richard Weinberger
2018-10-15 20:55         ` Christoph Hellwig
2018-10-15 20:55           ` Christoph Hellwig
2018-10-15 21:46           ` Richard Weinberger
2018-10-15 21:46             ` Richard Weinberger
2018-10-15 22:04             ` Jens Axboe
2018-10-15 22:04               ` Jens Axboe
2018-10-15 22:44               ` Richard Weinberger
2018-10-15 22:44                 ` Richard Weinberger
2018-10-16  2:19                 ` Jens Axboe
2018-10-16  2:19                   ` Jens Axboe
2018-10-16  8:38                   ` Richard Weinberger
2018-10-16  8:38                     ` Richard Weinberger
2018-10-16 14:26                     ` Jens Axboe
2018-10-16 14:26                       ` Jens Axboe
2018-10-17  6:21                       ` Christoph Hellwig
2018-10-17  6:21                         ` Christoph Hellwig
2018-10-18 21:04                         ` Richard Weinberger
2018-10-18 21:04                           ` Richard Weinberger
2018-10-15  8:46   ` Anton Ivanov
2018-10-16 22:43 ` Richard Weinberger
2018-10-16 22:43   ` Richard Weinberger
2018-10-17  6:14   ` Christoph Hellwig [this message]
2018-10-17  6:14     ` Christoph Hellwig

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