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From: Christoph Hellwig <hch@infradead.org>
To: Ming Lei <ming.lei@canonical.com>
Cc: linux-kernel@vger.kernel.org,
	Dave Kleikamp <dave.kleikamp@oracle.com>,
	Jens Axboe <axboe@kernel.dk>, Zach Brown <zab@zabbo.net>,
	Christoph Hellwig <hch@infradead.org>,
	Maxim Patlasov <mpatlasov@parallels.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Benjamin LaHaise <bcrl@kvack.org>
Subject: Re: [PATCH v2 4/4] block: loop: support to submit I/O via kernel aio based
Date: Sun, 25 Jan 2015 05:40:38 -0800	[thread overview]
Message-ID: <20150125134038.GD19445@infradead.org> (raw)
In-Reply-To: <1421163888-21452-5-git-send-email-ming.lei@canonical.com>

> +{
> +	unsigned int i = 0;
> +	struct iov_iter iter;
> +	struct bio_vec *bvec, bv;
> +	size_t nr_segs = 0;
> +	struct req_iterator r_iter;
> +
> +	rq_for_each_segment(bv, cmd->rq, r_iter)
> +		nr_segs++;
> +
> +	if (nr_segs > LOOP_CMD_BVEC_CNT) {
> +		cmd->alloc_bv = kmalloc(nr_segs * sizeof(*cmd->alloc_bv),
> +					GFP_NOIO);
> +		if (!cmd->alloc_bv)
> +			return -ENOMEM;
> +		bvec = cmd->alloc_bv;
> +	} else {
> +		bvec = cmd->bv;
> +		cmd->alloc_bv = NULL;
> +	}
> +
> +	rq_for_each_segment(bv, cmd->rq, r_iter)
> +		bvec[i++] = bv;

What prevents us from simplify using the bvecs in the request?  Sure
we'd need to disable merging for this case, but it would avoid the
copy, and the potentival memory allocation.

  reply	other threads:[~2015-01-25 13:41 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-13 15:44 [PATCH v2 0/4] block & aio: improve loop with kernel aio Ming Lei
2015-01-13 15:44 ` [PATCH v2 1/4] aio: add aio_kernel_() interface Ming Lei
2015-01-25 13:31   ` Christoph Hellwig
2015-01-26 16:18     ` Ming Lei
2015-01-26 17:00       ` Christoph Hellwig
2015-01-27 13:57         ` Ming Lei
2015-01-27 17:59       ` Christoph Hellwig
2015-01-13 15:44 ` [PATCH v2 2/4] fd/direct-io: introduce should_dirty for kernel aio Ming Lei
2015-01-25 13:34   ` Christoph Hellwig
2015-01-27 16:05     ` Ming Lei
2015-01-13 15:44 ` [PATCH v2 3/4] block: loop: introduce 'use_aio' sysfs file Ming Lei
2015-01-25 13:35   ` Christoph Hellwig
2015-01-27  5:26     ` Ming Lei
2015-01-26 17:57   ` Jeff Moyer
2015-01-13 15:44 ` [PATCH v2 4/4] block: loop: support to submit I/O via kernel aio based Ming Lei
2015-01-25 13:40   ` Christoph Hellwig [this message]
2015-03-18 18:28   ` Maxim Patlasov
2015-03-19  2:57     ` Ming Lei
2015-03-19 16:37       ` Maxim Patlasov
2015-03-20  5:27         ` Ming Lei
2015-01-13 16:23 ` [PATCH v2 0/4] block & aio: improve loop with kernel aio Christoph Hellwig
2015-01-14 10:17   ` Ming Lei

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