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Date: Fri, 11 Aug 2017 12:46:15 +0200
From: Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v1 2/6] fs: use on-stack-bio if backing device has
	BDI_CAP_SYNC capability
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References: <1502175024-28338-1-git-send-email-minchan@kernel.org> <1502175024-28338-3-git-send-email-minchan@kernel.org> <20170808124959.GB31390@bombadil.infradead.org> <20170808132904.GC31390@bombadil.infradead.org> <20170809015113.GB32338@bbox> <20170809023122.GF31390@bombadil.infradead.org> <20170809024150.GA32471@bbox> <20170810030433.GG31390@bombadil.infradead.org> <CAA9_cmekE9_PYmNnVmiOkyH2gq5o8=uvEKnAbMWw5nBX-zE69g@mail.gmail.com>
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To: Dan Williams <dan.j.williams@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>, Minchan Kim <minchan@kernel.org>, Andrew Morton <akpm@linux-foundation.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>, Ross Zwisler <ross.zwisler@linux.intel.com>, "karam . lee" <karam.lee@lge.com>, seungho1.park@lge.com, Christoph Hellwig <hch@lst.de>, Dave Chinner <david@fromorbit.com>, Jan Kara <jack@suse.cz>, Jens Axboe <axboe@kernel.dk>, Vishal Verma <vishal.l.verma@intel.com>, "linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>, kernel-team <kernel-team@lge.com>

On Wed, Aug 09, 2017 at 08:06:24PM -0700, Dan Williams wrote:
> I like it, but do you think we should switch to sbvec[<constant>] to
> preclude pathological cases where nr_pages is large?

Yes, please.

Then I'd like to see that the on-stack bio even matters for
mpage_readpage / mpage_writepage.  Compared to all the buffer head
overhead the bio allocation should not actually matter in practice.

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