linux-kernel - Re: [PATCH] block: make sure big bio is splitted into at most 256 bvecs

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Message-ID: <20160406003025.GC31161@kmo-pixel>
Date:	Tue, 5 Apr 2016 16:30:25 -0800
From:	Kent Overstreet <kent.overstreet@...il.com>
To:	Ming Lei <ming.lei@...onical.com>
Cc:	Jens Axboe <axboe@...com>, linux-kernel@...r.kernel.org,
	linux-block@...r.kernel.org, Christoph Hellwig <hch@...radead.org>,
	Eric Wheeler <bcache@...ts.ewheeler.net>,
	Sebastian Roesner <sroesner-kernelorg@...sner-online.de>,
	"4.2+" <stable@...r.kernel.org>, Shaohua Li <shli@...com>
Subject: Re: [PATCH] block: make sure big bio is splitted into at most 256
 bvecs

On Wed, Apr 06, 2016 at 01:44:06AM +0800, Ming Lei wrote:
> After arbitrary bio size is supported, the incoming bio may
> be very big. We have to split the bio into small bios so that
> each holds at most BIO_MAX_PAGES bvecs for safety reason, such
> as bio_clone().
> 
> This patch fixes the following kernel crash:

Ming, let's not do it this way; drivers that don't clone biovecs are the norm -
instead, md has its own queue limits that it ought to be setting up correctly.