linux-kernel - Re: [PATCH] block: don't optimize for non-cloned bio in bio_get_last

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Date:	Sat, 12 Mar 2016 21:20:40 -0700
From:	Jens Axboe <axboe@...nel.dk>
To:	Ming Lei <ming.lei@...onical.com>, linux-kernel@...r.kernel.org
Cc:	linux-block@...r.kernel.org, Christoph Hellwig <hch@...radead.org>,
	Sagi Grimberg <sagig@....mellanox.co.il>,
	Kent Overstreet <kent.overstreet@...il.com>,
	stable@...r.kernel.org
Subject: Re: [PATCH] block: don't optimize for non-cloned bio in
 bio_get_last_bvec()

On 03/12/2016 08:58 PM, Jens Axboe wrote:
> On 03/12/2016 07:56 AM, Ming Lei wrote:
>> For !BIO_CLONED bio, we can use .bi_vcnt safely, but it
>> doesn't mean we can just simply return .bi_io_vec[.bi_vcnt - 1]
>> because the start postion may have been moved in the middle of
>> the bvec, such as splitting in the middle of bvec.
>
> Added and tested.

And Ming, let's not get a repeat of this situation. For critical fixes, 
it has to be spot on for post -rc1, especially for code that is 
notoriously difficult to get right. Fixes are obviously fine, but it has 
to be just enough to fix the regression, no more. This has been too lax, 
I expect this to improve.

-- 
Jens Axboe