linux-kernel - Re: [GIT PULL] SG changes for 4.3

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Message-ID: <55E77B00.4040302@fb.com>
Date:	Wed, 2 Sep 2015 16:41:04 -0600
From:	Jens Axboe <axboe@...com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [GIT PULL] SG changes for 4.3

On 09/02/2015 04:34 PM, Linus Torvalds wrote:
> Jens,
>
> On Wed, Sep 2, 2015 at 9:58 AM, Jens Axboe <axboe@...com> wrote:
>>
>> This pull request contains a set of scatter-gather related changes/fixes
>> for 4.3. It contains:
>
> This results in several new and annoying warnings. They may all be ok
> code, but they are very distracting. Please stop introducing new
> warnings to the build, because by now most of the warnings I see come
> from the block layer.
>
>     block/blk-merge.c: In function ‘blk_queue_split’:
>     include/linux/blkdev.h:1368:21: warning: ‘bvprv.bv_offset’ may be
> used uninitialized in this function [-Wmaybe-uninitialized]
>       ((bprv->bv_offset + bprv->bv_len) & queue_virt_boundary(q));
>
> (it gives this for bv_len too). The reason seems to be that disgusting
> situation where "bvprv" is uninitiatlized unless "split" is true, and
> the code looks like it is correct, but the compiler clearly has a hard
> time seeing it. It took me a while too, so I can't really blame it.
>
> Either initialize bvprv to something explicit, or make the code clear
> enough that the compiler can see that it is never used uninitialized.
> Because those compiler warnings are sometimes real, and we can't just
> ignore them.
>
> There was another type-based warning introduced by your core block
> pull (size_t vs unsigned int).

I think it's a repeat offender that got reintroduced. I'll fix it up.

-- 
Jens Axboe

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