linux-kernel - Re: [PATCH] block: Fix compiler warnings in blk-merge.c

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Date:	Tue, 8 Sep 2015 09:19:12 -0600
From:	Jens Axboe <axboe@...nel.dk>
To:	Geliang Tang <geliangtang@....com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] block: Fix compiler warnings in blk-merge.c

On 09/06/2015 09:24 AM, Geliang Tang wrote:
> Fix the following warnings:
>
>    CC      block/blk-merge.o
> In file included from block/blk-merge.c:7:0:
> 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));
>                       ^
> block/blk-merge.c:70:21: note: ‘bvprv.bv_offset’ was declared here
>    struct bio_vec bv, bvprv;
>                       ^
> In file included from block/blk-merge.c:7:0:
> include/linux/blkdev.h:1368:21: warning: ‘bvprv.bv_len’ may be used
> uninitialized in this function [-Wmaybe-uninitialized]
>     ((bprv->bv_offset + bprv->bv_len) & queue_virt_boundary(q));
>                       ^
> block/blk-merge.c:70:21: note: ‘bvprv.bv_len’ was declared here
>    struct bio_vec bv, bvprv;
>                       ^
> In file included from ./arch/x86/include/asm/page.h:70:0,
>                   from ./arch/x86/include/asm/thread_info.h:11,
>                   from include/linux/thread_info.h:54,
>                   from ./arch/x86/include/asm/preempt.h:6,
>                   from include/linux/preempt.h:64,
>                   from include/linux/spinlock.h:50,
>                   from include/linux/seqlock.h:35,
>                   from include/linux/time.h:5,
>                   from include/linux/stat.h:18,
>                   from include/linux/module.h:10,
>                   from block/blk-merge.c:5:
> include/asm-generic/memory_model.h:52:52: warning: ‘bvprv.bv_page’ may
> be used uninitialized in this function [-Wmaybe-uninitialized]
>   #define __page_to_pfn(page) (unsigned long)((page) - vmemmap)
>                                                      ^
> block/blk-merge.c:70:21: note: ‘bvprv.bv_page’ was declared here
>    struct bio_vec bv, bvprv;

There's already a fix queued up for that, which doesn't require bvprv to 
be cleared to 0:

http://git.kernel.dk/cgit/linux-block/commit/?h=for-linus&id=5014c311baa2b21384321fa4a9f617a92e3e56f0

-- 
Jens Axboe

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