blk-merge warning in for-5.2/block

blk-merge warning in for-5.2/block

[Jens Axboe]

Hi Ming,

I'm getting this one when building the new set with gcc 8.3.0:


-- In file included from block/blk-merge.c:13:
block/blk-merge.c: In function ‘blk_rq_map_sg’:
block/blk.h:73:56: warning: ‘bvec.bv_offset’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  phys_addr_t addr1 = page_to_phys(vec1->bv_page) + vec1->bv_offset;
                                                    ~~~~^~~~~~~~~~~
block/blk-merge.c:530:17: note: ‘bvec.bv_offset’ was declared here
  struct bio_vec bvec, bvprv = { NULL };
                 ^~~~
In file included from block/blk-merge.c:13:
block/blk.h:76:18: warning: ‘bvec.bv_len’ may be used uninitialized in this function [-Wmaybe-uninitialized]
  if (addr1 + vec1->bv_len != addr2)
              ~~~~^~~~~~~~
block/blk-merge.c:530:17: note: ‘bvec.bv_len’ was declared here
  struct bio_vec bvec, bvprv = { NULL };
                 ^~~~
In file included from ./arch/x86/include/asm/page.h:76,
                 from ./arch/x86/include/asm/thread_info.h:12,
                 from ./include/linux/thread_info.h:38,
                 from ./arch/x86/include/asm/preempt.h:7,
                 from ./include/linux/preempt.h:78,
                 from ./include/linux/spinlock.h:51,
                 from ./include/linux/seqlock.h:36,
                 from ./include/linux/time.h:6,
                 from ./include/linux/stat.h:19,
                 from ./include/linux/module.h:10,
                 from block/blk-merge.c:6:
./include/asm-generic/memory_model.h:55:52: warning: ‘bvec.bv_page’ may be used uninitialized in this function [-Wmaybe-uninitialized]
 #define __page_to_pfn(page) (unsigned long)((page) - vmemmap)
                                                    ^
block/blk-merge.c:530:17: note: ‘bvec.bv_page’ was declared here
  struct bio_vec bvec, bvprv = { NULL };
                 ^~~~


Jens Axboe

Re: blk-merge warning in for-5.2/block

[Ming Lei]

On Mon, Apr 01, 2019 at 08:25:00AM -0600, Jens Axboe wrote:
> Hi Ming,
> 
> I'm getting this one when building the new set with gcc 8.3.0:
> 
> 
> -- In file included from block/blk-merge.c:13:
> block/blk-merge.c: In function ‘blk_rq_map_sg’:
> block/blk.h:73:56: warning: ‘bvec.bv_offset’ may be used uninitialized in this function [-Wmaybe-uninitialized]
>   phys_addr_t addr1 = page_to_phys(vec1->bv_page) + vec1->bv_offset;
>                                                     ~~~~^~~~~~~~~~~
> block/blk-merge.c:530:17: note: ‘bvec.bv_offset’ was declared here
>   struct bio_vec bvec, bvprv = { NULL };
>                  ^~~~
> In file included from block/blk-merge.c:13:
> block/blk.h:76:18: warning: ‘bvec.bv_len’ may be used uninitialized in this function [-Wmaybe-uninitialized]
>   if (addr1 + vec1->bv_len != addr2)
>               ~~~~^~~~~~~~
> block/blk-merge.c:530:17: note: ‘bvec.bv_len’ was declared here
>   struct bio_vec bvec, bvprv = { NULL };
>                  ^~~~
> In file included from ./arch/x86/include/asm/page.h:76,
>                  from ./arch/x86/include/asm/thread_info.h:12,
>                  from ./include/linux/thread_info.h:38,
>                  from ./arch/x86/include/asm/preempt.h:7,
>                  from ./include/linux/preempt.h:78,
>                  from ./include/linux/spinlock.h:51,
>                  from ./include/linux/seqlock.h:36,
>                  from ./include/linux/time.h:6,
>                  from ./include/linux/stat.h:19,
>                  from ./include/linux/module.h:10,
>                  from block/blk-merge.c:6:
> ./include/asm-generic/memory_model.h:55:52: warning: ‘bvec.bv_page’ may be used uninitialized in this function [-Wmaybe-uninitialized]
>  #define __page_to_pfn(page) (unsigned long)((page) - vmemmap)
>                                                     ^
> block/blk-merge.c:530:17: note: ‘bvec.bv_page’ was declared here
>   struct bio_vec bvec, bvprv = { NULL };
>                  ^~~~

It is one issue only if one bio doesn't include any bvec, I will post a
patch soon to fix it.

Thanks,
Ming