Hi Juergen,

I love your patch! Perhaps something to improve:

[auto build test WARNING on block/for-next]
[also build test WARNING on v4.18-rc8 next-20180809]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Juergen-Gross/xen-blk-persistent-grant-rework/20180810-003229
base:   https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git for-next
reproduce:
        # apt-get install sparse
        make ARCH=x86_64 allmodconfig
        make C=1 CF=-D__CHECK_ENDIAN__


sparse warnings: (new ones prefixed by >>)

quoted

drivers/block/xen-blkback/blkback.c:91:14: sparse: symbol 'xen_blkif_pgrant_timeout' was not declared. Should it be static?

   drivers/block/xen-blkback/blkback.c:1368:41: sparse: expression using sizeof(void)
   drivers/block/xen-blkback/blkback.c:409:29: sparse: expression using sizeof(void)
   drivers/block/xen-blkback/blkback.c:409:29: sparse: expression using sizeof(void)
   drivers/block/xen-blkback/blkback.c:791:38: sparse: expression using sizeof(void)
   drivers/block/xen-blkback/common.h:434:21: sparse: expression using sizeof(void)
   drivers/block/xen-blkback/common.h:482:21: sparse: expression using sizeof(void)

Please review and possibly fold the followup patch.

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