Re: [PATCH] scsi: target: tcmu: Call flush_dcache_page() with proper page struct

Henry Willard
2020-06-23T17:49:38Z

On 6/19/20 6:31 PM, kernel test robot wrote:
> Hi Henry,
>
> Thank you for the patch! Perhaps something to improve:
>
> [auto build test WARNING on mkp-scsi/for-next]
> [also build test WARNING on scsi/for-next v5.8-rc1 next-20200618]
> [If your patch is applied to the wrong git tree, kindly drop us a note.
> And when submitting patch, we suggest to use as documented in
> https://git-scm.com/docs/git-format-patch]
>
> url: https://github.com/0day-ci/linux/commits/Henry-Willard/scsi-target-tcmu-Call-flush_dcache_page-with-proper-page-struct/20200620-024740
> base: https://git.kernel.org/pub/scm/linux/kernel/git/mkp/scsi.git for-next
> config: xtensa-allyesconfig (attached as .config)
> compiler: xtensa-linux-gcc (GCC) 9.3.0
> reproduce (this is a W=1 build):
> wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> chmod +x ~/bin/make.cross
> # save the attached .config to linux build tree
> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=xtensa
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
>
> All warnings (new ones prefixed by >>, old ones prefixed by <<):
>
> In file included from include/linux/kernel.h:11,
> from include/linux/list.h:9,
> from include/linux/preempt.h:11,
> from include/linux/spinlock.h:51,
> from drivers/target/target_core_user.c:9:
> include/linux/scatterlist.h: In function 'sg_set_buf':
> arch/xtensa/include/asm/page.h:193:9: warning: comparison of unsigned expression >= 0 is always true [-Wtype-limits]
> 193 | ((pfn) >= ARCH_PFN_OFFSET && ((pfn) - ARCH_PFN_OFFSET) < max_mapnr)
> | ^~
> include/linux/compiler.h:78:42: note: in definition of macro 'unlikely'
> 78 | # define unlikely(x) __builtin_expect(!!(x), 0)
> | ^
> include/linux/scatterlist.h:143:2: note: in expansion of macro 'BUG_ON'
> 143 | BUG_ON(!virt_addr_valid(buf));
> | ^~~~~~
> arch/xtensa/include/asm/page.h:201:32: note: in expansion of macro 'pfn_valid'
> 201 | #define virt_addr_valid(kaddr) pfn_valid(__pa(kaddr) >> PAGE_SHIFT)
> | ^~~~~~~~~
> include/linux/scatterlist.h:143:10: note: in expansion of macro 'virt_addr_valid'
> 143 | BUG_ON(!virt_addr_valid(buf));
> | ^~~~~~~~~~~~~~~
> In file included from ./arch/xtensa/include/generated/asm/bug.h:1,
> from include/linux/bug.h:5,
> from include/linux/thread_info.h:12,
> from include/asm-generic/preempt.h:5,
> from ./arch/xtensa/include/generated/asm/preempt.h:1,
> from include/linux/preempt.h:78,
> from include/linux/spinlock.h:51,
> from drivers/target/target_core_user.c:9:
> include/linux/dma-mapping.h: In function 'dma_map_resource':
> arch/xtensa/include/asm/page.h:193:9: warning: comparison of unsigned expression >= 0 is always true [-Wtype-limits]
> 193 | ((pfn) >= ARCH_PFN_OFFSET && ((pfn) - ARCH_PFN_OFFSET) < max_mapnr)
> | ^~
> include/asm-generic/bug.h:144:27: note: in definition of macro 'WARN_ON_ONCE'
> 144 | int __ret_warn_once = !!(condition); | ^~~~~~~~~
> include/linux/dma-mapping.h:352:19: note: in expansion of macro 'pfn_valid'
> 352 | if (WARN_ON_ONCE(pfn_valid(PHYS_PFN(phys_addr))))
> | ^~~~~~~~~
> In file included from include/linux/mm_types_task.h:16,
> from include/linux/mm_types.h:5,
> from include/linux/mmzone.h:21,
> from include/linux/gfp.h:6,
> from include/linux/umh.h:4,
> from include/linux/kmod.h:9,
> from include/linux/module.h:16,
> from drivers/target/target_core_user.c:10:
> drivers/target/target_core_user.c: In function 'tcmu_flush_dcache_range':
> arch/xtensa/include/asm/page.h:193:9: warning: comparison of unsigned expression >= 0 is always true [-Wtype-limits]
> 193 | ((pfn) >= ARCH_PFN_OFFSET && ((pfn) - ARCH_PFN_OFFSET) < max_mapnr)
> | ^~
> arch/xtensa/include/asm/page.h:201:32: note: in expansion of macro 'pfn_valid'
> 201 | #define virt_addr_valid(kaddr) pfn_valid(__pa(kaddr) >> PAGE_SHIFT)
> | ^~~~~~~~~
> drivers/target/target_core_user.c:605:7: note: in expansion of macro 'virt_addr_valid'
> 605 | if (virt_addr_valid(start))
> | ^~~~~~~~~~~~~~~
>>> drivers/target/target_core_user.c:600:15: warning: variable 'pg' set but not used [-Wunused-but-set-variable]
> 600 | struct page *pg;
> | ^~
>
> vim +/pg +600 drivers/target/target_core_user.c
>
> 595
> 596 static inline void tcmu_flush_dcache_range(void *vaddr, size_t size)
> 597 {
> 598 unsigned long offset = offset_in_page(vaddr);
> 599 void *start = vaddr - offset;
> > 600 struct page *pg;
> 601
> 602 size = round_up(size+offset, PAGE_SIZE);
> 603
> 604 while (size) {
> 605 if (virt_addr_valid(start))
> 606 pg = virt_to_page(start);
> 607 else if (is_vmalloc_addr(start))
> 608 pg = vmalloc_to_page(start);
> 609 else
> 610 break;
> 611
> 612 flush_dcache_page(pg);
> 613 start += PAGE_SIZE;
> 614 size -= PAGE_SIZE;
> 615 }
> 616 }
> 617
>
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
It doesn't really matter in this case because this patch has been
superseded by a different fix, but the warning appears to be caused by
an incorrect implementation of flush_dcache_page() in
arch/xtensa/include/asm/cacheflush.h. Depending on the variant and
options, flush_dcache_page can be defined as "do { } while (0)", which
covers the default null implementation of flush_dcache_page().

Thanks,
Henry