[trace:ring-buffer/for-next 1/1] kernel/trace/ring_buffer.c:6279:11: warning: unsequenced modification and access to 'p'

[kernel test robot <lkp@intel.com>]

tree:   git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace ring-buffer/for-next
head:   ff74f987504fe90e88fdba8d80197202868ce342
commit: ff74f987504fe90e88fdba8d80197202868ce342 [1/1] ring-buffer: Align meta-page to sub-buffers for improved TLB usage
config: s390-defconfig (https://download.01.org/0day-ci/archive/20240607/202406070523.lVekXLDq-lkp@intel.com/config)
compiler: clang version 19.0.0git (https://github.com/llvm/llvm-project d7d2d4f53fc79b4b58e8d8d08151b577c3699d4a)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240607/202406070523.lVekXLDq-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202406070523.lVekXLDq-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from kernel/trace/ring_buffer.c:8:
   In file included from include/linux/trace_events.h:6:
   In file included from include/linux/ring_buffer.h:5:
   In file included from include/linux/mm.h:2253:
   include/linux/vmstat.h:500:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
     500 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~ ^
     501 |                            item];
         |                            ~~~~
   include/linux/vmstat.h:507:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
     507 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~ ^
     508 |                            NR_VM_NUMA_EVENT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~~
   include/linux/vmstat.h:514:36: warning: arithmetic between different enumeration types ('enum node_stat_item' and 'enum lru_list') [-Wenum-enum-conversion]
     514 |         return node_stat_name(NR_LRU_BASE + lru) + 3; // skip "nr_"
         |                               ~~~~~~~~~~~ ^ ~~~
   include/linux/vmstat.h:519:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
     519 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~ ^
     520 |                            NR_VM_NUMA_EVENT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~~
   include/linux/vmstat.h:528:43: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum numa_stat_item') [-Wenum-enum-conversion]
     528 |         return vmstat_text[NR_VM_ZONE_STAT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~ ^
     529 |                            NR_VM_NUMA_EVENT_ITEMS +
         |                            ~~~~~~~~~~~~~~~~~~~~~~
>> kernel/trace/ring_buffer.c:6279:11: warning: unsequenced modification and access to 'p' [-Wunsequenced]
    6279 |                         pages[p++] = ZERO_PAGE(vma->vm_start + (PAGE_SIZE * p));
         |                                ^                                            ~
   6 warnings generated.


vim +/p +6279 kernel/trace/ring_buffer.c

  6213	
  6214	/*
  6215	 *   +--------------+  pgoff == 0
  6216	 *   |   meta page  |
  6217	 *   +--------------+  pgoff == 1
  6218	 *   | subbuffer 0  |
  6219	 *   |              |
  6220	 *   +--------------+  pgoff == (1 + (1 << subbuf_order))
  6221	 *   | subbuffer 1  |
  6222	 *   |              |
  6223	 *         ...
  6224	 */
  6225	#ifdef CONFIG_MMU
  6226	static int __rb_map_vma(struct ring_buffer_per_cpu *cpu_buffer,
  6227				struct vm_area_struct *vma)
  6228	{
  6229		unsigned long nr_subbufs, nr_pages, vma_pages, pgoff = vma->vm_pgoff;
  6230		unsigned int subbuf_pages, subbuf_order;
  6231		struct page **pages;
  6232		int p = 0, s = 0;
  6233		int err;
  6234	
  6235		/* Refuse MP_PRIVATE or writable mappings */
  6236		if (vma->vm_flags & VM_WRITE || vma->vm_flags & VM_EXEC ||
  6237		    !(vma->vm_flags & VM_MAYSHARE))
  6238			return -EPERM;
  6239	
  6240		subbuf_order = cpu_buffer->buffer->subbuf_order;
  6241		subbuf_pages = 1 << subbuf_order;
  6242	
  6243		if (subbuf_order && pgoff % subbuf_pages)
  6244			return -EINVAL;
  6245	
  6246		/*
  6247		 * Make sure the mapping cannot become writable later. Also tell the VM
  6248		 * to not touch these pages (VM_DONTCOPY | VM_DONTEXPAND).
  6249		 */
  6250		vm_flags_mod(vma, VM_DONTCOPY | VM_DONTEXPAND | VM_DONTDUMP,
  6251			     VM_MAYWRITE);
  6252	
  6253		lockdep_assert_held(&cpu_buffer->mapping_lock);
  6254	
  6255		nr_subbufs = cpu_buffer->nr_pages + 1; /* + reader-subbuf */
  6256		nr_pages = ((nr_subbufs + 1) << subbuf_order) - pgoff; /* + meta-page */
  6257	
  6258		vma_pages = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
  6259		if (!vma_pages || vma_pages > nr_pages)
  6260			return -EINVAL;
  6261	
  6262		nr_pages = vma_pages;
  6263	
  6264		pages = kcalloc(nr_pages, sizeof(*pages), GFP_KERNEL);
  6265		if (!pages)
  6266			return -ENOMEM;
  6267	
  6268		if (!pgoff) {
  6269			unsigned long meta_page_padding;
  6270	
  6271			pages[p++] = virt_to_page(cpu_buffer->meta_page);
  6272	
  6273			/*
  6274			 * Pad with the zero-page to align the meta-page with the
  6275			 * sub-buffers.
  6276			 */
  6277			meta_page_padding = subbuf_pages - 1;
  6278			while (meta_page_padding-- && p < nr_pages)
> 6279				pages[p++] = ZERO_PAGE(vma->vm_start + (PAGE_SIZE * p));
  6280		} else {
  6281			/* Skip the meta-page */
  6282			pgoff -= subbuf_pages;
  6283	
  6284			s += pgoff / subbuf_pages;
  6285		}
  6286	
  6287		while (p < nr_pages) {
  6288			struct page *page = virt_to_page((void *)cpu_buffer->subbuf_ids[s]);
  6289			int off = 0;
  6290	
  6291			if (WARN_ON_ONCE(s >= nr_subbufs)) {
  6292				err = -EINVAL;
  6293				goto out;
  6294			}
  6295	
  6296			for (; off < (1 << (subbuf_order)); off++, page++) {
  6297				if (p >= nr_pages)
  6298					break;
  6299	
  6300				pages[p++] = page;
  6301			}
  6302			s++;
  6303		}
  6304	
  6305		err = vm_insert_pages(vma, vma->vm_start, pages, &nr_pages);
  6306	
  6307	out:
  6308		kfree(pages);
  6309	
  6310		return err;
  6311	}
  6312	#else
  6313	static int __rb_map_vma(struct ring_buffer_per_cpu *cpu_buffer,
  6314				struct vm_area_struct *vma)
  6315	{
  6316		return -EOPNOTSUPP;
  6317	}
  6318	#endif
  6319	

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