[PATCH v3 13/17] tracing: Recover trace buffers from kexec handover

[kernel test robot]

Hi Alexander,

kernel test robot noticed the following build warnings:

[auto build test WARNING on linus/master]
[cannot apply to tip/x86/core arm64/for-next/core akpm-mm/mm-everything v6.7 next-20240117]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Alexander-Graf/mm-memblock-Add-support-for-scratch-memory/20240117-225136
base:   linus/master
patch link:    https://lore.kernel.org/r/20240117144704.602-14-graf%40amazon.com
patch subject: [PATCH v3 13/17] tracing: Recover trace buffers from kexec handover
config: arc-defconfig (https://download.01.org/0day-ci/archive/20240118/202401181457.dzB2femp-lkp@intel.com/config)
compiler: arc-elf-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240118/202401181457.dzB2femp-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 at intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202401181457.dzB2femp-lkp@intel.com/

All warnings (new ones prefixed by >>):

   kernel/trace/ring_buffer.c: In function 'rb_kho_replace_buffers':
>> kernel/trace/ring_buffer.c:5936:66: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
    5936 |                         cpu_buffer->head_page->list.prev->next = (struct list_head *)
         |                                                                  ^
   kernel/trace/ring_buffer.c:5939:44: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
    5939 |                         bpage->list.next = (struct list_head *)((ulong)new_lhead | rb_page_head);
         |                                            ^
--
>> kernel/trace/ring_buffer.c:1783: warning: Function parameter or struct member 'tr_off' not described in '__ring_buffer_alloc'


vim +5936 kernel/trace/ring_buffer.c

  5896	
  5897	static int rb_kho_replace_buffers(struct ring_buffer_per_cpu *cpu_buffer,
  5898					     struct rb_kho_cpu *kho)
  5899	{
  5900		bool first_loop = true;
  5901		struct list_head *tmp;
  5902		int err = 0;
  5903		int i = 0;
  5904	
  5905		if (!IS_ENABLED(CONFIG_FTRACE_KHO))
  5906			return -EINVAL;
  5907	
  5908		if (kho->nr_mems != cpu_buffer->nr_pages * 2)
  5909			return -EINVAL;
  5910	
  5911		for (tmp = rb_list_head(cpu_buffer->pages);
  5912		     tmp != rb_list_head(cpu_buffer->pages) || first_loop;
  5913		     tmp = rb_list_head(tmp->next), first_loop = false) {
  5914			struct buffer_page *bpage = (struct buffer_page *)tmp;
  5915			const struct kho_mem *mem_bpage = &kho->mem[i++];
  5916			const struct kho_mem *mem_page = &kho->mem[i++];
  5917			const uint64_t rb_page_head = 1;
  5918			struct buffer_page *old_bpage;
  5919			void *old_page;
  5920	
  5921			old_bpage = __va(mem_bpage->addr);
  5922			if (!bpage)
  5923				goto out;
  5924	
  5925			if ((ulong)old_bpage->list.next & rb_page_head) {
  5926				struct list_head *new_lhead;
  5927				struct buffer_page *new_head;
  5928	
  5929				new_lhead = rb_list_head(bpage->list.next);
  5930				new_head = (struct buffer_page *)new_lhead;
  5931	
  5932				/* Assume the buffer is completely full */
  5933				cpu_buffer->tail_page = bpage;
  5934				cpu_buffer->commit_page = bpage;
  5935				/* Set the head pointers to what they were before */
> 5936				cpu_buffer->head_page->list.prev->next = (struct list_head *)
  5937					((ulong)cpu_buffer->head_page->list.prev->next & ~rb_page_head);
  5938				cpu_buffer->head_page = new_head;
  5939				bpage->list.next = (struct list_head *)((ulong)new_lhead | rb_page_head);
  5940			}
  5941	
  5942			if (rb_page_entries(old_bpage) || rb_page_write(old_bpage)) {
  5943				/*
  5944				 * We want to recycle the pre-kho page, it contains
  5945				 * trace data. To do so, we unreserve it and swap the
  5946				 * current data page with the pre-kho one
  5947				 */
  5948				old_page = kho_claim_mem(mem_page);
  5949	
  5950				/* Recycle the old page, it contains data */
  5951				free_page((ulong)bpage->page);
  5952				bpage->page = old_page;
  5953	
  5954				bpage->write = old_bpage->write;
  5955				bpage->entries = old_bpage->entries;
  5956				bpage->real_end = old_bpage->real_end;
  5957	
  5958				local_inc(&cpu_buffer->pages_touched);
  5959			} else {
  5960				kho_return_mem(mem_page);
  5961			}
  5962	
  5963			kho_return_mem(mem_bpage);
  5964		}
  5965	
  5966	out:
  5967		return err;
  5968	}
  5969	

-- 
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