Re: [PATCH v2 bpf-next 1/7] bpf: implement BPF ring buffer and verifier support for it

Hi Andrii,

I love your patch! Perhaps something to improve:

[auto build test WARNING on bpf-next/master]
[also build test WARNING on next-20200518]
[cannot apply to bpf/master rcu/dev v5.7-rc6]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Andrii-Nakryiko/BPF-ring-buffer/20200518-040019
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
config: nds32-allmodconfig (attached as .config)
compiler: nds32le-linux-gcc (GCC) 9.3.0
reproduce:
        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=nds32 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <redacted>

All warnings (new ones prefixed by >>, old ones prefixed by <<):

In file included from ./arch/nds32/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/nds32/include/generated/asm/preempt.h:1,
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/ktime.h:24,
from include/linux/timer.h:6,
from include/linux/workqueue.h:9,
from include/linux/bpf.h:9,
from kernel/bpf/ringbuf.c:1:
include/linux/dma-mapping.h: In function 'dma_map_resource':
arch/nds32/include/asm/memory.h:82:32: warning: comparison of unsigned expression >= 0 is always true [-Wtype-limits]
82 | #define pfn_valid(pfn)  ((pfn) >= PHYS_PFN_OFFSET && (pfn) < (PHYS_PFN_OFFSET + max_mapnr))
|                                ^~
include/asm-generic/bug.h:139:27: note: in definition of macro 'WARN_ON_ONCE'
139 |  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))))
|                   ^~~~~~~~~
kernel/bpf/ringbuf.c: In function 'bpf_ringbuf_alloc':

quoted

kernel/bpf/ringbuf.c:133:14: warning: comparison is always false due to limited range of data type [-Wtype-limits]

133 |  if (data_sz > RINGBUF_MAX_DATA_SZ)
|              ^

vim +133 kernel/bpf/ringbuf.c

   125	
   126	static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node)
   127	{
   128		struct bpf_ringbuf *rb;
   129	
   130		if (!data_sz || !PAGE_ALIGNED(data_sz))
   131			return ERR_PTR(-EINVAL);
   132	
 > 133		if (data_sz > RINGBUF_MAX_DATA_SZ)
   134			return ERR_PTR(-E2BIG);
   135	
   136		rb = bpf_ringbuf_area_alloc(data_sz, numa_node);
   137		if (!rb)
   138			return ERR_PTR(-ENOMEM);
   139	
   140		spin_lock_init(&rb->spinlock);
   141		init_waitqueue_head(&rb->waitq);
   142		init_irq_work(&rb->work, bpf_ringbuf_notify);
   143	
   144		rb->mask = data_sz - 1;
   145		rb->consumer_pos = 0;
   146		rb->producer_pos = 0;
   147	
   148		return rb;
   149	}
   150	

---
0-DAY CI Kernel Test Service, Intel Corporation
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