Hi Michel,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on rdma/for-next]
[also build test ERROR on linus/master v5.6-rc7]
[cannot apply to powerpc/next next-20200326]
[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/Michel-Lespinasse/Add-a-new-mmap-locking-API-wrapping-mmap_sem-calls/20200327-035215
base:   https://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma.git for-next
config: i386-randconfig-a002-20200326 (attached as .config)
compiler: gcc-4.9 (Ubuntu 4.9.3-13ubuntu2) 4.9.3
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   drivers/dma-buf/dma-resv.c: In function 'dma_resv_lockdep':
>> drivers/dma-buf/dma-resv.c:112:2: error: implicit declaration of function 'mmap_read_lock' [-Werror=implicit-function-declaration]
     mmap_read_lock(mm);
     ^
>> drivers/dma-buf/dma-resv.c:121:2: error: implicit declaration of function 'mmap_read_unlock' [-Werror=implicit-function-declaration]
     mmap_read_unlock(mm);
     ^
   cc1: some warnings being treated as errors

vim +/mmap_read_lock +112 drivers/dma-buf/dma-resv.c

    98	
    99	#if IS_ENABLED(CONFIG_LOCKDEP)
   100	static int __init dma_resv_lockdep(void)
   101	{
   102		struct mm_struct *mm = mm_alloc();
   103		struct ww_acquire_ctx ctx;
   104		struct dma_resv obj;
   105		int ret;
   106	
   107		if (!mm)
   108			return -ENOMEM;
   109	
   110		dma_resv_init(&obj);
   111	
 > 112		mmap_read_lock(mm);
   113		ww_acquire_init(&ctx, &reservation_ww_class);
   114		ret = dma_resv_lock(&obj, &ctx);
   115		if (ret == -EDEADLK)
   116			dma_resv_lock_slow(&obj, &ctx);
   117		fs_reclaim_acquire(GFP_KERNEL);
   118		fs_reclaim_release(GFP_KERNEL);
   119		ww_mutex_unlock(&obj.lock);
   120		ww_acquire_fini(&ctx);
 > 121		mmap_read_unlock(mm);
   122		
   123		mmput(mm);
   124	
   125		return 0;
   126	}
   127	subsys_initcall(dma_resv_lockdep);
   128	#endif
   129	

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