Hi Jesper,

I love your patch! Perhaps something to improve:

[auto build test WARNING on bpf/master]

url:    https://github.com/0day-ci/linux/commits/Jesper-Dangaard-Brouer/bpf-avoid-using-returning-file-descriptor-value-zero/20200609-005457
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git master
config: um-allmodconfig (attached as .config)
compiler: gcc-9 (Debian 9.3.0-13) 9.3.0
reproduce (this is a W=1 build):
        # save the attached .config to linux build tree
        make W=1 ARCH=um 

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 <<):

cc1: warning: arch/um/include/uapi: No such file or directory [-Wmissing-include-dirs]
In file included from include/linux/kernel.h:11,
from include/linux/list.h:9,
from include/linux/timer.h:5,
from include/linux/workqueue.h:9,
from include/linux/bpf.h:9,
from kernel/bpf/syscall.c:4:
include/asm-generic/fixmap.h: In function 'fix_to_virt':
include/asm-generic/fixmap.h:32:19: warning: comparison of unsigned expression >= 0 is always true [-Wtype-limits]
32 |  BUILD_BUG_ON(idx >= __end_of_fixed_addresses);
|                   ^~
include/linux/compiler.h:383:9: note: in definition of macro '__compiletime_assert'
383 |   if (!(condition))              |         ^~~~~~~~~
include/linux/compiler.h:403:2: note: in expansion of macro '_compiletime_assert'
403 |  _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
|  ^~~~~~~~~~~~~~~~~~~
include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
|                                     ^~~~~~~~~~~~~~~~~~
include/linux/build_bug.h:50:2: note: in expansion of macro 'BUILD_BUG_ON_MSG'
50 |  BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
|  ^~~~~~~~~~~~~~~~
include/asm-generic/fixmap.h:32:2: note: in expansion of macro 'BUILD_BUG_ON'
32 |  BUILD_BUG_ON(idx >= __end_of_fixed_addresses);
|  ^~~~~~~~~~~~
In file included from include/linux/uaccess.h:11,
from include/linux/sched/task.h:11,
from include/linux/sched/signal.h:9,
from include/linux/rcuwait.h:6,
from include/linux/percpu-rwsem.h:7,
from include/linux/fs.h:34,
from include/linux/huge_mm.h:8,
from include/linux/mm.h:675,
from include/linux/kallsyms.h:12,
from include/linux/bpf.h:21,
from kernel/bpf/syscall.c:4:
arch/um/include/asm/uaccess.h: In function '__access_ok':
arch/um/include/asm/uaccess.h:17:29: warning: comparison of unsigned expression >= 0 is always true [-Wtype-limits]
17 |    (((unsigned long) (addr) >= FIXADDR_USER_START) &&          |                             ^~
arch/um/include/asm/uaccess.h:45:3: note: in expansion of macro '__access_ok_vsyscall'
45 |   __access_ok_vsyscall(addr, size) ||
|   ^~~~~~~~~~~~~~~~~~~~
kernel/bpf/syscall.c: At top level:
>> kernel/bpf/syscall.c:692:5: warning: no previous prototype for 'bpf_anon_inode_getfd' [-Wmissing-prototypes]
692 | int bpf_anon_inode_getfd(const char *name, const struct file_operations *fops,
|     ^~~~~~~~~~~~~~~~~~~~

vim +/bpf_anon_inode_getfd +692 kernel/bpf/syscall.c

   690	
   691	/* Code is similar to anon_inode_getfd(), except starts at FD 1 */
 > 692	int bpf_anon_inode_getfd(const char *name, const struct file_operations *fops,
   693				 void *priv, int flags)
   694	{
   695		int error, fd;
   696		struct file *file;
   697	
   698		error = alloc_fd(1, flags);
   699		if (error < 0)
   700			return error;
   701		fd = error;
   702	
   703		file = anon_inode_getfile(name, fops, priv, flags);
   704		if (IS_ERR(file)) {
   705			error = PTR_ERR(file);
   706			goto err_put_unused_fd;
   707		}
   708		fd_install(fd, file);
   709	
   710		return fd;
   711	
   712	err_put_unused_fd:
   713		put_unused_fd(fd);
   714		return error;
   715	}
   716	

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