Hi Gabriel,

I love your patch! Yet something to improve:

[auto build test ERROR on ext3/fsnotify]
[also build test ERROR on ext4/dev linus/master v5.13 next-20210629]
[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]

url:    https://github.com/0day-ci/linux/commits/Gabriel-Krisman-Bertazi/File-system-wide-monitoring/20210630-031347
base:   https://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs.git fsnotify
config: x86_64-allyesconfig (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build):
        # https://github.com/0day-ci/linux/commit/746524d8db08a041fed90e41b15c8e8ca69cb22d
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Gabriel-Krisman-Bertazi/File-system-wide-monitoring/20210630-031347
        git checkout 746524d8db08a041fed90e41b15c8e8ca69cb22d
        # save the attached .config to linux build tree
        mkdir build_dir
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash samples/

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

All errors (new ones prefixed by >>):

   samples/fanotify/fs-monitor.c: In function 'handle_notifications':
>> samples/fanotify/fs-monitor.c:84:32: error: 'mount_fd' undeclared (first use in this function)
      84 |   bad_file = open_by_handle_at(mount_fd, file_handle,  O_PATH);
         |                                ^~~~~~~~
   samples/fanotify/fs-monitor.c:84:32: note: each undeclared identifier is reported only once for each function it appears in
   samples/fanotify/fs-monitor.c: In function 'main':
   samples/fanotify/fs-monitor.c:111:2: error: 'mount_fd' undeclared (first use in this function)
     111 |  mount_fd = open(argv[1], O_RDONLY);
         |  ^~~~~~~~


vim +/mount_fd +84 samples/fanotify/fs-monitor.c

    30	
    31	static void handle_notifications(char *buffer, int len)
    32	{
    33		struct fanotify_event_metadata *metadata;
    34		struct fanotify_event_info_error *error;
    35		struct fanotify_event_info_fid *fid;
    36		struct file_handle *file_handle;
    37		int bad_file;
    38		int ret;
    39		struct stat stat;
    40		char *next;
    41	
    42		for (metadata = (struct fanotify_event_metadata *) buffer;
    43		     FAN_EVENT_OK(metadata, len);
    44		     metadata = FAN_EVENT_NEXT(metadata, len)) {
    45			next = (char *)metadata + metadata->event_len;
    46			if (metadata->mask != FAN_FS_ERROR) {
    47				printf("unexpected FAN MARK: %llx\n", metadata->mask);
    48				goto next_event;
    49			} else if (metadata->fd != FAN_NOFD) {
    50				printf("Unexpected fd (!= FAN_NOFD)\n");
    51				goto next_event;
    52			}
    53	
    54			printf("FAN_FS_ERROR found len=%d\n", metadata->event_len);
    55	
    56			error = (struct fanotify_event_info_error *) (metadata+1);
    57			if (error->hdr.info_type != FAN_EVENT_INFO_TYPE_ERROR) {
    58				printf("unknown record: %d (Expecting TYPE_ERROR)\n",
    59				       error->hdr.info_type);
    60				goto next_event;
    61			}
    62	
    63			printf("\tGeneric Error Record: len=%d\n", error->hdr.len);
    64			printf("\terror: %d\n", error->error);
    65			printf("\terror_count: %d\n", error->error_count);
    66	
    67			fid = (struct fanotify_event_info_fid *) (error + 1);
    68	
    69			if ((char *) fid >= next) {
    70				printf("Event doesn't have FID\n");
    71				goto next_event;
    72			}
    73			printf("FID record found\n");
    74	
    75			if (fid->hdr.info_type != FAN_EVENT_INFO_TYPE_FID) {
    76				printf("unknown record: %d (Expecting TYPE_FID)\n",
    77				       fid->hdr.info_type);
    78				goto next_event;
    79			}
    80			printf("\tfsid: %x%x\n", fid->fsid.val[0], fid->fsid.val[1]);
    81	
    82	
    83			file_handle = (struct file_handle *) &fid->handle;
  > 84			bad_file = open_by_handle_at(mount_fd, file_handle,  O_PATH);
    85			if (bad_file < 0) {
    86				printf("open_by_handle_at %d\n", errno);
    87				goto next_event;
    88			}
    89	
    90			ret = fstat(bad_file, &stat);
    91			if (ret < 0)
    92				printf("fstat %d\n", errno);
    93	
    94			printf("\tinode=%ld\n", stat.st_ino);
    95	
    96	next_event:
    97			printf("---\n\n");
    98		}
    99	}
   100	

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