samples: Add fs error monitoring example
Introduce an example of a FAN_FS_ERROR fanotify user to track filesystem
errors.
Link: https://lore.kernel.org/r/20211025192746.66445-31-krisman@collabora.com
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Jan Kara <jack@suse.cz>
diff --git a/samples/fanotify/fs-monitor.c b/samples/fanotify/fs-monitor.c
new file mode 100644
index 0000000..a0e44cd
--- /dev/null
+++ b/samples/fanotify/fs-monitor.c
@@ -0,0 +1,142 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2021, Collabora Ltd.
+ */
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <err.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <fcntl.h>
+#include <sys/fanotify.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <sys/types.h>
+
+#ifndef FAN_FS_ERROR
+#define FAN_FS_ERROR 0x00008000
+#define FAN_EVENT_INFO_TYPE_ERROR 5
+
+struct fanotify_event_info_error {
+ struct fanotify_event_info_header hdr;
+ __s32 error;
+ __u32 error_count;
+};
+#endif
+
+#ifndef FILEID_INO32_GEN
+#define FILEID_INO32_GEN 1
+#endif
+
+#ifndef FILEID_INVALID
+#define FILEID_INVALID 0xff
+#endif
+
+static void print_fh(struct file_handle *fh)
+{
+ int i;
+ uint32_t *h = (uint32_t *) fh->f_handle;
+
+ printf("\tfh: ");
+ for (i = 0; i < fh->handle_bytes; i++)
+ printf("%hhx", fh->f_handle[i]);
+ printf("\n");
+
+ printf("\tdecoded fh: ");
+ if (fh->handle_type == FILEID_INO32_GEN)
+ printf("inode=%u gen=%u\n", h[0], h[1]);
+ else if (fh->handle_type == FILEID_INVALID && !fh->handle_bytes)
+ printf("Type %d (Superblock error)\n", fh->handle_type);
+ else
+ printf("Type %d (Unknown)\n", fh->handle_type);
+
+}
+
+static void handle_notifications(char *buffer, int len)
+{
+ struct fanotify_event_metadata *event =
+ (struct fanotify_event_metadata *) buffer;
+ struct fanotify_event_info_header *info;
+ struct fanotify_event_info_error *err;
+ struct fanotify_event_info_fid *fid;
+ int off;
+
+ for (; FAN_EVENT_OK(event, len); event = FAN_EVENT_NEXT(event, len)) {
+
+ if (event->mask != FAN_FS_ERROR) {
+ printf("unexpected FAN MARK: %llx\n", event->mask);
+ goto next_event;
+ }
+
+ if (event->fd != FAN_NOFD) {
+ printf("Unexpected fd (!= FAN_NOFD)\n");
+ goto next_event;
+ }
+
+ printf("FAN_FS_ERROR (len=%d)\n", event->event_len);
+
+ for (off = sizeof(*event) ; off < event->event_len;
+ off += info->len) {
+ info = (struct fanotify_event_info_header *)
+ ((char *) event + off);
+
+ switch (info->info_type) {
+ case FAN_EVENT_INFO_TYPE_ERROR:
+ err = (struct fanotify_event_info_error *) info;
+
+ printf("\tGeneric Error Record: len=%d\n",
+ err->hdr.len);
+ printf("\terror: %d\n", err->error);
+ printf("\terror_count: %d\n", err->error_count);
+ break;
+
+ case FAN_EVENT_INFO_TYPE_FID:
+ fid = (struct fanotify_event_info_fid *) info;
+
+ printf("\tfsid: %x%x\n",
+ fid->fsid.val[0], fid->fsid.val[1]);
+ print_fh((struct file_handle *) &fid->handle);
+ break;
+
+ default:
+ printf("\tUnknown info type=%d len=%d:\n",
+ info->info_type, info->len);
+ }
+ }
+next_event:
+ printf("---\n\n");
+ }
+}
+
+int main(int argc, char **argv)
+{
+ int fd;
+
+ char buffer[BUFSIZ];
+
+ if (argc < 2) {
+ printf("Missing path argument\n");
+ return 1;
+ }
+
+ fd = fanotify_init(FAN_CLASS_NOTIF|FAN_REPORT_FID, O_RDONLY);
+ if (fd < 0)
+ errx(1, "fanotify_init");
+
+ if (fanotify_mark(fd, FAN_MARK_ADD|FAN_MARK_FILESYSTEM,
+ FAN_FS_ERROR, AT_FDCWD, argv[1])) {
+ errx(1, "fanotify_mark");
+ }
+
+ while (1) {
+ int n = read(fd, buffer, BUFSIZ);
+
+ if (n < 0)
+ errx(1, "read");
+
+ handle_notifications(buffer, n);
+ }
+
+ return 0;
+}