Introduce an example of a FAN_FS_ERROR fanotify user to track filesystem
errors.
Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
---
Changes since v1:
- minor fixes
---
samples/Kconfig | 9 +++
samples/Makefile | 1 +
samples/fanotify/Makefile | 3 +
samples/fanotify/fs-monitor.c | 134 ++++++++++++++++++++++++++++++++++
4 files changed, 147 insertions(+)
create mode 100644 samples/fanotify/Makefile
create mode 100644 samples/fanotify/fs-monitor.c
diff --git a/samples/Kconfig b/samples/Kconfig
index b5a1a7aa7e23..f2f9c939035f 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -120,6 +120,15 @@ config SAMPLE_CONNECTOR
with it.
See also Documentation/driver-api/connector.rst
+config SAMPLE_FANOTIFY_ERROR
+ bool "Build fanotify error monitoring sample"
+ depends on FANOTIFY
+ help
+ When enabled, this builds an example code that uses the
+ FAN_FS_ERROR fanotify mechanism to monitor filesystem
+ errors.
+ See also Documentation/admin-guide/filesystem-monitoring.rst.
+
config SAMPLE_HIDRAW
bool "hidraw sample"
depends on CC_CAN_LINK && HEADERS_INSTALL
diff --git a/samples/Makefile b/samples/Makefile
index 087e0988ccc5..931a81847c48 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -5,6 +5,7 @@ subdir-$(CONFIG_SAMPLE_AUXDISPLAY) += auxdisplay
subdir-$(CONFIG_SAMPLE_ANDROID_BINDERFS) += binderfs
obj-$(CONFIG_SAMPLE_CONFIGFS) += configfs/
obj-$(CONFIG_SAMPLE_CONNECTOR) += connector/
+obj-$(CONFIG_SAMPLE_FANOTIFY_ERROR) += fanotify/
subdir-$(CONFIG_SAMPLE_HIDRAW) += hidraw
obj-$(CONFIG_SAMPLE_HW_BREAKPOINT) += hw_breakpoint/
obj-$(CONFIG_SAMPLE_KDB) += kdb/
diff --git a/samples/fanotify/Makefile b/samples/fanotify/Makefile
new file mode 100644
index 000000000000..b3d5cc826e6f
--- /dev/null
+++ b/samples/fanotify/Makefile
@@ -0,0 +1,3 @@
+userprogs-always-y += fs-monitor
+
+userccflags += -I usr/include
diff --git a/samples/fanotify/fs-monitor.c b/samples/fanotify/fs-monitor.c
new file mode 100644
index 000000000000..f949ea00271d
--- /dev/null
+++ b/samples/fanotify/fs-monitor.c
@@ -0,0 +1,134 @@
+// 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/stat.h>
+#include <sys/types.h>
+
+#ifndef FAN_FS_ERROR
+#define FAN_FS_ERROR 0x00008000
+#define FAN_EVENT_INFO_TYPE_ERROR 4
+
+int mount_fd;
+
+struct fanotify_event_info_error {
+ struct fanotify_event_info_header hdr;
+ __s32 error;
+ __u32 error_count;
+};
+#endif
+
+static void handle_notifications(char *buffer, int len)
+{
+ struct fanotify_event_metadata *metadata;
+ struct fanotify_event_info_error *error;
+ struct fanotify_event_info_fid *fid;
+ struct file_handle *file_handle;
+ int bad_file;
+ int ret;
+ struct stat stat;
+ char *next;
+
+ for (metadata = (struct fanotify_event_metadata *) buffer;
+ FAN_EVENT_OK(metadata, len);
+ metadata = FAN_EVENT_NEXT(metadata, len)) {
+ next = (char *)metadata + metadata->event_len;
+ if (metadata->mask != FAN_FS_ERROR) {
+ printf("unexpected FAN MARK: %llx\n", metadata->mask);
+ goto next_event;
+ } else if (metadata->fd != FAN_NOFD) {
+ printf("Unexpected fd (!= FAN_NOFD)\n");
+ goto next_event;
+ }
+
+ printf("FAN_FS_ERROR found len=%d\n", metadata->event_len);
+
+ error = (struct fanotify_event_info_error *) (metadata+1);
+ if (error->hdr.info_type != FAN_EVENT_INFO_TYPE_ERROR) {
+ printf("unknown record: %d (Expecting TYPE_ERROR)\n",
+ error->hdr.info_type);
+ goto next_event;
+ }
+
+ printf("\tGeneric Error Record: len=%d\n", error->hdr.len);
+ printf("\terror: %d\n", error->error);
+ printf("\terror_count: %d\n", error->error_count);
+
+ fid = (struct fanotify_event_info_fid *) (error + 1);
+
+ if ((char *) fid >= next) {
+ printf("Event doesn't have FID\n");
+ goto next_event;
+ }
+ printf("FID record found\n");
+
+ if (fid->hdr.info_type != FAN_EVENT_INFO_TYPE_FID) {
+ printf("unknown record: %d (Expecting TYPE_FID)\n",
+ fid->hdr.info_type);
+ goto next_event;
+ }
+ printf("\tfsid: %x%x\n", fid->fsid.val[0], fid->fsid.val[1]);
+
+
+ file_handle = (struct file_handle *) &fid->handle;
+ bad_file = open_by_handle_at(mount_fd, file_handle, O_PATH);
+ if (bad_file < 0) {
+ printf("open_by_handle_at %d\n", errno);
+ goto next_event;
+ }
+
+ ret = fstat(bad_file, &stat);
+ if (ret < 0)
+ printf("fstat %d\n", errno);
+
+ printf("\tinode=%ld\n", stat.st_ino);
+
+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;
+ }
+
+ mount_fd = open(argv[1], O_RDONLY);
+ if (mount_fd < 0)
+ errx(1, "mount_fd");
+
+ 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;
+}
--
2.32.0
