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/Kconfig b/samples/Kconfig
index b0503ef058d3343abf159e7378663979128c997b..88353b8eac0b48b5ae05ee85dff808c1fcde5e08 100644 (file)
--- 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 087e0988ccc569580240bcc719c2593be83f8b46..931a81847c4883d9a9c02e4d84a27a78bf2c783f 100644 (file)
--- 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 (file)
index 0000000..e20db1b
--- /dev/null
+++ b/samples/fanotify/Makefile
@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0-only
+userprogs-always-y += fs-monitor
+
+userccflags += -I usr/include -Wall
+

diff --git a/samples/fanotify/fs-monitor.c b/samples/fanotify/fs-monitor.c
new file mode 100644 (file)
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;
+}