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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/[email protected] Reviewed-by: Amir Goldstein <[email protected]> Reviewed-by: Jan Kara <[email protected]> Signed-off-by: Gabriel Krisman Bertazi <[email protected]> Signed-off-by: Jan Kara <[email protected]>
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‎samples/Kconfig

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@@ -120,6 +120,15 @@ config SAMPLE_CONNECTOR
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with it.
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See also Documentation/driver-api/connector.rst
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config SAMPLE_FANOTIFY_ERROR
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bool "Build fanotify error monitoring sample"
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depends on FANOTIFY
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help
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When enabled, this builds an example code that uses the
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FAN_FS_ERROR fanotify mechanism to monitor filesystem
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errors.
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See also Documentation/admin-guide/filesystem-monitoring.rst.
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config SAMPLE_HIDRAW
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bool "hidraw sample"
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depends on CC_CAN_LINK && HEADERS_INSTALL

‎samples/Makefile

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@@ -5,6 +5,7 @@ subdir-$(CONFIG_SAMPLE_AUXDISPLAY) += auxdisplay
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subdir-$(CONFIG_SAMPLE_ANDROID_BINDERFS) += binderfs
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obj-$(CONFIG_SAMPLE_CONFIGFS) += configfs/
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obj-$(CONFIG_SAMPLE_CONNECTOR) += connector/
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obj-$(CONFIG_SAMPLE_FANOTIFY_ERROR) += fanotify/
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subdir-$(CONFIG_SAMPLE_HIDRAW) += hidraw
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obj-$(CONFIG_SAMPLE_HW_BREAKPOINT) += hw_breakpoint/
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obj-$(CONFIG_SAMPLE_KDB) += kdb/

‎samples/fanotify/Makefile

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# SPDX-License-Identifier: GPL-2.0-only
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userprogs-always-y += fs-monitor
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userccflags += -I usr/include -Wall
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‎samples/fanotify/fs-monitor.c

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// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright 2021, Collabora Ltd.
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*/
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#define _GNU_SOURCE
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#include <errno.h>
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#include <err.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <fcntl.h>
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#include <sys/fanotify.h>
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#include <sys/types.h>
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#include <unistd.h>
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#include <sys/types.h>
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#ifndef FAN_FS_ERROR
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#define FAN_FS_ERROR 0x00008000
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#define FAN_EVENT_INFO_TYPE_ERROR 5
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struct fanotify_event_info_error {
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struct fanotify_event_info_header hdr;
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__s32 error;
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__u32 error_count;
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};
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#endif
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#ifndef FILEID_INO32_GEN
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#define FILEID_INO32_GEN 1
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#endif
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#ifndef FILEID_INVALID
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#define FILEID_INVALID 0xff
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#endif
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static void print_fh(struct file_handle *fh)
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{
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int i;
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uint32_t *h = (uint32_t *) fh->f_handle;
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printf("\tfh: ");
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for (i = 0; i < fh->handle_bytes; i++)
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printf("%hhx", fh->f_handle[i]);
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printf("\n");
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printf("\tdecoded fh: ");
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if (fh->handle_type == FILEID_INO32_GEN)
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printf("inode=%u gen=%u\n", h[0], h[1]);
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else if (fh->handle_type == FILEID_INVALID && !fh->handle_bytes)
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printf("Type %d (Superblock error)\n", fh->handle_type);
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else
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printf("Type %d (Unknown)\n", fh->handle_type);
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}
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static void handle_notifications(char *buffer, int len)
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{
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struct fanotify_event_metadata *event =
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(struct fanotify_event_metadata *) buffer;
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struct fanotify_event_info_header *info;
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struct fanotify_event_info_error *err;
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struct fanotify_event_info_fid *fid;
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int off;
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for (; FAN_EVENT_OK(event, len); event = FAN_EVENT_NEXT(event, len)) {
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if (event->mask != FAN_FS_ERROR) {
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printf("unexpected FAN MARK: %llx\n", event->mask);
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goto next_event;
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}
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if (event->fd != FAN_NOFD) {
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printf("Unexpected fd (!= FAN_NOFD)\n");
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goto next_event;
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}
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printf("FAN_FS_ERROR (len=%d)\n", event->event_len);
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for (off = sizeof(*event) ; off < event->event_len;
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off += info->len) {
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info = (struct fanotify_event_info_header *)
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((char *) event + off);
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switch (info->info_type) {
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case FAN_EVENT_INFO_TYPE_ERROR:
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err = (struct fanotify_event_info_error *) info;
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printf("\tGeneric Error Record: len=%d\n",
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err->hdr.len);
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printf("\terror: %d\n", err->error);
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printf("\terror_count: %d\n", err->error_count);
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break;
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case FAN_EVENT_INFO_TYPE_FID:
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fid = (struct fanotify_event_info_fid *) info;
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printf("\tfsid: %x%x\n",
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fid->fsid.val[0], fid->fsid.val[1]);
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print_fh((struct file_handle *) &fid->handle);
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break;
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default:
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printf("\tUnknown info type=%d len=%d:\n",
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info->info_type, info->len);
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}
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}
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next_event:
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printf("---\n\n");
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}
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}
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int main(int argc, char **argv)
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{
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int fd;
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char buffer[BUFSIZ];
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if (argc < 2) {
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printf("Missing path argument\n");
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return 1;
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}
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fd = fanotify_init(FAN_CLASS_NOTIF|FAN_REPORT_FID, O_RDONLY);
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if (fd < 0)
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errx(1, "fanotify_init");
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if (fanotify_mark(fd, FAN_MARK_ADD|FAN_MARK_FILESYSTEM,
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FAN_FS_ERROR, AT_FDCWD, argv[1])) {
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errx(1, "fanotify_mark");
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}
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while (1) {
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int n = read(fd, buffer, BUFSIZ);
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if (n < 0)
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errx(1, "read");
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handle_notifications(buffer, n);
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}
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return 0;
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}

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