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samples: Add fs error monitoring example

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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>
This commit is contained in:
Gabriel Krisman Bertazi 2021-10-25 16:27:45 -03:00 committed by Jan Kara
parent 9a089b21f7
commit 5451093081
4 changed files with 157 additions and 0 deletions
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9
samples/Kconfig
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@ -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

1
samples/Makefile
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@ -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/

5
samples/fanotify/Makefile Normal file
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@ -0,0 +1,5 @@
# SPDX-License-Identifier: GPL-2.0-only
userprogs-always-y += fs-monitor
userccflags += -I usr/include -Wall

142
samples/fanotify/fs-monitor.c Normal file
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@ -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;
}