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Date: Fri, 21 May 2021 12:48:18 +0300
From: Amir Goldstein <amir73il@...il.com>
To: Gabriel Krisman Bertazi <krisman@...labora.com>
Cc: kernel@...labora.com, "Darrick J . Wong" <djwong@...nel.org>,
"Theodore Ts'o" <tytso@....edu>,
Dave Chinner <david@...morbit.com>, Jan Kara <jack@...e.com>,
David Howells <dhowells@...hat.com>,
Khazhismel Kumykov <khazhy@...gle.com>,
linux-fsdevel <linux-fsdevel@...r.kernel.org>,
Ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 10/11] samples: Add fs error monitoring example
On Fri, May 21, 2021 at 5:42 AM Gabriel Krisman Bertazi
<krisman@...labora.com> wrote:
>
> Introduce an example of a FAN_ERROR fanotify user to track filesystem
> errors.
>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com>
> ---
> samples/Kconfig | 8 +++
> samples/Makefile | 1 +
> samples/fanotify/Makefile | 3 ++
> samples/fanotify/fs-monitor.c | 91 +++++++++++++++++++++++++++++++++++
> 4 files changed, 103 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..e421556ec3e5 100644
> --- a/samples/Kconfig
> +++ b/samples/Kconfig
> @@ -120,6 +120,14 @@ 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_ERROR
> + fanotify mechanism to monitor filesystem errors.
> + 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..49d3e2a872e4
> --- /dev/null
> +++ b/samples/fanotify/fs-monitor.c
> @@ -0,0 +1,91 @@
> +// 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_ERROR
> +#define FAN_ERROR 0x00008000
> +#define FAN_EVENT_INFO_TYPE_ERROR 5
> +
> +struct fanotify_event_info_error {
> + struct fanotify_event_info_header hdr;
> + int error;
> + __kernel_fsid_t fsid;
> + unsigned long inode;
> + __u32 error_count;
> +};
> +#endif
> +
> +static void handle_notifications(char *buffer, int len)
> +{
> + struct fanotify_event_metadata *metadata;
> + struct fanotify_event_info_error *error;
> +
> + for (metadata = (struct fanotify_event_metadata *) buffer;
> + FAN_EVENT_OK(metadata, len); metadata = FAN_EVENT_NEXT(metadata, len)) {
> + if (!(metadata->mask == FAN_ERROR)) {
Nit: != FAN_ERROR
> + printf("unexpected FAN MARK: %llx\n", metadata->mask);
> + continue;
> + } else if (metadata->fd != FAN_NOFD) {
> + printf("Unexpected fd (!= FAN_NOFD)\n");
> + continue;
> + }
> +
> + printf("FAN_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) {
You meant != FAN_EVENT_INFO_TYPE_ERROR ?
> + printf("unknown record: %d\n", error->hdr.info_type);
> + continue;
> + }
> +
> + printf(" Generic Error Record: len=%d\n", error->hdr.len);
> + printf(" fsid: %llx\n", error->fsid);
> + printf(" error: %d\n", error->error);
> + printf(" inode: %lu\n", error->inode);
> + printf(" error_count: %d\n", error->error_count);
> + }
> +}
> +
> +int main(int argc, char **argv)
> +{
> + int fd;
> + char buffer[BUFSIZ];
BUFSIZ not defined?
> +
> + if (argc < 2) {
> + printf("Missing path argument\n");
> + return 1;
> + }
> +
> + fd = fanotify_init(FAN_CLASS_NOTIF, O_RDONLY);
> + if (fd < 0)
> + errx(1, "fanotify_init");
> +
> + if (fanotify_mark(fd, FAN_MARK_ADD|FAN_MARK_FILESYSTEM,
> + FAN_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;
> +}
> --
> 2.31.0
>
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