From: Jan Kara <jack@suse.cz>
To: Gabriel Krisman Bertazi <krisman@collabora.com>
Cc: amir73il@gmail.com, jack@suse.com, linux-api@vger.kernel.org,
linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org,
khazhy@google.com, dhowells@redhat.com, david@fromorbit.com,
tytso@mit.edu, djwong@kernel.org, repnop@google.com,
kernel@collabora.com
Subject: Re: [PATCH v6 21/21] docs: Document the FAN_FS_ERROR event
Date: Mon, 16 Aug 2021 18:40:43 +0200 [thread overview]
Message-ID: <20210816164043.GK30215@quack2.suse.cz> (raw)
In-Reply-To: <20210812214010.3197279-22-krisman@collabora.com>
On Thu 12-08-21 17:40:10, Gabriel Krisman Bertazi wrote:
> Document the FAN_FS_ERROR event for user administrators and user space
> developers.
>
> Reviewed-by: Amir Goldstein <amir73il@gmail.com>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
<snip>
> diff --git a/Documentation/admin-guide/filesystem-monitoring.rst b/Documentation/admin-guide/filesystem-monitoring.rst
> new file mode 100644
> index 000000000000..b03093567a93
> --- /dev/null
> +++ b/Documentation/admin-guide/filesystem-monitoring.rst
> @@ -0,0 +1,70 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +====================================
> +File system Monitoring with fanotify
> +====================================
> +
> +File system Error Reporting
> +===========================
> +
> +fanotify supports the FAN_FS_ERROR mark for file system-wide error
^ Capital 'F'. ^^^ I'd rather write "event type".
> +reporting. It is meant to be used by file system health monitoring
> +daemons who listen on that interface and take actions (notify sysadmin,
^^^ which ^^^^^^^^^^^^^^^^^ for these events
> +start recovery) when a file system problem is detected by the kernel.
> +
> +By design, A FAN_FS_ERROR notification exposes sufficient information for a
> +monitoring tool to know a problem in the file system has happened. It
> +doesn't necessarily provide a user space application with semantics to
> +verify an IO operation was successfully executed. That is outside of
> +scope of this feature. Instead, it is only meant as a framework for
> +early file system problem detection and reporting recovery tools.
> +
> +When a file system operation fails, it is common for dozens of kernel
> +errors to cascade after the initial failure, hiding the original failure
> +log, which is usually the most useful debug data to troubleshoot the
> +problem. For this reason, FAN_FS_ERROR only reports the first error that
> +occurred since the last notification, and it simply counts addition
^^^ additional
> +errors. This ensures that the most important piece of error information
> +is never lost.
> +
> +FAN_FS_ERROR requires the fanotify group to be setup with the
> +FAN_REPORT_FID flag.
> +
> +At the time of this writing, the only file system that emits FAN_FS_ERROR
> +notifications is Ext4.
> +
> +A user space example code is provided at ``samples/fanotify/fs-monitor.c``.
> +
> +A FAN_FS_ERROR Notification has the following format::
> +
> + [ Notification Metadata (Mandatory) ]
> + [ Generic Error Record (Mandatory) ]
> + [ FID record (Mandatory) ]
> +
> +Generic error record
> +--------------------
> +
> +The generic error record provides enough information for a file system
> +agnostic tool to learn about a problem in the file system, without
> +providing any additional details about the problem. This record is
> +identified by ``struct fanotify_event_info_header.info_type`` being set
> +to FAN_EVENT_INFO_TYPE_ERROR.
> +
> + struct fanotify_event_info_error {
> + struct fanotify_event_info_header hdr;
> + __s32 error;
> + __u32 error_count;
> + };
> +
> +The `error` field identifies the type of error. `error_count` count
> +tracks the number of errors that occurred and were suppressed to
> +preserve the original error, since the last notification.
So is 'error' expected to be errno? Or is that some fs-specific error
identifier? Will it be positive (i.e. real errno) or negative (as errno is
usually passed in the kernel)? I think it should be specified here.
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
prev parent reply other threads:[~2021-08-16 16:40 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-12 21:39 [PATCH v6 00/21] File system wide monitoring Gabriel Krisman Bertazi
2021-08-12 21:39 ` [PATCH v6 01/21] fsnotify: Don't insert unmergeable events in hashtable Gabriel Krisman Bertazi
2021-08-12 21:39 ` [PATCH v6 02/21] fanotify: Fold event size calculation to its own function Gabriel Krisman Bertazi
2021-08-12 21:39 ` [PATCH v6 03/21] fanotify: Split fsid check from other fid mode checks Gabriel Krisman Bertazi
2021-08-12 21:39 ` [PATCH v6 04/21] fsnotify: Reserve mark flag bits for backends Gabriel Krisman Bertazi
2021-08-13 7:28 ` Amir Goldstein
2021-08-16 13:15 ` Jan Kara
2021-08-23 14:36 ` Gabriel Krisman Bertazi
2021-08-12 21:39 ` [PATCH v6 05/21] fanotify: Split superblock marks out to a new cache Gabriel Krisman Bertazi
2021-08-16 13:18 ` Jan Kara
2021-08-12 21:39 ` [PATCH v6 06/21] inotify: Don't force FS_IN_IGNORED Gabriel Krisman Bertazi
2021-08-12 21:39 ` [PATCH v6 07/21] fsnotify: Add helper to detect overflow_event Gabriel Krisman Bertazi
2021-08-12 21:39 ` [PATCH v6 08/21] fsnotify: Add wrapper around fsnotify_add_event Gabriel Krisman Bertazi
2021-08-12 21:39 ` [PATCH v6 09/21] fsnotify: Allow events reported with an empty inode Gabriel Krisman Bertazi
2021-08-13 7:58 ` Amir Goldstein
2021-08-25 18:40 ` Gabriel Krisman Bertazi
2021-08-25 19:45 ` Amir Goldstein
2021-08-25 21:50 ` Gabriel Krisman Bertazi
2021-08-26 10:44 ` Amir Goldstein
2021-08-27 2:26 ` Paul Moore
2021-08-12 21:39 ` [PATCH v6 10/21] fsnotify: Support FS_ERROR event type Gabriel Krisman Bertazi
2021-08-13 7:48 ` Amir Goldstein
2021-08-16 13:23 ` Jan Kara
2021-08-12 21:40 ` [PATCH v6 11/21] fanotify: Allow file handle encoding for unhashed events Gabriel Krisman Bertazi
2021-08-13 7:59 ` Amir Goldstein
2021-08-12 21:40 ` [PATCH v6 12/21] fanotify: Encode invalid file handle when no inode is provided Gabriel Krisman Bertazi
2021-08-13 8:27 ` Amir Goldstein
2021-08-16 14:06 ` Jan Kara
2021-08-16 15:54 ` Amir Goldstein
2021-08-16 16:11 ` Jan Kara
2021-08-12 21:40 ` [PATCH v6 13/21] fanotify: Require fid_mode for any non-fd event Gabriel Krisman Bertazi
2021-08-13 8:28 ` Amir Goldstein
2021-08-12 21:40 ` [PATCH v6 14/21] fanotify: Reserve UAPI bits for FAN_FS_ERROR Gabriel Krisman Bertazi
2021-08-13 8:29 ` Amir Goldstein
2021-08-12 21:40 ` [PATCH v6 15/21] fanotify: Preallocate per superblock mark error event Gabriel Krisman Bertazi
2021-08-13 8:40 ` Amir Goldstein
2021-08-16 15:57 ` Jan Kara
2021-08-27 18:18 ` Gabriel Krisman Bertazi
2021-09-02 21:24 ` Gabriel Krisman Bertazi
2021-09-03 4:16 ` Amir Goldstein
2021-09-15 10:31 ` Jan Kara
2021-08-12 21:40 ` [PATCH v6 16/21] fanotify: Handle FAN_FS_ERROR events Gabriel Krisman Bertazi
2021-08-13 9:35 ` Amir Goldstein
2021-08-12 21:40 ` [PATCH v6 17/21] fanotify: Report fid info for file related file system errors Gabriel Krisman Bertazi
2021-08-13 9:00 ` Amir Goldstein
2021-08-13 9:03 ` Amir Goldstein
2021-08-16 16:18 ` Jan Kara
2021-08-12 21:40 ` [PATCH v6 18/21] fanotify: Emit generic error info type for error event Gabriel Krisman Bertazi
2021-08-13 8:47 ` Amir Goldstein
2021-08-16 16:23 ` Jan Kara
2021-08-16 21:41 ` Darrick J. Wong
2021-08-17 9:05 ` Jan Kara
2021-08-17 10:08 ` Amir Goldstein
2021-08-18 0:16 ` Darrick J. Wong
2021-08-18 3:24 ` Amir Goldstein
2021-08-18 9:58 ` Jan Kara
2021-08-19 3:58 ` Darrick J. Wong
2021-08-18 0:10 ` Darrick J. Wong
2021-08-24 16:53 ` Gabriel Krisman Bertazi
2021-08-25 4:09 ` Darrick J. Wong
2021-08-12 21:40 ` [PATCH v6 19/21] ext4: Send notifications on error Gabriel Krisman Bertazi
2021-08-16 16:26 ` Jan Kara
2021-08-12 21:40 ` [PATCH v6 20/21] samples: Add fs error monitoring example Gabriel Krisman Bertazi
2021-08-18 13:02 ` Jan Kara
2021-08-23 14:49 ` Gabriel Krisman Bertazi
2021-08-12 21:40 ` [PATCH v6 21/21] docs: Document the FAN_FS_ERROR event Gabriel Krisman Bertazi
2021-08-16 16:40 ` Jan Kara [this message]
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