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Date:   Sat, 22 May 2021 19:25:05 -0400
From:   "Theodore Y. Ts'o" <tytso@mit.edu>
To:     Gabriel Krisman Bertazi <krisman@collabora.com>
Cc:     amir73il@gmail.com, kernel@collabora.com,
        "Darrick J . Wong" <djwong@kernel.org>,
        Dave Chinner <david@fromorbit.com>, jack@suse.com,
        dhowells@redhat.com, khazhy@google.com,
        linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org
Subject: Re: [PATCH 00/11] File system wide monitoring
Message-ID: <YKmS0KyZ6RoCw4We@mit.edu>
References: <20210521024134.1032503-1-krisman@collabora.com>
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Hi Gabriel,

Quick question; what userspace program are you using to test this
feature?  Do you have a custom testing program you are using?  If so,
could share it?

Many thanks!!

						- Ted

On Thu, May 20, 2021 at 10:41:23PM -0400, Gabriel Krisman Bertazi wrote:
> Hi,
> 
> This series follow up on my previous proposal [1] to support file system
> wide monitoring.  As suggested by Amir, this proposal drops the ring
> buffer in favor of a single slot associated with each mark.  This
> simplifies a bit the implementation, as you can see in the code.
> 
> As a reminder, This proposal is limited to an interface for
> administrators to monitor the health of a file system, instead of a
> generic inteface for file errors.  Therefore, this doesn't solve the
> problem of writeback errors or the need to watch a specific subtree.
> 
> In comparison to the previous RFC, this implementation also drops the
> per-fs data and location, and leave those as future extensions.
> 
> * Implementation
> 
> The feature is implemented on top of fanotify, as a new type of fanotify
> mark, FAN_ERROR, which a file system monitoring tool can register to
> receive error notifications.  When an error occurs a new notification is
> generated, in addition followed by this info field:
> 
>  - FS generic data: A file system agnostic structure that has a generic
>  error code and identifies the filesystem.  Basically, it let's
>  userspace know something happened on a monitored filesystem.  Since
>  only the first error is recorded since the last read, this also
>  includes a counter of errors that happened since the last read.
> 
> * Testing
> 
> This was tested by watching notifications flowing from an intentionally
> corrupted filesystem in different places.  In addition, other events
> were watched in an attempt to detect regressions.
> 
> Is there a specific testsuite for fanotify I should be running?
> 
> * Patches
> 
> This patchset is divided as follows: Patch 1 through 5 are refactoring
> to fsnotify/fanotify in preparation for FS_ERROR/FAN_ERROR; patch 6 and
> 7 implement the FS_ERROR API for filesystems to report error; patch 8
> add support for FAN_ERROR in fanotify; Patch 9 is an example
> implementation for ext4; patch 10 and 11 provide a sample userspace code
> and documentation.
> 
> I also pushed the full series to:
> 
>   https://gitlab.collabora.com/krisman/linux -b fanotify-notifications-single-slot
> 
> [1] https://lwn.net/Articles/854545/
> 
> Cc: Darrick J. Wong <djwong@kernel.org>
> Cc: Theodore Ts'o <tytso@mit.edu>
> Cc: Dave Chinner <david@fromorbit.com>
> Cc: jack@suse.com
> To: amir73il@gmail.com
> Cc: dhowells@redhat.com
> Cc: khazhy@google.com
> Cc: linux-fsdevel@vger.kernel.org
> Cc: linux-ext4@vger.kernel.org
> 
> Gabriel Krisman Bertazi (11):
>   fanotify: Fold event size calculation to its own function
>   fanotify: Split fsid check from other fid mode checks
>   fanotify: Simplify directory sanity check in DFID_NAME mode
>   fanotify: Expose fanotify_mark
>   inotify: Don't force FS_IN_IGNORED
>   fsnotify: Support FS_ERROR event type
>   fsnotify: Introduce helpers to send error_events
>   fanotify: Introduce FAN_ERROR event
>   ext4: Send notifications on error
>   samples: Add fs error monitoring example
>   Documentation: Document the FAN_ERROR event
> 
>  .../admin-guide/filesystem-monitoring.rst     |  52 +++++
>  Documentation/admin-guide/index.rst           |   1 +
>  fs/ext4/super.c                               |   8 +
>  fs/notify/fanotify/fanotify.c                 |  80 ++++++-
>  fs/notify/fanotify/fanotify.h                 |  38 +++-
>  fs/notify/fanotify/fanotify_user.c            | 213 ++++++++++++++----
>  fs/notify/inotify/inotify_user.c              |   6 +-
>  include/linux/fanotify.h                      |   6 +-
>  include/linux/fsnotify.h                      |  13 ++
>  include/linux/fsnotify_backend.h              |  15 +-
>  include/uapi/linux/fanotify.h                 |  10 +
>  samples/Kconfig                               |   8 +
>  samples/Makefile                              |   1 +
>  samples/fanotify/Makefile                     |   3 +
>  samples/fanotify/fs-monitor.c                 |  91 ++++++++
>  15 files changed, 485 insertions(+), 60 deletions(-)
>  create mode 100644 Documentation/admin-guide/filesystem-monitoring.rst
>  create mode 100644 samples/fanotify/Makefile
>  create mode 100644 samples/fanotify/fs-monitor.c
> 
> -- 
> 2.31.0
>