2021-07-20 16:14:26

by Gabriel Krisman Bertazi

[permalink] [raw]
Subject: [PATCH v4 00/16] File system wide monitoring


This is the fourth version of the FAN_FS_ERROR patches. This applies
the feedback from last version (thanks Amir, Jan), in particular how we
report file handlers for errors not related to a file. Now it is
reported as an invalid, empty fh.

This was tested with LTP for regressions, and also using the sample on
the last patch, with a corrupted image. I can publish the bad image
upon request.

In addition, I wrote a man-page that can be pulled from:

https://gitlab.collabora.com/krisman/man-pages.git -b fan-fs-error

And I'm sending it shortly for review.

I'm automating my tests in LTP next and will be sharing shortly.

I also pushed the full series to:

https://gitlab.collabora.com/krisman/linux -b fanotify-notifications-single-slot

Thank you

Original cover letter

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/
[2] https://lwn.net/Articles/856916/

Cc: Darrick J. Wong <[email protected]>
Cc: Theodore Ts'o <[email protected]>
Cc: Dave Chinner <[email protected]>
Cc: [email protected]
To: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]

Amir Goldstein (1):
fsnotify: pass arguments of fsnotify() in struct fsnotify_event_info

Gabriel Krisman Bertazi (15):
fsnotify: Don't insert unmergeable events in hashtable
fanotify: Fold event size calculation to its own function
fanotify: Split fsid check from other fid mode checks
fsnotify: Reserve mark bits for backends
fanotify: Split superblock marks out to a new cache
inotify: Don't force FS_IN_IGNORED
fsnotify: Add helper to detect overflow_event
fsnotify: Add wrapper around fsnotify_add_event
fsnotify: Support passing argument to insert callback on add_event
fsnotify: Support FS_ERROR event type
fsnotify: Introduce helpers to send error_events
fanotify: Introduce FAN_FS_ERROR event
ext4: Send notifications on error
samples: Add fs error monitoring example
docs: Document the FAN_FS_ERROR event

.../admin-guide/filesystem-monitoring.rst | 70 +++++
Documentation/admin-guide/index.rst | 1 +
fs/ext4/super.c | 8 +
fs/notify/fanotify/fanotify.c | 217 ++++++++++----
fs/notify/fanotify/fanotify.h | 79 ++++-
fs/notify/fanotify/fanotify_user.c | 278 +++++++++++++++---
fs/notify/fsnotify.c | 75 ++---
fs/notify/inotify/inotify_fsnotify.c | 2 +-
fs/notify/inotify/inotify_user.c | 6 +-
fs/notify/notification.c | 16 +-
include/linux/fanotify.h | 8 +-
include/linux/fsnotify.h | 13 +
include/linux/fsnotify_backend.h | 140 +++++++--
include/uapi/linux/fanotify.h | 8 +
samples/Kconfig | 9 +
samples/Makefile | 1 +
samples/fanotify/Makefile | 5 +
samples/fanotify/fs-monitor.c | 134 +++++++++
18 files changed, 897 insertions(+), 173 deletions(-)
create mode 100644 Documentation/admin-guide/filesystem-monitoring.rst
create mode 100644 samples/fanotify/Makefile
create mode 100644 samples/fanotify/fs-monitor.c