Hi, This is the 6th version of the FAN_FS_ERROR patches. This applies the feedback from last version (thanks Amir, Jan). There are important changes in this version. some of which brings us back to previous versions of this series. I did my best to avoid problems that were mentioned during earlier revisions, and I think I covered everything. But I apologize if this requires reviewers to repeat some comments. First of all, despite initializing the error event from inside the insert callback and abusing the merge logic for err_count update, this version reverts to a simple insertion code, and configures the event before sending it to be queued by fsnotify. This makes the submission code less trivial, but addresses the potential problem of encoding the FH while holding the group->notification_lock. This version also drops the slot replacement code when dequeueing, and reverts back to the copy-to-stack mechanism. This simplifies the code a lot. The way we report superblock errors also changed. Now, the handle is omitted and we return the handle_bytes as 0. Finally, we no longer play games with predicting the file handle size beforehand. Now, the code just allocates space for the largest handle possible, and assume that is enough. On another note, this also restores the mark reference owned by the error event while it is queued. As Amir explained, this is required to prevent the mark from going away while the event is queued. This was tested with LTP for regressions and also using the sample code on the last patch, with a corrupted image. I wrote a new ltp test for this feature which is being reviewed and is available at: https://gitlab.collabora.com/krisman/ltp -b fan-fs-error 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 is being reviewed at the list. I also pushed this full series to: https://gitlab.collabora.com/krisman/linux -b fanotify-notifications-single-slot Thank you Original cover letter --------------------- 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/ [2] https://lwn.net/Articles/856916/ Cc: Darrick J. Wong <djwong@xxxxxxxxxx> Cc: Theodore Ts'o <tytso@xxxxxxx> Cc: Dave Chinner <david@xxxxxxxxxxxxx> Cc: jack@xxxxxxxx To: amir73il@xxxxxxxxx Cc: dhowells@xxxxxxxxxx Cc: khazhy@xxxxxxxxxx Cc: linux-fsdevel@xxxxxxxxxxxxxxx Cc: linux-ext4@xxxxxxxxxxxxxxx Cc: linux-api@xxxxxxxxxxxxxxx Cc: linux-api@xxxxxxxxxxxxxxx Gabriel Krisman Bertazi (21): 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 flag 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: Allow events reported with an empty inode fsnotify: Support FS_ERROR event type fanotify: Allow file handle encoding for unhashed events fanotify: Encode invalid file handle when no inode is provided fanotify: Require fid_mode for any non-fd event fanotify: Reserve UAPI bits for FAN_FS_ERROR fanotify: Preallocate per superblock mark error event fanotify: Handle FAN_FS_ERROR events fanotify: Report fid info for file related file system errors fanotify: Emit generic error info type for 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 | 139 +++++++++- fs/notify/fanotify/fanotify.h | 69 ++++- fs/notify/fanotify/fanotify_user.c | 256 ++++++++++++++---- fs/notify/fsnotify.c | 19 +- fs/notify/inotify/inotify_fsnotify.c | 2 +- fs/notify/inotify/inotify_user.c | 6 +- fs/notify/notification.c | 12 +- include/linux/fanotify.h | 9 +- include/linux/fsnotify.h | 13 + include/linux/fsnotify_backend.h | 64 ++++- include/uapi/linux/fanotify.h | 8 + samples/Kconfig | 9 + samples/Makefile | 1 + samples/fanotify/Makefile | 5 + samples/fanotify/fs-monitor.c | 138 ++++++++++ 18 files changed, 740 insertions(+), 89 deletions(-) create mode 100644 Documentation/admin-guide/filesystem-monitoring.rst create mode 100644 samples/fanotify/Makefile create mode 100644 samples/fanotify/fs-monitor.c -- 2.32.0
