Hi, This attempts to get the ball rolling again for the FAN_FS_ERROR. This version is slightly different from the previous approaches, since it uses mempool for memory allocation, as suggested by Jan. It has the advantage of simplifying a lot the enqueue/dequeue, which is now much more similar to other event types, but it also means the guarantee that an error event will be available is diminished. The way we propagate superblock errors also changed. Now we use FILEID_ROOT internally, and mangle it prior to copy_to_user. I am no longer sure how to guarantee that at least one mempoll slot will be available for each filesystem. Since we are now tying the poll to the entire group, a stream of errors in a single file system might prevent others from emitting an error. The possibility of this is reduced since we merge errors to the same filesystem, but it is still possible that they occur during the small window where the event is dequeued and before it is freed, in which case another filesystem might not be able to obtain a slot. I'm also creating a poll of 32 entries initially to avoid spending too much memory. This means that only 32 filesystems can be watched per group with the FAN_FS_ERROR mark, before fanotify_mark starts returning ENOMEM. 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 Amir Goldstein (3): fsnotify: pass data_type to fsnotify_name() fsnotify: pass dentry instead of inode data fsnotify: clarify contract for create event hooks Gabriel Krisman Bertazi (25): 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 inotify: Don't force FS_IN_IGNORED fsnotify: Add helper to detect overflow_event fsnotify: Add wrapper around fsnotify_add_event fsnotify: Retrieve super block from the data field fsnotify: Pass group argument to free_event fanotify: Support null inode event in fanotify_dfid_inode fanotify: Allow file handle encoding for unhashed events fanotify: Encode empty file handle when no inode is provided fanotify: Require fid_mode for any non-fd event fsnotify: Support FS_ERROR event type fanotify: Reserve UAPI bits for FAN_FS_ERROR fanotify: Pre-allocate pool of error events fanotify: Limit number of marks with FAN_FS_ERROR per group fanotify: Support enqueueing of error events fanotify: Support merging of error events fanotify: Report FID entry even for zero-length file_handle fanotify: Report fid info for file related file system errors fanotify: Emit generic error info for error event fanotify: Allow users to request FAN_FS_ERROR events ext4: Send notifications on error samples: Add fs error monitoring example docs: Document the FAN_FS_ERROR event .../admin-guide/filesystem-monitoring.rst | 76 ++++++++ Documentation/admin-guide/index.rst | 1 + fs/ext4/super.c | 8 + fs/notify/fanotify/fanotify.c | 122 +++++++++++- fs/notify/fanotify/fanotify.h | 31 +++- fs/notify/fanotify/fanotify_user.c | 173 ++++++++++++++---- fs/notify/fsnotify.c | 7 +- fs/notify/group.c | 2 +- fs/notify/inotify/inotify_fsnotify.c | 5 +- fs/notify/inotify/inotify_user.c | 6 +- fs/notify/notification.c | 14 +- include/linux/fanotify.h | 9 +- include/linux/fsnotify.h | 58 ++++-- include/linux/fsnotify_backend.h | 96 +++++++++- include/uapi/linux/fanotify.h | 8 + kernel/audit_fsnotify.c | 3 +- kernel/audit_watch.c | 3 +- samples/Kconfig | 9 + samples/Makefile | 1 + samples/fanotify/Makefile | 5 + samples/fanotify/fs-monitor.c | 142 ++++++++++++++ 21 files changed, 685 insertions(+), 94 deletions(-) create mode 100644 Documentation/admin-guide/filesystem-monitoring.rst create mode 100644 samples/fanotify/Makefile create mode 100644 samples/fanotify/fs-monitor.c -- 2.33.0
