Hi, After the two previous RFCs this is an attempt to get the ball spinning again. The problem I'm trying to solve is providing an interface to monitor filesystem errors. This patchset includes an example implementation of ext4 error notification. This goes obviously on top of the watch_queue mechanism. Regarding the buffer overrun issue that would require fsinfo or another method to expose counters, I think they can be added at a later date with no change to what this patch series attempts to do, therefore I'm proposing we don't wait for fsinfo before getting this merged. I mostly tested this with the samples program I have published in the last patch. In addition I will be sharing a patchset shortly with proper documentation and some selftests for the feature. David, can you please reply to this patchset? What do you think about the watch_queue modifications I'm proposing? I really don't want to waste more time on this code if it doesn't fit the watch_queue API. Can I have some guidance in having this upstreamed? In addition, I'm carrying "watch_queue: Make watch_sizeof() check record size" on this patchset for now, but is it in anyone's tree going to Linus any time soon? I haven't found it. I also shared this patchset in a branch at: Repo: https://gitlab.collabora.com/krisman/linux.git -b notifications Previous RFC submissions can be found at: RFC: https://www.spinics.net/lists/linux-ext4/msg74596.html RFC v2: https://lore.kernel.org/linux-fsdevel/20201111215213.4152354-1-krisman@xxxxxxxxxxxxx/ Original cover letter: ====================== Google has been using an out-of-tree mechanism for error notification in Ext4 and we decided it is time to push for an upstream solution. This would surely fit on top of David's notification work. This patchset is an attempt to restart that discussion. It forward ports some code from David on top of Linus tree, adds features to watch_queue and implements ext4 support. The new notifications are designed after ext4 messages, so it exposes notifications types to fit that filesystem, but it doesn't change much to other filesystems, so it should be easily extensible. I'm aware of the discussion around fsinfo, but I'd like to ask if there are other missing pieces and what we could do to help that work go upstream. From a previous mailing list discussion, Linus complained about lack of users as a main reason for it to not be merged, so hey! :) In addition, I'd like to ask for feedback on the current implementation, specifically regarding the passing of extra unformatted information at the end of the notification and the ext4 support. The work, as shared on this patchset can be found at: https://gitlab.collabora.com/krisman/linux.git -b ext4-error-notifications And there is an example code at: https://gitlab.collabora.com/krisman/ext4-watcher I'm Cc'ing Khazhismel Kumykov, from Google, who can provide more information about their use case, if requested. David Howells (3): watch_queue: Make watch_sizeof() check record size security: Add hooks to rule on setting a watch for superblock vfs: Add superblock notifications Gabriel Krisman Bertazi (5): watch_queue: Support a text field at the end of the notification vfs: Include origin of the SB error notification fs: Add more superblock error subtypes ext4: Implement SB error notification through watch_sb samples: watch_queue: Add sample of SB notifications arch/x86/entry/syscalls/syscall_32.tbl | 1 + arch/x86/entry/syscalls/syscall_64.tbl | 1 + fs/Kconfig | 12 ++ fs/ext4/super.c | 31 +++-- fs/super.c | 127 +++++++++++++++++++++ include/linux/fs.h | 150 +++++++++++++++++++++++++ include/linux/lsm_hook_defs.h | 1 + include/linux/lsm_hooks.h | 4 + include/linux/security.h | 13 +++ include/linux/syscalls.h | 2 + include/linux/watch_queue.h | 21 +++- include/uapi/asm-generic/unistd.h | 4 +- include/uapi/linux/watch_queue.h | 54 ++++++++- kernel/sys_ni.c | 3 + kernel/watch_queue.c | 29 ++++- samples/watch_queue/Makefile | 2 +- samples/watch_queue/watch_sb.c | 114 +++++++++++++++++++ security/security.c | 6 + 18 files changed, 556 insertions(+), 19 deletions(-) create mode 100644 samples/watch_queue/watch_sb.c -- 2.29.2
