On Tue, Apr 28, 2015 at 03:56:53PM +0200, Jan Kara wrote: > On Mon 27-04-15 17:37:11, Greg KH wrote: > > On Mon, Apr 27, 2015 at 05:08:27PM +0200, Beata Michalska wrote: > > > On 04/27/2015 04:24 PM, Greg KH wrote: > > > > On Mon, Apr 27, 2015 at 01:51:41PM +0200, Beata Michalska wrote: > > > >> Introduce configurable generic interface for file > > > >> system-wide event notifications, to provide file > > > >> systems with a common way of reporting any potential > > > >> issues as they emerge. > > > >> > > > >> The notifications are to be issued through generic > > > >> netlink interface by newly introduced multicast group. > > > >> > > > >> Threshold notifications have been included, allowing > > > >> triggering an event whenever the amount of free space drops > > > >> below a certain level - or levels to be more precise as two > > > >> of them are being supported: the lower and the upper range. > > > >> The notifications work both ways: once the threshold level > > > >> has been reached, an event shall be generated whenever > > > >> the number of available blocks goes up again re-activating > > > >> the threshold. > > > >> > > > >> The interface has been exposed through a vfs. Once mounted, > > > >> it serves as an entry point for the set-up where one can > > > >> register for particular file system events. > > > >> > > > >> Signed-off-by: Beata Michalska <b.michalska@xxxxxxxxxxx> > > > >> --- > > > >> Documentation/filesystems/events.txt | 231 ++++++++++ > > > >> fs/Makefile | 1 + > > > >> fs/events/Makefile | 6 + > > > >> fs/events/fs_event.c | 770 ++++++++++++++++++++++++++++++++++ > > > >> fs/events/fs_event.h | 25 ++ > > > >> fs/events/fs_event_netlink.c | 99 +++++ > > > >> fs/namespace.c | 1 + > > > >> include/linux/fs.h | 6 +- > > > >> include/linux/fs_event.h | 58 +++ > > > >> include/uapi/linux/fs_event.h | 54 +++ > > > >> include/uapi/linux/genetlink.h | 1 + > > > >> net/netlink/genetlink.c | 7 +- > > > >> 12 files changed, 1257 insertions(+), 2 deletions(-) > > > >> create mode 100644 Documentation/filesystems/events.txt > > > >> create mode 100644 fs/events/Makefile > > > >> create mode 100644 fs/events/fs_event.c > > > >> create mode 100644 fs/events/fs_event.h > > > >> create mode 100644 fs/events/fs_event_netlink.c > > > >> create mode 100644 include/linux/fs_event.h > > > >> create mode 100644 include/uapi/linux/fs_event.h > > > > > > > > Any reason why you just don't do uevents for the block devices today, > > > > and not create a new type of netlink message and userspace tool required > > > > to read these? > > > > > > The idea here is to have support for filesystems with no backing device as well. > > > Parsing the message with libnl is really simple and requires few lines of code > > > (sample application has been presented in the initial version of this RFC) > > > > I'm not saying it's not "simple" to parse, just that now you are doing > > something that requires a different tool. If you have a block device, > > you should be able to emit uevents for it, you don't need a backing > > device, we handle virtual filesystems in /sys/block/ just fine :) > > > > People already have tools that listen to libudev for system monitoring > > and management, why require them to hook up to yet-another-library? And > > what is going to provide the ability for multiple userspace tools to > > listen to these netlink messages in case you have more than one program > > that wants to watch for these things (i.e. multiple desktop filesystem > > monitoring tools, system-health checkers, etc.)? > As much as I understand your concerns I'm not convinced uevent interface > is a good fit. There are filesystems that don't have underlying block > device - think of e.g. tmpfs or filesystems working directly on top of > flash devices. These still want to send notification to userspace (one of > primary motivation for this interfaces was so that tmpfs can notify about > something). And creating some fake nodes in /sys/block for tmpfs and > similar filesystems seems like doing more harm than good to me... If these are "fake" block devices, what's going to be present in the block major/minor fields of the netlink message? For some reason I thought it was a required field, and because of that, I thought we had a "real" filesystem somewhere to refer to, otherwise how would userspace know what filesystem was creating these events? What am I missing here? confused, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
