On Fri, Sep 17, 2021 at 3:05 PM Sheng Yong <shengyong2021@xxxxxxxxx> wrote: > > Hi, Honza, > > On 2021/9/17 16:49, Jan Kara wrote: > > On Thu 16-09-21 22:06:49, Sheng Yong wrote: > >> This patch adds a new ioctl cmd INOTIFY_IOC_SUPRESS to stop queueing > >> events temporarily. A second ioctl could resume queueing events again. > >> With it enabled, we could easily suppress events instead of updating > >> or removing watches, especially if we have losts of watches referring > >> to one inotify instance, for example watching a directory recursively. > >> > >> Signed-off-by: Sheng Yong <shengyong2021@xxxxxxxxx> > > > > Thanks for the patch! This ioctl on its own is equivalent to shutting down > > the notification group so I don't think it is really useful on its own. > > Thanks for your reply. > Yes, this ioctl reuses the stop-queueing-events procedure of shutdown. > > > If you add ioctl to resume queueing, it makes some sense but can you > > ellaborate a bit more why you need to stop receiving events temporarily? > > The usecase is that we use rsync+inotify to backup files. Let's say there are > two tasks: 1) "real-time" task reads events and syncs the file; 2) periodic > task syncs all files recursively in the source directory. > > If the queue get overflowed and new events are discarded, we have to start a > recursive sync. But recursive sync takes a very long time to scan, compare and > transmit data, we prefer a periodic task to do that, so that we could ignore > overflow events. > > When the periodic task is working, I think the "real-time" task should stop > reading and handling new events temporarily to avoid duplicated IO in both > sides. I think stop queueing new events is the easiest way to do that. > Having some experience with similar applications, I have highs doubts about this models. Anyway, you should be able to achieve better results with fanotify by adding an FAN_MARK_FILESYSTEM mark with ignored mask or by using a FAN_MARK_FILESYSTEM instead of recursive inotify to begin with. See: https://github.com/inotify-tools/inotify-tools/pull/134 Thanks, Amir.
