On Sun, Mar 28, 2021 at 6:56 PM Amir Goldstein <amir73il@xxxxxxxxx> wrote: > > Add a high level hook fsnotify_path_create() which is called from > syscall context where mount context is available, so that FAN_CREATE > event can be added to a mount mark mask. > > This high level hook is called in addition to fsnotify_create(), > fsnotify_mkdir() and fsnotify_link() hooks in vfs helpers where the mount > context is not available. > > In the context where fsnotify_path_create() will be called, a dentry flag > flag is set on the new dentry the suppress the FS_CREATE event in the vfs > level hooks. > > This functionality was requested by Christian Brauner to replace > recursive inotify watches for detecting when some path was created under > an idmapped mount without having to monitor FAN_CREATE events in the > entire filesystem. > > In combination with more changes to allow unprivileged fanotify listener > to watch an idmapped mount, this functionality would be usable also by > nested container managers. > > Link: https://lore.kernel.org/linux-fsdevel/20210318143140.jxycfn3fpqntq34z@wittgenstein/ > Cc: Christian Brauner <christian.brauner@xxxxxxxxxx> > Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx> > --- > > Jan, > > After trying several different approaches, I finally realized that > making FAN_CREATE available for mount marks is not that hard and it could > be very useful IMO. > > Adding support for other "inode events" with mount mark, such as > FAN_ATTRIB, FAN_DELETE, FAN_MOVE may also be possible, but adding support > for FAN_CREATE was really easy due to the fact that all call sites are > already surrounded by filename_creat()/done_path_create() calls. > FWIW, adding support for FAN_DELETE and FAN_MOVE_SELF was not so hard. The move event at least will also be needed for the use case where watching when a negative path is instantiated. https://github.com/amir73il/linux/commits/fsnotify_path_hooks Thanks, Amir.
