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SubjectRe: [PATCH 1/5] fsnotify/vfsmount: add fsnotify fields to struct vfsmount
Date
On Friday 04 December 2009 16:39:25 Christoph Hellwig wrote:
> What's the rationale for adding them?

The idea is to provide a mechanism to watch for "all events", but in a
namespace aware way: for that, a process registers interest in all mount
points it can reach. With the previous hack, a global "I want it all" flag,
per-namespace listeners were not possible.

Root can use bind mounts onto themselves (e.g., mount --bind /foo/bar
/foo/bar) to watch arbitrary directories with the per-mount-point mechanism.
Mount as user will open up additional use cases.

It would be nice to be able to register interest in all events below a
directory which is not a mount point, too. The problem with that is that the
number of cached inodes below a given directory could be huge -- and we would
have to visit them all atomically in order to "mark" them, which is not
feasible. The per-mount-point mechanism will eventually give us *almost* the
same, and so I believe it's good enough.

Thanks,
Andreas


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