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    SubjectRe: fanotify - overall design before I start sending patches
    Eric Paris wrote:
    > On Fri, 2009-07-24 at 23:48 +0100, Jamie Lokier wrote:
    > > Eric Paris wrote:
    > > > It is a new notification system that has a limited set of events (open,
    > > > close, read, write) in which notification not only comes with metadata
    > > > the describes what happened it also comes with an open file descriptor
    > > > to the object in question. fanotify will also allow the listener to
    > > > make access decisions on open and read events. This allows the
    > > > implementation of hierarchical storage management systems or an access
    > > > file scanning or integrity checking.
    > >
    > > My first thought was to wonder, why not make it the same set of events
    > > that inotify and dnotify provide? That is: open, close, read, write,
    > > create, delete, rename, attribute change? In other words, I don't see
    > > a good reason for it to be a subset of events.
    > The two real reasons?
    > 1) These were the only 4 my original use case cared about.
    > 2) These are the only 4 where the notification hook has enough
    > information to open a fd in the context of the listener.
    > In the kernel most notification is done with either an inode or a dentry
    > as that is enough for inotify, dnotify, audit_watch and audit_tree.
    > Opening a file descriptor, and thus fanotify, requires a dentry and a
    > vfsmnt, which is much harder to come by in the kernel.
    > Maybe as future work I'll try to convince Al to allow me to have that
    > information in more places, but for today, those 4 are the only ones I
    > can probably slip past him...

    For the other events, maybe there is no need for a file descriptor

    -- Jamie

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