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    SubjectRe: [patch] stop inotify from sending random DELETE_SELF event under load
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    On Tue, 2005-09-20 at 04:31 +0100, Al Viro wrote:
    > On Mon, Sep 19, 2005 at 06:37:43PM -0700, Linus Torvalds wrote:
    > >
    > >
    > > On Mon, 19 Sep 2005, John McCutchan wrote:
    > > >
    > > > Below is a patch that fixes the random DELETE_SELF events when the
    > > > system is under load. The problem is that the DELETE_SELF event is sent
    > > > from dentry_iput, which is called in two code paths,
    > > >
    > > > 1) When a dentry is being deleted
    > > > 2) When the dcache is being pruned.
    > >
    > > No no.
    > >
    > > The problem is that you put the "fsnotify_inoderemove(inode);" in the
    > > wrong place, and I and Al never noticed.
    > >
    > > iput() doesn't have anything to do with delete at all, and adding a flag
    > > to it would be wrong. The inode may stay around _after_ the unlink() for
    > > as long as it has users (or much longer, if you have hardlinks ;).
    > >
    > > You should probably move the "fsnotify_inoderemove(inode);" call into
    > > generic_delete_inode() instead, just after "security_inode_delete()". No
    > > new flags, just a new place.
    > >
    > > (Oh, I think you need to add it to "hugetlbfs_delete_inode()" too).
    > >
    > > There's still a potential problem there: some network filesystems seem to
    > > use "generic_delete_inode()" as their "drop_inode" thing. Which may mean
    > > that you get spurious delete messages when the reference is dropped. I
    > > don't see how to avoid that, though - we fundamentally don't _know_ when
    > > the inode actually gets deleted.
    > >
    > > Al, do you have any comments? Anything stupid I missed?
    >
    > One fundamentally stupid thing is exposing to userland events that
    > are none of its fscking business. Link removal - sure. Last link
    > removal - perhaps, but that's not obvious; in any case it should be
    > tied to notification of link removal. But inode getting freed or
    > last dentry going away is none of the userland concern.

    I just thought I should clarify exactly when we want to send the
    DELETE_SELF event to user space:

    A path which points to inode X has been deleted.

    --
    John McCutchan <ttb@tentacle.dhs.org>
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