[lkml]   [2012]   [May]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: nfsd changes for 3.5
    On Thu, May 31, 2012 at 01:17:26PM -0700, Linus Torvalds wrote:
    > On Thu, May 31, 2012 at 1:01 PM, J. Bruce Fields <> wrote:
    > >
    > > Right.  By default it's 90 seconds before we'll give up on the client.
    > So a slightly buggy client can basically DoS the server by getting a
    > delegation and then crashing or something. Everybody else that tries
    > to read that directory (not that file) will be dead in the water.
    > Definitely not good.
    > > I hate that too, and originally tried to avoid it with something like:
    > >
    > >        retry:
    > >                acquire locks
    > >                lookup inode
    > >                ret = try_to_break_deleg(inode);
    > >                if (ret)
    > >                        drop locks
    > >                        really_break_deleg(inode);
    > >                        goto retry;
    > >                ... do the real work ...
    > >                drop locks
    > >
    > > I felt like I was making already complicated code logic like rename's
    > > even harder to follow.
    > I do think it's the only thing we can reasonably do.

    OK, I can give that another try. Al, does that sound like the more
    sensible choice to you?

    Uh, that means ditching some work in my public git tree. Which I
    haven't rebased in years. So, a stupid process question; would you
    rather I:

    - continue to be strict about rebasing and apply a bunch of
    - ditch it and start over?

    #1 looks like a mess to me, so I guess #2's my default. Probably nobody
    will notice but me.

    > I'd love to have
    > some kind of per-dentry lock for unlink/rename, but we don't.
    > Long-term, we really do need to do something about the directory
    > locking, though, because it's also a huge problem for readdir()
    > concurrency. Or at least it used to be (samba in particular). Making
    > it an rwsem might help readdir a tiny amount, but I suspect people
    > actually depend on the mutex in readdir right now.

    Al called this all "highly non-trivial":

    I don't know who'd have the cycles.


    > > And those operations don't really know the inode till they acquire the
    > > locks, so in pathological cases that could continue forever.
    > I suspect at some point you just have to say "screw it".
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    More majordomo info at
    Please read the FAQ at

     \ /
      Last update: 2012-05-31 23:21    [W:0.024 / U:62.648 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site