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    SubjectRe: dcache shrink list corruption?
    On Wed, Apr 30, 2014 at 07:33:38PM +0200, Miklos Szeredi wrote:
    > On Wed, Apr 30, 2014 at 6:03 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
    > > On Wed, Apr 30, 2014 at 05:49:58PM +0200, Miklos Szeredi wrote:
    > >> > FWIW, the first two are really straightforward expanding the function
    > >> > into its only callsite. The last needs more splitup. Not sure if the
    > >> > following is good enough, but it ought to be at least somewhat cleaner.
    > >> > Combined change is identical to the original, so it doesn't invalidate
    > >> > the testing so far...
    > >>
    > >> Hmm, patches look okay, but I'm wondering if we really need the morgue list and
    > >> the waiting. Why not just skip dentries that are presently being handled by
    > >> dentry_kill()?
    > >
    > > Who will be freeing them? If we do that from dentry_kill(), we are back to
    > > needing them removed from shrink list by something called by dput(). And
    > > if we do that from shrink_dentry_list(), we'd damn better wait for
    > > dentry_iput() et.al. to finish.
    >
    > We can do it from dput if the shrinker gets there first and from the
    > shrinker if dput manages to finish before. See the updated patch in
    > the previous mail.

    Er? The only patch I see is removal of RCU from shrink_dentry_list(), which
    is fine, but doesn't do anything of that sort. What was the Message-ID?

    Let me see if I understand what you are proposing:
    dentry_kill(dentry, 0) seeing DCACHE_DENTRY_KILLED
    check DCACHE_MAY_FREE, free it's been set
    dentry_kill(dentry, 1) seeing that we are on shrinker list
    leave on the list, do the work on killing, retake ->d_lock,
    if we are still on shrinker list
    set DCACHE_MAY_FREE,
    else
    free it

    That would probably work...


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