From: NeilBrown <neilb@suse.com>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Kinglong Mee <kinglongmee@gmail.com>,
"J. Bruce Fields" <bfields@fieldses.org>,
"linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>,
linux-fsdevel@vger.kernel.org,
Trond Myklebust <trond.myklebust@primarydata.com>
Subject: Re: [PATCH 10/10 v7] nfsd: Allows user un-mounting filesystem where nfsd exports base on
Date: Wed, 15 Jul 2015 16:51:13 +1000 [thread overview]
Message-ID: <20150715165113.5e8b3fa2@noble> (raw)
In-Reply-To: <20150715045756.GS17109@ZenIV.linux.org.uk>
On Wed, 15 Jul 2015 05:57:56 +0100 Al Viro <viro@ZenIV.linux.org.uk>
wrote:
> On Wed, Jul 15, 2015 at 01:49:48PM +1000, NeilBrown wrote:
>
> > > In any case, you have two possibilities - explicit unexport triggering that
> > > dput(), etc. and umount(2) triggering the same. Whoever comes second gets
> > > to wait until it's done. So why not make the point where we commit to
> > > unexporting the sucker the place where we do pin_kill()? And have ->kill()
> > > of that thing prevent appearance of new entries, then wait for them to run
> > > down. Which is precisely the same thing you want to happen on umount...
> >
> > The "wait for them to run down" part is the sticking point. We don't
> > have any easy way to wait for there to be no more references, so I'd
> > really like to use the waiting that pin_kill() already does.
>
> > I want the ->kill function to just unhash the cache entry, and then
> > wait for pin_delete() to be called.
>
> pin_remove, presumably?
Presumably, yes.
>
> > The final 'put' on the cache entry calls dput on the dentry and then
> > pin_remove().
> >
> > The ->kill function can wait for that to happen by calling pin_kill().
>
> > I guess there is no real need for a return value from pin_remove().
> >
> > So
> > static void expkey_pin_kill(struct fs_pin *pin)
> > {
> > struct svc_expkey *key = container_of(pin, ....);
> >
> > cache_delete_entry(key->cd, &key->h);
>
>
> ... and another CPU drops the last reference, freeing the sucker.
*That's* why I wanted pin_remove to return something.
Why didn't you like that option again?
To recap:
pin_remove does:
tmp = pin->done;
pin->done = 1;
...
return tmp;
path_put_unpin() returns the return value of pin_remove()
expkey_put() does:
auth_domain_put(key->ek_client);
if (test some bits)
if (path_put_unpin() < 0)
/* pin_kill has taken over */
return
kfree_rcu(key, rcu_head);
}
and expkey_pin_kill() does:
cache_delete_entry(key->cd, &key->h);
pin_kill(&key->ek_pin);
kfee_rcu(key, rcu_head);
}
Thanks,
NeilBrown
next prev parent reply other threads:[~2015-07-15 6:51 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-11 12:46 [PATCH 00/10 v7] NFSD: Pin to vfsmount for nfsd exports cache Kinglong Mee
2015-07-11 12:49 ` [PATCH 05/10 v7] sunrpc: Store cache_detail in seq_file's private, directly Kinglong Mee
2015-07-11 12:49 ` [PATCH 06/10 v7] sunrpc/nfsd: Remove redundant code by exports seq_operations functions Kinglong Mee
[not found] ` <55A11010.6050005-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2015-07-11 12:47 ` [PATCH 01/10 v7] fs_pin: Initialize value for fs_pin explicitly Kinglong Mee
2015-07-11 12:47 ` [PATCH 02/10 v7] fs_pin: Export functions for specific filesystem Kinglong Mee
2015-07-11 12:48 ` [PATCH 03/10 v7] path: New helpers path_get_pin/path_put_unpin for path pin Kinglong Mee
2015-07-11 12:48 ` [PATCH 04/10 v7] fs: New helper legitimize_mntget() for getting a legitimize mnt Kinglong Mee
2015-07-11 12:50 ` [PATCH 07/10 v7] sunrpc: Switch to using list_head instead single list Kinglong Mee
[not found] ` <55A11112.8080502-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2015-07-11 12:54 ` Christoph Hellwig
2015-07-13 1:30 ` NeilBrown
2015-07-13 8:27 ` Kinglong Mee
2015-07-11 12:51 ` [PATCH 09/10 v7] sunrpc: Support get_ref/put_ref for reference change in cache_head Kinglong Mee
2015-07-11 12:52 ` [PATCH 10/10 v7] nfsd: Allows user un-mounting filesystem where nfsd exports base on Kinglong Mee
[not found] ` <55A111A8.2040701-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2015-07-13 3:39 ` NeilBrown
2015-07-13 4:02 ` Al Viro
[not found] ` <20150713040258.GM17109-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2015-07-13 5:19 ` NeilBrown
2015-07-13 6:02 ` Al Viro
2015-07-13 4:20 ` NeilBrown
2015-07-13 4:45 ` Al Viro
[not found] ` <20150713044553.GN17109-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2015-07-13 5:21 ` NeilBrown
2015-07-13 6:02 ` NeilBrown
2015-07-13 6:08 ` Al Viro
[not found] ` <20150713060802.GP17109-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2015-07-13 6:32 ` NeilBrown
2015-07-13 6:43 ` Al Viro
2015-07-15 3:49 ` NeilBrown
2015-07-15 4:57 ` Al Viro
2015-07-15 6:51 ` NeilBrown [this message]
2015-07-24 2:05 ` NeilBrown
2015-07-27 2:28 ` Kinglong Mee
[not found] ` <55B59764.1020506-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2015-07-27 2:51 ` NeilBrown
2015-07-27 3:17 ` Kinglong Mee
2015-07-15 21:07 ` J. Bruce Fields
[not found] ` <20150715210756.GE21669-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org>
2015-07-15 23:40 ` NeilBrown
2015-07-16 20:51 ` J. Bruce Fields
[not found] ` <20150716205148.GC10673-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org>
2015-07-21 21:58 ` NeilBrown
2015-07-22 15:08 ` J. Bruce Fields
[not found] ` <20150722150840.GH22718-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org>
2015-07-23 23:46 ` export table lookup: was " NeilBrown
2015-07-24 19:48 ` J. Bruce Fields
2015-07-25 0:40 ` NeilBrown
2015-07-11 12:51 ` [PATCH 08/10 v7] sunrpc: New helper cache_delete_entry for deleting cache_head directly Kinglong Mee
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