linux-kernel - Re: [PATCH] nfs: Don't return referenced delegations

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <4FA345DA4F4AE44899BD2B03EEEC2FA91192A73F@SACEXCMBX04-PRD.hq.netapp.com>
Date:	Thu, 13 Dec 2012 14:34:53 +0000
From:	"Myklebust, Trond" <Trond.Myklebust@...app.com>
To:	"ycnian@...il.com" <ycnian@...il.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>
Subject: Re: [PATCH] nfs: Don't return referenced delegations

On Thu, 2012-12-13 at 14:37 +0800, ycnian@...il.com wrote:
> From: Yanchuan Nian <ycnian@...il.com>
> 
> The client returns unreferenced delegations in state management. It scans all
> delegations and tests the NFS_DELEGATION_REFERENCED flag. if this flag is not
> set, NFS_DELEGATION_RETURN will be set and the delegation will be returned. 
> But unfortunately NFS_DELEGATION_REFERENCED is cleared after the testing, so 
> delegations which are still being used will be returned in the next state
> management.
> 
> Signed-off-by: Yanchuan Nian <ycnian@...il.com>
> ---
>  fs/nfs/delegation.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
> index 81c5eec..485e8c0 100644
> --- a/fs/nfs/delegation.c
> +++ b/fs/nfs/delegation.c
> @@ -506,7 +506,7 @@ static void nfs_mark_return_unreferenced_delegations(struct nfs_server *server)
>  	struct nfs_delegation *delegation;
>  
>  	list_for_each_entry_rcu(delegation, &server->delegations, super_list) {
> -		if (test_and_clear_bit(NFS_DELEGATION_REFERENCED, &delegation->flags))
> +		if (test_bit(NFS_DELEGATION_REFERENCED, &delegation->flags))
>  			continue;
>  		nfs_mark_return_delegation(server, delegation);
>  	}

The clearing of the bit here is 100% intentional. This is a variant on
basic mark-and-sweep garbage collection where if the bit hasn't been set
again the next time we scan, then we assume the delegation isn't being
used.

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@...app.com
www.netapp.com