Return-Path: linux-nfs-owner@vger.kernel.org Received: from mx12.netapp.com ([216.240.18.77]:39826 "EHLO mx12.netapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756537Ab3J1Sx1 convert rfc822-to-8bit (ORCPT ); Mon, 28 Oct 2013 14:53:27 -0400 From: Weston Andros Adamson To: "Myklebust, Trond" CC: linux-nfs list Subject: Re: [PATCH 5/5] NFSv4: clean up nfs4_state reference counting Date: Mon, 28 Oct 2013 18:53:24 +0000 Message-ID: <60C20061-9F32-4CBB-BC7B-94C4DD1A7AFF@netapp.com> References: <1382375414-5854-1-git-send-email-dros@netapp.com> <1382375414-5854-6-git-send-email-dros@netapp.com> <1382985949.3314.5.camel@leira.trondhjem.org> In-Reply-To: <1382985949.3314.5.camel@leira.trondhjem.org> Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Sender: linux-nfs-owner@vger.kernel.org List-ID: On Oct 28, 2013, at 2:45 PM, Myklebust, Trond wrote: > On Mon, 2013-10-21 at 13:10 -0400, Weston Andros Adamson wrote: >> Use atomic_inc_not_zero() to avoid referencing a state that is currently >> being freed. >> >> Signed-off-by: Weston Andros Adamson >> --- >> fs/nfs/nfs4proc.c | 8 ++++++-- >> fs/nfs/nfs4state.c | 3 ++- >> 2 files changed, 8 insertions(+), 3 deletions(-) >> >> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c >> index a3b78df..005543d 100644 >> --- a/fs/nfs/nfs4proc.c >> +++ b/fs/nfs/nfs4proc.c >> @@ -1275,7 +1275,8 @@ static struct nfs4_state *nfs4_try_open_cached(struct nfs4_opendata *opendata) >> out: >> return ERR_PTR(ret); >> out_return_state: >> - atomic_inc(&state->count); >> + if (!atomic_inc_not_zero(&state->count)) >> + return ERR_PTR(-EINVAL); >> return state; >> } >> >> @@ -1429,7 +1430,10 @@ static struct nfs4_opendata *nfs4_open_recoverdata_alloc(struct nfs_open_context >> if (opendata == NULL) >> return ERR_PTR(-ENOMEM); >> opendata->state = state; >> - atomic_inc(&state->count); >> + if (!atomic_inc_not_zero(&state->count)) { >> + nfs4_opendata_put(opendata); >> + return ERR_PTR(-EINVAL); >> + } >> return opendata; >> } >> >> diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c >> index cc14cbb..1c71907 100644 >> --- a/fs/nfs/nfs4state.c >> +++ b/fs/nfs/nfs4state.c >> @@ -1416,7 +1416,8 @@ restart: >> continue; >> if (state->state == 0) >> continue; >> - atomic_inc(&state->count); >> + if (!atomic_inc_not_zero(&state->count)) >> + continue; >> spin_unlock(&sp->so_lock); >> status = ops->recover_open(sp, state); >> if (status >= 0) { > > Is this patch needed? We should already be holding a reference to the > open_context, so AFAICS we know that the state->count is non-zero. I have no evidence that this is needed, it was purely for consistency. Feel free to drop this patch. -dros > > Cheers > Trond > -- > Trond Myklebust > Linux NFS client maintainer > > NetApp > Trond.Myklebust@netapp.com > www.netapp.com