From: Trond Myklebust Subject: Re: [PATCH 07/10] pnfs-submit: avoid race handling return on close Date: Tue, 15 Jun 2010 14:19:51 -0400 Message-ID: <1276625991.2988.1.camel@heimdal.trondhjem.org> References: <1276566375-24566-1-git-send-email-iisaman@netapp.com> <1276566375-24566-2-git-send-email-iisaman@netapp.com> <1276566375-24566-3-git-send-email-iisaman@netapp.com> <1276566375-24566-4-git-send-email-iisaman@netapp.com> <1276566375-24566-5-git-send-email-iisaman@netapp.com> <1276566375-24566-6-git-send-email-iisaman@netapp.com> <1276566375-24566-7-git-send-email-iisaman@netapp.com> <1276566375-24566-8-git-send-email-iisaman@netapp.com> <4C17B304.4070308@panasas.com> <1276623230.8767.48.camel@heimdal.trondhjem.org> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Cc: Benny Halevy , Fred Isaman , linux-nfs@vger.kernel.org To: Fred Isaman Return-path: Received: from mail-out2.uio.no ([129.240.10.58]:41242 "EHLO mail-out2.uio.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754682Ab0FOSUB (ORCPT ); Tue, 15 Jun 2010 14:20:01 -0400 In-Reply-To: Sender: linux-nfs-owner@vger.kernel.org List-ID: On Tue, 2010-06-15 at 13:52 -0400, Fred Isaman wrote: > On Tue, Jun 15, 2010 at 1:33 PM, Trond Myklebust > wrote: > > On Tue, 2010-06-15 at 13:32 -0400, Fred Isaman wrote: > >> On Tue, Jun 15, 2010 at 1:06 PM, Benny Halevy wrote: > >> > On Jun. 14, 2010, 21:46 -0400, Fred Isaman wrote: > >> >> This prepares for the next patch. > >> >> > >> >> NOTE this doesn't really fix any current race, since > >> >> layout going to NULL is OK. But layout changing from NULL to nonNULL > >> >> is a real race that is not fixed > >> >> > >> >> Signed-off-by: Fred Isaman > >> >> --- > >> >> fs/nfs/nfs4state.c | 5 +++-- > >> >> fs/nfs/pnfs.c | 11 +++++++++++ > >> >> include/linux/nfs4_pnfs.h | 2 ++ > >> >> 3 files changed, 16 insertions(+), 2 deletions(-) > >> >> > >> >> diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c > >> >> index d5144bd..8a7a64c 100644 > >> >> --- a/fs/nfs/nfs4state.c > >> >> +++ b/fs/nfs/nfs4state.c > >> >> @@ -594,11 +594,12 @@ static void __nfs4_close(struct path *path, struct nfs4_state *state, > >> >> } else { > >> >> #ifdef CONFIG_NFS_V4_1 > >> >> struct nfs_inode *nfsi = NFS_I(state->inode); > >> >> + int roc = nfs4_roc_iomode(nfsi); > >> >> > >> >> - if (has_layout(nfsi) && nfsi->layout.roc_iomode) { > >> >> + if (roc) { > >> >> struct nfs4_pnfs_layout_segment range; > >> >> > >> >> - range.iomode = nfsi->layout.roc_iomode; > >> >> + range.iomode = roc; > >> >> range.offset = 0; > >> >> range.length = NFS4_MAX_UINT64; > >> >> pnfs_return_layout(state->inode, &range, NULL, > >> >> diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c > >> >> index 6def09c..bd11ec7 100644 > >> >> --- a/fs/nfs/pnfs.c > >> >> +++ b/fs/nfs/pnfs.c > >> >> @@ -321,6 +321,17 @@ pnfs_unregister_layoutdriver(struct pnfs_layoutdriver_type *ld_type) > >> >> #define BUG_ON_UNLOCKED_LO(lo) do {} while (0) > >> >> #endif /* CONFIG_SMP */ > >> >> > >> >> +int nfs4_roc_iomode(struct nfs_inode *nfsi) > >> >> +{ > >> >> + int rv = 0; > >> >> + > >> >> + spin_lock(&pnfs_spinlock); > >> > > >> > Why take the global lock rather than nfsi->lo_lock? > >> > > >> > Benny > >> > >> You are right. That would be a copy-paste error. > > > > What's an nfsi->lo_lock, and why do we need one? > > > > Trond > > > > > > It protects nfsi->layout and its contents. > > Fred Yes, but why do we need an extra spinlock? We already have inode->i_lock. Why can't you just reuse that?