From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chuck Lever Subject: Re: [PATCH] NFS: Use GFP_NOFS in nfs_direct_req_alloc Date: Tue, 8 Sep 2009 18:43:02 -0400 Message-ID: <931F30AB-DC64-4A02-A96C-FABF0DD4059A@oracle.com> References: <20090908220230.7590.69833.stgit@matisse.1015granger.net> <1252449178.8099.64.camel@heimdal.trondhjem.org> Mime-Version: 1.0 (Apple Message framework v936) Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Cc: linux-nfs@vger.kernel.org To: Trond Myklebust Return-path: Received: from acsinet12.oracle.com ([141.146.126.234]:26984 "EHLO acsinet12.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751089AbZIHWnG (ORCPT ); Tue, 8 Sep 2009 18:43:06 -0400 In-Reply-To: <1252449178.8099.64.camel-rJ7iovZKK19ZJLDQqaL3InhyD016LWXt@public.gmane.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Sep 8, 2009, at 6:32 PM, Trond Myklebust wrote: > On Tue, 2009-09-08 at 18:05 -0400, Chuck Lever wrote: >> Don't dive into memory reclaim in the NFS direct I/O paths, otherwise >> we can deadlock. >> >> Reported by: Wengang Wang >> Fix-suggested-by: Zach Brown >> Signed-off-by: Chuck Lever > > Wait... What??? How does an O_DIRECT read or write allocation deadlock > with memory reclaim? Both the read and the write path call > nfs_direct_req_alloc() before they pin any user pages in memory. This may be an issue only for loopback mounts where the backing device is an NFS O_DIRECT file. This type of deadlock may not be able to happen in upstream kernels at this point. Even so, it makes sense for this allocation to be consistent with similar allocations in the other NFS I/O paths. > Trond > >> --- >> >> Trond- >> >> Thoughts? >> >> fs/nfs/direct.c | 2 +- >> 1 files changed, 1 insertions(+), 1 deletions(-) >> >> diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c >> index e4e089a..00f06b8 100644 >> --- a/fs/nfs/direct.c >> +++ b/fs/nfs/direct.c >> @@ -149,7 +149,7 @@ static inline struct nfs_direct_req >> *nfs_direct_req_alloc(void) >> { >> struct nfs_direct_req *dreq; >> >> - dreq = kmem_cache_alloc(nfs_direct_cachep, GFP_KERNEL); >> + dreq = kmem_cache_alloc(nfs_direct_cachep, GFP_NOFS); >> if (!dreq) >> return NULL; >> >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux- >> nfs" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > -- > Trond Myklebust > Linux NFS client maintainer > > NetApp > Trond.Myklebust@netapp.com > www.netapp.com > -- > To unsubscribe from this list: send the line "unsubscribe linux-nfs" > in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Chuck Lever chuck[dot]lever[at]oracle[dot]com