From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ee0-f41.google.com (mail-ee0-f41.google.com [74.125.83.41]) by kanga.kvack.org (Postfix) with ESMTP id D4D9D6B003C for ; Wed, 16 Apr 2014 00:19:02 -0400 (EDT) Received: by mail-ee0-f41.google.com with SMTP id t10so8404240eei.28 for ; Tue, 15 Apr 2014 21:19:02 -0700 (PDT) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id 43si28084703eer.297.2014.04.15.21.19.01 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 15 Apr 2014 21:19:01 -0700 (PDT) From: NeilBrown Date: Wed, 16 Apr 2014 14:03:36 +1000 Subject: [PATCH 10/19] NET: set PF_FSTRANS while holding sk_lock Message-ID: <20140416040336.10604.96000.stgit@notabene.brown> In-Reply-To: <20140416033623.10604.69237.stgit@notabene.brown> References: <20140416033623.10604.69237.stgit@notabene.brown> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Cc: xfs@oss.sgi.com, netdev@vger.kernel.org sk_lock can be taken while reclaiming memory (in nfsd for loop-back NFS mounts, and presumably in nfs), and memory can be allocated while holding sk_lock, at least via: inet_listen -> inet_csk_listen_start ->reqsk_queue_alloc So to avoid deadlocks, always set PF_FSTRANS while holding sk_lock. This deadlock was found by lockdep. Signed-off-by: NeilBrown --- include/net/sock.h | 1 + net/core/sock.c | 2 ++ 2 files changed, 3 insertions(+) diff --git a/include/net/sock.h b/include/net/sock.h index b9586a137cad..27c355637e44 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -324,6 +324,7 @@ struct sock { #define sk_v6_rcv_saddr __sk_common.skc_v6_rcv_saddr socket_lock_t sk_lock; + unsigned int sk_pflags; /* process flags before taking lock */ struct sk_buff_head sk_receive_queue; /* * The backlog queue is special, it is always used with diff --git a/net/core/sock.c b/net/core/sock.c index cf9bd24e4099..8bc677ef072e 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -2341,6 +2341,7 @@ void lock_sock_nested(struct sock *sk, int subclass) /* * The sk_lock has mutex_lock() semantics here: */ + current_set_flags_nested(&sk->sk_pflags, PF_FSTRANS); mutex_acquire(&sk->sk_lock.dep_map, subclass, 0, _RET_IP_); local_bh_enable(); } @@ -2352,6 +2353,7 @@ void release_sock(struct sock *sk) * The sk_lock has mutex_unlock() semantics: */ mutex_release(&sk->sk_lock.dep_map, 1, _RET_IP_); + current_restore_flags_nested(&sk->sk_pflags, PF_FSTRANS); spin_lock_bh(&sk->sk_lock.slock); if (sk->sk_backlog.tail) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org