Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754311AbaDPETy (ORCPT ); Wed, 16 Apr 2014 00:19:54 -0400 Received: from cantor2.suse.de ([195.135.220.15]:38876 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754272AbaDPETv (ORCPT ); Wed, 16 Apr 2014 00:19:51 -0400 From: NeilBrown To: linux-mm@kvack.org, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Date: Wed, 16 Apr 2014 14:03:37 +1000 Subject: [PATCH 17/19] VFS: set PF_FSTRANS while namespace_sem is held. Cc: xfs@oss.sgi.com Message-ID: <20140416040337.10604.86740.stgit@notabene.brown> In-Reply-To: <20140416033623.10604.69237.stgit@notabene.brown> References: <20140416033623.10604.69237.stgit@notabene.brown> User-Agent: StGit/0.16 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org namespace_sem can be taken while various i_mutex locks are held, so we need to avoid reclaim from blocking on an FS (particularly loop-back NFS). A memory allocation happens under namespace_sem at least in: [] kmem_cache_alloc+0x4f/0x290 [] alloc_vfsmnt+0x1f/0x1d0 [] clone_mnt+0x2a/0x310 [] copy_tree+0x53/0x380 [] copy_mnt_ns+0x7f/0x280 [] create_new_namespaces+0x5c/0x190 [] unshare_nsproxy_namespaces+0x59/0x90 So set PF_FSTRANS in namespace_lock() and restore in namespace_unlock(). Signed-off-by: NeilBrown --- fs/namespace.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/fs/namespace.c b/fs/namespace.c index 2ffc5a2905d4..83dcd5083dbb 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -63,6 +63,7 @@ static struct hlist_head *mount_hashtable __read_mostly; static struct hlist_head *mountpoint_hashtable __read_mostly; static struct kmem_cache *mnt_cache __read_mostly; static DECLARE_RWSEM(namespace_sem); +static unsigned long namespace_sem_pflags; /* /sys/fs */ struct kobject *fs_kobj; @@ -1196,6 +1197,8 @@ static void namespace_unlock(void) struct mount *mnt; struct hlist_head head = unmounted; + current_restore_flags_nested(&namespace_sem_pflags, PF_FSTRANS); + if (likely(hlist_empty(&head))) { up_write(&namespace_sem); return; @@ -1220,6 +1223,7 @@ static void namespace_unlock(void) static inline void namespace_lock(void) { down_write(&namespace_sem); + current_set_flags_nested(&namespace_sem_pflags, PF_FSTRANS); } /* -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/