From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932959Ab0JEKd0 (ORCPT ); Tue, 5 Oct 2010 06:33:26 -0400 Received: from fxip-0047f.externet.hu ([88.209.222.127]:56706 "EHLO pomaz-ex.szeredi.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932869Ab0JEKby (ORCPT ); Tue, 5 Oct 2010 06:31:54 -0400 Message-Id: <20101005103140.601636569@szeredi.hu> References: <20101005103108.288743609@szeredi.hu> User-Agent: quilt/0.46-1 Date: Tue, 05 Oct 2010 12:31:13 +0200 From: Miklos Szeredi To: viro@zeniv.linux.org.uk Cc: dave@linux.vnet.ibm.com, akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 5/9] vfs: allow mnt_want_write() to sleep Content-Disposition: inline; filename=vfs-sleeping-mnt_want_write.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Miklos Szeredi Allow mnt_want_write() to sleep. This is necessary to enable holding off write requests for the duration of ->remount_fs(), which may sleep. A quick audit didn't turn up any callers from atomic context. Signed-off-by: Miklos Szeredi --- fs/namespace.c | 11 +++++++---- fs/super.c | 1 + include/linux/fs.h | 5 +++++ 3 files changed, 13 insertions(+), 4 deletions(-) Index: linux-2.6/fs/namespace.c =================================================================== --- linux-2.6.orig/fs/namespace.c 2010-10-04 12:15:17.000000000 +0200 +++ linux-2.6/fs/namespace.c 2010-10-04 16:50:44.000000000 +0200 @@ -281,8 +281,12 @@ int mnt_want_write(struct vfsmount *mnt) * incremented count after it has set MNT_WRITE_HOLD. */ smp_mb(); - while (mnt->mnt_flags & MNT_WRITE_HOLD) - cpu_relax(); + if (unlikely(mnt->mnt_flags & MNT_WRITE_HOLD)) { + preempt_enable(); + wait_event(mnt->mnt_sb->s_wait_remount_readonly, + !(mnt->mnt_flags & MNT_WRITE_HOLD)); + preempt_disable(); + } /* * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will * be set to match its requirements. So we must not load that until @@ -292,9 +296,7 @@ int mnt_want_write(struct vfsmount *mnt) if (__mnt_is_readonly(mnt)) { dec_mnt_writers(mnt); ret = -EROFS; - goto out; } -out: preempt_enable(); return ret; } @@ -395,6 +397,7 @@ static int mnt_make_readonly(struct vfsm */ smp_wmb(); mnt->mnt_flags &= ~MNT_WRITE_HOLD; + wake_up_all(&mnt->mnt_sb->s_wait_remount_readonly); br_write_unlock(vfsmount_lock); return ret; } Index: linux-2.6/fs/super.c =================================================================== --- linux-2.6.orig/fs/super.c 2010-10-04 12:12:01.000000000 +0200 +++ linux-2.6/fs/super.c 2010-10-04 16:50:25.000000000 +0200 @@ -107,6 +107,7 @@ static struct super_block *alloc_super(s mutex_init(&s->s_dquot.dqonoff_mutex); init_rwsem(&s->s_dquot.dqptr_sem); init_waitqueue_head(&s->s_wait_unfrozen); + init_waitqueue_head(&s->s_wait_remount_readonly); s->s_maxbytes = MAX_NON_LFS; s->s_op = &default_op; s->s_time_gran = 1000000000; Index: linux-2.6/include/linux/fs.h =================================================================== --- linux-2.6.orig/include/linux/fs.h 2010-10-04 12:13:00.000000000 +0200 +++ linux-2.6/include/linux/fs.h 2010-10-04 16:50:25.000000000 +0200 @@ -1385,6 +1385,11 @@ struct super_block { * generic_show_options() */ char *s_options; + + /* + * Wait queue for remouting read-only + */ + wait_queue_head_t s_wait_remount_readonly; }; extern struct timespec current_fs_time(struct super_block *sb); --