From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Backlund Subject: Re: [BUGFIX] [PATCH] freeze_bdev: don't deactivate successfully frozen MS_RDONLY sb Date: Sat, 30 Jan 2010 20:44:57 +0200 Message-ID: <4B647E29.7060606@mandriva.org> References: <20100122160740.6c16c22d.akpm@linux-foundation.org> <20100128134205.352044bd@notabene> <4B612F89.7020503@ce.jp.nec.com> <20100128182528.GA29926@infradead.org> <4B623236.90003@ce.jp.nec.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4B623236.90003@ce.jp.nec.com> Sender: linux-kernel-owner@vger.kernel.org To: Jun'ichi Nomura Cc: Christoph Hellwig , "linux-kernel@vger.kernel.org" , "tmb@mandriva.org" , Fran?ois Figarola , device-mapper development , Neil Brown , Andrew Morton , "linux-raid@vger.kernel.org" , Al Viro , "stable@kernel.org" List-Id: linux-raid.ids 29.01.2010 02:56, Jun'ichi Nomura skrev: > Thanks Thomas and Christoph for testing and review. > I removed 'smp_wmb()' before up_write from the previous patch, > since up_write() should have necessary ordering constraints. > (I.e. the change of s_frozen is visible to others after up_write) > I'm quite sure the change is harmless but if you are uncomfortable > with Tested-by/Reviewed-by on the modified patch, please remove them. > I've just verified that this patch works as intended on both 2.6.32 and 2.6.33-rc6, so for me it's still OK. > > If MS_RDONLY, freeze_bdev should just up_write(s_umount) instead of > deactivate_locked_super(). > Also, keep sb->s_frozen consistent so that remount can check the frozen state. > > Otherwise a crash reported here can happen: > http://lkml.org/lkml/2010/1/16/37 > http://lkml.org/lkml/2010/1/28/53 > > > This patch should be applied for 2.6.32 stable series, too. > > Reviewed-by: Christoph Hellwig > Tested-by: Thomas Backlund > Signed-off-by: Jun'ichi Nomura > Cc: stable@kernel.org > > diff --git a/fs/block_dev.c b/fs/block_dev.c > index 73d6a73..d11d028 100644 > --- a/fs/block_dev.c > +++ b/fs/block_dev.c > @@ -246,7 +246,8 @@ struct super_block *freeze_bdev(struct block_device *bdev) > if (!sb) > goto out; > if (sb->s_flags& MS_RDONLY) { > - deactivate_locked_super(sb); > + sb->s_frozen = SB_FREEZE_TRANS; > + up_write(&sb->s_umount); > mutex_unlock(&bdev->bd_fsfreeze_mutex); > return sb; > } > @@ -307,7 +308,7 @@ int thaw_bdev(struct block_device *bdev, struct super_block *sb) > BUG_ON(sb->s_bdev != bdev); > down_write(&sb->s_umount); > if (sb->s_flags& MS_RDONLY) > - goto out_deactivate; > + goto out_unfrozen; > > if (sb->s_op->unfreeze_fs) { > error = sb->s_op->unfreeze_fs(sb); > @@ -321,11 +322,11 @@ int thaw_bdev(struct block_device *bdev, struct super_block *sb) > } > } > > +out_unfrozen: > sb->s_frozen = SB_UNFROZEN; > smp_wmb(); > wake_up(&sb->s_wait_unfrozen); > > -out_deactivate: > if (sb) > deactivate_locked_super(sb); > out_unlock: > . >