From: Christoph Hellwig Subject: Re: [PATCH 1/3] Implement generic freeze feature Date: Tue, 1 Jul 2008 04:08:44 -0400 Message-ID: <20080701080844.GA16691@infradead.org> References: <20080630212323t-sato@mail.jp.nec.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: akpm@linux-foundation.org, viro@ZenIV.linux.org.uk, "linux-ext4@vger.kernel.org" , "xfs@oss.sgi.com" , "dm-devel@redhat.com" , "linux-fsdevel@vger.kernel.org" , "linux-kernel@vger.kernel.org" , axboe@kernel.dk, mtk.manpages@googlemail.com To: Takashi Sato Return-path: Received: from bombadil.infradead.org ([18.85.46.34]:49402 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752190AbYGAIIt (ORCPT ); Tue, 1 Jul 2008 04:08:49 -0400 Content-Disposition: inline In-Reply-To: <20080630212323t-sato@mail.jp.nec.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: > { > struct super_block *sb; > > + if (test_and_set_bit(BD_FREEZE_OP, &bdev->bd_state)) > + return ERR_PTR(-EBUSY); > + > + sb = get_super(bdev); > + > + /* If super_block has been already frozen, return. */ > + if (sb && sb->s_frozen != SB_UNFROZEN) { > + drop_super(sb); > + clear_bit(BD_FREEZE_OP, &bdev->bd_state); > + return sb; > + } > + > + if (sb) > + drop_super(sb); > + > down(&bdev->bd_mount_sem); > sb = get_super(bdev); > if (sb && !(sb->s_flags & MS_RDONLY)) { > @@ -219,6 +234,8 @@ struct super_block *freeze_bdev(struct b > } > > sync_blockdev(bdev); > + clear_bit(BD_FREEZE_OP, &bdev->bd_state); > + Please only clear BD_FREEZE_OP in thaw_bdev, that way you can also get rid of the frozen check above, and the double-get_super. Also bd_mount_sem could be removed that way by checking for BD_FREEZE_OP in the unmount path. > /* > + * ioctl_freeze - Freeze the filesystem. > + * > + * @filp: target file > + * > + * Call freeze_bdev() to freeze the filesystem. > + */ This is not a kerneldoc comment. But I think it can be simply removed anyway, as it's a quite trivial function with static scope. > +/* > + * ioctl_thaw - Thaw the filesystem. > + * > + * @filp: target file > + * > + * Call thaw_bdev() to thaw the filesystem. > + */ Same here.