From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: [PATCH] writeback: fix pin_sb_for_writeback Date: Wed, 9 Jun 2010 15:31:01 +0200 Message-ID: <20100609133101.GA25876@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org To: axboe@kernel.dk Return-path: Received: from verein.lst.de ([213.95.11.210]:57554 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753111Ab0FINbF (ORCPT ); Wed, 9 Jun 2010 09:31:05 -0400 Content-Disposition: inline Sender: linux-fsdevel-owner@vger.kernel.org List-ID: We need to check for s_instances to make sure we don't bother working against a filesystem that is beeing unmounted, and we need to call put_super to make sure a superblock is freed when we race against umount. Also no need to keep sb_lock after we got a reference on it. Signed-off-by: Christoph Hellwig --- Note: this is against Jens' tree with the writeback changes applied. The logic in mainline is the same, but the context is slightl different. Index: linux-2.6/fs/fs-writeback.c =================================================================== --- linux-2.6.orig/fs/fs-writeback.c 2010-06-09 13:15:29.152004893 +0200 +++ linux-2.6/fs/fs-writeback.c 2010-06-09 13:15:29.946253462 +0200 @@ -534,19 +534,21 @@ select_queue: static bool pin_sb_for_writeback(struct super_block *sb) { spin_lock(&sb_lock); + if (list_empty(&sb->s_instances)) { + spin_unlock(&sb_lock); + return false; + } + sb->s_count++; + spin_unlock(&sb_lock); + if (down_read_trylock(&sb->s_umount)) { - if (sb->s_root) { - spin_unlock(&sb_lock); + if (sb->s_root) return true; - } - /* - * umounted, drop rwsem again and fall through to failure - */ up_read(&sb->s_umount); } - sb->s_count--; - spin_unlock(&sb_lock); + + put_super(sb); return false; }