From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mo-p00-ob.rzone.de ([81.169.146.162]:60951 "EHLO mo-p00-ob.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751984Ab3KDIt5 (ORCPT ); Mon, 4 Nov 2013 03:49:57 -0500 Message-ID: <52775FB7.7080506@giantdisaster.de> Date: Mon, 04 Nov 2013 09:49:59 +0100 From: Stefan Behrens MIME-Version: 1.0 To: Liu Bo , linux-btrfs@vger.kernel.org Subject: Re: [PATCH] Btrfs: avoid heavy operations in btrfs_commit_super References: <1383492274-30311-1-git-send-email-bo.li.liu@oracle.com> In-Reply-To: <1383492274-30311-1-git-send-email-bo.li.liu@oracle.com> Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Sun, 3 Nov 2013 23:24:34 +0800, Liu Bo wrote: > The 'git blame' history shows that, the old transaction commit code has to do > twice to ensure roots are updated and we have to flush metadata and super block > manually, however, right now all of these can be handled well inside > the transaction commit code without extra efforts. > > And the error handling part remains same with the current code, -- 'return to > caller once we get error'. > > This saves us a transaction commit and a flush of super block, which are both > heavy operations according to ftrace output analysis. > > Signed-off-by: Liu Bo > --- > fs/btrfs/disk-io.c | 20 +------------------- > 1 file changed, 1 insertion(+), 19 deletions(-) > > diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c > index 62176ad..d6728c3 100644 > --- a/fs/btrfs/disk-io.c > +++ b/fs/btrfs/disk-io.c > @@ -3542,25 +3542,7 @@ int btrfs_commit_super(struct btrfs_root *root) > trans = btrfs_join_transaction(root); > if (IS_ERR(trans)) > return PTR_ERR(trans); > - ret = btrfs_commit_transaction(trans, root); > - if (ret) > - return ret; > - /* run commit again to drop the original snapshot */ > - trans = btrfs_join_transaction(root); > - if (IS_ERR(trans)) > - return PTR_ERR(trans); > - ret = btrfs_commit_transaction(trans, root); > - if (ret) > - return ret; > - ret = btrfs_write_and_wait_transaction(NULL, root); > - if (ret) { > - btrfs_error(root->fs_info, ret, > - "Failed to sync btree inode to disk."); > - return ret; > - } > - > - ret = write_ctree_super(NULL, root, 0); > - return ret; > + return btrfs_commit_transaction(trans, root); > } > > int close_ctree(struct btrfs_root *root) > fs/btrfs/disk-io.c: In function 'btrfs_commit_super': fs/btrfs/disk-io.c:3520: warning: unused variable 'ret'