From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from aserp1040.oracle.com ([141.146.126.69]:49282 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750773Ab3KDJ6l (ORCPT ); Mon, 4 Nov 2013 04:58:41 -0500 Date: Mon, 4 Nov 2013 17:58:30 +0800 From: Liu Bo To: Stefan Behrens Cc: linux-btrfs@vger.kernel.org Subject: Re: [PATCH] Btrfs: avoid heavy operations in btrfs_commit_super Message-ID: <20131104095829.GA6261@localhost.localdomain> Reply-To: bo.li.liu@oracle.com References: <1383492274-30311-1-git-send-email-bo.li.liu@oracle.com> <52775FB7.7080506@giantdisaster.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <52775FB7.7080506@giantdisaster.de> Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Mon, Nov 04, 2013 at 09:49:59AM +0100, Stefan Behrens wrote: > 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' > Oops, sorry for that, will fix it soon. thanks, -liubo