From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762494AbZEANve (ORCPT ); Fri, 1 May 2009 09:51:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753538AbZEANvY (ORCPT ); Fri, 1 May 2009 09:51:24 -0400 Received: from mail-ew0-f176.google.com ([209.85.219.176]:59621 "EHLO mail-ew0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752580AbZEANvX (ORCPT ); Fri, 1 May 2009 09:51:23 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=gg/t9OKNi0G6I//5kdmEzXALIvWPCysGRmDaTIp05M9Xj/Jjflt6Z0rMdURh107oJ6 ByLAl4ZzFuSzQr1wcsJtUHby3HaRH84ZLP0muYw01CT8dNcyWWRx5NRTRJ+kMSHCZ+SD KQ7ZylR+xOLZaNjKHXAodOAbwsnl8mjjjPX/Q= Date: Fri, 1 May 2009 15:51:19 +0200 From: Frederic Weisbecker To: Chris Mason Cc: Ingo Molnar , LKML , Jeff Mahoney , ReiserFS Development List , Alexander Beregalov , Alessio Igor Bogani , Jonathan Corbet , Alexander Viro Subject: Re: [PATCH 5/6] kill-the-BKL/reiserfs: release the write lock inside reiserfs_read_bitmap_block() Message-ID: <20090501135118.GH6011@nowhere> References: <1241145862-21700-1-git-send-email-fweisbec@gmail.com> <1241145862-21700-6-git-send-email-fweisbec@gmail.com> <20090501054734.GE5983@elte.hu> <20090501131955.GC6011@nowhere> <1241184651.13084.15.camel@think.oraclecorp.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1241184651.13084.15.camel@think.oraclecorp.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 01, 2009 at 09:30:51AM -0400, Chris Mason wrote: > On Fri, 2009-05-01 at 15:19 +0200, Frederic Weisbecker wrote: > > On Fri, May 01, 2009 at 07:47:34AM +0200, Ingo Molnar wrote: > > > > > > * Frederic Weisbecker wrote: > > > > > > > reiserfs_read_bitmap_block() uses sb_bread() to read the bitmap block. This > > > > helper might sleep. > > > > > > > > Then, when the bkl was used, it was released at this point. We can then > > > > relax the write lock too here. > > > > > > > > [ Impact: release the reiserfs write lock when it is not needed ] > > > > > > > > Cc: Jeff Mahoney > > > > Cc: Chris Mason > > > > Cc: Alexander Beregalov > > > > Signed-off-by: Frederic Weisbecker > > > > --- > > > > fs/reiserfs/bitmap.c | 2 ++ > > > > 1 files changed, 2 insertions(+), 0 deletions(-) > > > > > > > > diff --git a/fs/reiserfs/bitmap.c b/fs/reiserfs/bitmap.c > > > > index 1470334..6854957 100644 > > > > --- a/fs/reiserfs/bitmap.c > > > > +++ b/fs/reiserfs/bitmap.c > > > > @@ -1249,7 +1249,9 @@ struct buffer_head *reiserfs_read_bitmap_block(struct super_block *sb, > > > > else if (bitmap == 0) > > > > block = (REISERFS_DISK_OFFSET_IN_BYTES >> sb->s_blocksize_bits) + 1; > > > > > > > > + reiserfs_write_unlock(sb); > > > > bh = sb_bread(sb, block); > > > > + reiserfs_write_lock(sb); > > > > if (bh == NULL) > > > > reiserfs_warning(sb, "sh-2029: %s: bitmap block (#%u) " > > > > "reading failed", __func__, block); > > > > > > Note, there's a side-effect here: the access to sb->b_blocksize is > > > moved outside of the lock. Previously it was accessed via the BKL. > > > On a mounted filesystem sb->b_blocksize is not supposed to change, > > > so it's probably not an issue - but wanted to mention it. > > > Indeed. Well I guess it can't be dynamically changed. > > This is something that can be chosen with mkfs on filesystem creation > > but I guess it can't be changed, at least not while the filesystem > > is mounted. I hope... > > The blocksize should only be changing very early in the mount. It is > basically: > > set the block size to something > read the super block > read the block size from the super block > set the block size to the correct value > use it from then on. > > This should all be done with by the time we read bitmaps. > > -chris Ok, thanks. So I guess we can keep it as is without a local variable.