From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id D41C76B005A for ; Wed, 17 Jun 2009 06:34:40 -0400 (EDT) Date: Wed, 17 Jun 2009 12:35:43 +0200 From: Nick Piggin Subject: Re: [PATCH 07/11] vfs: Unmap underlying metadata of new data buffers only when buffer is mapped Message-ID: <20090617103543.GB29931@wotan.suse.de> References: <1245088797-29533-1-git-send-email-jack@suse.cz> <1245088797-29533-8-git-send-email-jack@suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1245088797-29533-8-git-send-email-jack@suse.cz> Sender: owner-linux-mm@kvack.org To: Jan Kara Cc: LKML , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org List-ID: On Mon, Jun 15, 2009 at 07:59:54PM +0200, Jan Kara wrote: > When we do delayed allocation of some buffer, we want to signal to VFS that > the buffer is new (set buffer_new) so that it properly zeros out everything. > But we don't have the buffer mapped yet so we cannot really unmap underlying > metadata in this state. Make VFS avoid doing unmapping of metadata when the > buffer is not yet mapped. Is this a seperate bugfix for delalloc filesystems? What is the error case of attempting to unmap underlying metadata of non mapped buffer? Won't translate to a serious bug will it? > > Signed-off-by: Jan Kara > --- > fs/buffer.c | 12 +++++++----- > 1 files changed, 7 insertions(+), 5 deletions(-) > > diff --git a/fs/buffer.c b/fs/buffer.c > index 80e2630..7eb1710 100644 > --- a/fs/buffer.c > +++ b/fs/buffer.c > @@ -1683,8 +1683,9 @@ static int __block_write_full_page(struct inode *inode, struct page *page, > if (buffer_new(bh)) { > /* blockdev mappings never come here */ > clear_buffer_new(bh); > - unmap_underlying_metadata(bh->b_bdev, > - bh->b_blocknr); > + if (buffer_mapped(bh)) > + unmap_underlying_metadata(bh->b_bdev, > + bh->b_blocknr); > } > } > bh = bh->b_this_page; > @@ -1869,8 +1870,9 @@ static int __block_prepare_write(struct inode *inode, struct page *page, > if (err) > break; > if (buffer_new(bh)) { > - unmap_underlying_metadata(bh->b_bdev, > - bh->b_blocknr); > + if (buffer_mapped(bh)) > + unmap_underlying_metadata(bh->b_bdev, > + bh->b_blocknr); > if (PageUptodate(page)) { > clear_buffer_new(bh); > set_buffer_uptodate(bh); > @@ -2683,7 +2685,7 @@ int nobh_write_begin(struct file *file, struct address_space *mapping, > goto failed; > if (!buffer_mapped(bh)) > is_mapped_to_disk = 0; > - if (buffer_new(bh)) > + if (buffer_new(bh) && buffer_mapped(bh)) > unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr); > if (PageUptodate(page)) { > set_buffer_uptodate(bh); > -- > 1.6.0.2 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org