From: "Darrick J. Wong" Subject: [PATCH v3 2/3] ext4: Wait for writeback to complete while making pages writable Date: Wed, 4 May 2011 10:41:36 -0700 Message-ID: <20110504174136.GG20579@tux1.beaverton.ibm.com> References: <20110321164305.GC7153@quack.suse.cz> <20110406232938.GF1110@tux1.beaverton.ibm.com> <20110407165700.GB7363@quack.suse.cz> <20110408203135.GH1110@tux1.beaverton.ibm.com> <20110411124229.47bc28f6@corrin.poochiereds.net> <1302543595-sup-4352@think> <1302569212.2580.13.camel@mingming-laptop> <20110412005719.GA23077@infradead.org> <1302742128.2586.274.camel@mingming-laptop> <20110422000226.GA22189@tux1.beaverton.ibm.com> Reply-To: djwong@us.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Christoph Hellwig , Chris Mason , Jeff Layton , Jan Kara , Dave Chinner , Joel Becker , "Martin K. Petersen" , Jens Axboe , linux-kernel , linux-fsdevel , Mingming Cao , linux-scsi , Dave Hansen , linux-mm@kvack.org, linux-ext4 To: "Theodore Ts'o" Return-path: Received: from e38.co.us.ibm.com ([32.97.110.159]:49661 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753747Ab1EDRlp (ORCPT ); Wed, 4 May 2011 13:41:45 -0400 Content-Disposition: inline In-Reply-To: <20110422000226.GA22189@tux1.beaverton.ibm.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: In order to stabilize pages during disk writes, ext4_page_mkwrite must wait for writeback operations to complete before making a page writable. Furthermore, the function must return locked pages, and recheck the writeback status if the page lock is ever dropped. Signed-off-by: Darrick J. Wong --- fs/ext4/inode.c | 24 +++++++++++++++++++----- 1 files changed, 19 insertions(+), 5 deletions(-) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 3db34b2..1d162a2 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -5809,15 +5809,19 @@ int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf) goto out_unlock; } ret = 0; - if (PageMappedToDisk(page)) - goto out_unlock; + + lock_page(page); + wait_on_page_writeback(page); + if (PageMappedToDisk(page)) { + up_read(&inode->i_alloc_sem); + return VM_FAULT_LOCKED; + } if (page->index == size >> PAGE_CACHE_SHIFT) len = size & ~PAGE_CACHE_MASK; else len = PAGE_CACHE_SIZE; - lock_page(page); /* * return if we have all the buffers mapped. This avoid * the need to call write_begin/write_end which does a @@ -5827,8 +5831,8 @@ int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf) if (page_has_buffers(page)) { if (!walk_page_buffers(NULL, page_buffers(page), 0, len, NULL, ext4_bh_unmapped)) { - unlock_page(page); - goto out_unlock; + up_read(&inode->i_alloc_sem); + return VM_FAULT_LOCKED; } } unlock_page(page); @@ -5848,6 +5852,16 @@ int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf) if (ret < 0) goto out_unlock; ret = 0; + + /* + * write_begin/end might have created a dirty page and someone + * could wander in and start the IO. Make sure that hasn't + * happened. + */ + lock_page(page); + wait_on_page_writeback(page); + up_read(&inode->i_alloc_sem); + return VM_FAULT_LOCKED; out_unlock: if (ret) ret = VM_FAULT_SIGBUS;