From: Andrew Morton Subject: Re: [PATCH] ext3: Use page_mkwrite vma_operations to get mmap write notification. Date: Mon, 24 Mar 2008 16:01:41 -0700 Message-ID: <20080324160141.67746905.akpm@linux-foundation.org> References: <1206378298-10341-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1206378298-10341-2-git-send-email-aneesh.kumar@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: cmm@us.ibm.com, linux-ext4@vger.kernel.org, aneesh.kumar@linux.vnet.ibm.com, Nick Piggin , linux-mm@kvack.org To: "Aneesh Kumar K.V" Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:59786 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752949AbYCXXBu (ORCPT ); Mon, 24 Mar 2008 19:01:50 -0400 In-Reply-To: <1206378298-10341-2-git-send-email-aneesh.kumar@linux.vnet.ibm.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Mon, 24 Mar 2008 22:34:56 +0530 "Aneesh Kumar K.V" wrote: > We would like to get notified when we are doing a write on mmap section. > The changes are needed to handle ENOSPC when writing to an mmap section > of files with holes. > umm, > > diff --git a/fs/ext3/file.c b/fs/ext3/file.c > index acc4913..09e22e4 100644 > --- a/fs/ext3/file.c > +++ b/fs/ext3/file.c > @@ -106,6 +106,23 @@ force_commit: > return ret; > } > > +static struct vm_operations_struct ext3_file_vm_ops = { > + .fault = filemap_fault, > + .page_mkwrite = ext3_page_mkwrite, > +}; > + > +static int ext3_file_mmap(struct file *file, struct vm_area_struct *vma) > +{ > + struct address_space *mapping = file->f_mapping; > + > + if (!mapping->a_ops->readpage) > + return -ENOEXEC; > + file_accessed(file); > + vma->vm_ops = &ext3_file_vm_ops; > + vma->vm_flags |= VM_CAN_NONLINEAR; > + return 0; > +} > + > const struct file_operations ext3_file_operations = { > .llseek = generic_file_llseek, > .read = do_sync_read, > @@ -116,7 +133,7 @@ const struct file_operations ext3_file_operations = { > #ifdef CONFIG_COMPAT > .compat_ioctl = ext3_compat_ioctl, > #endif > - .mmap = generic_file_mmap, > + .mmap = ext3_file_mmap, > .open = generic_file_open, > .release = ext3_release_file, > .fsync = ext3_sync_file, > diff --git a/fs/ext3/inode.c b/fs/ext3/inode.c > index eb95670..2293506 100644 > --- a/fs/ext3/inode.c > +++ b/fs/ext3/inode.c > @@ -3306,3 +3306,8 @@ int ext3_change_inode_journal_flag(struct inode *inode, int val) > > return err; > } > + > +int ext3_page_mkwrite(struct vm_area_struct *vma, struct page *page) > +{ > + return block_page_mkwrite(vma, page, ext3_get_block); > +} This gets called within the pagefault handler. And block_page_mkwrite() does lock_page(). But the pagefault handler can be called with a page already locked, from generic_perform_write(). Nick, why are we not vulnerable to A-A or to AB-BA deadlocks here?