Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753888AbaBDEDT (ORCPT ); Mon, 3 Feb 2014 23:03:19 -0500 Received: from mail-qc0-f171.google.com ([209.85.216.171]:40076 "EHLO mail-qc0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752773AbaBDEDR (ORCPT ); Mon, 3 Feb 2014 23:03:17 -0500 MIME-Version: 1.0 In-Reply-To: <87a9e7wq6w.fsf@devron.myhome.or.jp> References: <1387953112-2828-1-git-send-email-linkinjeon@gmail.com> <87eh3kx1n6.fsf@devron.myhome.or.jp> <87a9e7wq6w.fsf@devron.myhome.or.jp> Date: Tue, 4 Feb 2014 13:03:16 +0900 Message-ID: Subject: Re: [PATCH v3 5/6] fat: permit to return phy block number by fibmap in fallocated region From: Namjae Jeon To: OGAWA Hirofumi Cc: akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Namjae Jeon , Amit Sahrawat Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2014-02-04, OGAWA Hirofumi : > Namjae Jeon writes: > >>>> /* fat_get_cluster() assumes the requested blocknr isn't truncated. >>>> */ >>>> down_read(&MSDOS_I(mapping->host)->truncate_lock); >>>> + /* To get block number beyond file size in fallocated region */ >>>> + atomic_set(&MSDOS_I(mapping->host)->beyond_isize, 1); >>>> blocknr = generic_block_bmap(mapping, block, fat_get_block); >>>> + atomic_set(&MSDOS_I(mapping->host)->beyond_isize, 0); >>>> up_read(&MSDOS_I(mapping->host)->truncate_lock); >>> >>> This is racy. While user is using bmap, kernel can allocate new blocks. >>> We should use another function for this. >> I understand that fat can map fallocated blocks in read case while >> user is using bmap. >> But I can not find the case allocate new blocks. >> If I am missing something, Could you please elaborate more ? >> Is it a case of _bmap request returning the block number for block >> allocated in parallel write path ? > > ->beyond_size is global for inode. So, write(2) path on same inode with > bmap() also can see 1 set by bmap() while another process is using bmap(). 'create' flag will be 1 in write(2) path. ->beyond_isize will only be checked when 'create' flag is 0. Is there any case to be racy by beyond_isize in write(2) path ? Thanks. > -- > OGAWA Hirofumi > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/