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 SMTP id E92AA6B0095 for ; Tue, 22 Nov 2011 23:31:00 -0500 (EST) Message-ID: <4ECC76F3.9050001@redhat.com> Date: Wed, 23 Nov 2011 12:30:43 +0800 From: Cong Wang MIME-Version: 1.0 Subject: Re: [V2 PATCH] tmpfs: add fallocate support References: <1321612791-4764-1-git-send-email-amwang@redhat.com> <20111122140630.9f37c907.akpm@linux-foundation.org> In-Reply-To: <20111122140630.9f37c907.akpm@linux-foundation.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: linux-kernel@vger.kernel.org, Pekka Enberg , Hugh Dickins , Dave Hansen , Lennart Poettering , Kay Sievers , KOSAKI Motohiro , linux-mm@kvack.org ao? 2011a1'11ae??23ae?JPY 06:06, Andrew Morton a??e??: > On Fri, 18 Nov 2011 18:39:50 +0800 > Cong Wang wrote: > >> It seems that systemd needs tmpfs to support fallocate, >> see http://lkml.org/lkml/2011/10/20/275. This patch adds >> fallocate support to tmpfs. >> >> As we already have shmem_truncate_range(), it is also easy >> to add FALLOC_FL_PUNCH_HOLE support too. >> >> >> ... >> >> +static long shmem_fallocate(struct file *file, int mode, >> + loff_t offset, loff_t len) >> +{ >> + struct inode *inode = file->f_path.dentry->d_inode; >> + pgoff_t start = offset>> PAGE_CACHE_SHIFT; >> + pgoff_t end = DIV_ROUND_UP((offset + len), PAGE_CACHE_SIZE); >> + pgoff_t index = start; >> + loff_t i_size = i_size_read(inode); >> + struct page *page = NULL; >> + int ret = 0; >> + >> + mutex_lock(&inode->i_mutex); > > It would be saner and less racy-looking to read i_size _after_ taking > i_mutex. > > And if you do that, there's no need to use i_size_read() - just a plain > old > > i_size = inode->i_size; > > is OK. Fair enough, I will fix that in V3. Thanks, Andrew! -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org