From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id 51C0E6B00A9 for ; Tue, 22 Nov 2011 17:06:34 -0500 (EST) Date: Tue, 22 Nov 2011 14:06:30 -0800 From: Andrew Morton Subject: Re: [V2 PATCH] tmpfs: add fallocate support Message-Id: <20111122140630.9f37c907.akpm@linux-foundation.org> In-Reply-To: <1321612791-4764-1-git-send-email-amwang@redhat.com> References: <1321612791-4764-1-git-send-email-amwang@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Cong Wang Cc: linux-kernel@vger.kernel.org, Pekka Enberg , Hugh Dickins , Dave Hansen , Lennart Poettering , Kay Sievers , KOSAKI Motohiro , linux-mm@kvack.org 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. -- 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