From mboxrd@z Thu Jan 1 00:00:00 1970 From: Theodore Ts'o Subject: Re: mkfs.ext4 -D option fails to mount Date: Thu, 29 Jun 2017 13:53:19 -0400 Message-ID: <20170629175319.s75rdncvejil357p@thunk.org> References: <20170629153538.GA4268@linux.intel.com> <20170629155727.GA8536@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-ext4@vger.kernel.org To: Ross Zwisler Return-path: Received: from imap.thunk.org ([74.207.234.97]:59354 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751936AbdF2RxW (ORCPT ); Thu, 29 Jun 2017 13:53:22 -0400 Content-Disposition: inline In-Reply-To: <20170629155727.GA8536@linux.intel.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Thu, Jun 29, 2017 at 09:57:27AM -0600, Ross Zwisler wrote: > On Thu, Jun 29, 2017 at 09:35:38AM -0600, Ross Zwisler wrote: > > Our validation team noticed that in some configurations mkfs.ext4 with the > > -D option creates a filesystem that can't be mounted: The -D option just means that we're doing the I/O using Direct I/O (as opposed to buffered I/O). It shouldn't make any difference to what gets written, so this very much smells like a bug in how /dev/pmem supports Direct I/O... > One more bit of info - this seems to be strongly tied to the size of the > block device. With a 32 GB block device it works fine, with 248 GB you get > overlap messages for groups 1 through 63, and with a 250 GB device you get > overlaps for groups 1 through 1999. This very much sounds like Direct I/O is just getting completely botched for the pmem device, and writes to a block group descriptor block is affecting the wrong place on the storage device. - Ted