From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f170.google.com ([209.85.128.170]:35184 "EHLO mail-wr0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752143AbdFONts (ORCPT ); Thu, 15 Jun 2017 09:49:48 -0400 Date: Thu, 15 Jun 2017 15:49:39 +0200 From: Pali =?utf-8?B?Um9ow6Fy?= To: Jan Kara Cc: Fabian Frederick , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: udf: allow implicit blocksize specification during mount Message-ID: <20170615134939.GR5248@pali> References: <201706122240.14996@pali> <20170613125955.GA20258@quack2.suse.cz> <201706142136.45895@pali> <20170615083427.GE1764@quack2.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20170615083427.GE1764@quack2.suse.cz> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Thursday 15 June 2017 10:34:27 Jan Kara wrote: > On Wed 14-06-17 21:36:45, Pali Rohár wrote: > > On Tuesday 13 June 2017 14:59:55 Jan Kara wrote: > > > Hi, > > > > > > On Mon 12-06-17 22:40:14, Pali Rohár wrote: > > > > Hi! I found that following UDF patch was included into linus tree: > > > > https://patchwork.kernel.org/patch/9524557/ > > > > > > > > It is really a good improvement to recognize UDF file system which > > > > have block size different from disk sector size and also different > > > > from 2048. > > > > > > > > But should not detection on 4K native disks (4096/4096) try to also > > > > use block size of 512 bytes? Because current loop is from logical > > > > sector size to 4096. > > > > > > By definition, bdev_logical_block_size() is the smallest block size a > > > device can support. So if it is larger than 512, the device driver > > > had explicitely declared that it cannot handle smaller blocks... > > > > Ok, but it is a really problem when trying to read data from filesystem > > which has smaller blocks as the smallest block size of a device? > > > > In the worst case filesystem driver needs to read 512 bytes, but device > > can send only block of 4096 bytes (as it does not support smaller > > block). Driver receives 4096 bytes, then it process just first 512 bytes > > and do not care about remaining data... > > Well, as much as I agree this is possible in principle, the block layer, > block device page cache etc. don't handle this so it would be a non-trivial > effort to support this. Ok, so it is not a problem in UDF driver nor hardware, just it is limitation of kernel block layer which do not support it. -- Pali Rohár pali.rohar@gmail.com