From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f51.google.com ([74.125.83.51]:34764 "EHLO mail-pg0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751183AbdHXHDw (ORCPT ); Thu, 24 Aug 2017 03:03:52 -0400 Received: by mail-pg0-f51.google.com with SMTP id s14so12546989pgs.1 for ; Thu, 24 Aug 2017 00:03:52 -0700 (PDT) From: Omar Sandoval To: linux-block@vger.kernel.org Cc: kernel-team@fb.com, Hannes Reinecke , Ming Lei , Karel Zak , Milan Broz Subject: [PATCH 0/4] loop: support different logical block sizes Date: Thu, 24 Aug 2017 00:03:40 -0700 Message-Id: Sender: linux-block-owner@vger.kernel.org List-Id: linux-block@vger.kernel.org From: Omar Sandoval Hi, everyone, Here's another attempt at supporting different logical block sizes for loop devices. First, some terminology: * Logical block size: the lowest possible block size that the storage device can address. * Physical block size: the lowest possible sector size that the hardware can operate on without reverting to read-modify-write operations. Always greater than or equal to the logical block size. These are characteristics of the device itself tracked in the request_queue. For loop devices, both are currently always 512 bytes. struct block_device also has another block size, basically a "soft" block size which is the preferred I/O size and can be changed from userspace. For loop devices, this is PAGE_SIZE if the backing file is a regular file or otherwise the soft block size of the backing block device. Patch 1 simplifies how the soft block size is set. I'm tempted to not set it at all and use the default of PAGE_SIZE, but maybe someone is depending on inheriting the soft block size from the backing block device... Patch 2 sets the physical block size of loop devices to a more meaningful value for loop, PAGE_SIZE. Patch 3 allows us to change the logical block size. It adds a new ioctl instead of the previous approach (which extends LOOP_{GET,SET}_STATUS). Hannes, I assume you had a specific reason for doing it the way you did, care to explain? Patch 4 is a cleanup. This is based on my patch reverting the original block size support, targeting 4.14. Thanks! Omar Sandoval (4): loop: get rid of lo_blocksize loop: set physical block size to PAGE_SIZE loop: add ioctl for changing logical block size loop: fold loop_switch() into callers drivers/block/loop.c | 112 ++++++++++++++++------------------------------ drivers/block/loop.h | 1 - include/uapi/linux/loop.h | 1 + 3 files changed, 40 insertions(+), 74 deletions(-) -- 2.14.1