From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from zinan.dashjr.org ([192.3.11.21]:50200 "EHLO zinan.dashjr.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752595AbbEOQfu (ORCPT ); Fri, 15 May 2015 12:35:50 -0400 From: Luke Dashjr To: dsterba@suse.cz Subject: Re: [PATCH] btrfs: bugfix: handle FS_IOC32_{GETFLAGS,SETFLAGS,GETVERSION} in btrfs_ioctl Date: Fri, 15 May 2015 16:35:45 +0000 Cc: Chris Mason , Josef Bacik , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org References: <201505131715.27483.luke@dashjr.org> <201505141627.56205.luke@dashjr.org> <20150515111922.GB23255@twin.jikos.cz> In-Reply-To: <20150515111922.GB23255@twin.jikos.cz> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Message-Id: <201505151635.47489.luke@dashjr.org> Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Friday, May 15, 2015 11:19:22 AM David Sterba wrote: > On Thu, May 14, 2015 at 04:27:54PM +0000, Luke Dashjr wrote: > > On Thursday, May 14, 2015 2:06:17 PM David Sterba wrote: > > > On Wed, May 13, 2015 at 05:15:26PM +0000, Luke Dashjr wrote: > > > > 32-bit ioctl uses these rather than the regular FS_IOC_* versions. > > > > They can be handled in btrfs using the same code. Without this, > > > > 32-bit {ch,ls}attr fail. > > > > > > Yes, but this has to be implemented in another way. See eg. > > > https://git.kernel.org/linus/e9750824114ff > > > > I don't see what is different with that implementation. All > > f2fs_compat_ioctl does is change cmd to the plain-IOC equivalent and > > call f2fs_ioctl with the same arg (compat_ptr merely causes a cast to > > void* and back, which AFAIK is a noop on 64-bit?). Am I missing > > something? > > No, that's the idea. Add new calback for compat_ioctl, put it under > #ifdef CONFIG_COMPAT and do the same number switch. The idea is to wrap it in a way that doesn't actually change any of the logic? I'm not sure I understand still :( > > I could try to just imitate it, but > > I'd rather know what is significant/going on to ensure I don't waste your > > time with code I don't even properly understand myself. > > > > Perhaps by coincidence, the patch does at least in practice work > > (although at least `btrfs send` appears to be broken still, and I'm at a > > loss for how to approach fixing that). > > The 'receive' 32bit/64bit was broken due to size difference in the ioctl > structure that led to different ioctl. This is transparently fixed, see > BTRFS_IOC_SET_RECEIVED_SUBVOL_32 at the top of ioctl.c. > > In what way is SEND broken? There are only u64/s64 members in > btrfs_ioctl_send_args, I don't see how this could break on 32/64 > userspace/kernel. # btrfs send -p home/initial/ home/20150514_1431573370/ At subvol home/20150514_1431573370/ ERROR: send ioctl failed with -25: Inappropriate ioctl for device But I am stuck on 3.14.41 due to Linux being unstable in newer versions[1], so maybe this is unrelated to 32-bit and already fixed in 4.0? Luke 1. https://bugzilla.kernel.org/show_bug.cgi?id=87891