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[212.85.88.110]) by smtp.gmail.com with ESMTPSA id r2sm1493279lfn.13.2020.01.08.06.37.58 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 08 Jan 2020 06:37:59 -0800 (PST) From: Mikael Magnusson To: david@fromorbit.com Cc: akpm@linux-foundation.org, amir73il@gmail.com, chris@chrisdown.name, hannes@cmpxchg.org, hughd@google.com, jlayton@kernel.org, kernel-team@fb.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, tj@kernel.org, viro@zeniv.linux.org Subject: Re: [PATCH v5 2/2] tmpfs: Support 64-bit inums per-sb Date: Wed, 8 Jan 2020 15:37:52 +0100 Message-Id: <20200108143752.9475-1-mikachu@gmail.com> X-Mailer: git-send-email 2.15.1 In-Reply-To: <20200107001039.GM23195@dread.disaster.area> References: <20200107001039.GM23195@dread.disaster.area> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Dave Chinner writes: > On Sun, Jan 05, 2020 at 12:06:05PM +0000, Chris Down wrote: > > The default is still set to inode32 for backwards compatibility, but > > system administrators can opt in to the new 64-bit inode numbers by > > either: > > > > 1. Passing inode64 on the command line when mounting, or > > 2. Configuring the kernel with CONFIG_TMPFS_INODE64=y > > > > The inode64 and inode32 names are used based on existing precedent from > > XFS. > > Please don't copy this misfeature of XFS. > > The inode32/inode64 XFS options were a horrible hack made more than > 20 years ago when NFSv2 was still in use and 64 bit inodes could > not be used for NFSv2 exports. It was then continued to be used > because 32bit NFSv3 clients were unable to handle 64 bit inodes. > > It took 15 years for us to be able to essentially deprecate > inode32 (inode64 is the default behaviour), and we were very happy > to get that albatross off our necks. In reality, almost everything > out there in the world handles 64 bit inodes correctly > including 32 bit machines and 32bit binaries on 64 bit machines. > And, IMNSHO, there no excuse these days for 32 bit binaries that > don't using the *64() syscall variants directly and hence support > 64 bit inodes correctlyi out of the box on all platforms. > > I don't think we should be repeating past mistakes by trying to > cater for broken 32 bit applications on 64 bit machines in this day > and age. Hi, It's unfortunately not true that everything handles this correctly. 32-bit binaries for games on Steam that use stat() without the 64 is so prevalent that I got tired of adding the LD_PRELOAD wrapper script and just patched out the EOVERFLOW return from glibc instead. (They obviously don't care about the inode value at all, and I don't use any other 32-bit binaries that do). This is probably a class of binaries you don't care very much about, and not very likely to be installed on a tmpfs that has wrapped around, but I thought it was worth mentioning that they do exist anyway. -- Mikael Magnusson