From: Arnd Bergmann Subject: Re: [PATCH 1/2] ext4: fix warning about stack corruption Date: Sun, 6 Aug 2017 22:34:14 +0200 Message-ID: References: <20170726185219.GA57833@beast> <20170801120438.1582336-1-arnd@arndb.de> <20170806015324.yg7gc45c77zemtlh@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" To: "Theodore Ts'o" , Arnd Bergmann , Andreas Dilger , Kees Cook , Andrew Morton , Jan Kara , Chandan Rajendra , linux-ext4@vger.kernel.org, Linux Kernel Mailing List Return-path: In-Reply-To: <20170806015324.yg7gc45c77zemtlh@thunk.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Sun, Aug 6, 2017 at 3:53 AM, Theodore Ts'o wrote: > On Tue, Aug 01, 2017 at 02:04:03PM +0200, Arnd Bergmann wrote: >> There is one remaining issue with the function that I'm not addressing >> here: With s_blocksize_bits==16, we don't actually print the last two >> members of the array, as we loop though just the first 14 members. >> This could be easily addressed by adding two extra columns in the output, >> but that could in theory break parsers in user space, and should be >> a separate patch if we decide to modify it. > > Actually, the counters array is blocksize_bits+2 in length. So for > all block sizes greater than 4k (blocksize_bits == 12), we're not > iterating over all of the free space counters maintained by mballoc. Ah, makes sense. > However, since most Linux systems run architectures where the page > size is 4k, and the Linux VM really doesn't easily support file system > block sizes greater than the page size, this really isn't an issue > except on Itanics and Power systems. Red Hat also build their arm64 kernels with 64k pages for some odd reason I could never quite understand. > Thanks, I'll apply this patch. Thanks! Arnd