Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752959AbaFXWDg (ORCPT ); Tue, 24 Jun 2014 18:03:36 -0400 Received: from eddie.linux-mips.org ([78.24.191.182]:34538 "EHLO cvs.linux-mips.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751590AbaFXWDf (ORCPT ); Tue, 24 Jun 2014 18:03:35 -0400 Date: Tue, 24 Jun 2014 23:03:32 +0100 (BST) From: "Maciej W. Rozycki" To: T Makphaibulchoke cc: "Theodore Ts'o" , Linus Torvalds , linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org Subject: Re: [GIT PULL] ext4 changes for 3.15 In-Reply-To: <20140403191558.GA8745@thunk.org> Message-ID: References: <20140403191558.GA8745@thunk.org> User-Agent: Alpine 2.11 (LFD 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 3 Apr 2014, Theodore Ts'o wrote: > fs/mbcache.c: doucple the locking of local from global data This change causes breakage: fs/built-in.o: In function `__mb_cache_entry_release': mbcache.c:(.text+0x56b3c): undefined reference to `log2' mbcache.c:(.text+0x56b3c): relocation truncated to fit: R_MIPS_26 against `log2' mbcache.c:(.text+0x56b74): undefined reference to `__fixunsdfsi' mbcache.c:(.text+0x56b74): relocation truncated to fit: R_MIPS_26 against `__fixunsdfsi' mbcache.c:(.text+0x56be4): undefined reference to `log2' mbcache.c:(.text+0x56be4): relocation truncated to fit: R_MIPS_26 against `log2' mbcache.c:(.text+0x56bf0): undefined reference to `__fixunsdfsi' mbcache.c:(.text+0x56bf0): relocation truncated to fit: R_MIPS_26 against `__fixunsdfsi' and so on, and so on. It uses __builtin_log2() that is a floating-point function, its corresponding prototype is: -- Function: double log2 (double X) (GCC builtins are of course implicitly prototyped). Please note that floating-point calculations are not allowed in the kernel and relying on the compiler to optimise them away is risky to say the least. Can you please rewrite the fragment using __builtin_log2() so as to avoid the floating-point calculation, using ffs() or suchlike perhaps? Maciej -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/