From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sandeen.net ([63.231.237.45]:39222 "EHLO sandeen.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934232AbdDST3X (ORCPT ); Wed, 19 Apr 2017 15:29:23 -0400 Subject: Re: [PATCH] xfs: remove use of do_div with 32-bit dividend in quota debug code References: <20170417185959.GA5193@birch.djwong.org> From: Eric Sandeen Message-ID: <615e5f75-282f-affc-fe3b-e6410dedaccf@sandeen.net> Date: Wed, 19 Apr 2017 14:29:22 -0500 MIME-Version: 1.0 In-Reply-To: <20170417185959.GA5193@birch.djwong.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: "Darrick J. Wong" , Eric Sandeen Cc: linux-xfs On 4/17/17 1:59 PM, Darrick J. Wong wrote: > On Sat, Apr 15, 2017 at 09:46:09AM -0500, Eric Sandeen wrote: >> The kbuild test robot caught this; in debug code we have another >> caller of do_div with a 32-bit dividend (j) which is caught now >> that we are using the kernel-supplied do_div. >> >> None of the values used here are 64-bit; just use simple division. >> >> Signed-off-by: Eric Sandeen >> --- >> >> diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c >> index b669b12..dedeb7f 100644 >> --- a/fs/xfs/xfs_qm.c >> +++ b/fs/xfs/xfs_qm.c >> @@ -851,8 +851,7 @@ struct xfs_qm_isolate { >> * started afresh by xfs_qm_quotacheck. >> */ >> #ifdef DEBUG >> - j = XFS_FSB_TO_B(mp, XFS_DQUOT_CLUSTER_SIZE_FSB); >> - do_div(j, sizeof(xfs_dqblk_t)); >> + j = XFS_FSB_TO_B(mp, XFS_DQUOT_CLUSTER_SIZE_FSB) / sizeof(xfs_dqblk_t); > > Uh... > > #define XFS_FSB_TO_B(mp,fsbno) ((xfs_fsize_t)(fsbno) << (mp)->m_sb.sb_blocklog) > typedef __int64_t xfs_fsize_t; /* bytes in a file */ Assigned to "int j", riiiiight. hohum. > So the macro resolves to a 64-bit value, which is then fed directly into > an integer division, which breaks the i386 build with the usual __divdi3 > complaint. sandeen-- > --D > >> ASSERT(mp->m_quotainfo->qi_dqperchunk == j); >> #endif >> dqb = bp->b_addr; >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-xfs" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >