From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 83ECE3E5EE0; Mon, 16 Mar 2026 18:50:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773687028; cv=none; b=lHtqgqRBTlUIUxGjoDtjTatR0eBT0GKBBwdCZdq8O5y9PLTyu/vsCgFmF6uJu9z0KC4HDMPyxql5XfePG5IeTKN8cZ6ZufWzLAX7NqxgctPPmKaAtJQ0+oewGSwpdiB8FWeyg1FNcab/2Nux/PsM7tDcJtLVYAF9UgMvqnxv+xc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773687028; c=relaxed/simple; bh=E9JENZD0mkiWjjRdMcGyoo7gJmB6pU96OleUaRnZa9U=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=YbDtfa5e8nPYeg/Z2PkgbreE42atwVcx68QyhQeqd92sC4YS6R2Xdt1zdRElSJX0QlPwFxgtk3Xp1K+y9ABnrM8oOmB9FAWx4X379ZGiqjDqiM+gSf59hxYmA+hLWA8yj6ysxTlGInmSw+hH6a0NnyDRKcC7RXecaj6wYcPGp00= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=sH4ecE8T; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="sH4ecE8T" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CFE5EC19421; Mon, 16 Mar 2026 18:50:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773687028; bh=E9JENZD0mkiWjjRdMcGyoo7gJmB6pU96OleUaRnZa9U=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=sH4ecE8TQebEZEUAIuC+Nhhrja0nVrM0YyfZa7Ua7sU3lJ9PBDkt2umtJjUcUfamY 6+Tro0ZnAhWQfIbm/t+q89Z6/ZKel6R9fXJe8Ah0NyAqtMKQ6+FNZS9JETkZAYISe/ p5HAT2LTL42DDWCri2v7SbjkUKYovy1Y0YuRxlC3vQgQFAZ2tif3Z0j3aybd8oqu/V 7gdA3lrymryjFEUEW/jkO9J2dQAOyE+JuJC01s0vR9QJH2e9gRFThbdXzlFS4+R5z1 VxOwaUy3UY55fYn4R+Okl5TE7Z+spNN2nZoKcaU/R5o3TQYWzWwpxpxzVARkzFVbqJ oSPE8BRngoUXQ== Message-ID: <1f85d6a99d7421d050ed9ab1928ffc956a94955c.camel@kernel.org> Subject: Re: [PATCH v2 1/2] nilfs2: fix 64-bit division operations in nilfs_bmap_find_target_in_group() From: Jeff Layton To: Ryusuke Konishi , David Laight Cc: Viacheslav Dubeyko , Christian Brauner , Mimi Zohar , Roberto Sassu , Dmitry Kasatkin , Eric Snowberg , Paul Moore , James Morris , "Serge E. Hallyn" , linux-nilfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, linux-fsdevel@vger.kernel.org, kernel test robot Date: Mon, 16 Mar 2026 14:50:24 -0400 In-Reply-To: References: <20260313-iino-u64-v2-0-f9abda2464d5@kernel.org> <20260313-iino-u64-v2-1-f9abda2464d5@kernel.org> <20260314124748.1ccdf93b@pumpkin> <361258925536e2280ce62c5e49531af5c42aa491.camel@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 0OX6MYPtv76hka8lW4mnRmZqqx3UtfHX/hF/zH24Gj7A6sYKYLCU3YrI2Ogiu7/ksKcl7goQjpvtV YrOOI5VGLHge0awt7bhMCTM9KAfPc+xL/ZxAMVWd3NCk5SamL2cE99UWgtvNOIYU8m6EjTLhsj8sn 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DfX/sn9XcfoVZIxMpCRE750zvJvcCUz9HojsrMQ1NFc7MFT1z3MOW2/RlzPcog7xvR5ENPH19ojRD CHqumUHRry+RF0lH00clzX/W8OrQJZtoBPXv9ahka/Vp7kEulcBJr1cH5Wz/WprhsIM7U9pse1f1g Yy9YbXtWctUz8uvDR7shsQxAhX3qO7DilMtuGo1v97I/Kx4gXQ52syh/w6EBny71CZrOgD6kJwPVV AaM1LRC28muq91WCFhs/nzHozpbzcheyGtMUI2Ao4K6mnY+3zIuXPygZMFr9KXE6fF7HzKxKuZMJO aEZCiDOq0anx6FmOzs5E6Jqdpo/mtI8beK+BE7Va6ni7YrQlnT0i3vaTVMTiCThbqsB20VrbMjlhp f8lfK1XVNbRq/R7GZ9zHESlsa35ha60yd/j3pu5hT2xyy8krV8vGhHvnJ1XRMJBAB/UYb6FyC7S+m QZIQXVeAA+smfTT0tDrisj1U5x6ZB9b3nBg65kc= Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.3 (3.58.3-1.fc43) Precedence: bulk X-Mailing-List: linux-integrity@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Tue, 2026-03-17 at 03:06 +0900, Ryusuke Konishi wrote: > On Sat, Mar 14, 2026 at 9:59=E2=80=AFPM Jeff Layton wrote: > >=20 > > On Sat, 2026-03-14 at 12:47 +0000, David Laight wrote: > > > On Fri, 13 Mar 2026 14:45:20 -0400 > > > Jeff Layton wrote: > > >=20 > > > > With the change to make inode->i_ino a u64, the build started faili= ng on > > > > 32-bit ARM with: > > > >=20 > > > > ERROR: modpost: "__aeabi_uldivmod" [fs/nilfs2/nilfs2.ko] undefi= ned! > > > >=20 > > > > Fix this by using the 64-bit division interfaces in > > > > nilfs_bmap_find_target_in_group(). > > > >=20 > > > > Fixes: 998a59d371c2 ("treewide: fix missed i_ino format specifier c= onversions") > > > > Reported-by: kernel test robot > > > > Closes: https://lore.kernel.org/oe-kbuild-all/202603100602.KPxiClIO= -lkp@intel.com/ > > > > Reviewed-by: Viacheslav Dubeyko > > > > Acked-by: Ryusuke Konishi > > > > Signed-off-by: Jeff Layton > > > > --- > > > > fs/nilfs2/bmap.c | 9 ++++++--- > > > > 1 file changed, 6 insertions(+), 3 deletions(-) > > > >=20 > > > > diff --git a/fs/nilfs2/bmap.c b/fs/nilfs2/bmap.c > > > > index 824f2bd91c167965ec3a660202b6e6c5f1fe007e..abcf5252578ad24f694= bfccf525893674bfcb4bc 100644 > > > > --- a/fs/nilfs2/bmap.c > > > > +++ b/fs/nilfs2/bmap.c > > > > @@ -455,11 +455,14 @@ __u64 nilfs_bmap_find_target_in_group(const s= truct nilfs_bmap *bmap) > > > > { > > > > struct inode *dat =3D nilfs_bmap_get_dat(bmap); > > > > unsigned long entries_per_group =3D nilfs_palloc_entries_per_gr= oup(dat); > > > > - unsigned long group =3D bmap->b_inode->i_ino / entries_per_grou= p; > > >=20 > > > Are you sure entries_per_group can be more than 32 bits? > > > It looks like something that will be the same size on 32 and 64bit. > > >=20 > >=20 > > I'm not sure of anything here. I'm just want to get this to compile on > > all arches. FWIW, I'm not looking to optimize anything in this patch. > >=20 > > > > + unsigned long group; > > > > + u32 index; > > > > + > > > > + group =3D div_u64(bmap->b_inode->i_ino, entries_per_group); > > >=20 > > > You don't need the full 64 by 64 divide. > > > IIRC there are both div_u64_u32() and div_u64_ulong(). >=20 > Isn't the type of divisor in div_u64() u32? > Since entries_per_group cannot exceed 32 bits according to the current > specification, I think using div_u64() is fine. >=20 Yep, it is: static inline u64 div_u64(u64 dividend, u32 divisor) =20 > > >=20 > > > > + div_u64_rem(bmap->b_inode->i_ino, NILFS_BMAP_GROUP_DIV, &index)= ; > > >=20 > > > NILFD_BMAP_GROUP_DIV is 8 (and probably has to be a power of 2). > > > So: > > > index =3D bmap->b_inode->i_ino & (NILFS_BMAP_GROUP_DIV - 1); > > > is the same and likely much faster to calculate. > > > (The compiler will have done that optimisation before.) > > >=20 > > >=20 > >=20 > > That all sounds reasonable to me. At this point though, it would be > > better if the NILFS2 folks stepped in with how they'd prefer this be > > done. >=20 > Yes, indeed. It seems that the application of optimizations will > change, so this proposed correction is better. >=20 > Since NILFS_BMAP_GROUP_DIV is a fixed constant and cannot be anything > other than a power of 2, could you please adopt this proposed > correction with the following comment? >=20 > #define NILFS_BMAP_GROUP_DIV 8 /* must be a power of 2 */ >=20 Even better, lets use a compile-time assertion: BUILD_BUG_ON_NOT_POWER_OF_TWO(NILFS_BMAP_GROUP_DIV); I'll send a respin. Thanks! --=20 Jeff Layton