From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:36155 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752065AbaIKOfF (ORCPT ); Thu, 11 Sep 2014 10:35:05 -0400 Message-ID: <5411B304.4000203@fb.com> Date: Thu, 11 Sep 2014 10:34:44 -0400 From: Chris Mason MIME-Version: 1.0 To: , CC: , , =?UTF-8?B?Vmluw61jaXVzIFRpbnRp?= , =?UTF-8?B?SmFuLVNpbW9uIE3DtmxsZXI=?= , Mark Charlebois Subject: Re: [PATCH v2] btrfs: LLVMLinux: Remove VLAIS References: <1409957901-28962-1-git-send-email-behanw@converseincode.com> In-Reply-To: <1409957901-28962-1-git-send-email-behanw@converseincode.com> Content-Type: text/plain; charset="UTF-8" Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 09/05/2014 06:58 PM, behanw@converseincode.com wrote: > From: Vinícius Tinti > > Replaced the use of a Variable Length Array In Struct (VLAIS) with a C99 > compliant equivalent. This is the original VLAIS struct. > > struct { > struct shash_desc shash; > char ctx[crypto_shash_descsize(tfm)]; > } desc; > > This patch instead allocates the appropriate amount of memory using an char > array. > > The new code can be compiled with both gcc and clang. > > struct shash_desc contains a flexible array member member ctx declared with > CRYPTO_MINALIGN_ATTR, so sizeof(struct shash_desc) aligns the beginning > of the array declared after struct shash_desc with long long. > > No trailing padding is required because it is not a struct type that can > be used in an array. > > The CRYPTO_MINALIGN_ATTR is required so that desc is aligned with long long > as would be the case for a struct containing a member with > CRYPTO_MINALIGN_ATTR. We copied this from one of the other crypto api users, and I'm sure cooking up all these patches was not a great way to your afternoon. But, can I talk you into making a helper macro of some kind for this and putting it into the crypto api headers? Honestly this setup seems really error prone. -chris > > Signed-off-by: Jan-Simon Möller > Signed-off-by: Behan Webster > Signed-off-by: Vinícius Tinti > Signed-off-by: Mark Charlebois > --- > fs/btrfs/hash.c | 18 +++++++++--------- > 1 file changed, 9 insertions(+), 9 deletions(-) > > diff --git a/fs/btrfs/hash.c b/fs/btrfs/hash.c > index 85889aa..a62743f 100644 > --- a/fs/btrfs/hash.c > +++ b/fs/btrfs/hash.c > @@ -33,18 +33,18 @@ void btrfs_hash_exit(void) > > u32 btrfs_crc32c(u32 crc, const void *address, unsigned int length) > { > - struct { > - struct shash_desc shash; > - char ctx[crypto_shash_descsize(tfm)]; > - } desc; > + char desc[sizeof(struct shash_desc) + > + crypto_shash_descsize(tfm)] CRYPTO_MINALIGN_ATTR; > + struct shash_desc *shash = (struct shash_desc *)desc; > + u32 *ctx = (u32 *)shash_desc_ctx(shash); > int err; > > - desc.shash.tfm = tfm; > - desc.shash.flags = 0; > - *(u32 *)desc.ctx = crc; > + shash->tfm = tfm; > + shash->flags = 0; > + *ctx = crc; > > - err = crypto_shash_update(&desc.shash, address, length); > + err = crypto_shash_update(shash, address, length); > BUG_ON(err); > > - return *(u32 *)desc.ctx; > + return *ctx; > } >