linux-kernel - [PATCH v3 02/12] btrfs: LLVMLinux: Remove VLAIS

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Date:	Mon, 15 Sep 2014 00:30:24 -0700
From:	behanw@...verseincode.com
To:	agk@...hat.com, clm@...com, davem@...emloft.net,
	dm-devel@...hat.com, fabf@...net.be, herbert@...dor.apana.org.au,
	jbacik@...com, snitzer@...hat.com, tadeusz.struk@...el.com
Cc:	akpm@...ux-foundation.org, bruce.w.allan@...el.com,
	d.kasatkin@...sung.com, james.l.morris@...cle.com,
	john.griffin@...el.com, linux-btrfs@...r.kernel.org,
	linux-crypto@...r.kernel.org,
	linux-ima-devel@...ts.sourceforge.net,
	linux-ima-user@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	linux-raid@...r.kernel.org, linux-security-module@...r.kernel.org,
	neilb@...e.de, qat-linux@...el.com, serge@...lyn.com,
	thomas.lendacky@....com, zohar@...ux.vnet.ibm.com,
	torvalds@...ux-foundation.org,
	Vinícius Tinti <viniciustinti@...il.com>,
	Behan Webster <behanw@...verseincode.com>
Subject: [PATCH v3 02/12] btrfs: LLVMLinux: Remove VLAIS

From: Vinícius Tinti <viniciustinti@...il.com>

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 a
char array using the SHASH_DESC_ON_STACK macro.

The new code can be compiled with both gcc and clang.

Signed-off-by: Vinícius Tinti <viniciustinti@...il.com>
Reviewed-by: Jan-Simon Möller <dl9pf@....de>
Reviewed-by: Mark Charlebois <charlebm@...il.com>
Signed-off-by: Behan Webster <behanw@...verseincode.com>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Herbert Xu <herbert@...dor.apana.org.au>
---
 fs/btrfs/hash.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/fs/btrfs/hash.c b/fs/btrfs/hash.c
index 85889aa..4bf4d3a 100644
--- a/fs/btrfs/hash.c
+++ b/fs/btrfs/hash.c
@@ -33,18 +33,16 @@ 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;
+	SHASH_DESC_ON_STACK(shash, tfm);
+	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;
 }
-- 
1.9.1

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