* [PATCH v2] btrfs: LLVMLinux: Remove VLAIS
@ 2014-09-05 22:58 behanw
2014-09-11 14:34 ` Chris Mason
0 siblings, 1 reply; 3+ messages in thread
From: behanw @ 2014-09-05 22:58 UTC (permalink / raw)
To: clm, jbacik
Cc: linux-btrfs, linux-kernel, Vinícius Tinti,
Jan-Simon Möller, Behan Webster, Mark Charlebois
From: Vinícius Tinti <viniciustinti@gmail.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 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.
Signed-off-by: Jan-Simon Möller <dl9pf@gmx.de>
Signed-off-by: Behan Webster <behanw@converseincode.com>
Signed-off-by: Vinícius Tinti <viniciustinti@gmail.com>
Signed-off-by: Mark Charlebois <charlebm@gmail.com>
---
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;
}
--
1.9.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2] btrfs: LLVMLinux: Remove VLAIS
2014-09-05 22:58 [PATCH v2] btrfs: LLVMLinux: Remove VLAIS behanw
@ 2014-09-11 14:34 ` Chris Mason
2014-09-11 21:38 ` Behan Webster
0 siblings, 1 reply; 3+ messages in thread
From: Chris Mason @ 2014-09-11 14:34 UTC (permalink / raw)
To: behanw, jbacik
Cc: linux-btrfs, linux-kernel, Vinícius Tinti,
Jan-Simon Möller, Mark Charlebois
On 09/05/2014 06:58 PM, behanw@converseincode.com wrote:
> From: Vinícius Tinti <viniciustinti@gmail.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 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 <dl9pf@gmx.de>
> Signed-off-by: Behan Webster <behanw@converseincode.com>
> Signed-off-by: Vinícius Tinti <viniciustinti@gmail.com>
> Signed-off-by: Mark Charlebois <charlebm@gmail.com>
> ---
> 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;
> }
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] btrfs: LLVMLinux: Remove VLAIS
2014-09-11 14:34 ` Chris Mason
@ 2014-09-11 21:38 ` Behan Webster
0 siblings, 0 replies; 3+ messages in thread
From: Behan Webster @ 2014-09-11 21:38 UTC (permalink / raw)
To: Chris Mason, jbacik
Cc: linux-btrfs, linux-kernel, Vinícius Tinti,
Jan-Simon Möller, Mark Charlebois
On 09/11/14 09:34, Chris Mason wrote:
>
> On 09/05/2014 06:58 PM, behanw@converseincode.com wrote:
>> From: Vinícius Tinti <viniciustinti@gmail.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 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.
You're not the only person to ask for this. I've got one already coded
up based on suggestions from tglx.
I've regenerated all the patches. I will resubmit soon.
Will fix.
Behan
--
Behan Webster
behanw@converseincode.com
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2014-09-11 21:43 UTC | newest]
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2014-09-05 22:58 [PATCH v2] btrfs: LLVMLinux: Remove VLAIS behanw
2014-09-11 14:34 ` Chris Mason
2014-09-11 21:38 ` Behan Webster
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