On Fri, 2015-05-01 at 15:23 +0900, Akinobu Mita wrote:
> This introduces crc_t10dif_update() which enables to calculate CRC
> for a block which straddles multiple SG elements by calling multiple
> times. This also converts crc_t10dif() to use crc_t10dif_update() as
> they are almost same.
>
> Signed-off-by: Akinobu Mita <akinobu.mita@xxxxxxxxx>
> Acked-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
> Cc: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>
> Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: linux-crypto@xxxxxxxxxxxxxxx
> Cc: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
> Cc: Sagi Grimberg <sagig@xxxxxxxxxxxx>
> Cc: "Martin K. Petersen" <martin.petersen@xxxxxxxxxx>
> Cc: Christoph Hellwig <hch@xxxxxx>
> Cc: "James E.J. Bottomley" <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
> Cc: target-devel@xxxxxxxxxxxxxxx
> ---
> * Changes from v3:
> - Reduce duplicated code between crc_t10dif_update and crc_t10dif,
> suggested by Tim and Herbert
>
> include/linux/crc-t10dif.h | 1 +
> lib/crc-t10dif.c | 13 ++++++++++---
> 2 files changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/crc-t10dif.h b/include/linux/crc-t10dif.h
> index cf53d07..d81961e 100644
> --- a/include/linux/crc-t10dif.h
> +++ b/include/linux/crc-t10dif.h
> @@ -9,5 +9,6 @@
> extern __u16 crc_t10dif_generic(__u16 crc, const unsigned char *buffer,
> size_t len);
> extern __u16 crc_t10dif(unsigned char const *, size_t);
> +extern __u16 crc_t10dif_update(__u16 crc, unsigned char const *, size_t);
>
> #endif
> diff --git a/lib/crc-t10dif.c b/lib/crc-t10dif.c
> index dfe6ec1..d775737 100644
> --- a/lib/crc-t10dif.c
> +++ b/lib/crc-t10dif.c
> @@ -19,7 +19,7 @@
> static struct crypto_shash *crct10dif_tfm;
> static struct static_key crct10dif_fallback __read_mostly;
>
> -__u16 crc_t10dif(const unsigned char *buffer, size_t len)
> +__u16 crc_t10dif_update(__u16 crc, const unsigned char *buffer, size_t len)
> {
> struct {
> struct shash_desc shash;
> @@ -28,17 +28,24 @@ __u16 crc_t10dif(const unsigned char *buffer, size_t len)
> int err;
>
> if (static_key_false(&crct10dif_fallback))
> - return crc_t10dif_generic(0, buffer, len);
> + return crc_t10dif_generic(crc, buffer, len);
>
> desc.shash.tfm = crct10dif_tfm;
> desc.shash.flags = 0;
> - *(__u16 *)desc.ctx = 0;
>
> + err = crypto_shash_import(&desc.shash, &crc);
> + BUG_ON(err);
> err = crypto_shash_update(&desc.shash, buffer, len);
> BUG_ON(err);
>
> return *(__u16 *)desc.ctx;
> }
> +EXPORT_SYMBOL(crc_t10dif_update);
> +
> +__u16 crc_t10dif(const unsigned char *buffer, size_t len)
> +{
> + return crc_t10dif_update(0, buffer, len);
Nitpicking a bit:
Will putting an extra function call to crc_t10dif_update will add extra
overhead to crc_t10dif, which is what most driver uses? As
we are calling crc_t10dif a lot (millions of times) as we go
through a block device, this extra function call
is undesirable. Using a __crc_t10dif_update
inline function that both crc_t10dif_update and crc_t10dif
invokes can will avoid this overhead.
Tim
> +}
> EXPORT_SYMBOL(crc_t10dif);
>
> static int __init crc_t10dif_mod_init(void)
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