2015-05-02 1:15 GMT+09:00 Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>:
> 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.
I'll convert crc_t10dif to inline function. But do we also need to
make crc_t10dif_update inline function? (i.e. is there any difference
between __crc_t10dif_update and crc_t10dif_update?)
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