On Sat, 2015-05-02 at 10:38 +0900, Akinobu Mita wrote:
> 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?)
I don't mean convert crc_t10dif to inline, but make a local inline function
__crc_t10dif_update that both crc_t10dif_update and crc_t10dif can use
so crc_t10dif don't have to do one more function call. Yes, crc_t10dif_update
and __crc_t10dif_update are equivalent but since the latter is inlined, so there's no
performance impact and we get rid of the overhead of the extra function
call in crc_t10dif.
Like
+
+__u16 crc_t10dif_update(__u16 crc, const unsigned char *buffer, size_t len)
+{
+ return __crc_t10dif_update(crc, buffer, len, true);
+}
+EXPORT_SYMBOL(crc_t10dif_update);
+
+__u16 crc_t10dif(const unsigned char *buffer, size_t len)
+{
+ return __crc_t10dif_update(0, buffer, len, false);
+}
EXPORT_SYMBOL(crc_t10dif);
Thanks.
Tim
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