Messages in this thread | | | Date | Thu, 10 May 2007 03:43:31 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH 7/13] i386 sg: add support for chaining scatterlists |
| |
On Thu, 10 May 2007 12:21:49 +0200 Jens Axboe <jens.axboe@oracle.com> wrote:
> The core of the patch - allow the last sg element in a scatterlist > table to point to the start of a new table. We overload the LSB of > the page pointer to indicate whether this is a valid sg entry, or > merely a link to the next list. > > Signed-off-by: Jens Axboe <jens.axboe@oracle.com> > --- > include/asm-i386/scatterlist.h | 2 + > include/linux/scatterlist.h | 52 +++++++++++++++++++++++++++++++++++++-- > 2 files changed, 51 insertions(+), 3 deletions(-) > > diff --git a/include/asm-i386/scatterlist.h b/include/asm-i386/scatterlist.h > index d7e45a8..bd5164a 100644 > --- a/include/asm-i386/scatterlist.h > +++ b/include/asm-i386/scatterlist.h > @@ -10,6 +10,8 @@ struct scatterlist { > unsigned int length; > }; > > +#define ARCH_HAS_SG_CHAIN > + > /* These macros should be used after a pci_map_sg call has been done > * to get bus addresses of each of the SG entries and their lengths. > * You should only work with the number of sg entries pci_map_sg > diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h > index c5bffde..bad6b9e 100644 > --- a/include/linux/scatterlist.h > +++ b/include/linux/scatterlist.h > @@ -20,13 +20,59 @@ static inline void sg_init_one(struct scatterlist *sg, const void *buf, > sg_set_buf(sg, buf, buflen); > } > > ... > > /* > * Loop over each sg element, following the pointer to a new list if necessary > */ > #define for_each_sg(sglist, sg, nr, __i) \ > - for (__i = 0, sg = (sglist); __i < nr; __i++, sg = sg_next(sg)) > + for (__i = 0, sg = (sglist); __i < (nr); __i++, sg = sg_next(sg)) > + > +/* > + * We could improve this by passing in the maximum size of an sglist, so > + * we could jump directly to the last table. That would eliminate this > + * (potentially) lengthy scan. > + */ > +static inline struct scatterlist *sg_last(struct scatterlist *sgl, > + unsigned int nents) > +{ > +#ifdef ARCH_HAS_SG_CHAIN > + struct scatterlist *ret = &sgl[nents - 1]; > +#else > + struct scatterlist *sg, *ret = NULL; > + int i; > + > + for_each_sg(sgl, sg, nents, i) > + ret = sg; > + > +#endif > + return ret; > +}
Looks too large to be inlined.
> +/* > + * Chain previous sglist to this one > + */ > +static inline void sg_chain(struct scatterlist *prv, unsigned int prv_nents, > + struct scatterlist *sgl) > +{ > +#ifndef ARCH_HAS_SG_CHAIN > + BUG(); > +#endif
Can use BUILD_BUG_ON here. Or just #error.
> + prv[prv_nents - 1].page = (struct page *) ((unsigned long) sgl | 0x01); > +}
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |