On Thu, May 10 2007, Andrew Morton wrote: > On Thu, 10 May 2007 12:21:49 +0200 Jens Axboe <[EMAIL PROTECTED]> 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 <[EMAIL PROTECTED]> > > --- > > 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.
Yeah, I'm inclined to agree. Perhaps it would be better to put this stuff in lib/scatterlist.c or something like that instead? > > +/* > > + * 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. Good idea, thanks! -- Jens Axboe - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/