Messages in this thread | | | Date | Tue, 9 Jul 2002 10:16:15 +0200 | From | Ingo Oeser <> | Subject | Re: direct-to-BIO for O_DIRECT |
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On Mon, Jul 08, 2002 at 09:26:48PM -0700, Andrew Morton wrote: > > > It would be nice if we could just map a set of user pages > > > to a scatterlist. > > > > After disabling kiobufs in sg I would like such a drop > > in replacement. > > Ben had lightweight sg structures called `kvecs' and `kveclets'. And > library functions to map pages into them. And code to attach them > to BIOs. So we'll be looking at getting that happening.
BIOs are for BLOCK devices we want sth. like this for CHARACTER devices.
I just want sth. along the lines of this:
/* Pin down (COMPLETE!) user pages and put them into a scatter gather list */ int sg_map_user_pages(struct scatterlist *sgl, const unsigned int nr_pages, unsigned long uaddr, int rw) { int res, i; struct page *pages[nr_pages];
down_read(¤t->mm->mmap_sem); res = get_user_pages( current, current->mm, uaddr, nr_pages, rw == READ, /* logic is perversed^Wreversed here :-( */ 0, /* don't force */ &pages[0], NULL); up_read(¤t->mm->mmap_sem);
/* Errors and no page mapped should return here */ if (res <= 0) return res;
for (i=1; i < res; i++) { sgl[i].page = pages[i]; } return res; }
/* And unmap them... */ int sg_unmap_user_pages(struct scatterlist *sgl, const unsigned int nr_pages) { int i;
for (i=0; i < nr_pages; i++) page_cache_release(sgl[i].page);
return 0; }
Possibly more complicated and less error prone, but you get the idea ;-)
Regards
Ingo Oeser -- Science is what we can tell a computer. Art is everything else. --- D.E.Knuth - 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/
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