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
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