On Mon, Jan 14 2008, Matthew Wilcox wrote:
> On Tue, Dec 04, 2007 at 05:26:28AM +0100, Nick Piggin wrote:
> > +static void copy_to_brd(struct brd_device *brd, const void *src,
> > + sector_t sector, size_t n)
> > +{
> > + struct page *page;
> > + void *dst;
> > + unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
> > + size_t copy;
> > +
> > + copy = min((unsigned long)n, PAGE_SIZE - offset);
> > + page = brd_lookup_page(brd, sector);
> > + BUG_ON(!page);
> > +
> > + dst = kmap_atomic(page, KM_USER1);
> > + memcpy(dst + offset, src, copy);
> > + kunmap_atomic(dst, KM_USER1);
>
> You're using kmap_atomic, but I see no reason you can't be preempted.
> Don't you need to at least disable preemption while you have stuff
> atomically kmapped?
kmap_atomic() disables preemption through pagefault_disable().
--
Jens Axboe
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