On Tue, 23 Sep 2008 11:10:17 +0200
Nick Piggin <[EMAIL PROTECTED]> wrote:
> +void *pageable_vmap_object(pgobj_t *object, unsigned long start, unsigned
> long end)
> +{
> + struct file *filp = (struct file *)object;
> + struct address_space *mapping = filp->f_dentry->d_inode->i_mapping;
> + unsigned int offset = start & ~PAGE_CACHE_MASK;
> + pgoff_t first, last, i;
> + struct page **pages;
> + int nr;
> + void *ret;
> +
> + BUG_ON(start >= end);
> +
> + first = start / PAGE_SIZE;
> + last = DIV_ROUND_UP(end, PAGE_SIZE);
> + nr = last - first;
> +
> +#ifndef CONFIG_HIGHMEM
> + if (nr == 1) {
> + struct page *page;
> +
> + rcu_read_lock();
> + page = radix_tree_lookup(&mapping->page_tree, first);
> + rcu_read_unlock();
> + BUG_ON(!page);
> + BUG_ON(page_count(page) < 2);
> +
> + ret = page_address(page);
> +
> + goto out;
> + }
> +#endif
> +
> + pages = kmalloc(sizeof(struct page *) * nr, GFP_KERNEL);
> + if (!pages)
> + return NULL;
> +
> + for (i = first; i < last; i++) {
> + struct page *page;
> +
> + rcu_read_lock();
> + page = radix_tree_lookup(&mapping->page_tree, i);
> + rcu_read_unlock();
> + BUG_ON(!page);
> + BUG_ON(page_count(page) < 2);
> +
> + pages[i] = page;
> + }
> +
> + ret = vmap(pages, nr, VM_MAP, PAGE_KERNEL);
> + kfree(pages);
> + if (!ret)
> + return NULL;
> +
> +out:
> + return ret + offset;
> +}
> +
> +void pageable_vunmap_object(pgobj_t *object, void *ptr, unsigned long start,
> unsigned long end)
> +{
> +#ifndef CONFIG_HIGHMEM
> + pgoff_t first, last;
> + int nr;
> +
> + BUG_ON(start >= end);
> +
> + first = start / PAGE_SIZE;
> + last = DIV_ROUND_UP(end, PAGE_SIZE);
> + nr = last - first;
> + if (nr == 1)
> + return;
> +#endif
> +
> + vunmap((void *)((unsigned long)ptr & PAGE_CACHE_MASK));
> +}
> +
Some questions..
- could you use GFP_HIGHUSER rather than GFP_HIGHUSER_MOVABLE ?
I think setting mapping_gfp_mask() (address_space->flags) to appropriate
value is enough.
- Can we mlock pages while it's vmapped ? (or Reserve and remove from LRU)
Then, new split-lru can ignore these pages while there are mapped.
over-killing ?
- Doesn't we need to increase page->mapcount ?
- memory resource contorller should account these pages ?
(Maybe this is question to myself....)
Thanks,
-Kame
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