On Thu, Oct 18, 2018 at 04:42:07PM +0200, Christoph Hellwig wrote:
> This all seems quite complicated.
>
> I think the interface we'd want is more one that has a little
> cache of a single page in the queue, and a little bitmap which
> sub-page size blocks of it are used.
>
> Something like (pseudo code minus locking):
>
> void *blk_alloc_sector_buffer(struct block_device *bdev, gfp_t gfp)
> {
> unsigned block_size = block_size(bdev);
>
> if (blocksize >= PAGE_SIZE)
> return (void *)__get_free_pages(gfp, get_order(blocksize));
>
> if (bdev->fragment_cache_page) {
> [ <find fragment in bdev->fragment_cache_page using
> e.g. bitmap and return if found]
> }
>
> bdev->fragment_cache_page = (void *)__get_free_page(gfp);
> goto find_again;
> }
This looks a lot like page_frag_alloc() except I think page_frag_alloc()
may be more efficient.
