On Fri, 23 Jul 2010 12:25:47 +0300
Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
> +/*
> + * Allocate a lot of memory, preferrably max_sz but at least min_sz. In case
> + * there isn't much memory do not exceed 1/16th total RAM.
> + */
> +static struct mmc_test_mem *mmc_test_alloc_mem(unsigned int min_sz,
> + unsigned int max_sz)
> +{
> + unsigned int max_page_cnt = DIV_ROUND_UP(max_sz, PAGE_SIZE);
> + unsigned int min_page_cnt = DIV_ROUND_UP(min_sz, PAGE_SIZE);
> + unsigned int page_cnt = 0;
> + struct mmc_test_mem *mem;
> + struct sysinfo si;
> +
> + si_meminfo(&si);
> + if (max_page_cnt > si.totalram >> 4)
> + max_page_cnt = si.totalram >> 4;
> + if (max_page_cnt < min_page_cnt)
> + max_page_cnt = min_page_cnt;
> +
> + mem = kzalloc(sizeof(struct mmc_test_mem), GFP_KERNEL);
>
> ...
>
> + gfp_t flags = GFP_KERNEL | GFP_DMA | __GFP_NOWARN |
> + __GFP_NORETRY;
> +
> + order = get_order(page_cnt << PAGE_SHIFT);
> + while (1) {
> + page = alloc_pages(flags, order);
>
> ...
>
struct sysinfo.totalram returns the total number of pages including
highmem. But a GFP_KERNEL allocation can only return lowmem pages.
The difference between the two can be 20x (on a 16G i386 box).
nr_free_buffer_pages() would be a more accurate thing to use.
Also, I worry about overflows here. For example, `page_cnt <<
PAGE_SHIFT' could overflow the unsigned int? Please check all of that.
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