Hi all,
please ignore this patch since it includes a build error
i resend the fixed patch in v2 version
i am sorry for my incaution
On 2016/10/11 21:03, zijun_hu wrote:
> From: zijun_hu <zijun...@htc.com>
>
> as shown by pcpu_build_alloc_info(), the number of units within a percpu
> group is educed by rounding up the number of CPUs within the group to
> @upa boundary, therefore, the number of CPUs isn't equal to the units's
> if it isn't aligned to @upa normally. however, pcpu_page_first_chunk()
> uses BUG_ON() to assert one number is equal the other roughly, so a panic
> is maybe triggered by the BUG_ON() falsely.
>
> in order to fix this issue, the number of CPUs is rounded up then compared
> with units's, the BUG_ON() is replaced by warning and returning error code
> as well to keep system alive as much as possible.
>
> Signed-off-by: zijun_hu <zijun...@htc.com>
> ---
> mm/percpu.c | 16 ++++++++++++----
> 1 file changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/mm/percpu.c b/mm/percpu.c
> index 32e2d8d128c1..c2f0d9734d8c 100644
> --- a/mm/percpu.c
> +++ b/mm/percpu.c
> @@ -2095,6 +2095,8 @@ int __init pcpu_page_first_chunk(size_t reserved_size,
> size_t pages_size;
> struct page **pages;
> int unit, i, j, rc;
> + int upa;
> + int nr_g0_units;
>
> snprintf(psize_str, sizeof(psize_str), "%luK", PAGE_SIZE >> 10);
>
> @@ -2102,7 +2104,12 @@ int __init pcpu_page_first_chunk(size_t reserved_size,
> if (IS_ERR(ai))
> return PTR_ERR(ai);
> BUG_ON(ai->nr_groups != 1);
> - BUG_ON(ai->groups[0].nr_units != num_possible_cpus());
> + upa = ai->alloc_size/ai->unit_size;
> + g0_nr_units = roundup(num_possible_cpus(), upa);
> + if (unlikely(WARN_ON(ai->groups[0].nr_units != nr_g0_units))) {
> + pcpu_free_alloc_info(ai);
> + return -EINVAL;
> + }
>
> unit_pages = ai->unit_size >> PAGE_SHIFT;
>
> @@ -2113,21 +2120,22 @@ int __init pcpu_page_first_chunk(size_t reserved_size,
>
> /* allocate pages */
> j = 0;
> - for (unit = 0; unit < num_possible_cpus(); unit++)
> + for (unit = 0; unit < num_possible_cpus(); unit++) {
> + unsigned int cpu = ai->groups[0].cpu_map[unit];
> for (i = 0; i < unit_pages; i++) {
> - unsigned int cpu = ai->groups[0].cpu_map[unit];
> void *ptr;
>
> ptr = alloc_fn(cpu, PAGE_SIZE, PAGE_SIZE);
> if (!ptr) {
> pr_warn("failed to allocate %s page for
> cpu%u\n",
> - psize_str, cpu);
> + psize_str, cpu);
> goto enomem;
> }
> /* kmemleak tracks the percpu allocations separately */
> kmemleak_free(ptr);
> pages[j++] = virt_to_page(ptr);
> }
> + }
>
> /* allocate vm area, map the pages and copy static data */
> vm.flags = VM_ALLOC;
>
