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Commit 8f606604 authored by zijun_hu's avatar zijun_hu Committed by Linus Torvalds
Browse files

mm/percpu.c: fix panic triggered by BUG_ON() falsely 

As shown by pcpu_build_alloc_info(), the number of units within a percpu
group is deduced 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 that one number is equal to the other roughly,
so a panic is maybe triggered by the BUG_ON() incorrectly.

In order to fix this issue, the number of CPUs is rounded up then
compared with units's and the BUG_ON() is replaced with a warning and
return of an error code as well, to keep system alive as much as
possible.

Link: http://lkml.kernel.org/r/57FCF07C.2020103@zoho.com


Signed-off-by: default avatarzijun_hu <zijun_hu@htc.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c5caf21a

mm/percpu.c

+12 −4
Original line number Original line Diff line number Diff line
@@ -2093,6 +2093,8 @@ int __init pcpu_page_first_chunk(size_t reserved_size, 
	size_t pages_size;

	size_t pages_size;

	struct page **pages;

	struct page **pages;

	int unit, i, j, rc;

	int unit, i, j, rc;

	int upa;

	int nr_g0_units;





	snprintf(psize_str, sizeof(psize_str), "%luK", PAGE_SIZE >> 10);

	snprintf(psize_str, sizeof(psize_str), "%luK", PAGE_SIZE >> 10);
@@ -2100,7 +2102,12 @@ int __init pcpu_page_first_chunk(size_t reserved_size, 
	if (IS_ERR(ai))

	if (IS_ERR(ai))

		return PTR_ERR(ai);

		return PTR_ERR(ai);

	BUG_ON(ai->nr_groups != 1);

	BUG_ON(ai->nr_groups != 1);

	BUG_ON(ai->groups[0].nr_units != num_possible_cpus());

	upa = ai->alloc_size/ai->unit_size;

	nr_g0_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;

	unit_pages = ai->unit_size >> PAGE_SHIFT;
@@ -2111,9 +2118,9 @@ int __init pcpu_page_first_chunk(size_t reserved_size, 




	/* allocate pages */

	/* allocate pages */

	j = 0;

	j = 0;

	for (unit = 0; unit < num_possible_cpus(); unit++)

	for (unit = 0; unit < num_possible_cpus(); unit++) {

		for (i = 0; i < unit_pages; i++) {

		unsigned int cpu = ai->groups[0].cpu_map[unit];

		unsigned int cpu = ai->groups[0].cpu_map[unit];

		for (i = 0; i < unit_pages; i++) {

			void *ptr;

			void *ptr;





			ptr = alloc_fn(cpu, PAGE_SIZE, PAGE_SIZE);

			ptr = alloc_fn(cpu, PAGE_SIZE, PAGE_SIZE);
@@ -2126,6 +2133,7 @@ int __init pcpu_page_first_chunk(size_t reserved_size, 
			kmemleak_free(ptr);

			kmemleak_free(ptr);

			pages[j++] = virt_to_page(ptr);

			pages[j++] = virt_to_page(ptr);

		}

		}

	}





	/* allocate vm area, map the pages and copy static data */

	/* allocate vm area, map the pages and copy static data */

	vm.flags = VM_ALLOC;

	vm.flags = VM_ALLOC;