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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: zijun_hu <zijun_hu@htc.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
zijun_hu 2016-12-12 16:45:02 -08:00 committed by Linus Torvalds
parent c5caf21ab0
commit 8f6066049c
1 changed files with 12 additions and 4 deletions
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14
mm/percpu.c
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@ -2093,6 +2093,8 @@ 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);
@ -2100,7 +2102,12 @@ 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;
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;
@ -2111,9 +2118,9 @@ int __init pcpu_page_first_chunk(size_t reserved_size,
/* allocate pages */
j = 0;
for (unit = 0; unit < num_possible_cpus(); unit++)
for (i = 0; i < unit_pages; i++) {
for (unit = 0; unit < num_possible_cpus(); unit++) {
unsigned int cpu = ai->groups[0].cpu_map[unit];
for (i = 0; i < unit_pages; i++) {
void *ptr;
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);
pages[j++] = virt_to_page(ptr);
}
}
/* allocate vm area, map the pages and copy static data */
vm.flags = VM_ALLOC;