[PATCH 04/11] RAS/CEC: Check count_threshold unconditionally

Borislav Petkov
2019-05-09T18:10:17Z

The count_threshold should be checked unconditionally, after insertion
too, so that a count_threshold value of 1 can cause an immediate
offlining. I.e., offline the page on the *first* error encountered.

Add comments to make it clear what cec_add_elem() does, while at it.

Reported-by: WANG Chao <chao.wang@ucloud.cn>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: linux-edac@vger.kernel.org
Link: https://lkml.kernel.org/r/20190418034115.75954-3-chao.wang@ucloud.cn
---
drivers/ras/cec.c | 27 ++++++++++-----------------
1 file changed, 10 insertions(+), 17 deletions(-)

diff --git a/drivers/ras/cec.c b/drivers/ras/cec.c
index 1275907ff21c..73216b7f67be 100644
--- a/drivers/ras/cec.c
+++ b/drivers/ras/cec.c
@@ -294,6 +294,7 @@ int cec_add_elem(u64 pfn)

ca->ces_entered++;

+ /* Array full, free the LRU slot. */
if (ca->n == MAX_ELEMS)
WARN_ON(!del_lru_elem_unlocked(ca));

@@ -306,24 +307,17 @@ int cec_add_elem(u64 pfn)
(void *)&ca->array[to],
(ca->n - to) * sizeof(u64));

- ca->array[to] = (pfn << PAGE_SHIFT) |
- (DECAY_MASK << COUNT_BITS) | 1;
-
+ ca->array[to] = pfn << PAGE_SHIFT;
ca->n++;
-
- ret = 0;
-
- goto decay;
}

- count = COUNT(ca->array[to]);
-
- if (count < count_threshold) {
- ca->array[to] |= (DECAY_MASK << COUNT_BITS);
- ca->array[to]++;
+ /* Add/refresh element generation and increment count */
+ ca->array[to] |= DECAY_MASK << COUNT_BITS;
+ ca->array[to]++;

- ret = 0;
- } else {
+ /* Check action threshold and soft-offline, if reached. */
+ count = COUNT(ca->array[to]);
+ if (count >= count_threshold) {
u64 pfn = ca->array[to] >> PAGE_SHIFT;

if (!pfn_valid(pfn)) {
@@ -338,15 +332,14 @@ int cec_add_elem(u64 pfn)
del_elem(ca, to);

/*
- * Return a >0 value to denote that we've reached the offlining
- * threshold.
+ * Return a >0 value to callers, to denote that we've reached
+ * the offlining threshold.
*/
ret = 1;

goto unlock;
}

-decay:
ca->decay_count++;

if (ca->decay_count >= CLEAN_ELEMS)
--
2.21.0