6.9-stable review patch. If anyone has any objections, please let me know.
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From: Chengming Zhou chengming.zhou@linux.dev
commit 730cdc2c72c6905a2eda2fccbbf67dcef1206590 upstream.
Patch series "mm/ksm: fix some accounting problems", v3.
We encountered some abnormal ksm_pages_scanned and ksm_zero_pages during some random tests.
1. ksm_pages_scanned unchanged even ksmd scanning has progress. 2. ksm_zero_pages maybe -1 in some rare cases.
This patch (of 2):
During testing, I found ksm_pages_scanned is unchanged although the scan_get_next_rmap_item() did return valid rmap_item that is not NULL.
The reason is the scan_get_next_rmap_item() will return NULL after a full scan, so ksm_do_scan() just return without accounting of the ksm_pages_scanned.
Fix it by just putting ksm_pages_scanned accounting in that loop, and it will be accounted more timely if that loop would last for a long time.
Link: https://lkml.kernel.org/r/20240528-b4-ksm-counters-v3-0-34bb358fdc13@linux.d... Link: https://lkml.kernel.org/r/20240528-b4-ksm-counters-v3-1-34bb358fdc13@linux.d... Fixes: b348b5fe2b5f ("mm/ksm: add pages scanned metric") Signed-off-by: Chengming Zhou chengming.zhou@linux.dev Acked-by: David Hildenbrand david@redhat.com Reviewed-by: xu xin xu.xin16@zte.com.cn Cc: Andrea Arcangeli aarcange@redhat.com Cc: Hugh Dickins hughd@google.com Cc: Ran Xiaokai ran.xiaokai@zte.com.cn Cc: Stefan Roesch shr@devkernel.io Cc: Yang Yang yang.yang29@zte.com.cn Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/ksm.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)
--- a/mm/ksm.c +++ b/mm/ksm.c @@ -2747,18 +2747,16 @@ static void ksm_do_scan(unsigned int sca { struct ksm_rmap_item *rmap_item; struct page *page; - unsigned int npages = scan_npages;
- while (npages-- && likely(!freezing(current))) { + while (scan_npages-- && likely(!freezing(current))) { cond_resched(); rmap_item = scan_get_next_rmap_item(&page); if (!rmap_item) return; cmp_and_merge_page(page, rmap_item); put_page(page); + ksm_pages_scanned++; } - - ksm_pages_scanned += scan_npages - npages; }
static int ksmd_should_run(void)