[PATCH 1/9] mm/rmap: make nr_pages signed in try_to_unmap_one

[Dev Jain <dev.jain@arm.com>]

Currently, nr_pages is defined as unsigned long. We use nr_pages to
manipulate mm rss counters for lazyfree folios as follows:

	add_mm_counter(mm, MM_ANONPAGES, -nr_pages);

Suppose nr_pages = 3. -nr_pages underflows and becomes ULONG_MAX - 2. Then,
since add_mm_counter() uses this -nr_pages as a long, ULONG_MAX - 2 does
not fit into the positive range of long, and is converted to -3. Eventually
all of this works out, but for keeping things simple, declare nr_pages as
a signed variable.

Signed-off-by: Dev Jain <dev.jain@arm.com>
---
 mm/rmap.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index 6398d7eef393f..087c9f5b884fe 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1979,9 +1979,10 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
 	struct page *subpage;
 	struct mmu_notifier_range range;
 	enum ttu_flags flags = (enum ttu_flags)(long)arg;
-	unsigned long nr_pages = 1, end_addr;
+	unsigned long end_addr;
 	unsigned long pfn;
 	unsigned long hsz = 0;
+	long nr_pages = 1;
 	int ptes = 0;
 
 	/*
-- 
2.34.1