[PATCH v3 06/10] mm/page_owner: Read stack traces with stack_depot_fetch_into()

[Matt Fleming <matt@readmodwrite.com>]

From: Matt Fleming <mfleming@cloudflare.com>

stack_print() reads stack_record->entries directly. A later patch
stores compressed frames inside struct stack_record, so rather than
decompressing those frames let's use stack_depot_fetch_into().

Copy the trace with stack_depot_fetch_into() into a stack-local buffer
with PAGE_OWNER_STACK_DEPTH elements, which is the maximum number of
frames page_owner saves.

Signed-off-by: Matt Fleming <mfleming@cloudflare.com>
---
 mm/page_owner.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/page_owner.c b/mm/page_owner.c
index cfc31c92d765..16429e70e00d 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -1068,8 +1068,8 @@ static int stack_print(struct seq_file *m, void *v)
 {
 	int i, nr_base_pages;
 	struct stack *stack = v;
-	unsigned long *entries;
-	unsigned long nr_entries;
+	unsigned long entries[PAGE_OWNER_STACK_DEPTH];
+	unsigned int nr_entries;
 	struct stack_record *stack_record = stack->stack_record;
 	struct stack_print_ctx *ctx = m->private;
 
@@ -1083,8 +1083,8 @@ static int stack_print(struct seq_file *m, void *v)
 		return 0;
 
 	if (ctx->flags & STACK_PRINT_FLAG_STACK) {
-		nr_entries = stack_record->size;
-		entries = stack_record->entries;
+		nr_entries = stack_depot_fetch_into(stack_record->handle.handle,
+						    entries, ARRAY_SIZE(entries));
 		for (i = 0; i < nr_entries; i++)
 			seq_printf(m, " %pS\n", (void *)entries[i]);
 	}
-- 
2.43.0