[PATCH 12/15] stackdepot: add refcount for records

[andrey.konovalov@linux.dev]

From: Andrey Konovalov <andreyknvl@google.com>

Add a reference counter for how many times a stack records has been added
to stack depot.

Do no yet decrement the refcount, this is implemented in one of the
following patches.

This is preparatory patch for implementing the eviction of stack records
from the stack depot.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 lib/stackdepot.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/stackdepot.c b/lib/stackdepot.c
index 5ad454367379..a84c0debbb9e 100644
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -22,6 +22,7 @@
 #include <linux/mutex.h>
 #include <linux/percpu.h>
 #include <linux/printk.h>
+#include <linux/refcount.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/stacktrace.h>
@@ -60,6 +61,7 @@ struct stack_record {
 	u32 hash;			/* Hash in hash table */
 	u32 size;			/* Number of stored frames */
 	union handle_parts handle;
+	refcount_t count;
 	unsigned long entries[DEPOT_STACK_MAX_FRAMES];	/* Frames */
 };
 
@@ -348,6 +350,7 @@ depot_alloc_stack(unsigned long *entries, int size, u32 hash, void **prealloc)
 	stack->hash = hash;
 	stack->size = size;
 	/* stack->handle is already filled in by depot_init_pool. */
+	refcount_set(&stack->count, 1);
 	memcpy(stack->entries, entries, flex_array_size(stack, entries, size));
 
 	/*
@@ -452,6 +455,7 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries,
 	/* Fast path: look the stack trace up without full locking. */
 	found = find_stack(*bucket, entries, nr_entries, hash);
 	if (found) {
+		refcount_inc(&found->count);
 		read_unlock_irqrestore(&pool_rwlock, flags);
 		goto exit;
 	}
-- 
2.25.1