[patch V3 03/29] lib/stackdepot: Provide functions which operate on plain storage arrays

[Thomas Gleixner]

The struct stack_trace indirection in the stack depot functions is a truly
pointless excercise which requires horrible code at the callsites.

Provide interfaces based on plain storage arrays.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Acked-by: Alexander Potapenko <glider@xxxxxxxxxx>
---
V3: Fix kernel-doc
---
 include/linux/stackdepot.h |    4 ++
 lib/stackdepot.c           |   70 ++++++++++++++++++++++++++++++++-------------
 2 files changed, 55 insertions(+), 19 deletions(-)

--- a/include/linux/stackdepot.h
+++ b/include/linux/stackdepot.h
@@ -26,7 +26,11 @@ typedef u32 depot_stack_handle_t;
 struct stack_trace;
 
 depot_stack_handle_t depot_save_stack(struct stack_trace *trace, gfp_t flags);
+depot_stack_handle_t stack_depot_save(unsigned long *entries,
+				      unsigned int nr_entries, gfp_t gfp_flags);
 
 void depot_fetch_stack(depot_stack_handle_t handle, struct stack_trace *trace);
+unsigned int stack_depot_fetch(depot_stack_handle_t handle,
+			       unsigned long **entries);
 
 #endif
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -194,40 +194,60 @@ static inline struct stack_record *find_
 	return NULL;
 }
 
-void depot_fetch_stack(depot_stack_handle_t handle, struct stack_trace *trace)
+/**
+ * stack_depot_fetch - Fetch stack entries from a depot
+ *
+ * @handle:		Stack depot handle which was returned from
+ *			stack_depot_save().
+ * @entries:		Pointer to store the entries address
+ *
+ * Return: The number of trace entries for this depot.
+ */
+unsigned int stack_depot_fetch(depot_stack_handle_t handle,
+			       unsigned long **entries)
 {
 	union handle_parts parts = { .handle = handle };
 	void *slab = stack_slabs[parts.slabindex];
 	size_t offset = parts.offset << STACK_ALLOC_ALIGN;
 	struct stack_record *stack = slab + offset;
 
-	trace->nr_entries = trace->max_entries = stack->size;
-	trace->entries = stack->entries;
-	trace->skip = 0;
+	*entries = stack->entries;
+	return stack->size;
+}
+EXPORT_SYMBOL_GPL(stack_depot_fetch);
+
+void depot_fetch_stack(depot_stack_handle_t handle, struct stack_trace *trace)
+{
+	unsigned int nent = stack_depot_fetch(handle, &trace->entries);
+
+	trace->max_entries = trace->nr_entries = nent;
 }
 EXPORT_SYMBOL_GPL(depot_fetch_stack);
 
 /**
- * depot_save_stack - save stack in a stack depot.
- * @trace - the stacktrace to save.
- * @alloc_flags - flags for allocating additional memory if required.
+ * stack_depot_save - Save a stack trace from an array
+ *
+ * @entries:		Pointer to storage array
+ * @nr_entries:		Size of the storage array
+ * @alloc_flags:	Allocation gfp flags
  *
- * Returns the handle of the stack struct stored in depot.
+ * Return: The handle of the stack struct stored in depot
  */
-depot_stack_handle_t depot_save_stack(struct stack_trace *trace,
-				    gfp_t alloc_flags)
+depot_stack_handle_t stack_depot_save(unsigned long *entries,
+				      unsigned int nr_entries,
+				      gfp_t alloc_flags)
 {
-	u32 hash;
-	depot_stack_handle_t retval = 0;
 	struct stack_record *found = NULL, **bucket;
-	unsigned long flags;
+	depot_stack_handle_t retval = 0;
 	struct page *page = NULL;
 	void *prealloc = NULL;
+	unsigned long flags;
+	u32 hash;
 
-	if (unlikely(trace->nr_entries == 0))
+	if (unlikely(nr_entries == 0))
 		goto fast_exit;
 
-	hash = hash_stack(trace->entries, trace->nr_entries);
+	hash = hash_stack(entries, nr_entries);
 	bucket = &stack_table[hash & STACK_HASH_MASK];
 
 	/*
@@ -235,8 +255,8 @@ depot_stack_handle_t depot_save_stack(st
 	 * The smp_load_acquire() here pairs with smp_store_release() to
 	 * |bucket| below.
 	 */
-	found = find_stack(smp_load_acquire(bucket), trace->entries,
-			   trace->nr_entries, hash);
+	found = find_stack(smp_load_acquire(bucket), entries,
+			   nr_entries, hash);
 	if (found)
 		goto exit;
 
@@ -264,10 +284,10 @@ depot_stack_handle_t depot_save_stack(st
 
 	spin_lock_irqsave(&depot_lock, flags);
 
-	found = find_stack(*bucket, trace->entries, trace->nr_entries, hash);
+	found = find_stack(*bucket, entries, nr_entries, hash);
 	if (!found) {
 		struct stack_record *new =
-			depot_alloc_stack(trace->entries, trace->nr_entries,
+			depot_alloc_stack(entries, nr_entries,
 					  hash, &prealloc, alloc_flags);
 		if (new) {
 			new->next = *bucket;
@@ -297,4 +317,16 @@ depot_stack_handle_t depot_save_stack(st
 fast_exit:
 	return retval;
 }
+EXPORT_SYMBOL_GPL(stack_depot_save);
+
+/**
+ * depot_save_stack - save stack in a stack depot.
+ * @trace - the stacktrace to save.
+ * @alloc_flags - flags for allocating additional memory if required.
+ */
+depot_stack_handle_t depot_save_stack(struct stack_trace *trace,
+				      gfp_t alloc_flags)
+{
+	return stack_depot_save(trace->entries, trace->nr_entries, alloc_flags);
+}
 EXPORT_SYMBOL_GPL(depot_save_stack);