lib/stackdepot: move documentation comments to stackdepot.h

Move all interface- and usage-related documentation comments to
include/linux/stackdepot.h.

It makes sense to have them in the header where they are available to
the interface users.

[[e-mail]: grammar fix, per Alexander]
Link: https://lkml.kernel.org/r/fb[e-mail]
Signed-off-by: Andrey Konovalov <[e-mail]>
Reviewed-by: Alexander Potapenko <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

include/linux/stackdepot.h

···
 /*
  * Stack depot - a stack trace storage that avoids duplication.
  *
+ * Stack depot is intended to be used by subsystems that need to store and
+ * later retrieve many potentially duplicated stack traces without wasting
+ * memory.
+ *
+ * For example, KASAN needs to save allocation and free stack traces for each
+ * object. Storing two stack traces per object requires a lot of memory (e.g.
+ * SLUB_DEBUG needs 256 bytes per object for that). Since allocation and free
+ * stack traces often repeat, using stack depot allows to save about 100x space.
+ *
+ * Stack traces are never removed from the stack depot.
+ *
  * Author: Alexander Potapenko <[e-mail]>
  * Copyright (C) 2016 Google, Inc.
  *
···
 static inline int stack_depot_early_init(void)	{ return 0; }
 #endif
 
+/**
+ * __stack_depot_save - Save a stack trace to stack depot
+ *
+ * @entries:		Pointer to the stack trace
+ * @nr_entries:		Number of frames in the stack
+ * @alloc_flags:	Allocation GFP flags
+ * @can_alloc:		Allocate stack pools (increased chance of failure if false)
+ *
+ * Saves a stack trace from @entries array of size @nr_entries. If @can_alloc is
+ * %true, stack depot can replenish the stack pools in case no space is left
+ * (allocates using GFP flags of @alloc_flags). If @can_alloc is %false, avoids
+ * any allocations and fails if no space is left to store the stack trace.
+ *
+ * If the provided stack trace comes from the interrupt context, only the part
+ * up to the interrupt entry is saved.
+ *
+ * Context: Any context, but setting @can_alloc to %false is required if
+ *          alloc_pages() cannot be used from the current context. Currently
+ *          this is the case for contexts where neither %GFP_ATOMIC nor
+ *          %GFP_NOWAIT can be used (NMI, raw_spin_lock).
+ *
+ * Return: Handle of the stack struct stored in depot, 0 on failure
+ */
 depot_stack_handle_t __stack_depot_save(unsigned long *entries,
 					unsigned int nr_entries,
 					gfp_t gfp_flags, bool can_alloc);
 
+/**
+ * stack_depot_save - Save a stack trace to stack depot
+ *
+ * @entries:		Pointer to the stack trace
+ * @nr_entries:		Number of frames in the stack
+ * @alloc_flags:	Allocation GFP flags
+ *
+ * Context: Contexts where allocations via alloc_pages() are allowed.
+ *          See __stack_depot_save() for more details.
+ *
+ * Return: Handle of the stack trace stored in depot, 0 on failure
+ */
 depot_stack_handle_t stack_depot_save(unsigned long *entries,
 				      unsigned int nr_entries, gfp_t gfp_flags);
 
+/**
+ * stack_depot_fetch - Fetch a stack trace from stack depot
+ *
+ * @handle:	Stack depot handle returned from stack_depot_save()
+ * @entries:	Pointer to store the address of the stack trace
+ *
+ * Return: Number of frames for the fetched stack
+ */
 unsigned int stack_depot_fetch(depot_stack_handle_t handle,
 			       unsigned long **entries);
 
+/**
+ * stack_depot_print - Print a stack trace from stack depot
+ *
+ * @stack:	Stack depot handle returned from stack_depot_save()
+ */
 void stack_depot_print(depot_stack_handle_t stack);
 
+/**
+ * stack_depot_snprint - Print a stack trace from stack depot into a buffer
+ *
+ * @handle:	Stack depot handle returned from stack_depot_save()
+ * @buf:	Pointer to the print buffer
+ * @size:	Size of the print buffer
+ * @spaces:	Number of leading spaces to print
+ *
+ * Return:	Number of bytes printed
+ */
 int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size,
 		       int spaces);
 
+/**
+ * stack_depot_set_extra_bits - Set extra bits in a stack depot handle
+ *
+ * @handle:	Stack depot handle returned from stack_depot_save()
+ * @extra_bits:	Value to set the extra bits
+ *
+ * Return: Stack depot handle with extra bits set
+ *
+ * Stack depot handles have a few unused bits, which can be used for storing
+ * user-specific information. These bits are transparent to the stack depot.
+ */
 depot_stack_handle_t __must_check stack_depot_set_extra_bits(
 			depot_stack_handle_t handle, unsigned int extra_bits);
 
+/**
+ * stack_depot_get_extra_bits - Retrieve extra bits from a stack depot handle
+ *
+ * @handle:	Stack depot handle with extra bits saved
+ *
+ * Return: Extra bits retrieved from the stack depot handle
+ */
 unsigned int stack_depot_get_extra_bits(depot_stack_handle_t handle);
 
 #endif

lib/stackdepot.c

···
 /*
  * Stack depot - a stack trace storage that avoids duplication.
  *
- * Stack depot is intended to be used by subsystems that need to store and
- * later retrieve many potentially duplicated stack traces without wasting
- * memory.
- *
- * For example, KASAN needs to save allocation and free stack traces for each
- * object. Storing two stack traces per object requires a lot of memory (e.g.
- * SLUB_DEBUG needs 256 bytes per object for that). Since allocation and free
- * stack traces often repeat, using stack depot allows to save about 100x space.
- *
  * Internally, stack depot maintains a hash table of unique stacktraces. The
  * stack traces themselves are stored contiguously one after another in a set
  * of separate page allocations.
- *
- * Stack traces are never removed from stack depot.
  *
  * Author: Alexander Potapenko <[e-mail]>
  * Copyright (C) 2016 Google, Inc.
···
 	return NULL;
 }
 
-/**
- * __stack_depot_save - Save a stack trace to stack depot
- *
- * @entries:		Pointer to the stack trace
- * @nr_entries:		Number of frames in the stack
- * @alloc_flags:	Allocation GFP flags
- * @can_alloc:		Allocate stack pools (increased chance of failure if false)
- *
- * Saves a stack trace from @entries array of size @nr_entries. If @can_alloc is
- * %true, stack depot can replenish the stack pools in case no space is left
- * (allocates using GFP flags of @alloc_flags). If @can_alloc is %false, avoids
- * any allocations and fails if no space is left to store the stack trace.
- *
- * If the provided stack trace comes from the interrupt context, only the part
- * up to the interrupt entry is saved.
- *
- * Context: Any context, but setting @can_alloc to %false is required if
- *          alloc_pages() cannot be used from the current context. Currently
- *          this is the case for contexts where neither %GFP_ATOMIC nor
- *          %GFP_NOWAIT can be used (NMI, raw_spin_lock).
- *
- * Return: Handle of the stack struct stored in depot, 0 on failure
- */
 depot_stack_handle_t __stack_depot_save(unsigned long *entries,
 					unsigned int nr_entries,
 					gfp_t alloc_flags, bool can_alloc)
···
 }
 EXPORT_SYMBOL_GPL(__stack_depot_save);
 
-/**
- * stack_depot_save - Save a stack trace to stack depot
- *
- * @entries:		Pointer to the stack trace
- * @nr_entries:		Number of frames in the stack
- * @alloc_flags:	Allocation GFP flags
- *
- * Context: Contexts where allocations via alloc_pages() are allowed.
- *          See __stack_depot_save() for more details.
- *
- * Return: Handle of the stack trace stored in depot, 0 on failure
- */
 depot_stack_handle_t stack_depot_save(unsigned long *entries,
 				      unsigned int nr_entries,
 				      gfp_t alloc_flags)
···
 }
 EXPORT_SYMBOL_GPL(stack_depot_save);
 
-/**
- * stack_depot_fetch - Fetch a stack trace from stack depot
- *
- * @handle:	Stack depot handle returned from stack_depot_save()
- * @entries:	Pointer to store the address of the stack trace
- *
- * Return: Number of frames for the fetched stack
- */
 unsigned int stack_depot_fetch(depot_stack_handle_t handle,
 			       unsigned long **entries)
 {
···
 }
 EXPORT_SYMBOL_GPL(stack_depot_fetch);
 
-/**
- * stack_depot_print - Print a stack trace from stack depot
- *
- * @stack:	Stack depot handle returned from stack_depot_save()
- */
 void stack_depot_print(depot_stack_handle_t stack)
 {
 	unsigned long *entries;
···
 }
 EXPORT_SYMBOL_GPL(stack_depot_print);
 
-/**
- * stack_depot_snprint - Print a stack trace from stack depot into a buffer
- *
- * @handle:	Stack depot handle returned from stack_depot_save()
- * @buf:	Pointer to the print buffer
- * @size:	Size of the print buffer
- * @spaces:	Number of leading spaces to print
- *
- * Return:	Number of bytes printed
- */
 int stack_depot_snprint(depot_stack_handle_t handle, char *buf, size_t size,
 		       int spaces)
 {
···
 }
 EXPORT_SYMBOL_GPL(stack_depot_snprint);
 
-/**
- * stack_depot_set_extra_bits - Set extra bits in a stack depot handle
- *
- * @handle:	Stack depot handle returned from stack_depot_save()
- * @extra_bits:	Value to set the extra bits
- *
- * Return: Stack depot handle with extra bits set
- *
- * Stack depot handles have a few unused bits, which can be used for storing
- * user-specific information. These bits are transparent to the stack depot.
- */
 depot_stack_handle_t __must_check stack_depot_set_extra_bits(
 			depot_stack_handle_t handle, unsigned int extra_bits)
 {
···
 }
 EXPORT_SYMBOL(stack_depot_set_extra_bits);
 
-/**
- * stack_depot_get_extra_bits - Retrieve extra bits from a stack depot handle
- *
- * @handle:	Stack depot handle with extra bits saved
- *
- * Return: Extra bits retrieved from the stack depot handle
- */
 unsigned int stack_depot_get_extra_bits(depot_stack_handle_t handle)
 {
 	union handle_parts parts = { .handle = handle };