docs/mm: update kmalloc kernel-doc description

Add references to GFP documentation and the memory-allocation.rst and remove
GFP_USER, GFP_DMA and GFP_NOIO descriptions.

While on it slightly change the formatting so that the list of GFP flags
will be rendered as "description" in the generated html.
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/core-api/memory-allocation.rst

+.. _memory_allocation:
+
 =======================
 Memory Allocation Guide
 =======================

include/linux/slab.h

@@ -486,48 +486,47 @@ static __always_inline void *kmalloc_large(size_t size, gfp_t flags)
  * kmalloc is the normal method of allocating memory
  * for objects smaller than page size in the kernel.
  *
- * The @flags argument may be one of:
+ * The @flags argument may be one of the GFP flags defined at
+ * include/linux/gfp.h and described at
+ * :ref:`Documentation/core-api/mm-api.rst <mm-api-gfp-flags>`
  *
- * %GFP_USER - Allocate memory on behalf of user.  May sleep.
+ * The recommended usage of the @flags is described at
+ * :ref:`Documentation/core-api/memory-allocation.rst <memory_allocation>`
  *
- * %GFP_KERNEL - Allocate normal kernel ram.  May sleep.
+ * Below is a brief outline of the most useful GFP flags
  *
- * %GFP_ATOMIC - Allocation will not sleep.  May use emergency pools.
- *   For example, use this inside interrupt handlers.
+ * %GFP_KERNEL
+ *	Allocate normal kernel ram. May sleep.
  *
- * %GFP_HIGHUSER - Allocate pages from high memory.
+ * %GFP_NOWAIT
+ *	Allocation will not sleep.
  *
- * %GFP_NOIO - Do not do any I/O at all while trying to get memory.
+ * %GFP_ATOMIC
+ *	Allocation will not sleep.  May use emergency pools.
  *
- * %GFP_NOFS - Do not make any fs calls while trying to get memory.
- *
- * %GFP_NOWAIT - Allocation will not sleep.
- *
- * %__GFP_THISNODE - Allocate node-local memory only.
- *
- * %GFP_DMA - Allocation suitable for DMA.
- *   Should only be used for kmalloc() caches. Otherwise, use a
- *   slab created with SLAB_DMA.
+ * %GFP_HIGHUSER
+ *	Allocate memory from high memory on behalf of user.
  *
  * Also it is possible to set different flags by OR'ing
  * in one or more of the following additional @flags:
  *
- * %__GFP_HIGH - This allocation has high priority and may use emergency pools.
- *
- * %__GFP_NOFAIL - Indicate that this allocation is in no way allowed to fail
- *   (think twice before using).
+ * %__GFP_HIGH
+ *	This allocation has high priority and may use emergency pools.
  *
- * %__GFP_NORETRY - If memory is not immediately available,
- *   then give up at once.
+ * %__GFP_NOFAIL
+ *	Indicate that this allocation is in no way allowed to fail
+ *	(think twice before using).
  *
- * %__GFP_NOWARN - If allocation fails, don't issue any warnings.
+ * %__GFP_NORETRY
+ *	If memory is not immediately available,
+ *	then give up at once.
  *
- * %__GFP_RETRY_MAYFAIL - Try really hard to succeed the allocation but fail
- *   eventually.
+ * %__GFP_NOWARN
+ *	If allocation fails, don't issue any warnings.
  *
- * There are other flags available as well, but these are not intended
- * for general use, and so are not documented here. For a full list of
- * potential flags, always refer to linux/gfp.h.
+ * %__GFP_RETRY_MAYFAIL
+ *	Try really hard to succeed the allocation but fail
+ *	eventually.
  */
 static __always_inline void *kmalloc(size_t size, gfp_t flags)
 {