mm/mempolicy: rewrite alloc_pages documentation

Document alloc_pages() for both NUMA and non-NUMA cases as kernel-doc
doesn't care.

Link: https://lkml.kernel.org/r/20210225150642.2582252-6-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/mempolicy.c

@@ -2245,19 +2245,18 @@ out:
 EXPORT_SYMBOL(alloc_pages_vma);
 
 /**
- * 	alloc_pages - Allocate pages.
+ * alloc_pages - Allocate pages.
+ * @gfp: GFP flags.
+ * @order: Power of two of number of pages to allocate.
  *
- *	@gfp:
- *		%GFP_USER   user allocation,
- *      	%GFP_KERNEL kernel allocation,
- *      	%GFP_HIGHMEM highmem allocation,
- *      	%GFP_FS     don't call back into a file system.
- *      	%GFP_ATOMIC don't sleep.
- *	@order: Power of two of allocation size in pages. 0 is a single page.
+ * Allocate 1 << @order contiguous pages.  The physical address of the
+ * first page is naturally aligned (eg an order-3 allocation will be aligned
+ * to a multiple of 8 * PAGE_SIZE bytes).  The NUMA policy of the current
+ * process is honoured when in process context.
  *
- *	Allocate a page from the kernel page pool.  When not in
- *	interrupt context and apply the current process NUMA policy.
- *	Returns NULL when no page can be allocated.
+ * Context: Can be called from any context, providing the appropriate GFP
+ * flags are used.
+ * Return: The page on success or NULL if allocation fails.
  */
 struct page *alloc_pages(gfp_t gfp, unsigned order)
 {