[PATCH] mm: page_state opt docs

/*

 * Global page accounting.  One instance per CPU.  Only unsigned longs are

 * allowed.

 *

 * - Fields can be modified with xxx_page_state and xxx_page_state_zone at

 * any time safely (which protects the instance from modification by

 * interrupt.

 * - The __xxx_page_state variants can be used safely when interrupts are

 * disabled.

 * - The __xxx_page_state variants can be used if the field is only

 * modified from process context, or only modified from interrupt context.

 * In this case, the field should be commented here.

 */

struct page_state {

	unsigned long nr_dirty;		/* Dirty writeable pages */

	unsigned long nr_writeback;	/* Pages under writeback */

	unsigned long nr_unstable;	/* NFS unstable pages */

	unsigned long nr_page_table_pages;/* Pages used for pagetables */

	unsigned long nr_mapped;	/* mapped into pagetables */

	unsigned long nr_mapped;	/* mapped into pagetables.

					 * only modified from process context */

	unsigned long nr_slab;		/* In slab */

#define GET_PAGE_STATE_LAST nr_slab