Function swap_pager_unswapped

freebsd/vm/swap_pager.c:1164–1210

* SWAP_PAGER_PAGE_UNSWAPPED() - remove swap backing store related to page * * This removes any associated swap backing store, whether valid or * not, from the page. * * This routine is typically called when a page is made dirty, at * which point any associated swap can be freed. MADV_FREE also * calls us in a special-case situation * * NOTE!!! If the page is clean and the swap was valid

 *	The object containing the page may be locked.
 */
static void
swap_pager_unswapped(vm_page_t m)
{
	struct swblk *sb;
	vm_object_t obj;

	/*
	 * Handle enqueing deferred frees first.  If we do not have the
	 * object lock we wait for the page daemon to clear the space.
	 */
	obj = m->object;
	if (!VM_OBJECT_WOWNED(obj)) {
		VM_PAGE_OBJECT_BUSY_ASSERT(m);
		/*
		 * The caller is responsible for synchronization but we
		 * will harmlessly handle races.  This is typically provided
		 * by only calling unswapped() when a page transitions from
		 * clean to dirty.
		 */
		if ((m->a.flags & (PGA_SWAP_SPACE | PGA_SWAP_FREE)) ==
		    PGA_SWAP_SPACE) {
			vm_page_aflag_set(m, PGA_SWAP_FREE);
			counter_u64_add(swap_free_deferred, 1);
		}
		return;
	}
	if ((m->a.flags & PGA_SWAP_FREE) != 0)
		counter_u64_add(swap_free_completed, 1);
	vm_page_aflag_clear(m, PGA_SWAP_FREE | PGA_SWAP_SPACE);

	/*
	 * The meta data only exists if the object is OBJT_SWAP
	 * and even then might not be allocated yet.
	 */
	KASSERT(m->object->type == OBJT_SWAP,
	    ("Free object not swappable"));

	sb = SWAP_PCTRIE_LOOKUP(&m->object->un_pager.swp.swp_blks,
	    rounddown(m->pindex, SWAP_META_PAGES));
	if (sb == NULL)
		return;
	if (sb->d[m->pindex % SWAP_META_PAGES] == SWAPBLK_NONE)
		return;
	swp_pager_freeswapspace(sb->d[m->pindex % SWAP_META_PAGES], 1);
	sb->d[m->pindex % SWAP_META_PAGES] = SWAPBLK_NONE;
	swp_pager_free_empty_swblk(m->object, sb);
}

/*
 * swap_pager_getpages() - bring pages in from swap