Function vnode_pager_putpages

freebsd/vm/vnode_pager.c:1209–1241

* EOPNOTSUPP is no longer legal. For local media VFS's that do not * implement their own VOP_PUTPAGES, their VOP_PUTPAGES should call to * vnode_pager_generic_putpages() to implement the previous behaviour. * * All other FS's should use the bypass to get to the local media * backing vp's VOP_PUTPAGES. */

 * backing vp's VOP_PUTPAGES.
 */
static void
vnode_pager_putpages(vm_object_t object, vm_page_t *m, int count,
    int flags, int *rtvals)
{
	int rtval;
	struct vnode *vp;
	int bytes = count * PAGE_SIZE;

	/*
	 * Force synchronous operation if we are extremely low on memory
	 * to prevent a low-memory deadlock.  VOP operations often need to
	 * allocate more memory to initiate the I/O ( i.e. do a BMAP
	 * operation ).  The swapper handles the case by limiting the amount
	 * of asynchronous I/O, but that sort of solution doesn't scale well
	 * for the vnode pager without a lot of work.
	 *
	 * Also, the backing vnode's iodone routine may not wake the pageout
	 * daemon up.  This should be probably be addressed XXX.
	 */

	if (vm_page_count_min())
		flags |= VM_PAGER_PUT_SYNC;

	/*
	 * Call device-specific putpages function
	 */
	vp = object->handle;
	VM_OBJECT_WUNLOCK(object);
	rtval = VOP_PUTPAGES(vp, m, bytes, flags, rtvals);
	KASSERT(rtval != EOPNOTSUPP, 
	    ("vnode_pager: stale FS putpages\n"));
	VM_OBJECT_WLOCK(object);
}

static int
vn_off2bidx(vm_ooffset_t offset)