Function l2arc_write_done

freebsd/contrib/openzfs/module/zfs/arc.c:8191–8369

* A write to a cache device has completed. Update all headers to allow * reads from these buffers to begin. */

 * reads from these buffers to begin.
 */
static void
l2arc_write_done(zio_t *zio)
{
	l2arc_write_callback_t	*cb;
	l2arc_lb_abd_buf_t	*abd_buf;
	l2arc_lb_ptr_buf_t	*lb_ptr_buf;
	l2arc_dev_t		*dev;
	l2arc_dev_hdr_phys_t	*l2dhdr;
	list_t			*buflist;
	arc_buf_hdr_t		*head, *hdr, *hdr_prev;
	kmutex_t		*hash_lock;
	int64_t			bytes_dropped = 0;

	cb = zio->io_private;
	ASSERT3P(cb, !=, NULL);
	dev = cb->l2wcb_dev;
	l2dhdr = dev->l2ad_dev_hdr;
	ASSERT3P(dev, !=, NULL);
	head = cb->l2wcb_head;
	ASSERT3P(head, !=, NULL);
	buflist = &dev->l2ad_buflist;
	ASSERT3P(buflist, !=, NULL);
	DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
	    l2arc_write_callback_t *, cb);

	/*
	 * All writes completed, or an error was hit.
	 */
top:
	mutex_enter(&dev->l2ad_mtx);
	for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) {
		hdr_prev = list_prev(buflist, hdr);

		hash_lock = HDR_LOCK(hdr);

		/*
		 * We cannot use mutex_enter or else we can deadlock
		 * with l2arc_write_buffers (due to swapping the order
		 * the hash lock and l2ad_mtx are taken).
		 */
		if (!mutex_tryenter(hash_lock)) {
			/*
			 * Missed the hash lock. We must retry so we
			 * don't leave the ARC_FLAG_L2_WRITING bit set.
			 */
			ARCSTAT_BUMP(arcstat_l2_writes_lock_retry);

			/*
			 * We don't want to rescan the headers we've
			 * already marked as having been written out, so
			 * we reinsert the head node so we can pick up
			 * where we left off.
			 */
			list_remove(buflist, head);
			list_insert_after(buflist, hdr, head);

			mutex_exit(&dev->l2ad_mtx);