Function dbuf_write

freebsd/contrib/openzfs/module/zfs/dbuf.c:4773–4899

Issue I/O to commit a dirty buffer to disk. */

/* Issue I/O to commit a dirty buffer to disk. */
static void
dbuf_write(dbuf_dirty_record_t *dr, arc_buf_t *data, dmu_tx_t *tx)
{
	dmu_buf_impl_t *db = dr->dr_dbuf;
	dnode_t *dn = dr->dr_dnode;
	objset_t *os;
	dmu_buf_impl_t *parent = db->db_parent;
	uint64_t txg = tx->tx_txg;
	zbookmark_phys_t zb;
	zio_prop_t zp;
	zio_t *pio; /* parent I/O */
	int wp_flag = 0;

	ASSERT(dmu_tx_is_syncing(tx));

	os = dn->dn_objset;

	if (db->db_state != DB_NOFILL) {
		if (db->db_level > 0 || dn->dn_type == DMU_OT_DNODE) {
			/*
			 * Private object buffers are released here rather
			 * than in dbuf_dirty() since they are only modified
			 * in the syncing context and we don't want the
			 * overhead of making multiple copies of the data.
			 */
			if (BP_IS_HOLE(db->db_blkptr)) {
				arc_buf_thaw(data);
			} else {
				dbuf_release_bp(db);
			}
			dbuf_remap(dn, db, tx);
		}
	}

	if (parent != dn->dn_dbuf) {
		/* Our parent is an indirect block. */
		/* We have a dirty parent that has been scheduled for write. */
		ASSERT(parent && parent->db_data_pending);
		/* Our parent's buffer is one level closer to the dnode. */
		ASSERT(db->db_level == parent->db_level-1);
		/*
		 * We're about to modify our parent's db_data by modifying
		 * our block pointer, so the parent must be released.
		 */
		ASSERT(arc_released(parent->db_buf));
		pio = parent->db_data_pending->dr_zio;
	} else {
		/* Our parent is the dnode itself. */
		ASSERT((db->db_level == dn->dn_phys->dn_nlevels-1 &&
		    db->db_blkid != DMU_SPILL_BLKID) ||
		    (db->db_blkid == DMU_SPILL_BLKID && db->db_level == 0));
		if (db->db_blkid != DMU_SPILL_BLKID)
			ASSERT3P(db->db_blkptr, ==,
			    &dn->dn_phys->dn_blkptr[db->db_blkid]);
		pio = dn->dn_zio;
	}

	ASSERT(db->db_level == 0 || data == db->db_buf);