Function dmu_buf_will_dirty_impl

freebsd/contrib/openzfs/module/zfs/dbuf.c:2429–2467

}

static void
dmu_buf_will_dirty_impl(dmu_buf_t *db_fake, int flags, dmu_tx_t *tx)
{
	dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;

	ASSERT(tx->tx_txg != 0);
	ASSERT(!zfs_refcount_is_zero(&db->db_holds));

	/*
	 * Quick check for dirtiness.  For already dirty blocks, this
	 * reduces runtime of this function by >90%, and overall performance
	 * by 50% for some workloads (e.g. file deletion with indirect blocks
	 * cached).
	 */
	mutex_enter(&db->db_mtx);

	if (db->db_state == DB_CACHED) {
		dbuf_dirty_record_t *dr = dbuf_find_dirty_eq(db, tx->tx_txg);
		/*
		 * It's possible that it is already dirty but not cached,
		 * because there are some calls to dbuf_dirty() that don't
		 * go through dmu_buf_will_dirty().
		 */
		if (dr != NULL) {
			/* This dbuf is already dirty and cached. */
			dbuf_redirty(dr);
			mutex_exit(&db->db_mtx);
			return;
		}
	}
	mutex_exit(&db->db_mtx);

	DB_DNODE_ENTER(db);
	if (RW_WRITE_HELD(&DB_DNODE(db)->dn_struct_rwlock))
		flags |= DB_RF_HAVESTRUCT;
	DB_DNODE_EXIT(db);
	(void) dbuf_read(db, NULL, flags);
	(void) dbuf_dirty(db, tx);
}

void
dmu_buf_will_dirty(dmu_buf_t *db_fake, dmu_tx_t *tx)