func libfuse_init()

in component/libfuse/libfuse_handler.go [258:341]

• 48 lines of code
• 12 McCabe index (conditional complexity)

func libfuse_init(conn *C.fuse_conn_info_t, cfg *C.fuse_config_t) (res unsafe.Pointer) {
	log.Trace("Libfuse::libfuse_init : init (read : %v, write %v, read-ahead %v)", conn.max_read, conn.max_write, conn.max_readahead)

	log.Info("Libfuse::NotifyMountToParent : Notifying parent for successful mount")
	if err := common.NotifyMountToParent(); err != nil {
		log.Err("Libfuse::NotifyMountToParent : Failed to notify parent, error: [%v]", err)
	}

	C.populate_uid_gid()

	log.Info("Libfuse::libfuse_init : Kernel Caps : %d", conn.capable)

	// Populate connection information
	// conn.want |= C.FUSE_CAP_NO_OPENDIR_SUPPORT

	// Allow fuse to perform parallel operations on a directory
	if (conn.capable & C.FUSE_CAP_PARALLEL_DIROPS) != 0 {
		log.Info("Libfuse::libfuse_init : Enable Capability : FUSE_CAP_PARALLEL_DIROPS")
		conn.want |= C.FUSE_CAP_PARALLEL_DIROPS
	}

	// Kernel shall invalidate the data in page cache if file size of LMT changes
	if (conn.capable & C.FUSE_CAP_AUTO_INVAL_DATA) != 0 {
		log.Info("Libfuse::libfuse_init : Enable Capability : FUSE_CAP_AUTO_INVAL_DATA")
		conn.want |= C.FUSE_CAP_AUTO_INVAL_DATA
	}

	// Enable read-dir plus where attributes of each file are returned back
	// in the list call itself and fuse does not need to fire getAttr after list
	if (conn.capable & C.FUSE_CAP_READDIRPLUS) != 0 {
		log.Info("Libfuse::libfuse_init : Enable Capability : FUSE_CAP_READDIRPLUS")
		conn.want |= C.FUSE_CAP_READDIRPLUS
	}

	// Allow fuse to read a file in parallel on different offsets
	if (conn.capable & C.FUSE_CAP_ASYNC_READ) != 0 {
		log.Info("Libfuse::libfuse_init : Enable Capability : FUSE_CAP_ASYNC_READ")
		conn.want |= C.FUSE_CAP_ASYNC_READ
	}

	if (conn.capable & C.FUSE_CAP_SPLICE_WRITE) != 0 {
		// While writing to fuse device let libfuse collate the data and write big chunks
		log.Info("Libfuse::libfuse_init : Enable Capability : FUSE_CAP_SPLICE_WRITE")
		conn.want |= C.FUSE_CAP_SPLICE_WRITE
	}

	/*
		FUSE_CAP_WRITEBACK_CACHE flag is not suitable for network filesystems.  If a partial page is
		written, then the page needs to be first read from userspace.  This means, that
		even for files opened for O_WRONLY it is possible that READ requests will be
		generated by the kernel.
	*/
	if (!fuseFS.directIO) && (!fuseFS.disableWritebackCache) && ((conn.capable & C.FUSE_CAP_WRITEBACK_CACHE) != 0) {
		// Buffer write requests at libfuse and then hand it off to application
		log.Info("Libfuse::libfuse_init : Enable Capability : FUSE_CAP_WRITEBACK_CACHE")
		conn.want |= C.FUSE_CAP_WRITEBACK_CACHE
	}

	// Max background thread on the fuse layer for high parallelism
	conn.max_background = C.uint(fuseFS.maxFuseThreads)

	// While reading a file let kernel do readahed for better perf
	conn.max_readahead = (4 * 1024 * 1024)
	conn.max_read = (1 * 1024 * 1024)

	// RHEL still has 3.3 fuse version and it does not allow max_write beyond 128K
	// Setting this value to 1 MB will fail the mount.
	fuse_minor := common.GetFuseMinorVersion()
	if fuse_minor > 4 {
		log.Info("Libfuse::libfuse_init : Setting 1MB max_write for fuse minor %v", fuse_minor)
		conn.max_write = (1 * 1024 * 1024)
	} else {
		log.Info("Libfuse::libfuse_init : Ignoring max_write for fuse minor %v", fuse_minor)
		conn.max_write = (128 * 1024)
	}

	// direct_io option is used to bypass the kernel cache. It disables the use of
	// page cache (file content cache) in the kernel for the filesystem.
	if fuseFS.directIO {
		cfg.direct_io = C.int(1)
	}

	return nil
}