mount: fuse fs performance fix, docstring #5371

Job	Run time
lint	7s
asan_ubsan	4m 34s
native_tests (ubuntu-24.04, 3.14, py314-fuse3)	10m 38s
vm_tests (openbsd, 7.7, OpenBSD, false)	21m 10s
native_tests (ubuntu-22.04, 3.10, py310-fuse2)	9m 54s
vm_tests (netbsd, 10.1, NetBSD, false)	15m 8s
vm_tests (haiku, r1beta5, Haiku, false)	22m 23s
vm_tests (freebsd, 14.3, FreeBSD, true, borg-freebsd-14-x86_64-gh)	12m 28s
	1h 36m 22s

Provide feedback