daemon/graphdriver/windows: various cleanups and fixes

[thaJeztah]

daemon/graphdriver/windows: InitFilter() don't use idtools.MkdirAllAndChown()

idtools.MkdirAllAndChown on Windows does not chown directories, which makes
idtools.MkdirAllAndChown() just an alias for system.MkDirAll().

Also setting the filemode to 0, as changing filemode is a no-op on Windows as
well; both of these changes should make it more transparent that no chown'ing,
nor changing filemode takes place.

daemon/graphdriver/windows: rename vars that collided with imports

daemon/graphdriver/windows: remove fileFlagSequentialScan const

Replace it with the const that's now defined in golang.org/x/sys/windows

daemon/graphdriver/windows: use strings.EqualFold()

Saves some allocations

BenchmarkTolower
BenchmarkTolower-5     7917788       150.4 ns/op      16 B/op       3 allocs/op
BenchmarkEqualFold
BenchmarkEqualFold-5   8248605       143.5 ns/op       8 B/op       1 allocs/op

daemon/graphdriver/windows: remove some intermediate variables

daemon/graphdriver/windows: cleanup errors

[thaJeztah]

@tianon @corhere ptal 🤗

[thaJeztah]

@corhere I think I addressed your comments; PTAL

[corhere]

New options should be case-sensitive, but I think we're stuck with case-folding for size for back-compat reasons unless we have a flag day.

[thaJeztah]

Yeah, we need to look how we can get out of this situation. Some of these came from situations where "Windows filesystem is case-insensitive, so options should be case-insensitive as well", or just "make it easier to use"). Reality is that in many cases this logic is "distributed", and in some cases may have some potential bugs lurking around. For example, in the overlay2 driver; parsing storage options is case-insensitive;

moby/daemon/graphdriver/overlay2/overlay.go

Lines 426 to 428 in b3428bc

	key := strings.ToLower(key)
	switch key {
	case "size":

But other parts in the same file doesn't take case-insensitivity into account;

moby/daemon/graphdriver/overlay2/overlay.go

Lines 322 to 340 in b3428bc

	// Merge daemon default config.
	if _, ok := opts.StorageOpt["size"]; !ok && d.options.quota.Size != 0 {
	opts.StorageOpt["size"] = strconv.FormatUint(d.options.quota.Size, 10)
	}
	if _, ok := opts.StorageOpt["size"]; ok && !projectQuotaSupported {
	return fmt.Errorf("--storage-opt is supported only for overlay over xfs with 'pquota' mount option")
	}
	return d.create(id, parent, opts)
	}
	// Create is used to create the upper, lower, and merge directories required for overlay fs for a given id.
	// The parent filesystem is used to configure these directories for the overlay.
	func (d *Driver) Create(id, parent string, opts *graphdriver.CreateOpts) (retErr error) {
	if opts != nil && len(opts.StorageOpt) != 0 {
	if _, ok := opts.StorageOpt["size"]; ok {
	return fmt.Errorf("--storage-opt size is only supported for ReadWrite Layers")
	}

[corhere]

LGTM!

[tianon]

Hmmmm, CI is being weird -- I think the # 2, # 3, and # 4 attempt failures are from trying to restart "only failed jobs" and that not working for some reason (thanks GitHub?) but the original failure was in the Windows tests, which feels related enough that it's maybe not the best idea for us to skip without doing a full restart? 😞

[thaJeztah]

let me try a close/reopen to see if that runs a full cycle

[thaJeztah]

Did a rebase to get a fresh run, and all green now 👍 bringing this in