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nixos/lib, nixos/filesystems: Make fsBefore more stable, and add depends option

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This commit is contained in:
jakobrs 2020-05-21 09:10:47 +02:00
parent c8e32eddf8
commit b07602a604
2 changed files with 42 additions and 4 deletions
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26
nixos/lib/utils.nix
View file

@ -14,8 +14,30 @@ rec {
fsNeededForBoot = fs: fs.neededForBoot || elem fs.mountPoint pathsNeededForBoot;
# Check whenever `b` depends on `a` as a fileSystem
fsBefore = a: b: a.mountPoint == b.device
|| hasPrefix "${a.mountPoint}${optionalString (!(hasSuffix "/" a.mountPoint)) "/"}" b.mountPoint;
fsBefore = a: b:
let
# normalisePath adds a slash at the end of the path if it didn't already
# have one.
#
# The reason slashes are added at the end of each path is to prevent `b`
# from accidentally depending on `a` in cases like
# a = { mountPoint = "/aaa"; ... }
# b = { device = "/aaaa"; ... }
# Here a.mountPoint *is* a prefix of b.device even though a.mountPoint is
# *not* a parent of b.device. If we add a slash at the end of each string,
# though, this is not a problem: "/aaa/" is not a prefix of "/aaaa/".
normalisePath = path: "${path}${optionalString (!(hasSuffix "/" path)) "/"}";
normalise = mount: mount // { device = normalisePath mount.device;
mountPoint = normalisePath mount.mountPoint;
depends = map normalisePath mount.depends;
};
a' = normalise a;
b' = normalise b;
in hasPrefix a'.mountPoint b'.device
|| hasPrefix a'.mountPoint b'.mountPoint
|| any (hasPrefix a'.mountPoint) b'.depends;
# Escape a path according to the systemd rules, e.g. /dev/xyzzy
# becomes dev-xyzzy. FIXME: slow.

20
nixos/modules/tasks/filesystems.nix
View file

@ -24,13 +24,15 @@ let
specialFSTypes = [ "proc" "sysfs" "tmpfs" "ramfs" "devtmpfs" "devpts" ];
nonEmptyWithoutTrailingSlash = addCheckDesc "non-empty without trailing slash" types.str
(s: isNonEmpty s && (builtins.match ".+/" s) == null);
coreFileSystemOpts = { name, config, ... }: {
options = {
mountPoint = mkOption {
example = "/mnt/usb";
type = addCheckDesc "non-empty without trailing slash" types.str
(s: isNonEmpty s && (builtins.match ".+/" s) == null);
type = nonEmptyWithoutTrailingSlash;
description = "Location of the mounted the file system.";
};
@ -55,6 +57,20 @@ let
type = types.listOf nonEmptyStr;
};
depends = mkOption {
default = [ ];
example = [ "/persist" ];
type = types.listOf nonEmptyWithoutTrailingSlash;
description = ''
List of paths that should be mounted before this one. This filesystem's
<option>device</option> and <option>mountPoint</option> are always
checked and do not need to be included explicitly. If a path is added
to this list, any other filesystem whose mount point is a parent of
the path will be mounted before this filesystem. The paths do not need
to actually be the <option>mountPoint</option> of some other filesystem.
'';
};
};
config = {