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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
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@ -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.