diff options
Diffstat (limited to 'nixos/modules/tasks/filesystems/btrfs.nix')
-rw-r--r-- | nixos/modules/tasks/filesystems/btrfs.nix | 149 |
1 files changed, 149 insertions, 0 deletions
diff --git a/nixos/modules/tasks/filesystems/btrfs.nix b/nixos/modules/tasks/filesystems/btrfs.nix new file mode 100644 index 00000000000..ae1dab5b8d8 --- /dev/null +++ b/nixos/modules/tasks/filesystems/btrfs.nix @@ -0,0 +1,149 @@ +{ config, lib, pkgs, utils, ... }: + +with lib; + +let + + inInitrd = any (fs: fs == "btrfs") config.boot.initrd.supportedFilesystems; + inSystem = any (fs: fs == "btrfs") config.boot.supportedFilesystems; + + cfgScrub = config.services.btrfs.autoScrub; + + enableAutoScrub = cfgScrub.enable; + enableBtrfs = inInitrd || inSystem || enableAutoScrub; + +in + +{ + options = { + # One could also do regular btrfs balances, but that shouldn't be necessary + # during normal usage and as long as the filesystems aren't filled near capacity + services.btrfs.autoScrub = { + enable = mkEnableOption "regular btrfs scrub"; + + fileSystems = mkOption { + type = types.listOf types.path; + example = [ "/" ]; + description = '' + List of paths to btrfs filesystems to regularily call <command>btrfs scrub</command> on. + Defaults to all mount points with btrfs filesystems. + If you mount a filesystem multiple times or additionally mount subvolumes, + you need to manually specify this list to avoid scrubbing multiple times. + ''; + }; + + interval = mkOption { + default = "monthly"; + type = types.str; + example = "weekly"; + description = '' + Systemd calendar expression for when to scrub btrfs filesystems. + The recommended period is a month but could be less + (<citerefentry><refentrytitle>btrfs-scrub</refentrytitle> + <manvolnum>8</manvolnum></citerefentry>). + See + <citerefentry><refentrytitle>systemd.time</refentrytitle> + <manvolnum>7</manvolnum></citerefentry> + for more information on the syntax. + ''; + }; + + }; + }; + + config = mkMerge [ + (mkIf enableBtrfs { + system.fsPackages = [ pkgs.btrfs-progs ]; + + boot.initrd.kernelModules = mkIf inInitrd [ "btrfs" ]; + boot.initrd.availableKernelModules = mkIf inInitrd ( + [ "crc32c" ] + ++ optionals (config.boot.kernelPackages.kernel.kernelAtLeast "5.5") [ + # Needed for mounting filesystems with new checksums + "xxhash_generic" + "blake2b_generic" + "sha256_generic" # Should be baked into our kernel, just to be sure + ] + ); + + boot.initrd.extraUtilsCommands = mkIf inInitrd + '' + copy_bin_and_libs ${pkgs.btrfs-progs}/bin/btrfs + ln -sv btrfs $out/bin/btrfsck + ln -sv btrfsck $out/bin/fsck.btrfs + ''; + + boot.initrd.extraUtilsCommandsTest = mkIf inInitrd + '' + $out/bin/btrfs --version + ''; + + boot.initrd.postDeviceCommands = mkIf inInitrd + '' + btrfs device scan + ''; + }) + + (mkIf enableAutoScrub { + assertions = [ + { + assertion = cfgScrub.enable -> (cfgScrub.fileSystems != []); + message = '' + If 'services.btrfs.autoScrub' is enabled, you need to have at least one + btrfs file system mounted via 'fileSystems' or specify a list manually + in 'services.btrfs.autoScrub.fileSystems'. + ''; + } + ]; + + # This will yield duplicated units if the user mounts a filesystem multiple times + # or additionally mounts subvolumes, but going the other way around via devices would + # yield duplicated units when a filesystem spans multiple devices. + # This way around seems like the more sensible default. + services.btrfs.autoScrub.fileSystems = mkDefault (mapAttrsToList (name: fs: fs.mountPoint) + (filterAttrs (name: fs: fs.fsType == "btrfs") config.fileSystems)); + + # TODO: Did not manage to do it via the usual btrfs-scrub@.timer/.service + # template units due to problems enabling the parameterized units, + # so settled with many units and templating via nix for now. + # https://github.com/NixOS/nixpkgs/pull/32496#discussion_r156527544 + systemd.timers = let + scrubTimer = fs: let + fs' = utils.escapeSystemdPath fs; + in nameValuePair "btrfs-scrub-${fs'}" { + description = "regular btrfs scrub timer on ${fs}"; + + wantedBy = [ "timers.target" ]; + timerConfig = { + OnCalendar = cfgScrub.interval; + AccuracySec = "1d"; + Persistent = true; + }; + }; + in listToAttrs (map scrubTimer cfgScrub.fileSystems); + + systemd.services = let + scrubService = fs: let + fs' = utils.escapeSystemdPath fs; + in nameValuePair "btrfs-scrub-${fs'}" { + description = "btrfs scrub on ${fs}"; + # scrub prevents suspend2ram or proper shutdown + conflicts = [ "shutdown.target" "sleep.target" ]; + before = [ "shutdown.target" "sleep.target" ]; + + serviceConfig = { + # simple and not oneshot, otherwise ExecStop is not used + Type = "simple"; + Nice = 19; + IOSchedulingClass = "idle"; + ExecStart = "${pkgs.btrfs-progs}/bin/btrfs scrub start -B ${fs}"; + # if the service is stopped before scrub end, cancel it + ExecStop = pkgs.writeShellScript "btrfs-scrub-maybe-cancel" '' + (${pkgs.btrfs-progs}/bin/btrfs scrub status ${fs} | ${pkgs.gnugrep}/bin/grep finished) || ${pkgs.btrfs-progs}/bin/btrfs scrub cancel ${fs} + ''; + }; + }; + in listToAttrs (map scrubService cfgScrub.fileSystems); + }) + ]; +} |