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authorJoey Hess2017-12-20 16:10:34 -0400
committerJoey Hess2017-12-20 17:10:40 -0400
commit4e20a920baa6c9106179c3d8a1e8e66ffd50ce9c (patch)
treee19903ae14197d0ebd7e676e7b5c070cf4499d50 /src/Propellor/Property/Parted.hs
parentad3cc8fb46b051e45ed51126abec4fda79a4deb6 (diff)
disk partition alignment
Cheap flash drives need partitions aligned to 4 MiB in order to not be slow (and to avoid extra writes). <https://lwn.net/Articles/428584/> And at least 1 MiB alignment is generally a good idea, and most people seem to think 4 MiB is for all drives. I noticed that Parted.partitioned does not do that; the first partition started at an offset of 1 MB, and subsequent partitions from where it ends. (The 1 MB offset came from the PartedVal PartSize instance, and note that it was not 1 MiB.) * Parted: Add an Alignment parameter. (API change) A good default to use is safeAlignment, which is 4MiB, well suited for inexpensive flash drives, and fine for other disks too. Previously, a very non-optimial 1MB (not 1MiB) alignment had been used. * DiskImage: Use safeAlignment. It didn't seem worth making the alignment configurable here. Alignment is implemented by offsetting the first partition's start position so it's aligned (making sure to leave room for the partition table). Each partition is then extended as needed so the next partition will start properly aligned. Note that parted rejects partition tables that don't fit in cylinder bounderies. Before, propellor let parted deal with the fine details of layout, so that was not a problem. Now it's possible to set some wacky Alignment not divisible by 512, or use Byte sizes for partitions and create a partition table that parted rejects. But, using safeAlignment and MegaBytes should always be safe. Also, this fixes a rounding bug in Parted.calcPartTable. It was rounding up to the nearest MegaByte when allocating remaining disk space, so returned partition table that was actually larger than the disk size. This commit was sponsored by an anonymous bitcoiner.
Diffstat (limited to 'src/Propellor/Property/Parted.hs')
-rw-r--r--src/Propellor/Property/Parted.hs77
1 files changed, 51 insertions, 26 deletions
diff --git a/src/Propellor/Property/Parted.hs b/src/Propellor/Property/Parted.hs
index d60d4a60..8afd62ea 100644
--- a/src/Propellor/Property/Parted.hs
+++ b/src/Propellor/Property/Parted.hs
@@ -13,6 +13,8 @@ module Propellor.Property.Parted (
toPartSize,
fromPartSize,
reducePartSize,
+ Alignment(..),
+ safeAlignment,
Partition.MkfsOpts,
PartType(..),
PartFlag(..),
@@ -50,19 +52,28 @@ data Eep = YesReallyDeleteDiskContents
--
-- This deletes any existing partitions in the disk! Use with EXTREME caution!
partitioned :: Eep -> FilePath -> PartTable -> Property DebianLike
-partitioned eep disk (PartTable tabletype parts) = property' desc $ \w -> do
+partitioned eep disk parttable@(PartTable _ _ parts) = property' desc $ \w -> do
isdev <- liftIO $ isBlockDevice <$> getFileStatus disk
ensureProperty w $ combineProperties desc $ props
- & parted eep disk partedparams
+ & parted eep disk (fst (calcPartedParamsSize parttable))
& if isdev
then formatl (map (\n -> disk ++ show n) [1 :: Int ..])
else Partition.kpartx disk (formatl . map Partition.partitionLoopDev)
where
desc = disk ++ " partitioned"
formatl devs = combineProperties desc (toProps $ map format (zip parts devs))
- partedparams = concat $ mklabel : mkparts (1 :: Integer) mempty parts []
format (p, dev) = Partition.formatted' (partMkFsOpts p)
Partition.YesReallyFormatPartition (partFs p) dev
+
+-- | Gets the total size of the disk specified by the partition table.
+partTableSize :: PartTable -> ByteSize
+partTableSize = snd . calcPartedParamsSize
+
+calcPartedParamsSize :: PartTable -> ([String], ByteSize)
+calcPartedParamsSize (PartTable tabletype alignment parts) =
+ let (ps, sz) = calcparts (1 :: Integer) firstpos parts []
+ in (concat (mklabel : ps), sz)
+ where
mklabel = ["mklabel", pval tabletype]
mkflag partnum (f, b) =
[ "set"
@@ -70,39 +81,43 @@ partitioned eep disk (PartTable tabletype parts) = property' desc $ \w -> do
, pval f
, pval b
]
- mkpart partnum offset p =
+ mkpart partnum startpos endpos p =
[ "mkpart"
, pval (partType p)
, pval (partFs p)
- , pval offset
- , pval (offset <> partSize p)
+ , partpos startpos
+ , partpos endpos
] ++ case partName p of
Just n -> ["name", show partnum, n]
Nothing -> []
- mkparts partnum offset (p:ps) c =
- mkparts (partnum+1) (offset <> partSize p) ps
- (c ++ mkpart partnum offset p : map (mkflag partnum) (partFlags p))
- mkparts _ _ [] c = c
+ calcparts partnum startpos (p:ps) c =
+ let endpos = startpos + align (partSize p)
+ in calcparts (partnum+1) endpos ps
+ (c ++ mkpart partnum startpos (endpos-1) p : map (mkflag partnum) (partFlags p))
+ calcparts _ endpos [] c = (c, endpos)
+ partpos n
+ | n > 0 = val n ++ "B"
+ -- parted can't make partitions smaller than 1MB;
+ -- avoid failure in edge cases
+ | otherwise = "1MB"
+ -- Location of the start of the first partition,
+ -- leaving space for the partition table, and aligning.
+ firstpos = align partitionTableOverhead
+ align = alignTo alignment
-- | Runs parted on a disk with the specified parameters.
--
-- Parted is run in script mode, so it will never prompt for input.
--- It is asked to use cylinder alignment for the disk.
parted :: Eep -> FilePath -> [String] -> Property (DebianLike + ArchLinux)
parted YesReallyDeleteDiskContents disk ps = p `requires` installed
where
- p = cmdProperty "parted" ("--script":"--align":"cylinder":disk:ps)
+ p = cmdProperty "parted" ("--script":"--align":"none":disk:ps)
`assume` MadeChange
-- | Gets parted installed.
installed :: Property (DebianLike + ArchLinux)
installed = Apt.installed ["parted"] `pickOS` Pacman.installed ["parted"]
--- | Gets the total size of the disk specified by the partition table.
-partTableSize :: PartTable -> ByteSize
-partTableSize (PartTable _ ps) = fromPartSize $
- mconcat (partitionTableOverhead : map partSize ps)
-
-- | Some disk is used to store the partition table itself. Assume less
-- than 1 mb.
partitionTableOverhead :: PartSize
@@ -112,27 +127,27 @@ partitionTableOverhead = MegaBytes 1
--
-- For example:
--
--- > calcPartTable (DiskSize (1024 * 1024 * 1024 * 100)) MSDOS
+-- > calcPartTable (DiskSize (1024 * 1024 * 1024 * 100)) MSDOS safeAlignment
-- > [ partition EXT2 `mountedAt` "/boot"
-- > `setSize` MegaBytes 256
-- > `setFlag` BootFlag
-- > , partition EXT4 `mountedAt` "/"
--- > `useDisk` RemainingSpace
+-- > `useDiskSpace` RemainingSpace
-- > ]
-calcPartTable :: DiskSize -> TableType -> [PartSpec DiskPart] -> PartTable
-calcPartTable (DiskSize disksize) tt l = PartTable tt (map go l)
+calcPartTable :: DiskSize -> TableType -> Alignment -> [PartSpec DiskPart] -> PartTable
+calcPartTable (DiskSize disksize) tt alignment l =
+ PartTable tt alignment (map go l)
where
go (_, _, mkpart, FixedDiskPart) = mkpart defSz
- go (_, _, mkpart, DynamicDiskPart (Percent p)) = mkpart $ toPartSize $
+ go (_, _, mkpart, DynamicDiskPart (Percent p)) = mkpart $ Bytes $
diskremainingafterfixed * fromIntegral p `div` 100
- go (_, _, mkpart, DynamicDiskPart RemainingSpace) = mkpart $ toPartSize $
+ go (_, _, mkpart, DynamicDiskPart RemainingSpace) = mkpart $ Bytes $
diskremaining `div` genericLength (filter isremainingspace l)
- diskremainingafterfixed =
+ diskremainingafterfixed =
disksize - sumsizes (filter isfixed l)
diskremaining =
disksize - sumsizes (filter (not . isremainingspace) l)
- sumsizes = sum . map fromPartSize . (partitionTableOverhead :) .
- map (partSize . go)
+ sumsizes = partTableSize . PartTable tt alignment . map go
isfixed (_, _, _, FixedDiskPart) = True
isfixed _ = False
isremainingspace (_, _, _, DynamicDiskPart RemainingSpace) = True
@@ -177,3 +192,13 @@ defSz = MegaBytes 128
-- Add an additional 200 mb for temp files, journals, etc.
fudgeSz :: PartSize -> PartSize
fudgeSz (MegaBytes n) = MegaBytes (n + n `div` 100 * 2 + 3 + 200)
+
+alignTo :: Alignment -> PartSize -> ByteSize
+alignTo _ (Bytes n) = n -- no alignment done for Bytes
+alignTo (Alignment alignment) partsize
+ | alignment < 1 = n
+ | otherwise = case rem n alignment of
+ 0 -> n
+ r -> n - r + alignment
+ where
+ n = fromPartSize partsize