Stability	provisional
Portability	non-portable (requires Linux)
Safe Haskell	None
Language	Haskell2010

System.Linux.Btrfs.ByteString

Contents

Basic types
File cloning/deduplication
Subvolumes and snapshots
Defragging
Sync
Inspect internal
Miscellaneous
Tree search

Description

Most functions in this module come in two flavors: one that operates on file descriptors and another one that operates on file paths. The former can be distinguished by the Fd suffix in their names.

Synopsis

Basic types

type FileSize = Word64 #

type ObjectType = Word8 #

type ObjectId = Word64 #

type InodeNum = ObjectId #

type SubvolId = ObjectId #

data CompressionType #

Constructors

Zlib
LZO

Instances

Bounded CompressionType #
Methods minBound :: CompressionType # maxBound :: CompressionType #
Enum CompressionType #
Methods succ :: CompressionType -> CompressionType # pred :: CompressionType -> CompressionType # toEnum :: Int -> CompressionType # fromEnum :: CompressionType -> Int # enumFrom :: CompressionType -> [CompressionType] # enumFromThen :: CompressionType -> CompressionType -> [CompressionType] # enumFromTo :: CompressionType -> CompressionType -> [CompressionType] # enumFromThenTo :: CompressionType -> CompressionType -> CompressionType -> [CompressionType] #
Eq CompressionType #
Methods (==) :: CompressionType -> CompressionType -> Bool # (/=) :: CompressionType -> CompressionType -> Bool #
Read CompressionType #
Methods readsPrec :: Int -> ReadS CompressionType # readList :: ReadS [CompressionType] # readPrec :: ReadPrec CompressionType # readListPrec :: ReadPrec [CompressionType] #
Show CompressionType #
Methods showsPrec :: Int -> CompressionType -> ShowS # show :: CompressionType -> String # showList :: [CompressionType] -> ShowS #

File cloning/deduplication

cloneFd :: Fd -> Fd -> IO () #

clone #

Arguments

:: RawFilePath	The source file.
-> RawFilePath	The destination file.
-> IO ()

Clone an entire file to an existing file.

Note: calls the BTRFS_IOC_CLONE/FICLONE ioctl.

cloneNew :: RawFilePath -> RawFilePath -> IO () #

Like clone except that it will create or truncate the destination file if necessary. This is similar to cp --reflink=always.

Note: calls the BTRFS_IOC_CLONE/FICLONE ioctl.

cloneRangeFd :: Fd -> FileSize -> FileSize -> Fd -> FileSize -> IO () #

cloneRange #

Arguments

:: RawFilePath	The source file.
-> FileSize	The offset within the source file.
-> FileSize	The length of the range. A length of 0 selects the range from the source offset to the end.
-> RawFilePath	The destination file.
-> FileSize	The offset within the destination file.
-> IO ()

Clones a range of bytes from a file to another file. All ranges must be block-aligned.

Note: calls the BTRFS_IOC_CLONE_RANGE/FICLONERANGE ioctl.

data CloneResult #

The result of a cloneRangeIfSame operation.

Constructors

CRError IOError	Cloning failed because of an error.
CRDataDiffers	No cloning was performed because the contents of the source and the destination file differ.
CRSuccess FileSize	Cloning succeeded, the returned integer indicates the number of bytes that were deduped.

Instances

Eq CloneResult #
Methods (==) :: CloneResult -> CloneResult -> Bool # (/=) :: CloneResult -> CloneResult -> Bool #
Show CloneResult #
Methods showsPrec :: Int -> CloneResult -> ShowS # show :: CloneResult -> String # showList :: [CloneResult] -> ShowS #

cloneRangeIfSameFd :: Fd -> FileSize -> FileSize -> [(Fd, FileSize)] -> IO [CloneResult] #

cloneRangeIfSame #

Arguments

:: RawFilePath	The source file.
-> FileSize	The offset within the source file.
-> FileSize	The length of the range.
-> [(RawFilePath, FileSize)]	The destination files and corresponding offsets.
-> IO [CloneResult]

Similar to cloneRange except that it performs the cloning only if the data ranges contain identical data. Additionally, it accepts multiple destination files. The same thing can be accomplished with cloneRange in conjunction with file locking but this function uses in-kernel locking to guarantee that the deduplicated data is identical at the time of the operation. On the other hand, this function will not clone arbitrarily large ranges; the kernel has an upper limit for the length and if cloning bigger ranges is desired then it has to be called multiple times. Note that cloning may succeed for some of the destination files and fail for others. Because of that, this function returns a list of outcomes, one for each destination file, and no exceptions will be raised for the failed files.

Note: calls the BTRFS_IOC_FILE_EXTENT_SAME/FIDEDUPERANGE ioctl.

Requires Linux 3.12 or later.

Subvolumes and snapshots

createSubvol :: RawFilePath -> IO () #

Create an (initially) empty new subvolume.

Note: calls the BTRFS_IOC_SUBVOL_CREATE ioctl.

destroySubvol :: RawFilePath -> IO () #

Destroy (delete) a subvolume. The directory that corresponds to the subvolume is removed asynchronously. As a result, the subvolume may appear again after a crash. If this is not acceptable, call startSync followed by a waitSync, after the destroySubvol call.

Note: calls the BTRFS_IOC_SNAP_DESTROY ioctl.

snapshotFd :: Fd -> RawFilePath -> Bool -> IO () #

snapshot #

Arguments

:: RawFilePath	The source subvolume.
-> RawFilePath	The destination subvolume (must not exist).
-> Bool	Create a read-only snapshot?
-> IO ()

Create a snapshot of an existing subvolume.

Note: calls the BTRFS_IOC_SNAP_CREATE_V2 ioctl.

getSubvolReadOnlyFd :: Fd -> IO Bool #

getSubvolReadOnly :: RawFilePath -> IO Bool #

Is the subvolume read-only?

Note: calls the BTRFS_IOC_SUBVOL_GETFLAGS ioctl.

setSubvolReadOnlyFd :: Fd -> Bool -> IO () #

setSubvolReadOnly :: RawFilePath -> Bool -> IO () #

Make a subvolume read-only (or read-write).

Note: calls the BTRFS_IOC_SUBVOL_GETFLAGS and BTRFS_IOC_SUBVOL_SETFLAGS ioctls.

getSubvolFd :: Fd -> IO SubvolId #

getSubvol :: RawFilePath -> IO SubvolId #

Find the id of the subvolume where the given file resides. This is merely a wrapper around lookupInode provided for convenience.

lookupSubvolFd :: Fd -> SubvolId -> IO (SubvolId, InodeNum, RawFilePath) #

lookupSubvol #

Arguments

:: RawFilePath	The mount point of the volume (or any file in that volume).
-> SubvolId	The id of the subvolume.
-> IO (SubvolId, InodeNum, RawFilePath)

Given the id of a subvolume, find the id of the parent subvolume, the inode number of the directory containing it, and its name. This is a wrapper around treeSearch.

resolveSubvolFd :: Fd -> SubvolId -> IO RawFilePath #

resolveSubvol #

Arguments

:: RawFilePath	The mount point of the volume (or any file in that volume).
-> SubvolId	The id of the subvolume.
-> IO RawFilePath

Given the id of a subvolume, find its path relative to the root of the volume. This function calls lookupSubvol recursively.

rootSubvol :: SubvolId #

The id the root subvolume.

listSubvolsFd :: Fd -> IO [(SubvolId, SubvolId, InodeNum, RawFilePath)] #

listSubvols :: RawFilePath -> IO [(SubvolId, SubvolId, InodeNum, RawFilePath)] #

Find all subvolumes of the given volume. For each subvolume found, it returns: its id, the id of its parent subvolume, the inode number of the directory containing it, and its name. This is a wrapper around treeSearch.

listSubvolPathsFd :: Fd -> IO [(SubvolId, SubvolId, RawFilePath)] #

listSubvolPaths :: RawFilePath -> IO [(SubvolId, SubvolId, RawFilePath)] #

Find all subvolumes of the given volume. For each subvolume found, it returns: its id, the id of its parent subvolume, and its path relative to the root of the volume. This is a wrapper around treeSearch and resolveSubvol.

childSubvolsFd :: Fd -> SubvolId -> IO [(SubvolId, InodeNum, RawFilePath)] #

childSubvols #

Arguments

:: RawFilePath	The mount point of the volume (or any file in that volume).
-> SubvolId	The id of the subvolume.
-> IO [(SubvolId, InodeNum, RawFilePath)]

Find all child subvolumes of the given subvolume. For each child, returns its id, the inode number of the directory containing it, and its name. This is a wrapper around treeSearch.

childSubvolPathsFd :: Fd -> SubvolId -> IO [(SubvolId, RawFilePath)] #

childSubvolPaths #

Arguments

:: RawFilePath	The mount point of the volume (or any file in that volume).
-> SubvolId	The id of the subvolume.
-> IO [(SubvolId, RawFilePath)]

Find all child subvolumes of the given subvolume. For each child, returns its id and its path relative to the root of the parent. This is a wrapper around treeSearch and lookupInode.

data SubvolInfo #

Information about a subvolume.

Constructors

SubvolInfo

Fields

siGeneration :: Word64
The generation when the subvolume was last modified.
siLastSnapshot :: Maybe Word64
The generation when the most recent snapshot of this subvolume was taken.
siParSnapGen :: Maybe Word64
The generation of the snapshot parent at the time when the snapshot was taken. Defined if only if this is a snapshot.
siReadOnly :: Bool
Is this a read-only subvolume?
siUuid :: Maybe UUID
The UUID of the subvolume.
siPUuid :: Maybe UUID
The UUID of the snapshot parent.
siReceivedUuid :: Maybe UUID
The UUID of the source subvolume that this subvolume was received from. This is always defined for received subvolumes.
siCTransId :: Maybe Word64
The generation when an inode was last modified.
siOTransId :: Maybe Word64
The generation when the subvolume was created.
siSTransId :: Maybe Word64
The generation of the source subvolume that this subvolume was received from. This is always defined for received subvolumes.
siRTransId :: Maybe Word64
The generation when the subvolume was received. This is always defined for received subvolumes.
siCTime :: Maybe UTCTime
The time when an inode was last modified.
siOTime :: Maybe UTCTime
The time when the subvolume was created.
siSTime :: Maybe UTCTime
The timestamp that corresponds to siSTransId.
siRTime :: Maybe UTCTime
The time when the subvolume was received. This is always defined for received subvolumes.

Instances

Eq SubvolInfo #
Methods (==) :: SubvolInfo -> SubvolInfo -> Bool # (/=) :: SubvolInfo -> SubvolInfo -> Bool #
Show SubvolInfo #
Methods showsPrec :: Int -> SubvolInfo -> ShowS # show :: SubvolInfo -> String # showList :: [SubvolInfo] -> ShowS #

getSubvolInfoFd :: Fd -> SubvolId -> IO SubvolInfo #

getSubvolInfo #

Arguments

:: RawFilePath	The mount point of the volume (or any file in that volume).
-> SubvolId	The id of the subvolume.
-> IO SubvolInfo

Retrieve information about a subvolume. This is a wrapper around treeSearch.

getSubvolByUuidFd :: Fd -> UUID -> IO SubvolId #

getSubvolByUuid #

Arguments

:: RawFilePath	The mount point of the volume (or any file in that volume).
-> UUID	The UUID of the subvolume.
-> IO SubvolId

Find the id of a subvolume, given its UUID. This is a wrapper around treeSearch.

Requires Linux 3.12 or later.

getSubvolByReceivedUuidFd :: Fd -> UUID -> IO SubvolId #

getSubvolByReceivedUuid #

Arguments

:: RawFilePath	The mount point of the volume (or any file in that volume).
-> UUID	The `siReceivedUuid` of the subvolume.
-> IO SubvolId

Find the id of a subvolume, given its siReceivedUuid. This is a wrapper around treeSearch.

Requires Linux 3.12 or later.

getDefaultSubvolFd :: Fd -> IO SubvolId #

getDefaultSubvol #

Arguments

:: RawFilePath	The mount point of the volume (or any file in that volume).
-> IO SubvolId

Find the id of the default subvolume. This is a wrapper around treeSearch.

setDefaultSubvolFd :: Fd -> ObjectId -> IO () #

setDefaultSubvol #

Arguments

:: RawFilePath	The mount point of the volume (or any file in that volume).
-> SubvolId	The id of the new default subvolume.
-> IO ()

Set the default subvolume.

Note: calls the BTRFS_IOC_DEFAULT_SUBVOL ioctl.

Defragging

defragFd :: Fd -> IO () #

defrag :: RawFilePath -> IO () #

Defrag a single file.

Note: calls the BTRFS_IOC_DEFRAG ioctl.

data DefragRangeArgs #

Argument to the defragRange operation.

Constructors

DefragRangeArgs

Fields

draStart :: FileSize
Beginning of the defrag range.
draLength :: FileSize
Number of bytes to defrag, use maxBound to say all.
draExtentThreshold :: Word32
Any extent of size bigger or equal to this number will be considered already defragged. Use 0 for the kernel default.
draCompress :: Maybe CompressionType
Compress the file while defragmenting.
draFlush :: Bool
Flush data to disk immediately after defragmenting.

Instances

Eq DefragRangeArgs #
Methods (==) :: DefragRangeArgs -> DefragRangeArgs -> Bool # (/=) :: DefragRangeArgs -> DefragRangeArgs -> Bool #
Show DefragRangeArgs #
Methods showsPrec :: Int -> DefragRangeArgs -> ShowS # show :: DefragRangeArgs -> String # showList :: [DefragRangeArgs] -> ShowS #

defaultDefragRangeArgs :: DefragRangeArgs #

Defaults for defragRange. Selects the entire file, no compression, and no flushing.

defragRangeFd :: Fd -> DefragRangeArgs -> IO () #

defragRange :: RawFilePath -> DefragRangeArgs -> IO () #

Defrag a range within a single file.

Note: calls the BTRFS_IOC_DEFRAG_RANGE ioctl.

Sync

syncFd :: Fd -> IO () #

sync :: RawFilePath -> IO () #

Sync the file system identified by the supplied path. The FilePath can refer to any file in the file system.

Note: calls the BTRFS_IOC_SYNC ioctl.

startSyncFd :: Fd -> IO () #

startSync :: RawFilePath -> IO () #

Initiate a sync for the file system identified by the supplied path.

Note: calls the BTRFS_IOC_START_SYNC ioctl.

waitSyncFd :: Fd -> IO () #

waitSync :: RawFilePath -> IO () #

Wait until the sync operation completes.

Note: calls the BTRFS_IOC_WAIT_SYNC ioctl.

Inspect internal

resolveLogicalFd :: Fd -> FileSize -> IO ([(InodeNum, FileSize, SubvolId)], Int) #

resolveLogical #

Arguments

:: RawFilePath	The mount point of the volume (or any file in that volume).
-> FileSize	The physical byte offset in the underlying block device.
-> IO ([(InodeNum, FileSize, SubvolId)], Int)

Given a physical offset, look for any inodes that this byte belongs to. For each inode, it returns the inode number, the logical offset (i.e. the offset within the inode), and the subvolume id. If a large number of inodes is found, then not all of them will be returned by this function. This is due to a current limitation in the kernel. The integer returned along with list of inodes indicates the number of inodes found but not included in the list.

Note: calls the BTRFS_IOC_LOGICAL_INO ioctl.

resolveInodeFd :: Fd -> InodeNum -> IO ([RawFilePath], Int) #

resolveInode #

Arguments

:: RawFilePath	The path to the subvolume (or any file in that subvolume).
-> InodeNum	The inode number.
-> IO ([RawFilePath], Int)

Find the file path(s) given an inode number. Returns a list of file paths and an integer indicating the number of paths found but not included in the resulting list. This is because of a limitation in the kernel (it will not return an arbitrarily large list). The paths returned are relative to the root of the subvolume.

Note: calls the BTRFS_IOC_INO_PATHS ioctl.

lookupInodeFd :: Fd -> SubvolId -> InodeNum -> IO (SubvolId, RawFilePath) #

lookupInode #

Arguments

:: RawFilePath	The path to any file in the volume. The subvolume where this file resides is ignored unless no `SubvolId` is provided (see below).
-> SubvolId	The id of the subvolume. Can be 0. In that case, the subvolume of the `FilePath` is used (see above).
-> InodeNum	The inode number.
-> IO (SubvolId, RawFilePath)

Find the path of a file given its inode number and the id of the subvolume. If multiple files share the same inode number, only one of them is returned. The id of the subvolume is also returned. This is useful when 0 is given for the SubvolId argument (also see getSubvol for this case).

Note: calls the BTRFS_IOC_INO_LOOKUP ioctl.

Miscellaneous

getFileNoCOWFd :: Fd -> IO Bool #

getFileNoCOW :: RawFilePath -> IO Bool #

Determine whether the NOCOW flag is enabled for the specified file.

Note: calls the FS_IOC_GETFLAGS ioctl.

setFileNoCOWFd :: Fd -> Bool -> IO () #

setFileNoCOW :: RawFilePath -> Bool -> IO () #

Set or clear the NOCOW flag for the specified file. If the file is not empty, this has no effect and no error will be reported.

Note: calls the FS_IOC_GETFLAGS and FS_IOC_GETFLAGS ioctls.

Tree search

Low-level API for tree search using the BTRFS_IOC_TREE_SEARCH ioctl.

data SearchKey #

Constructors

SearchKey
Fields skTreeId :: ObjectId skMinObjectId :: ObjectId skMinType :: ObjectType skMinOffset :: Word64 skMaxObjectId :: ObjectId skMaxType :: ObjectType skMaxOffset :: Word64 skMinTransId :: Word64 skMaxTransId :: Word64

Instances

Eq SearchKey #
Methods (==) :: SearchKey -> SearchKey -> Bool # (/=) :: SearchKey -> SearchKey -> Bool #
Show SearchKey #
Methods showsPrec :: Int -> SearchKey -> ShowS # show :: SearchKey -> String # showList :: [SearchKey] -> ShowS #

defaultSearchKey :: SearchKey #

data SearchHeader #

Constructors

SearchHeader
Fields shTransId :: Word64 shObjectId :: ObjectId shOffset :: Word64 shType :: ObjectType shLen :: Word32

Instances

Eq SearchHeader #
Methods (==) :: SearchHeader -> SearchHeader -> Bool # (/=) :: SearchHeader -> SearchHeader -> Bool #
Show SearchHeader #
Methods showsPrec :: Int -> SearchHeader -> ShowS # show :: SearchHeader -> String # showList :: [SearchHeader] -> ShowS #

treeSearchFd :: Fd -> SearchKey -> Int -> (SearchHeader -> Ptr i -> IO ()) -> IO () #

treeSearch :: RawFilePath -> SearchKey -> Int -> (SearchHeader -> Ptr i -> IO ()) -> IO () #

treeSearchListFd :: Fd -> SearchKey -> (SearchHeader -> Ptr i -> IO (Maybe a)) -> IO [a] #

treeSearchList :: RawFilePath -> SearchKey -> (SearchHeader -> Ptr i -> IO (Maybe a)) -> IO [a] #

findFirstItemFd :: Fd -> SearchKey -> (SearchHeader -> Ptr i -> IO a) -> IO a #

findFirstItem :: RawFilePath -> SearchKey -> (SearchHeader -> Ptr i -> IO a) -> IO a #