1 files changed, 337 insertions, 0 deletions
diff --git a/src/block/layout.rs b/src/block/layout.rs
new file mode 100644
index 00000000..e8339405
--- /dev/null
+++ b/src/block/layout.rs
@@ -0,0 +1,337 @@
+use std::path::PathBuf;
+
+use serde::{Deserialize, Serialize};
+
+use garage_util::config::DataDirEnum;
+use garage_util::data::Hash;
+use garage_util::error::{Error, OkOrMessage};
+use garage_util::migrate::*;
+
+type Idx = u16;
+
+const DRIVE_NPART: usize = 1024;
+
+const HASH_DRIVE_BYTES: (usize, usize) = (2, 3);
+
+#[derive(Serialize, Deserialize, Debug, Clone)]
+pub(crate) struct DataLayout {
+	pub(crate) data_dirs: Vec<DataDir>,
+
+	/// Primary storage location (index in data_dirs) for each partition
+	/// = the location where the data is supposed to be, blocks are always
+	/// written there (copies in other dirs may be deleted if they exist)
+	pub(crate) part_prim: Vec<Idx>,
+	/// Secondary storage locations for each partition = locations
+	/// where data blocks might be, we check from these dirs when reading
+	pub(crate) part_sec: Vec<Vec<Idx>>,
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone, Eq, PartialEq)]
+pub(crate) struct DataDir {
+	pub(crate) path: PathBuf,
+	pub(crate) state: DataDirState,
+}
+
+#[derive(Serialize, Deserialize, Debug, Clone, Copy, Eq, PartialEq)]
+pub(crate) enum DataDirState {
+	Active { capacity: u64 },
+	ReadOnly,
+}
+
+impl DataLayout {
+	pub(crate) fn initialize(dirs: &DataDirEnum) -> Result<Self, Error> {
+		let data_dirs = make_data_dirs(dirs)?;
+
+		// Split partitions proportionnally to capacity for all drives
+		// to affect primary storage location
+		let total_cap = data_dirs.iter().filter_map(|x| x.capacity()).sum::<u64>();
+		assert!(total_cap > 0);
+
+		let mut part_prim = Vec::with_capacity(DRIVE_NPART);
+		let mut cum_cap = 0;
+		for (i, dd) in data_dirs.iter().enumerate() {
+			if let DataDirState::Active { capacity } = dd.state {
+				cum_cap += capacity;
+				let n_total = (cum_cap * DRIVE_NPART as u64) / total_cap;
+				part_prim.resize(n_total as usize, i as Idx);
+			}
+		}
+		assert_eq!(cum_cap, total_cap);
+		assert_eq!(part_prim.len(), DRIVE_NPART);
+
+		// If any of the storage locations is non-empty, it probably existed before
+		// this algorithm was added, so add it as a secondary storage location for all partitions
+		// to make sure existing files are not lost
+		let mut part_sec = vec![vec![]; DRIVE_NPART];
+		for (i, dd) in data_dirs.iter().enumerate() {
+			if dir_not_empty(&dd.path)? {
+				for (sec, prim) in part_sec.iter_mut().zip(part_prim.iter()) {
+					if *prim != i as Idx {
+						sec.push(i as Idx);
+					}
+				}
+			}
+		}
+
+		Ok(Self {
+			data_dirs,
+			part_prim,
+			part_sec,
+		})
+	}
+
+	pub(crate) fn update(&mut self, dirs: &DataDirEnum) -> Result<(), Error> {
+		// Make list of new data directories, exit if nothing changed
+		let data_dirs = make_data_dirs(dirs)?;
+		if data_dirs == self.data_dirs {
+			return Ok(());
+		}
+
+		let total_cap = data_dirs.iter().filter_map(|x| x.capacity()).sum::<u64>();
+		assert!(total_cap > 0);
+
+		// Compute mapping of old indices to new indices
+		let old2new = self
+			.data_dirs
+			.iter()
+			.map(|x| {
+				data_dirs
+					.iter()
+					.position(|y| y.path == x.path)
+					.map(|x| x as Idx)
+			})
+			.collect::<Vec<_>>();
+
+		// Compute secondary location list for partitions based on existing
+		// folders, translating indices from old to new
+		let mut part_sec = self
+			.part_sec
+			.iter()
+			.map(|dl| {
+				dl.iter()
+					.filter_map(|old| old2new.get(*old as usize).copied().flatten())
+					.collect::<Vec<_>>()
+			})
+			.collect::<Vec<_>>();
+
+		// Compute a vector that, for each data dir,
+		// contains the list of partitions primarily stored on that drive
+		let mut dir_prim = vec![vec![]; data_dirs.len()];
+		for (ipart, prim) in self.part_prim.iter().enumerate() {
+			if let Some(new) = old2new.get(*prim as usize).copied().flatten() {
+				dir_prim[new as usize].push(ipart);
+			}
+		}
+
+		// Compute the target number of partitions per data directory
+		let mut cum_cap = 0;
+		let mut npart_per_dir = vec![0; data_dirs.len()];
+		for (idir, dd) in data_dirs.iter().enumerate() {
+			if let DataDirState::Active { capacity } = dd.state {
+				let begin = (cum_cap * DRIVE_NPART as u64) / total_cap;
+				cum_cap += capacity;
+				let end = (cum_cap * DRIVE_NPART as u64) / total_cap;
+				npart_per_dir[idir] = (end - begin) as usize;
+			}
+		}
+		assert_eq!(cum_cap, total_cap);
+		assert_eq!(npart_per_dir.iter().sum::<usize>(), DRIVE_NPART);
+
+		// For all directories that have too many primary partitions,
+		// move that partition to secondary
+		for (idir, (parts, tgt_npart)) in dir_prim.iter_mut().zip(npart_per_dir.iter()).enumerate()
+		{
+			while parts.len() > *tgt_npart {
+				let part = parts.pop().unwrap();
+				if !part_sec[part].contains(&(idir as Idx)) {
+					part_sec[part].push(idir as Idx);
+				}
+			}
+		}
+
+		// Calculate the vector of primary partition dir index
+		let mut part_prim = vec![None; DRIVE_NPART];
+		for (idir, parts) in dir_prim.iter().enumerate() {
+			for part in parts.iter() {
+				assert!(part_prim[*part].is_none());
+				part_prim[*part] = Some(idir as Idx)
+			}
+		}
+
+		// Calculate a vector of unassigned partitions
+		let mut unassigned = part_prim
+			.iter()
+			.enumerate()
+			.filter(|(_, dir)| dir.is_none())
+			.map(|(ipart, _)| ipart)
+			.collect::<Vec<_>>();
+
+		// For all directories that don't have enough primary partitions,
+		// add partitions from unassigned
+		for (idir, (parts, tgt_npart)) in dir_prim.iter_mut().zip(npart_per_dir.iter()).enumerate()
+		{
+			if parts.len() < *tgt_npart {
+				let required = *tgt_npart - parts.len();
+				assert!(unassigned.len() >= required);
+				for _ in 0..required {
+					let new_part = unassigned.pop().unwrap();
+					part_prim[new_part] = Some(idir as Idx);
+					part_sec[new_part].retain(|x| *x != idir as Idx);
+				}
+			}
+		}
+
+		// Sanity checks
+		assert!(part_prim.iter().all(|x| x.is_some()));
+		assert!(unassigned.is_empty());
+
+		// Transform part_prim from vec of Option<Idx> to vec of Idx
+		let part_prim = part_prim
+			.into_iter()
+			.map(|x| x.unwrap())
+			.collect::<Vec<_>>();
+		assert!(part_prim.iter().all(|p| data_dirs
+			.get(*p as usize)
+			.and_then(|x| x.capacity())
+			.unwrap_or(0)
+			> 0));
+
+		// If any of the newly added storage locations is non-empty,
+		// it might have been removed and added again and might contain data,
+		// so add it as a secondary storage location for all partitions
+		// to make sure existing files are not lost
+		for (i, dd) in data_dirs.iter().enumerate() {
+			if self.data_dirs.iter().any(|ed| ed.path == dd.path) {
+				continue;
+			}
+			if dir_not_empty(&dd.path)? {
+				for (sec, prim) in part_sec.iter_mut().zip(part_prim.iter()) {
+					if *prim != i as Idx && !sec.contains(&(i as Idx)) {
+						sec.push(i as Idx);
+					}
+				}
+			}
+		}
+
+		// Apply newly generated config
+		*self = Self {
+			data_dirs,
+			part_prim,
+			part_sec,
+		};
+		Ok(())
+	}
+
+	pub(crate) fn primary_block_dir(&self, hash: &Hash) -> PathBuf {
+		let ipart = self.partition_from(hash);
+		let idir = self.part_prim[ipart] as usize;
+		self.block_dir_from(hash, &self.data_dirs[idir].path)
+	}
+
+	pub(crate) fn secondary_block_dirs<'a>(
+		&'a self,
+		hash: &'a Hash,
+	) -> impl Iterator<Item = PathBuf> + 'a {
+		let ipart = self.partition_from(hash);
+		self.part_sec[ipart]
+			.iter()
+			.map(move |idir| self.block_dir_from(hash, &self.data_dirs[*idir as usize].path))
+	}
+
+	fn partition_from(&self, hash: &Hash) -> usize {
+		u16::from_be_bytes([
+			hash.as_slice()[HASH_DRIVE_BYTES.0],
+			hash.as_slice()[HASH_DRIVE_BYTES.1],
+		]) as usize % DRIVE_NPART
+	}
+
+	fn block_dir_from(&self, hash: &Hash, dir: &PathBuf) -> PathBuf {
+		let mut path = dir.clone();
+		path.push(hex::encode(&hash.as_slice()[0..1]));
+		path.push(hex::encode(&hash.as_slice()[1..2]));
+		path
+	}
+
+	pub(crate) fn without_secondary_locations(&self) -> Self {
+		Self {
+			data_dirs: self.data_dirs.clone(),
+			part_prim: self.part_prim.clone(),
+			part_sec: self.part_sec.iter().map(|_| vec![]).collect::<Vec<_>>(),
+		}
+	}
+}
+
+impl InitialFormat for DataLayout {
+	const VERSION_MARKER: &'static [u8] = b"G09bmdl";
+}
+
+impl DataDir {
+	pub fn capacity(&self) -> Option<u64> {
+		match self.state {
+			DataDirState::Active { capacity } => Some(capacity),
+			_ => None,
+		}
+	}
+}
+
+fn make_data_dirs(dirs: &DataDirEnum) -> Result<Vec<DataDir>, Error> {
+	let mut data_dirs = vec![];
+	match dirs {
+		DataDirEnum::Single(path) => data_dirs.push(DataDir {
+			path: path.clone(),
+			state: DataDirState::Active {
+				capacity: 1_000_000_000, // whatever, doesn't matter
+			},
+		}),
+		DataDirEnum::Multiple(dirs) => {
+			let mut ok = false;
+			for dir in dirs.iter() {
+				let state = match &dir.capacity {
+					Some(cap) if dir.read_only == false => {
+						let capacity = cap.parse::<bytesize::ByteSize>()
+							.ok_or_message("invalid capacity value")?.as_u64();
+						if capacity == 0 {
+							return Err(Error::Message(format!("data directory {} should have non-zero capacity", dir.path.to_string_lossy())));
+						}
+						ok = true;
+						DataDirState::Active {
+							capacity,
+						}
+					}
+					None if dir.read_only == true => {
+						DataDirState::ReadOnly
+					}
+					_ => return Err(Error::Message(format!("data directories in data_dir should have a capacity value or be marked read_only, not the case for {}", dir.path.to_string_lossy()))),
+				};
+				data_dirs.push(DataDir {
+					path: dir.path.clone(),
+					state,
+				});
+			}
+			if !ok {
+				return Err(Error::Message(
+					"incorrect data_dir configuration, no primary writable directory specified"
+						.into(),
+				));
+			}
+		}
+	}
+	Ok(data_dirs)
+}
+
+fn dir_not_empty(path: &PathBuf) -> Result<bool, Error> {
+	for entry in std::fs::read_dir(&path)? {
+		let dir = entry?;
+		if dir.file_type()?.is_dir()
+			&& dir
+				.file_name()
+				.into_string()
+				.ok()
+				.and_then(|hex| hex::decode(&hex).ok())
+				.is_some()
+		{
+			return Ok(true);
+		}
+	}
+	Ok(false)
+}