correct free data space accounting for multiple data dirs on same fs

src/rpc/system.rs

@@ -911,12 +911,30 @@ impl NodeStatus {
 		self.data_disk_avail = match data_dir {
 			DataDirEnum::Single(dir) => mount_avail(dir),
 			DataDirEnum::Multiple(dirs) => {
-				dirs.iter()
-					.map(|d| mount_avail(&d.path))
-					.fold(Some((0, 0)), |acc, cur| match (acc, cur) {
-						(Some((x, y)), Some((a, b))) => Some((x + a, y + b)),
-						_ => None,
+				// Take mounts corresponding to all specified data directories that
+				// can be used for writing data
+				let mounts = dirs
+					.iter()
+					.filter(|dir| dir.capacity.is_some())
+					.map(|dir| {
+						mounts
+							.iter()
+							.filter(|mnt| dir.path.starts_with(&mnt.fs_mounted_on))
+							.max_by_key(|mnt| mnt.fs_mounted_on.len())
 					})
+					.collect::<Vec<_>>();
+				if mounts.iter().any(|x| x.is_none()) {
+					None // could not get info for at least one mount
+				} else {
+					// dedup mounts in case several data directories are on the same filesystem
+					let mut mounts = mounts.iter().map(|x| x.unwrap()).collect::<Vec<_>>();
+					mounts.sort_by(|x, y| x.fs_mounted_on.cmp(&y.fs_mounted_on));
+					mounts.dedup_by(|x, y| x.fs_mounted_on == y.fs_mounted_on);
+					// calculate sum of available and total space
+					Some(mounts.iter().fold((0, 0), |(x, y), mnt| {
+						(x + mnt.avail.as_u64(), y + mnt.total.as_u64())
+					}))
+				}
 			}
 		};