Implement statfs with synthetic values

mountpoint-s3/Cargo.toml

@@ -29,7 +29,7 @@ lazy_static = "1.4.0"
 libc = "0.2.126"
 linked-hash-map = "0.5.6"
 metrics = "0.22.1"
-nix = { version = "0.27.1", features = ["user"] }
+nix = { version = "0.27.1", features = ["user", "fs"] }
 regex = "1.7.1"
 serde = { version = "1.0.190", features = ["derive"] }
 serde_json = "1.0.95"

mountpoint-s3/src/fs.rs

@@ -593,6 +593,43 @@ pub struct DirectoryEntry {
     lookup: LookedUp,
 }
 
+/// Reply to a `statfs` call
+#[derive(Debug)]
+pub struct StatFs {
+    /// Total number of blocks
+    pub total_blocks: u64,
+    /// Number of free blocks
+    pub free_blocks: u64,
+    /// Number of free blocks available to unprivileged user
+    pub available_blocks: u64,
+    /// Number of inodes in file system
+    pub total_inodes: u64,
+    /// Available inodes
+    pub free_inodes: u64,
+    /// Optimal transfer block size
+    pub block_size: u32,
+    /// Maximum name length
+    pub maximum_name_length: u32,
+    /// Fragement size
+    pub fragment_size: u32,
+}
+
+impl Default for StatFs {
+    fn default() -> Self {
+        // Derived from Fuser defaults (https://github.com/cberner/fuser/blob/bcff57cc5/src/lib.rs#L695-L698)
+        Self {
+            total_blocks: 0,
+            free_blocks: 0,
+            available_blocks: 0,
+            total_inodes: 0,
+            free_inodes: 0,
+            block_size: 512,
+            maximum_name_length: 255,
+            fragment_size: 0,
+        }
+    }
+}
+
 impl<Client, Prefetcher> S3Filesystem<Client, Prefetcher>
 where
     Client: ObjectClient + Send + Sync + 'static,
@@ -1251,6 +1288,20 @@ where
         }
         Ok(self.superblock.unlink(&self.client, parent_ino, name).await?)
     }
+
+    pub async fn statfs(&self, _ino: InodeNo) -> Result<StatFs, Error> {
+        // Let's pick some big numbers...
+        const FREE_BLOCKS: u64 = u64::MAX / 2;
+        const FREE_INODES: u64 = u64::MAX / 2;
+
+        let reply = StatFs {
+            free_blocks: FREE_BLOCKS,
+            available_blocks: FREE_BLOCKS,
+            free_inodes: FREE_INODES,
+            ..Default::default()
+        };
+        Ok(reply)
+    }
 }
 
 #[cfg(test)]

mountpoint-s3/src/fuse.rs

@@ -15,7 +15,7 @@ use crate::prefix::Prefix;
 use fuser::ReplyXTimes;
 use fuser::{
     Filesystem, KernelConfig, ReplyAttr, ReplyBmap, ReplyCreate, ReplyData, ReplyEmpty, ReplyEntry, ReplyIoctl,
-    ReplyLock, ReplyLseek, ReplyOpen, ReplyWrite, ReplyXattr, Request, TimeOrNow,
+    ReplyLock, ReplyLseek, ReplyOpen, ReplyStatfs, ReplyWrite, ReplyXattr, Request, TimeOrNow,
 };
 
 pub mod session;
@@ -388,6 +388,23 @@ where
         }
     }
 
+    #[instrument(level="warn", skip_all, fields(req=_req.unique(), ino=ino))]
+    fn statfs(&self, _req: &Request<'_>, ino: u64, reply: ReplyStatfs) {
+        match block_on(self.fs.statfs(ino).in_current_span()) {
+            Ok(statfs) => reply.statfs(
+                statfs.total_blocks,
+                statfs.free_blocks,
+                statfs.available_blocks,
+                statfs.total_inodes,
+                statfs.free_inodes,
+                statfs.block_size,
+                statfs.maximum_name_length,
+                statfs.fragment_size,
+            ),
+            Err(e) => fuse_error!("statfs", reply, e),
+        }
+    }
+
     // Everything below here is stubs for unsupported functions so we log them correctly
 
     #[instrument(level="warn", skip_all, fields(req=_req.unique(), ino=ino))]

mountpoint-s3/tests/fuse_tests/mod.rs

@@ -9,5 +9,6 @@ mod readdir_test;
 mod rmdir_test;
 mod semantics_doc_test;
 mod setattr_test;
+mod statfs_test;
 mod unlink_test;
 mod write_test;

mountpoint-s3/tests/fuse_tests/statfs_test.rs

@@ -0,0 +1,35 @@
+use fuser::BackgroundSession;
+use nix::sys::statvfs::statvfs;
+use tempfile::TempDir;
+
+use crate::common::fuse::{self, TestClientBox, TestSessionConfig};
+
+fn statfs_test<F>(creator_fn: F, prefix: &str)
+where
+    F: FnOnce(&str, TestSessionConfig) -> (TempDir, BackgroundSession, TestClientBox),
+{
+    let (mount_point, _session, mut test_client) = creator_fn(prefix, Default::default());
+
+    // Make sure there's an existing directory
+    test_client.put_object("dir/hello.txt", b"hello world").unwrap();
+
+    let path = mount_point.path().join("dir");
+
+    let reply = statvfs(&path).unwrap();
+
+    assert_eq!(reply.files(), 0, "inodes/files should not be counted and returned");
+    assert_eq!(
+        reply.name_max(),
+        255,
+        "name_max should return 255, matching Fuser default",
+    );
+    assert!(
+        reply.blocks_available() > 0,
+        "blocks available should be non-zero, even though we can't provide a real number",
+    );
+}
+
+#[test]
+fn statfs_test_mock() {
+    statfs_test(fuse::mock_session::new, "statfs_test_mock");
+}