[PATCH proxmox-fuse-rs v1] Add statfs support to proxmox-fuse

[Kefu Chai <k.chai@proxmox.com>]

- Add fuse_reply_statfs FFI binding in sys.rs
- Add Statfs request struct in requests.rs
- Add Statfs variant to Request enum
- Add statfs callback to FuseData
- Add enable_statfs() method to FuseSessionBuilder

This enables filesystems to handle statfs requests and return filesystem statistics.

Signed-off-by: Kefu Chai <k.chai@proxmox.com>
---
 examples/tmpfs/main.rs |  4 ++--
 src/requests.rs        | 24 ++++++++++++++++++++++++
 src/session.rs         | 17 +++++++++++++++++
 src/sys.rs             |  1 +
 4 files changed, 44 insertions(+), 2 deletions(-)

diff --git a/examples/tmpfs/main.rs b/examples/tmpfs/main.rs
index f3f7d26..36db9e8 100644
--- a/examples/tmpfs/main.rs
+++ b/examples/tmpfs/main.rs
@@ -3,11 +3,11 @@ use std::ffi::OsStr;
 use std::path::Path;
 use std::{io, mem};
 
-use anyhow::{bail, format_err, Error};
+use anyhow::{Error, bail, format_err};
 use futures::future::FutureExt;
 use futures::select;
 use futures::stream::TryStreamExt;
-use tokio::signal::unix::{signal, SignalKind};
+use tokio::signal::unix::{SignalKind, signal};
 
 use proxmox_fuse::requests::{self, FuseRequest, SetTime};
 use proxmox_fuse::{EntryParam, Fuse, ReplyBufState, Request};
diff --git a/src/requests.rs b/src/requests.rs
index d1846cc..458b956 100644
--- a/src/requests.rs
+++ b/src/requests.rs
@@ -106,6 +106,7 @@ pub enum Request {
     Forget(Forget),
     Getattr(Getattr),
     Setattr(Setattr),
+    Statfs(Statfs),
     Readdir(Readdir),
     ReaddirPlus(ReaddirPlus),
     Mkdir(Mkdir),
@@ -144,6 +145,7 @@ impl FuseRequest for Request {
             Request::Lookup(r) => r.fail(errno),
             Request::Getattr(r) => r.fail(errno),
             Request::Setattr(r) => r.fail(errno),
+            Request::Statfs(r) => r.fail(errno),
             Request::Readdir(r) => r.fail(errno),
             Request::ReaddirPlus(r) => r.fail(errno),
             Request::Mkdir(r) => r.fail(errno),
@@ -239,6 +241,28 @@ impl Getattr {
     }
 }
 
+/// Get filesystem statistics.
+///
+/// This is the equivalent of a `statfs` call.
+#[derive(Debug)]
+pub struct Statfs {
+    pub(crate) request: RequestGuard,
+    pub inode: u64,
+}
+
+impl FuseRequest for Statfs {
+    fn fail(self, errno: libc::c_int) -> io::Result<()> {
+        reply_err(self.request, errno)
+    }
+}
+
+impl Statfs {
+    /// Send a reply for a `Statfs` request.
+    pub fn reply(self, stbuf: &libc::statvfs) -> io::Result<()> {
+        reply_result!(self: sys::fuse_reply_statfs(self.request.raw, stbuf as *const _))
+    }
+}
+
 /// Get the contents of a directory without changing any lookup counts. (Contrary to
 /// `ReaddirPlus`).
 #[derive(Debug)]
diff --git a/src/session.rs b/src/session.rs
index 62a8a9e..3e4841c 100644
--- a/src/session.rs
+++ b/src/session.rs
@@ -94,6 +94,17 @@ impl FuseData {
             }));
     }
 
+    extern "C" fn statfs(request: sys::Request, inode: u64) {
+        let fuse_data = unsafe { &*(sys::fuse_req_userdata(request) as *mut FuseData) };
+        fuse_data
+            .pending_requests
+            .borrow_mut()
+            .push_back(Request::Statfs(requests::Statfs {
+                request: RequestGuard::from_raw(request),
+                inode,
+            }));
+    }
+
     extern "C" fn readdir(
         request: sys::Request,
         inode: u64,
@@ -547,6 +558,12 @@ impl FuseSessionBuilder {
         self
     }
 
+    /// Enable `Statfs` requests.
+    pub fn enable_statfs(mut self) -> Self {
+        self.operations.statfs = Some(FuseData::statfs);
+        self
+    }
+
     /// Enable `Unlink` requests.
     pub fn enable_unlink(mut self) -> Self {
         self.operations.unlink = Some(FuseData::unlink);
diff --git a/src/sys.rs b/src/sys.rs
index 17a01de..186b0ec 100644
--- a/src/sys.rs
+++ b/src/sys.rs
@@ -77,6 +77,7 @@ unsafe extern "C" {
     pub fn fuse_reply_readlink(req: Request, link: StrPtr) -> c_int;
     pub fn fuse_reply_none(req: Request);
     pub fn fuse_reply_write(req: Request, count: libc::size_t) -> c_int;
+    pub fn fuse_reply_statfs(req: Request, stbuf: *const libc::statvfs) -> c_int;
     pub fn fuse_req_userdata(req: Request) -> MutPtr;
     pub fn fuse_add_direntry_plus(req: Request, buf: MutStrPtr, bufsize: size_t, name: StrPtr, stbuf: Option<&EntryParam>, off: c_int) -> size_t;
     pub fn fuse_add_direntry(req: Request, buf: MutStrPtr, bufsize: size_t, name: StrPtr, stbuf: Option<&libc::stat>, off: c_int) -> size_t;
-- 
2.47.3