Add LoopControl::add (#56)

* Add LoopControl::add Add LoopControl::add for adding/creating new loop devices via the LOOP_CTL_ADD ioctl. * Fixup the tests for creating new loop devs It did not work for me as it counted the 'loop-control' file as an extra one so never failed with the file already existing. Co-authored-by: Michael Daffin <[email protected]>
mdaffin · Nov 11, 2022 · 64a8ddb · 64a8ddb
1 parent 99a3662
commit 64a8ddb
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diff --git a/src/lib.rs b/src/lib.rs
@@ -38,8 +38,8 @@
 //! ld.detach().unwrap();
 //! ```
 use crate::bindings::{
-    loop_info64, LOOP_CLR_FD, LOOP_CTL_GET_FREE, LOOP_SET_CAPACITY, LOOP_SET_FD, LOOP_SET_STATUS64,
-    LO_FLAGS_AUTOCLEAR, LO_FLAGS_PARTSCAN, LO_FLAGS_READ_ONLY,
+    loop_info64, LOOP_CLR_FD, LOOP_CTL_ADD, LOOP_CTL_GET_FREE, LOOP_SET_CAPACITY, LOOP_SET_FD,
+    LOOP_SET_STATUS64, LO_FLAGS_AUTOCLEAR, LO_FLAGS_PARTSCAN, LO_FLAGS_READ_ONLY,
 };
 #[cfg(feature = "direct_io")]
 use bindings::LOOP_SET_DIRECT_IO;
@@ -120,6 +120,32 @@ impl LoopControl {
         })?;
         LoopDevice::open(&format!("{}{}", LOOP_PREFIX, dev_num))
     }
+
+    /// Add and opens a new loop device.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// use loopdev::LoopControl;
+    /// let lc = LoopControl::open().unwrap();
+    /// let ld = lc.add(1).unwrap();
+    /// println!("{}", ld.path().unwrap().display());
+    /// ```
+    ///
+    /// # Errors
+    ///
+    /// This funcitons will return an error when a loop device with the passed
+    /// number exists or opening the newly created device fails.
+    pub fn add(&self, n: u32) -> io::Result<LoopDevice> {
+        let dev_num = ioctl_to_error(unsafe {
+            ioctl(
+                self.dev_file.as_raw_fd() as c_int,
+                LOOP_CTL_ADD as IoctlRequest,
+                n as c_int,
+            )
+        })?;
+        LoopDevice::open(&format!("{}{}", LOOP_PREFIX, dev_num))
+    }
 }
 
 impl AsRawFd for LoopControl {

diff --git a/tests/integration_test.rs b/tests/integration_test.rs
@@ -211,3 +211,24 @@ fn attach_a_backing_file_with_part_scan(file_size: i64) {
         "there should be only one partition for the device"
     );
 }
+
+#[test]
+fn add_a_loop_device() {
+    let _lock = setup();
+    let dev = std::fs::read_dir("/dev").expect("should be able to open /dev");
+    let device_count = dev
+        .map(|r| {
+            r.as_ref()
+                .expect("readdir failed")
+                .file_name()
+                .to_string_lossy()
+                .to_string()
+        })
+        .filter(|r| r != "loop-control")
+        .filter(|r| r.contains("loop"))
+        .count();
+
+    let lc = LoopControl::open().expect("should be able to open the LoopControl device");
+    assert!(lc.add(device_count as u32).is_err()); // EEXIST
+    assert!(lc.add(device_count as u32 + 1).is_ok())
+}