src/tools/fs.rs: impl ioctl calls to get/set fsxattr

This implements fs_ioc_fsgetxattr/fs_ioc_fssetxattr calls in order to read or
write fsxattr for a given file descriptor.
This is needed in order to read or write the quota project id for filesystems
which support project quotas (EXT4/XFS/FUSE).

Signed-off-by: Christian Ebner <c.ebner@proxmox.com>

src/tools/fs.rs

@@ -218,3 +218,43 @@ where
         }
     }
 }
+
+use nix::{convert_ioctl_res, request_code_read, request_code_write, ioc};
+
+// /usr/include/linux/fs.h: #define FS_IOC_GETFLAGS _IOR('f', 1, long)
+// read Linux file system attributes (see man chattr)
+nix::ioctl_read!(read_attr_fd, b'f', 1, usize);
+
+// /usr/include/linux/msdos_fs.h: #define FAT_IOCTL_GET_ATTRIBUTES _IOR('r', 0x10, __u32)
+// read FAT file system attributes
+nix::ioctl_read!(read_fat_attr_fd, b'r', 0x10, u32);
+
+// From /usr/include/linux/fs.h
+// #define FS_IOC_FSGETXATTR _IOR('X', 31, struct fsxattr)
+// #define FS_IOC_FSSETXATTR _IOW('X', 32, struct fsxattr)
+nix::ioctl_read!(fs_ioc_fsgetxattr, b'X', 31, FSXAttr);
+nix::ioctl_write_ptr!(fs_ioc_fssetxattr, b'X', 32, FSXAttr);
+
+#[repr(C)]
+#[derive(Debug)]
+pub struct FSXAttr {
+    pub fsx_xflags: u32,
+    pub fsx_extsize: u32,
+    pub fsx_nextents: u32,
+    pub fsx_projid: u32,
+    pub fsx_cowextsize: u32,
+    pub fsx_pad: [u8; 8],
+}
+
+impl Default for FSXAttr {
+    fn default() -> Self {
+        FSXAttr {
+            fsx_xflags: 0u32,
+            fsx_extsize: 0u32,
+            fsx_nextents: 0u32,
+            fsx_projid: 0u32,
+            fsx_cowextsize: 0u32,
+            fsx_pad: [0u8; 8],
+        }
+    }
+}