cleanup: switch drvfs.cpp to use common MountUtil helper (#13890)

* cleanup: switch drvfs.cpp to use common MountUtil helper

* adjust mount.drvfs error logging

* adjust mount.drvfs error logging

---------

Co-authored-by: Ben Hillis <benhill@ntdev.microsoft.com>

Author: benhillis

.gitignore

@@ -44,7 +44,7 @@ bin/
 *.nupkg
 build/
 generated/
-Microsoft.WSL.PluginApi.nuspec
+*.nuspec
 test/linux/unit_tests/wsl_unit_tests
 *.dir/
 UserConfig.cmake

src/linux/init/drvfs.cpp

@@ -220,11 +220,7 @@ int MountWithRetry(const char* Source, const char* Target, const char* FsType, c
 
 Routine Description:
 
-    This routine will perform a mount using the /bin/mount binary, and will
-    retry it if it fails.
-
-    N.B. This routine is used for virtio-9p and virtiofs which can transiently
-         fail to mount if the PCI device isn't ready yet.
+    This routine performs a mount with retry logic for DrvFs filesystems.
 
 Arguments:
 
@@ -246,52 +242,19 @@ Return Value:
 
 try
 {
-    int Result;
-    try
+    //
+    // Verify the target directory exists before mounting.
+    //
+
+    int Result = access(Target, F_OK);
+    if (Result < 0)
     {
-        bool PrintWarning = true;
-        wsl::shared::retry::RetryWithTimeout<void>(
-            [&]() { THROW_LAST_ERROR_IF(mountutil::MountFilesystem(Source, Target, FsType, Options) < 0); },
-            std::chrono::milliseconds{100},
-            std::chrono::seconds{2},
-            [&]() {
-                // For virtio-9p, there are two errors that could indicate the PCI device is not ready:
-                // EBUSY - Returned if all devices with the tag are already in use.
-                // ENOENT - Returned if there are no devices with the tag, which can happen after the VM first boots.
-                //   In this case, check if the target exists; if it doesn't, ENOENT is for that and there's no reason to retry.
-                //
-                // For virtiofs, EINVAL will be returned if the tag is not ready.
-                auto savedErrno = wil::ResultFromCaughtException();
-                if (strcmp(FsType, PLAN9_FS_TYPE) == 0)
-                {
-                    if (errno != EBUSY && (errno != ENOENT || access(Target, F_OK) != 0))
-                    {
-                        errno = savedErrno;
-                        return false;
-                    }
-                }
-                else if ((strcmp(FsType, VIRTIO_FS_TYPE) == 0) && (errno != EINVAL))
-                {
-                    return false;
-                }
-
-                if (PrintWarning)
-                {
-                    LOG_WARNING("mount: waiting for virtio device {}", Source);
-                    PrintWarning = false;
-                }
-
-                return true;
-            });
-
-        Result = 0;
+        LOG_STDERR(errno);
     }
-    catch (...)
+    else
     {
-        errno = wil::ResultFromCaughtException();
-        auto parsed = mountutil::MountParseFlags(Options);
-        LOG_ERROR("mount({}, {}, {}, {:#x}, {}) failed: {}", Source, Target, FsType, parsed.MountFlags, parsed.StringOptions.c_str(), strerror(errno));
-        Result = -1;
+        auto Parsed = mountutil::MountParseFlags(Options);
+        Result = UtilMount(Source, Target, FsType, Parsed.MountFlags, Parsed.StringOptions.c_str(), std::chrono::seconds{2});
     }
 
     if (ExitCode)

src/linux/init/util.cpp

@@ -1706,8 +1706,10 @@ Return Value:
     //
     // Mount the device to the mount point.
     //
-    // N.B. The mount operation is only retried if the mount source does not yet exist,
-    //      which can happen when hot-added devices are not yet available in the guest.
+    // N.B. The mount operation is retried if:
+    //      - The mount source does not yet exist (hot-added devices)
+    //      - For Plan9 (9p): device is busy or not found
+    //      - For VirtioFS: invalid tag (device not ready)
     //
 
     try
@@ -1720,7 +1722,23 @@ Return Value:
                 TimeoutSeconds.value(),
                 [&]() {
                     errno = wil::ResultFromCaughtException();
-                    return errno == ENOENT || errno == ENXIO || errno == EIO;
+
+                    // Generic device not ready errors
+                    if (errno == ENXIO || errno == EIO || errno == ENOENT)
+                    {
+                        return true;
+                    }
+
+                    // Filesystem-specific device readiness errors
+                    if (Type != nullptr)
+                    {
+                        if ((strcmp(Type, PLAN9_FS_TYPE) == 0 && errno == EBUSY) || (strcmp(Type, VIRTIO_FS_TYPE) == 0 && errno == EINVAL))
+                        {
+                            return true;
+                        }
+                    }
+
+                    return false;
                 });
         }
         else
@@ -1731,7 +1749,7 @@ Return Value:
     catch (...)
     {
         errno = wil::ResultFromCaughtException();
-        LOG_ERROR("mount({}, {}, {}, 0x{}x, {}) failed {}", Source, Target, Type, MountFlags, Options, errno);
+        LOG_ERROR("mount({}, {}, {}, {:#x}, {}) failed {}", Source, Target, Type, MountFlags, Options, errno);
         return -errno;
     }