OvmfPkg/VirtioFsDxe: flush, sync, release and forget in Close() / Delete()

The two member functions that free the EFI_FILE_PROTOCOL object are
Close() and Delete(). Before we create VIRTIO_FS_FILE objects with
EFI_FILE_PROTOCOL.Open() later in this patch series, extend each of these
"destructor" functions to get rid of the FuseHandle and NodeId resources
properly -- in a way that matches each function's own purpose.

For the time being, VirtioFsSimpleFileDelete() only gets a reminder about
its core task (namely, removing the file), as the needed machinery will
become only later. But we can already outline the "task list", and deal
with the FuseHandle and NodeId resources. The "task list" of
VirtioFsSimpleFileDelete() is different from that of
VirtioFsSimpleFileClose(), thus both destructors diverge at this point.

Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3097
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20201216211125.19496-16-lersek@redhat.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@arm.com>

1 files changed, 47 insertions, 8 deletions

diff --git a/OvmfPkg/VirtioFsDxe/SimpleFsDelete.c b/OvmfPkg/VirtioFsDxe/SimpleFsDelete.c
index 3209923d1e..bbad64bf78 100644
--- a/OvmfPkg/VirtioFsDxe/SimpleFsDelete.c
+++ b/OvmfPkg/VirtioFsDxe/SimpleFsDelete.c
@@ -6,6 +6,9 @@
   SPDX-License-Identifier: BSD-2-Clause-Patent

 **/

 

+#include <Library/BaseLib.h>             // RemoveEntryList()

+#include <Library/MemoryAllocationLib.h> // FreePool()

+

 #include "VirtioFsDxe.h"

 

 EFI_STATUS

@@ -14,16 +17,52 @@ VirtioFsSimpleFileDelete (
   IN EFI_FILE_PROTOCOL *This

   )

 {

+  VIRTIO_FS_FILE *VirtioFsFile;

+  VIRTIO_FS      *VirtioFs;

+  EFI_STATUS     Status;

+

+  VirtioFsFile = VIRTIO_FS_FILE_FROM_SIMPLE_FILE (This);

+  VirtioFs     = VirtioFsFile->OwnerFs;

+

+  //

+  // All actions in this function are "best effort"; the UEFI spec requires

+  // EFI_FILE_PROTOCOL.Delete() to release resources unconditionally. If a step

+  // related to removing the file fails, it's only reflected in the return

+  // status (EFI_WARN_DELETE_FAILURE rather than EFI_SUCCESS).

+  //

+  // Release, remove, and (if needed) forget. We don't waste time flushing and

+  // syncing; if the EFI_FILE_PROTOCOL user cares enough, they should keep the

+  // parent directory open until after this function call returns, and then

+  // force a sync on *that* EFI_FILE_PROTOCOL instance, using either the

+  // Flush() member function, or the Close() member function.

+  //

+  // If any action fails below, we still try the others.

+  //

+  VirtioFsFuseReleaseFileOrDir (VirtioFs, VirtioFsFile->NodeId,

+    VirtioFsFile->FuseHandle, VirtioFsFile->IsDirectory);

+

+  //

+  // VirtioFsFile->FuseHandle is gone at this point, but VirtioFsFile->NodeId

+  // is still valid. Continue with removing the file or directory. The result

+  // of this operation determines the return status of the function.

   //

-  // At this point, the implementation is only suitable for closing the

-  // VIRTIO_FS_FILE that was created by VirtioFsOpenVolume().

+  // TODO

   //

-  // Actually deleting the root directory is not possible, so we're only going

-  // to release resources, and return EFI_WARN_DELETE_FAILURE.

+  Status = EFI_WARN_DELETE_FAILURE;

+

   //

-  // In order to release resources, VirtioFsSimpleFileClose() is just right

-  // here.

+  // Finally, if we've known VirtioFsFile->NodeId from a lookup, then we should

+  // also ask the server to forget it *once*.

   //

-  VirtioFsSimpleFileClose (This);

-  return EFI_WARN_DELETE_FAILURE;

+  if (VirtioFsFile->NodeId != VIRTIO_FS_FUSE_ROOT_DIR_NODE_ID) {

+    VirtioFsFuseForget (VirtioFs, VirtioFsFile->NodeId);

+  }

+

+  //

+  // One fewer file left open for the owner filesystem.

+  //

+  RemoveEntryList (&VirtioFsFile->OpenFilesEntry);

+

+  FreePool (VirtioFsFile);

+  return Status;

 }