OvmfPkg/VirtioFsDxe: add EFI_FILE_INFO cache fields to VIRTIO_FS_FILE

For reading through a directory stream with tolerable performance, we'll
have to call FUSE_READDIRPLUS each time with such a buffer that can
deliver a good number of variable size records
(VIRTIO_FS_FUSE_DIRENTPLUS_RESPONSE elements). Every time we'll do that,
we'll turn the whole bunch into an array of EFI_FILE_INFOs immediately.
EFI_FILE_PROTOCOL.Read() invocations (on directories) will be served from
this EFI_FILE_INFO cache.

Add the fields for the EFI_FILE_INFO cache to VIRTIO_FS_FILE:
- initialize them in Open() and OpenVolume(),
- release the cache in Close() and Delete(),
- also release the cache when the directory is rewound, in SetPosition().

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: <20201216211125.19496-36-lersek@redhat.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@arm.com>

OvmfPkg/VirtioFsDxe/SimpleFsClose.c

@@ -60,6 +60,9 @@ VirtioFsSimpleFileClose (
   RemoveEntryList (&VirtioFsFile->OpenFilesEntry);
 
   FreePool (VirtioFsFile->CanonicalPathname);
+  if (VirtioFsFile->FileInfoArray != NULL) {
+    FreePool (VirtioFsFile->FileInfoArray);
+  }
   FreePool (VirtioFsFile);
   return EFI_SUCCESS;
 }

OvmfPkg/VirtioFsDxe/SimpleFsDelete.c

@@ -102,6 +102,9 @@ VirtioFsSimpleFileDelete (
   RemoveEntryList (&VirtioFsFile->OpenFilesEntry);
 
   FreePool (VirtioFsFile->CanonicalPathname);
+  if (VirtioFsFile->FileInfoArray != NULL) {
+    FreePool (VirtioFsFile->FileInfoArray);
+  }
   FreePool (VirtioFsFile);
   return Status;
 }

OvmfPkg/VirtioFsDxe/SimpleFsOpen.c

@@ -482,6 +482,10 @@ VirtioFsSimpleFileOpen (
   NewVirtioFsFile->FilePosition           = 0;
   NewVirtioFsFile->NodeId                 = NewNodeId;
   NewVirtioFsFile->FuseHandle             = NewFuseHandle;
+  NewVirtioFsFile->FileInfoArray          = NULL;
+  NewVirtioFsFile->SingleFileInfoSize     = 0;
+  NewVirtioFsFile->NumFileInfo            = 0;
+  NewVirtioFsFile->NextFileInfo           = 0;
 
   //
   // One more file is now open for the filesystem.

OvmfPkg/VirtioFsDxe/SimpleFsOpenVolume.c

@@ -75,6 +75,10 @@ VirtioFsOpenVolume (
   VirtioFsFile->FilePosition           = 0;
   VirtioFsFile->NodeId                 = VIRTIO_FS_FUSE_ROOT_DIR_NODE_ID;
   VirtioFsFile->FuseHandle             = RootDirHandle;
+  VirtioFsFile->FileInfoArray          = NULL;
+  VirtioFsFile->SingleFileInfoSize     = 0;
+  VirtioFsFile->NumFileInfo            = 0;
+  VirtioFsFile->NextFileInfo           = 0;
 
   //
   // One more file open for the filesystem.

OvmfPkg/VirtioFsDxe/SimpleFsSetPosition.c

@@ -7,6 +7,8 @@
   SPDX-License-Identifier: BSD-2-Clause-Patent
 **/
 
+#include <Library/MemoryAllocationLib.h> // FreePool()
+
 #include "VirtioFsDxe.h"
 
 EFI_STATUS
@@ -31,6 +33,13 @@ VirtioFsSimpleFileSetPosition (
       return EFI_UNSUPPORTED;
     }
     VirtioFsFile->FilePosition = 0;
+    if (VirtioFsFile->FileInfoArray != NULL) {
+      FreePool (VirtioFsFile->FileInfoArray);
+      VirtioFsFile->FileInfoArray = NULL;
+    }
+    VirtioFsFile->SingleFileInfoSize = 0;
+    VirtioFsFile->NumFileInfo        = 0;
+    VirtioFsFile->NextFileInfo       = 0;
     return EFI_SUCCESS;
   }
 

OvmfPkg/VirtioFsDxe/VirtioFsDxe.h

@@ -47,6 +47,11 @@
 //
 #define VIRTIO_FS_MAX_PATHNAME_LENGTH ((UINTN)65535)
 
+//
+// Maximum value for VIRTIO_FS_FILE.NumFileInfo.
+//
+#define VIRTIO_FS_FILE_MAX_FILE_INFO 256
+
 //
 // Filesystem label encoded in UCS-2, transformed from the UTF-8 representation
 // in "VIRTIO_FS_CONFIG.Tag", and NUL-terminated. Only the printable ASCII code
@@ -154,6 +159,20 @@ typedef struct {
   //
   UINT64 NodeId;
   UINT64 FuseHandle;
+  //
+  // EFI_FILE_INFO objects cached for an in-flight directory read.
+  //
+  // For reading through a directory stream with tolerable performance, we have
+  // to call FUSE_READDIRPLUS each time with such a buffer that can deliver a
+  // good number of variable size records (VIRTIO_FS_FUSE_DIRENTPLUS_RESPONSE
+  // elements). Every time we do that, we turn the whole bunch into an array of
+  // EFI_FILE_INFOs immediately. EFI_FILE_PROTOCOL.Read() invocations (on
+  // directories) will be served from this EFI_FILE_INFO cache.
+  //
+  UINT8 *FileInfoArray;
+  UINTN SingleFileInfoSize;
+  UINTN NumFileInfo;
+  UINTN NextFileInfo;
 } VIRTIO_FS_FILE;
 
 #define VIRTIO_FS_FILE_FROM_SIMPLE_FILE(SimpleFileReference) \