[SETUPLIB] Lock the BTRFS volume before installing the new bootsector code.

CORE-15334 CORE-15339

The BTRFS driver requires the volume to be locked in order to modify
the first sectors of the partition, even though they are outside the
file-system space / in the reserved area (they are situated before
the super-block at 0x1000) and is in principle allowed by the NT
storage stack.
So we lock here in order to write the bootsector at sector 0.
If locking fails, we ignore and continue nonetheless.

See also the following links for reference:
https://stackoverflow.com/a/12928934
https://docs.microsoft.com/en-us/windows/desktop/api/fileapi/nf-fileapi-writefile
https://support.microsoft.com/en-us/help/942448/changes-to-the-file-system-and-to-the-storage-stack-to-restrict-direct

base/setup/lib/bootsup.c

@@ -1613,6 +1613,7 @@ InstallBtrfsBootCodeToDisk(
     IN PCWSTR RootPath)
 {
     NTSTATUS Status;
+    NTSTATUS LockStatus;
     UNICODE_STRING Name;
     OBJECT_ATTRIBUTES ObjectAttributes;
     IO_STATUS_BLOCK IoStatusBlock;
@@ -1754,6 +1755,30 @@ InstallBtrfsBootCodeToDisk(
         return Status;
     }
 
+    /*
+     * The BTRFS driver requires the volume to be locked in order to modify
+     * the first sectors of the partition, even though they are outside the
+     * file-system space / in the reserved area (they are situated before
+     * the super-block at 0x1000) and is in principle allowed by the NT
+     * storage stack.
+     * So we lock here in order to write the bootsector at sector 0.
+     * If locking fails, we ignore and continue nonetheless.
+     */
+    LockStatus = NtFsControlFile(FileHandle,
+                                 NULL,
+                                 NULL,
+                                 NULL,
+                                 &IoStatusBlock,
+                                 FSCTL_LOCK_VOLUME,
+                                 NULL,
+                                 0,
+                                 NULL,
+                                 0);
+    if (!NT_SUCCESS(LockStatus))
+    {
+        DPRINT1("WARNING: Failed to lock BTRFS volume for writing bootsector! Operations may fail! (Status 0x%lx)\n", LockStatus);
+    }
+
     /* Obtaining partition info and writing it to bootsector */
     Status = NtDeviceIoControlFile(FileHandle,
                                    NULL,
@@ -1768,9 +1793,7 @@ InstallBtrfsBootCodeToDisk(
     if (!NT_SUCCESS(Status))
     {
         DPRINT1("IOCTL_DISK_GET_PARTITION_INFO_EX failed (Status %lx)\n", Status);
-        NtClose(FileHandle);
+        goto Quit;
-        RtlFreeHeap(ProcessHeap, 0, NewBootSector);
-        return Status;
     }
 
     /* Write new bootsector to RootPath */
@@ -1788,15 +1811,13 @@ InstallBtrfsBootCodeToDisk(
                          sizeof(BTRFS_BOOTSECTOR),
                          &FileOffset,
                          NULL);
-#if 0
     if (!NT_SUCCESS(Status))
     {
         DPRINT1("NtWriteFile() failed (Status %lx)\n", Status);
-        NtClose(FileHandle);
+        goto Quit;
-        RtlFreeHeap(ProcessHeap, 0, NewBootSector);
-        return Status;
     }
 
+#if 0
     /* Write backup boot sector */
     if ((BackupBootSector != 0x0000) && (BackupBootSector != 0xFFFF))
     {
@@ -1813,9 +1834,7 @@ InstallBtrfsBootCodeToDisk(
         if (!NT_SUCCESS(Status))
         {
             DPRINT1("NtWriteFile() failed (Status %lx)\n", Status);
-            NtClose(FileHandle);
+            goto Quit;
-            RtlFreeHeap(ProcessHeap, 0, NewBootSector);
-            return Status;
         }
     }
 
@@ -1835,6 +1854,25 @@ InstallBtrfsBootCodeToDisk(
         DPRINT1("NtWriteFile() failed (Status %lx)\n", Status);
     }
 #endif
+
+Quit:
+    /* Unlock the volume */
+    LockStatus = NtFsControlFile(FileHandle,
+                                 NULL,
+                                 NULL,
+                                 NULL,
+                                 &IoStatusBlock,
+                                 FSCTL_UNLOCK_VOLUME,
+                                 NULL,
+                                 0,
+                                 NULL,
+                                 0);
+    if (!NT_SUCCESS(LockStatus))
+    {
+        DPRINT1("Failed to unlock BTRFS volume (Status 0x%lx)\n", LockStatus);
+    }
+
+    /* Close the volume */
     NtClose(FileHandle);
 
     /* Free the new boot sector */