[DO NOT MERGE] Use FUSE_SHORTCIRCUIT if available

Use a non yet maintainer reviewed kernel patch from QCOM that greatly
improves IO speed in case it is available from the device specific
kernel headers.

Bug: 24216004
Change-Id: I4101d80082c9ad9d042dde5c620ddb309d193d52

sdcard/sdcard.c

diff --git a/sdcard/sdcard.c b/sdcard/sdcard.c
index 06452aa..e9aa770 100644
--- a/sdcard/sdcard.c
+++ b/sdcard/sdcard.c
@@ -1214,7 +1214,13 @@
     }
     out.fh = ptr_to_id(h);
     out.open_flags = 0;
+
+#ifdef FUSE_STACKED_IO
+    out.lower_fd = h->fd;
+#else
     out.padding = 0;
+#endif
+
     fuse_reply(fuse, hdr->unique, &out, sizeof(out));
     return NO_STATUS;
 }
@@ -1378,7 +1384,13 @@
     }
     out.fh = ptr_to_id(h);
     out.open_flags = 0;
+
+#ifdef FUSE_STACKED_IO
+    out.lower_fd = -1;
+#else
     out.padding = 0;
+#endif
+
     fuse_reply(fuse, hdr->unique, &out, sizeof(out));
     return NO_STATUS;
 }
@@ -1460,6 +1472,11 @@
     out.major = FUSE_KERNEL_VERSION;
     out.max_readahead = req->max_readahead;
     out.flags = FUSE_ATOMIC_O_TRUNC | FUSE_BIG_WRITES;
+
+#ifdef FUSE_STACKED_IO
+    out.flags |= FUSE_STACKED_IO;
+#endif
+
     out.max_background = 32;
     out.congestion_threshold = 32;
     out.max_write = MAX_WRITE;