From 20ca9836b9a780c41a22850f478a29f29677553e Mon Sep 17 00:00:00 2001
From: Jeff Sharkey <jsharkey@android.com>
Date: Thu, 7 Apr 2016 11:05:21 -0600
Subject: [PATCH] Give users and devices control over sdcardfs.

Instead of relying only on kernel support for sdcardfs, give each
device the ability to quickly toggle between sdcardfs and FUSE.  Also
add the ability to users to explicitly enable/disable the behavior
for testing and debugging purposes.

Bug: 27991427
Change-Id: Ie188cb044be2ad87166f2d43c32a1f6b97660de0
---
 sdcard/sdcard.c | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/sdcard/sdcard.c b/sdcard/sdcard.c
index d8fda676f0..befe38c9ea 100644
--- a/sdcard/sdcard.c
+++ b/sdcard/sdcard.c
@@ -43,6 +43,7 @@
 #include <cutils/hashmap.h>
 #include <cutils/log.h>
 #include <cutils/multiuser.h>
+#include <cutils/properties.h>
 #include <packagelistparser/packagelistparser.h>
 
 #include <private/android_filesystem_config.h>
@@ -89,6 +90,9 @@
 
 #define ERROR(x...) ALOGE(x)
 
+#define PROP_SDCARDFS_DEVICE "ro.sys.sdcardfs"
+#define PROP_SDCARDFS_USER "persist.sys.sdcardfs"
+
 #define FUSE_UNKNOWN_INO 0xffffffff
 
 /* Maximum number of bytes to write in one request. */
@@ -1993,6 +1997,29 @@ static bool supports_sdcardfs(void) {
     return false;
 }
 
+static bool should_use_sdcardfs(void) {
+    char property[PROPERTY_VALUE_MAX];
+
+    // Allow user to have a strong opinion about state
+    property_get(PROP_SDCARDFS_USER, property, "");
+    if (!strcmp(property, "force_on")) {
+        ALOGW("User explicitly enabled sdcardfs");
+        return supports_sdcardfs();
+    } else if (!strcmp(property, "force_off")) {
+        ALOGW("User explicitly disabled sdcardfs");
+        return false;
+    }
+
+    // Fall back to device opinion about state
+    if (property_get_bool(PROP_SDCARDFS_DEVICE, false)) {
+        ALOGW("Device explicitly enabled sdcardfs");
+        return supports_sdcardfs();
+    } else {
+        ALOGW("Device explicitly disabled sdcardfs");
+        return false;
+    }
+}
+
 int main(int argc, char **argv) {
     const char *source_path = NULL;
     const char *label = NULL;
@@ -2065,7 +2092,7 @@ int main(int argc, char **argv) {
         sleep(1);
     }
 
-    if (supports_sdcardfs()) {
+    if (should_use_sdcardfs()) {
         run_sdcardfs(source_path, label, uid, gid, userid, multi_user, full_write);
     } else {
         run(source_path, label, uid, gid, userid, multi_user, full_write);
-- 
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