From fc592327a94dcfaac0f14b991ed7cab36c72551b Mon Sep 17 00:00:00 2001 From: Daniel Rosenberg Date: Thu, 27 Oct 2016 17:43:37 -0700 Subject: [PATCH] Switch sdcardfs over to bind mounts. Sdcardfs has been modified to use bind mounts in place of three separate mounts. This lowers resource usage, and removes a number of race conditions around updates via differnt views. Test: Run storage cts tests with sdcardfs enabled Change-Id: Icdc196ba3d6f46d54d27ef91c01ffebcf81dd47e --- sdcard/sdcard.cpp | 30 +++++++++++++++++++++++++----- 1 file changed, 25 insertions(+), 5 deletions(-) diff --git a/sdcard/sdcard.cpp b/sdcard/sdcard.cpp index bc502a0ec..df3ce853c 100644 --- a/sdcard/sdcard.cpp +++ b/sdcard/sdcard.cpp @@ -331,6 +331,27 @@ static bool sdcardfs_setup(const std::string& source_path, const std::string& de return true; } +static bool sdcardfs_setup_bind_remount(const std::string& source_path, const std::string& dest_path, + gid_t gid, mode_t mask) { + std::string opts = android::base::StringPrintf("mask=%d,gid=%d", mask, gid); + + if (mount(source_path.c_str(), dest_path.c_str(), nullptr, + MS_BIND, nullptr) != 0) { + PLOG(ERROR) << "failed to bind mount sdcardfs filesystem"; + return false; + } + + if (mount(source_path.c_str(), dest_path.c_str(), "none", + MS_REMOUNT | MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_NOATIME, opts.c_str()) != 0) { + PLOG(ERROR) << "failed to mount sdcardfs filesystem"; + if (umount2(dest_path.c_str(), MNT_DETACH)) + PLOG(WARNING) << "Failed to unmount bind"; + return false; + } + + return true; +} + static void run_sdcardfs(const std::string& source_path, const std::string& label, uid_t uid, gid_t gid, userid_t userid, bool multi_user, bool full_write) { std::string dest_path_default = "/mnt/runtime/default/" + label; @@ -343,9 +364,8 @@ static void run_sdcardfs(const std::string& source_path, const std::string& labe // permissions are completely masked off. if (!sdcardfs_setup(source_path, dest_path_default, uid, gid, multi_user, userid, AID_SDCARD_RW, 0006) - || !sdcardfs_setup(source_path, dest_path_read, uid, gid, multi_user, userid, - AID_EVERYBODY, 0027) - || !sdcardfs_setup(source_path, dest_path_write, uid, gid, multi_user, userid, + || !sdcardfs_setup_bind_remount(dest_path_default, dest_path_read, AID_EVERYBODY, 0027) + || !sdcardfs_setup_bind_remount(dest_path_default, dest_path_write, AID_EVERYBODY, full_write ? 0007 : 0027)) { LOG(FATAL) << "failed to sdcardfs_setup"; } @@ -355,9 +375,9 @@ static void run_sdcardfs(const std::string& source_path, const std::string& labe // deep inside attr_from_stat(). if (!sdcardfs_setup(source_path, dest_path_default, uid, gid, multi_user, userid, AID_SDCARD_RW, 0006) - || !sdcardfs_setup(source_path, dest_path_read, uid, gid, multi_user, userid, + || !sdcardfs_setup_bind_remount(dest_path_default, dest_path_read, AID_EVERYBODY, full_write ? 0027 : 0022) - || !sdcardfs_setup(source_path, dest_path_write, uid, gid, multi_user, userid, + || !sdcardfs_setup_bind_remount(dest_path_default, dest_path_write, AID_EVERYBODY, full_write ? 0007 : 0022)) { LOG(FATAL) << "failed to sdcardfs_setup"; }