tequilaOS/platform_system_core
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Switch sdcardfs over to bind mounts.

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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
This commit is contained in:
Daniel Rosenberg 2016-10-27 17:43:37 -07:00
parent 16017b3fbb
commit fc592327a9
1 changed files with 25 additions and 5 deletions
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30
sdcard/sdcard.cpp
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@ -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";
}