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PrepareZramBackingDevice: use loop_control.h

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loop_control.h already provides loop device management APIs that we need
here. In addition, this change fixes a subtle race condition between
uevented creating a loop device node in userspace and
PrepareZramBackingDevice accessing it without waiting for it to be
created.

Test: device boots
Test: adb reboot userspace
Bug: 154500256
Change-Id: If80f18c8c337210030a6caf2aec6f7a47472b6fb
Merged-In: If80f18c8c337210030a6caf2aec6f7a47472b6fb
(cherry picked from commit c8313adf88)
This commit is contained in:
Nikita Ioffe 2020-04-20 17:38:17 +01:00
parent 4a0a6faa08
commit bcaeb70d80
1 changed files with 12 additions and 27 deletions
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39
fs_mgr/fs_mgr.cpp
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@ -62,6 +62,7 @@
#include <fs_mgr_overlayfs.h>
#include <fscrypt/fscrypt.h>
#include <libdm/dm.h>
#include <libdm/loop_control.h>
#include <liblp/metadata_format.h>
#include <linux/fs.h>
#include <linux/loop.h>
@ -105,6 +106,7 @@ using android::base::unique_fd;
using android::dm::DeviceMapper;
using android::dm::DmDeviceState;
using android::dm::DmTargetLinear;
using android::dm::LoopControl;
// Realistically, this file should be part of the android::fs_mgr namespace;
using namespace android::fs_mgr;
@ -1908,19 +1910,6 @@ static bool PrepareZramDevice(const std::string& loop, off64_t size, const std::
return InstallZramDevice(bdev);
}
// Get free loopback
unique_fd loop_fd(TEMP_FAILURE_RETRY(open("/dev/loop-control", O_RDWR | O_CLOEXEC)));
if (loop_fd.get() == -1) {
PERROR << "Cannot open loop-control";
return false;
}
int num = ioctl(loop_fd.get(), LOOP_CTL_GET_FREE);
if (num == -1) {
PERROR << "Cannot get free loop slot";
return false;
}
// Prepare target path
unique_fd target_fd(TEMP_FAILURE_RETRY(open(loop.c_str(), O_RDWR | O_CREAT | O_CLOEXEC, 0600)));
if (target_fd.get() == -1) {
@ -1932,25 +1921,21 @@ static bool PrepareZramDevice(const std::string& loop, off64_t size, const std::
return false;
}
// Connect loopback (device_fd) to target path (target_fd)
std::string device = android::base::StringPrintf("/dev/block/loop%d", num);
unique_fd device_fd(TEMP_FAILURE_RETRY(open(device.c_str(), O_RDWR | O_CLOEXEC)));
if (device_fd.get() == -1) {
PERROR << "Cannot open /dev/block/loop" << num;
return false;
}
if (ioctl(device_fd.get(), LOOP_SET_FD, target_fd.get())) {
PERROR << "Cannot set loopback to target path";
// Allocate loop device and attach it to file_path.
LoopControl loop_control;
std::string device;
if (!loop_control.Attach(target_fd.get(), 5s, &device)) {
return false;
}
// set block size & direct IO
if (ioctl(device_fd.get(), LOOP_SET_BLOCK_SIZE, 4096)) {
PWARNING << "Cannot set 4KB blocksize to /dev/block/loop" << num;
unique_fd device_fd(TEMP_FAILURE_RETRY(open(device.c_str(), O_RDWR | O_CLOEXEC)));
if (device_fd.get() == -1) {
PERROR << "Cannot open " << device;
return false;
}
if (ioctl(device_fd.get(), LOOP_SET_DIRECT_IO, 1)) {
PWARNING << "Cannot set direct_io to /dev/block/loop" << num;
if (!LoopControl::EnableDirectIo(device_fd.get())) {
return false;
}
return InstallZramDevice(device);