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fastbootd: add support to reset fd by handle

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There are cases where the flags the file descriptor was opened with need
to be modified. This CL adds functionality to reset the file descriptor
held by a PartitionHandle, reopening with new flags and repositioning
file offset to previous.

Bug: 225108941
Signed-off-by: Konstantin Vyshetsky <vkon@google.com>
Change-Id: I9adb0e7696bc6af74e14dd61a6cb0ef10b4c98c8
This commit is contained in:
Konstantin Vyshetsky 2022-03-17 17:57:28 -07:00
parent b3e1829421
commit 1cee2ed239
2 changed files with 44 additions and 9 deletions
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9
fastboot/device/utility.cpp
View file

@ -90,14 +90,7 @@ bool OpenPartition(FastbootDevice* device, const std::string& name, PartitionHan
return false;
}
flags |= (O_EXCL | O_CLOEXEC | O_BINARY);
unique_fd fd(TEMP_FAILURE_RETRY(open(handle->path().c_str(), flags)));
if (fd < 0) {
PLOG(ERROR) << "Failed to open block device: " << handle->path();
return false;
}
handle->set_fd(std::move(fd));
return true;
return handle->Open(flags);
}
std::optional<std::string> FindPhysicalPartition(const std::string& name) {

44
fastboot/device/utility.h
View file

@ -18,6 +18,8 @@
#include <optional>
#include <string>
#include <android-base/file.h>
#include <android-base/logging.h>
#include <android-base/unique_fd.h>
#include <android/hardware/boot/1.0/IBootControl.h>
#include <fstab/fstab.h>
@ -44,11 +46,51 @@ class PartitionHandle {
}
const std::string& path() const { return path_; }
int fd() const { return fd_.get(); }
void set_fd(android::base::unique_fd&& fd) { fd_ = std::move(fd); }
bool Open(int flags) {
flags |= (O_EXCL | O_CLOEXEC | O_BINARY);
// Attempts to open a second device can fail with EBUSY if the device is already open.
// Explicitly close any previously opened devices as unique_fd won't close them until
// after the attempt to open.
fd_.reset();
fd_ = android::base::unique_fd(TEMP_FAILURE_RETRY(open(path_.c_str(), flags)));
if (fd_ < 0) {
PLOG(ERROR) << "Failed to open block device: " << path_;
return false;
}
flags_ = flags;
return true;
}
bool Reset(int flags) {
if (fd_.ok() && (flags | O_EXCL | O_CLOEXEC | O_BINARY) == flags_) {
return true;
}
off_t offset = fd_.ok() ? lseek(fd_.get(), 0, SEEK_CUR) : 0;
if (offset < 0) {
PLOG(ERROR) << "Failed lseek on block device: " << path_;
return false;
}
sync();
if (Open(flags) == false) {
return false;
}
if (lseek(fd_.get(), offset, SEEK_SET) != offset) {
PLOG(ERROR) << "Failed lseek on block device: " << path_;
return false;
}
return true;
}
private:
std::string path_;
android::base::unique_fd fd_;
int flags_;
std::function<void()> closer_;
};