vold: Introduce android::vold::writeStringToFile

Remove static definition of writeStringToFile, and
move it from KeyStorage to Utils

(cherry picked from commit 0bd2d11692)

Bug: 71810347
Test: Build pass and reboot stress test.
Change-Id: I38bfd27370ac2372e446dc699f518122e73c6877
Merged-In: I38bfd27370ac2372e446dc699f518122e73c6877

KeyStorage.cpp

@@ -147,33 +147,6 @@ static bool readFileToString(const std::string& filename, std::string* result) {
     return true;
 }
 
-static bool writeStringToFile(const std::string& payload, const std::string& filename) {
-    android::base::unique_fd fd(TEMP_FAILURE_RETRY(
-        open(filename.c_str(), O_WRONLY | O_CREAT | O_NOFOLLOW | O_TRUNC | O_CLOEXEC, 0666)));
-    if (fd == -1) {
-        PLOG(ERROR) << "Failed to open " << filename;
-        return false;
-    }
-    if (!android::base::WriteStringToFd(payload, fd)) {
-        PLOG(ERROR) << "Failed to write to " << filename;
-        unlink(filename.c_str());
-        return false;
-    }
-    // fsync as close won't guarantee flush data
-    // see close(2), fsync(2) and b/68901441
-    if (fsync(fd) == -1) {
-        if (errno == EROFS || errno == EINVAL) {
-            PLOG(WARNING) << "Skip fsync " << filename
-                          << " on a file system does not support synchronization";
-        } else {
-            PLOG(ERROR) << "Failed to fsync " << filename;
-            unlink(filename.c_str());
-            return false;
-        }
-    }
-    return true;
-}
-
 static bool readRandomBytesOrLog(size_t count, std::string* out) {
     auto status = ReadRandomBytes(count, *out);
     if (status != OK) {

Utils.cpp

@@ -36,6 +36,7 @@
 #include <mntent.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <unistd.h>
 #include <sys/mount.h>
 #include <sys/stat.h>
 #include <sys/statvfs.h>
@@ -840,5 +841,32 @@ bool FsyncDirectory(const std::string& dirname) {
     return true;
 }
 
+bool writeStringToFile(const std::string& payload, const std::string& filename) {
+    android::base::unique_fd fd(TEMP_FAILURE_RETRY(
+        open(filename.c_str(), O_WRONLY | O_CREAT | O_NOFOLLOW | O_TRUNC | O_CLOEXEC, 0666)));
+    if (fd == -1) {
+        PLOG(ERROR) << "Failed to open " << filename;
+        return false;
+    }
+    if (!android::base::WriteStringToFd(payload, fd)) {
+        PLOG(ERROR) << "Failed to write to " << filename;
+        unlink(filename.c_str());
+        return false;
+    }
+    // fsync as close won't guarantee flush data
+    // see close(2), fsync(2) and b/68901441
+    if (fsync(fd) == -1) {
+        if (errno == EROFS || errno == EINVAL) {
+            PLOG(WARNING) << "Skip fsync " << filename
+                          << " on a file system does not support synchronization";
+        } else {
+            PLOG(ERROR) << "Failed to fsync " << filename;
+            unlink(filename.c_str());
+            return false;
+        }
+    }
+    return true;
+}
+
 }  // namespace vold
 }  // namespace android

Utils.h

@@ -134,6 +134,7 @@ status_t WaitForFile(const char* filename, std::chrono::nanoseconds timeout);
 
 bool FsyncDirectory(const std::string& dirname);
 
+bool writeStringToFile(const std::string& payload, const std::string& filename);
 }  // namespace vold
 }  // namespace android