Changed to use rename when serializing to FileCacheStat

src/fdcache_page.cpp

@@ -820,32 +820,21 @@ bool PageList::ClearAllModified()
     return Compress();
 }
 
-bool PageList::Serialize(CacheFileStat& file, ino_t inode)
+bool PageList::Serialize(const CacheFileStat& file, ino_t inode) const
 {
-    if(!file.Open()){
-        return false;
-    }
-
-    //
-    // put to file
-    //
+    // make contents
     std::ostringstream ssall;
     ssall << inode << ":" << Size();
 
     for(auto iter = pages.cbegin(); iter != pages.cend(); ++iter){
         ssall << "\n" << iter->offset << ":" << iter->bytes << ":" << (iter->loaded ? "1" : "0") << ":" << (iter->modified ? "1" : "0");
     }
-
-    if(-1 == ftruncate(file.GetFd(), 0)){
-        S3FS_PRN_ERR("failed to truncate file(to 0) for stats(%d)", errno);
-        return false;
-    }
     std::string strall = ssall.str();
-    if(0 >= pwrite(file.GetFd(), strall.c_str(), strall.length(), 0)){
-        S3FS_PRN_ERR("failed to write stats(%d)", errno);
+
+    // over write
+    if(!file.OverWriteFile(strall)){
         return false;
     }
-
     return true;
 }
 

src/fdcache_page.h

@@ -94,7 +94,7 @@ class PageList
 
         void Clear();
         bool Parse(off_t new_pos);
-        bool Serialize(CacheFileStat& file, ino_t inode);
+        bool Serialize(const CacheFileStat& file, ino_t inode) const;
 
     public:
         static void FreeList(fdpage_list_t& list);

src/fdcache_stat.cpp

@@ -193,6 +193,49 @@ bool CacheFileStat::SetPath(const char* tpath, bool is_open)
     return Open();
 }
 
+// [NOTE]
+// There is no need to check whether the file is open because using rename().
+//
+bool CacheFileStat::OverWriteFile(const std::string& strall) const
+{
+    // make temporary file path(in same cache directory)
+    std::string sfile_path;
+    if(0 != CacheFileStat::MakeCacheFileStatPath(path.c_str(), sfile_path, true)){
+        S3FS_PRN_ERR("failed to create cache stat file path(%s)", path.c_str());
+        return false;
+    }
+    std::string strTmpFile = mydirname(sfile_path) + "/.tmpstat.XXXXXX";
+    strTmpFile.push_back('\0');     // terminate with a null character and allocate space for it.
+
+    // open temporary file(mode: 0600)
+    //
+    // [TODO]
+    // Currently, use "&str[pos]" to make it possible to build with C++14.
+    // Once we support C++17 or later, we will use "str.data()".
+    //
+    int tmpfd;
+    if(-1 == (tmpfd = mkstemp(&strTmpFile[0]))){    // NOLINT(readability-container-data-pointer)
+        S3FS_PRN_ERR("failed to create temporary cache stat file path(%s) for %s cache", strTmpFile.c_str(), sfile_path.c_str());
+        return false;
+    }
+
+    // write contents
+    if(0 >= pwrite(tmpfd, strall.c_str(), strall.length(), 0)){
+        S3FS_PRN_ERR("failed to write stats to temporary file(%d)", errno);
+        close(tmpfd);
+        return false;
+    }
+    close(tmpfd);
+
+    // rename
+    if(0 != rename(strTmpFile.c_str(), sfile_path.c_str())){
+        S3FS_PRN_ERR("failed to rename temporary cache stat file path(%s) to %s cache", strTmpFile.c_str(), sfile_path.c_str());
+        unlink(strTmpFile.c_str());
+        return false;
+    }
+    return true;
+}
+
 bool CacheFileStat::RawOpen(bool readonly)
 {
     if(path.empty()){

src/fdcache_stat.h

@@ -56,6 +56,7 @@ class CacheFileStat
         bool Release();
         bool SetPath(const char* tpath, bool is_open = true);
         int GetFd() const { return fd; }
+        bool OverWriteFile(const std::string& strall) const;
 };
 
 #endif // S3FS_FDCACHE_STAT_H_

src/test_page_list.cpp

@@ -22,7 +22,8 @@
 #include "fdcache_stat.h"
 #include "test_util.h"
 
-bool CacheFileStat::Open() { return false; }  // NOLINT(readability-convert-member-functions-to-static)
+bool CacheFileStat::Open() { return false; }                                            // NOLINT(readability-convert-member-functions-to-static)
+bool CacheFileStat::OverWriteFile(const std::string& strall) const { return false; }    // NOLINT(readability-convert-member-functions-to-static)
 
 void test_compress()
 {