Use std::shared_ptr to refer to FdEntity (#2541)

FdEntity may have multiple references due to ChangeEntityToTempPath.
This relies on the std::enable_shared_from_this helper to create a
std::shared_ptr from this.  Fixes #2532.

src/fdcache.cpp

@@ -587,7 +587,7 @@ FdEntity* FdManager::Open(int& fd, const char* path, const headers_t* pmeta, off
             return nullptr;
         }
         // make new obj
-        std::unique_ptr<FdEntity> ent(new FdEntity(path, cache_path.c_str()));
+        auto ent = std::make_shared<FdEntity>(path, cache_path.c_str());
 
         // open
         if(0 > (fd = ent->Open(pmeta, size, ts_mctime, flags))){
@@ -696,7 +696,7 @@ void FdManager::Rename(const std::string &from, const std::string &to)
         // found
         S3FS_PRN_DBG("[from=%s][to=%s]", from.c_str(), to.c_str());
 
-        std::unique_ptr<FdEntity> ent(std::move(iter->second));
+        auto ent(std::move(iter->second));
 
         // retrieve old fd entity from map
         fent.erase(iter);
@@ -746,10 +746,10 @@ bool FdManager::Close(FdEntity* ent, int fd)
     return false;
 }
 
-bool FdManager::ChangeEntityToTempPath(FdEntity* ent, const char* path)
+bool FdManager::ChangeEntityToTempPath(std::shared_ptr<FdEntity> ent, const char* path)
 {
     const std::lock_guard<std::mutex> lock(FdManager::except_entmap_lock);
-    except_fent[path] = ent;
+    except_fent[path] = std::move(ent);
     return true;
 }
 
@@ -762,7 +762,7 @@ bool FdManager::UpdateEntityToTempPath()
         FdManager::MakeRandomTempPath(except_iter->first.c_str(), tmppath);
 
         auto iter = fent.find(except_iter->first);
-        if(fent.cend() != iter && iter->second.get() == except_iter->second){
+        if(fent.cend() != iter && iter->second.get() == except_iter->second.get()){
             // Move the entry to the new key
             fent[tmppath] = std::move(iter->second);
             fent.erase(iter);
@@ -778,7 +778,7 @@ bool FdManager::UpdateEntityToTempPath()
             S3FS_PRN_WARN("For some reason the FdEntity pointer(for %s) is not found in the fent map. Recovery procedures are being performed, but the cause needs to be identified.", except_iter->first.c_str());
 
             // Add the entry for recovery procedures
-            fent[tmppath] = std::unique_ptr<FdEntity>(except_iter->second);
+            fent[tmppath] = except_iter->second;
             except_iter   = except_fent.erase(except_iter);
         }
     }

src/fdcache.h

@@ -48,7 +48,7 @@ class FdManager
       static std::string     tmp_dir;
 
       fdent_map_t            fent GUARDED_BY(fd_manager_lock);
-      fdent_direct_map_t     except_fent GUARDED_BY(except_entmap_lock);  // A map of delayed deletion fdentity
+      fdent_map_t            except_fent GUARDED_BY(except_entmap_lock);  // A map of delayed deletion fdentity
 
   private:
       static off_t GetFreeDiskSpaceHasLock(const char* path) REQUIRES(FdManager::reserved_diskspace_lock);
@@ -115,7 +115,7 @@ class FdManager
       FdEntity* OpenExistFdEntity(const char* path, int& fd, int flags = O_RDONLY);
       void Rename(const std::string &from, const std::string &to);
       bool Close(FdEntity* ent, int fd);
-      bool ChangeEntityToTempPath(FdEntity* ent, const char* path);
+      bool ChangeEntityToTempPath(std::shared_ptr<FdEntity> ent, const char* path);
       void CleanupCacheDir();
 
       bool CheckAllCache();

src/fdcache_entity.cpp

@@ -1086,7 +1086,7 @@ int FdEntity::NoCacheLoadAndPost(PseudoFdInfo* pseudo_obj, off_t start, off_t si
     }
 
     // Change entity key in manager mapping
-    FdManager::get()->ChangeEntityToTempPath(this, path.c_str());
+    FdManager::get()->ChangeEntityToTempPath(get_shared_ptr(), path.c_str());
 
     // open temporary file
     int tmpfd;

src/fdcache_entity.h

@@ -41,7 +41,7 @@ typedef std::map<int, std::unique_ptr<PseudoFdInfo>> fdinfo_map_t;
 //------------------------------------------------
 // class FdEntity
 //------------------------------------------------
-class FdEntity
+class FdEntity : public std::enable_shared_from_this<FdEntity>
 {
     private:
         // [NOTE]
@@ -109,6 +109,8 @@ class FdEntity
 
         bool IsDirtyMetadata() const REQUIRES(FdEntity::fdent_data_lock);
 
+        std::shared_ptr<FdEntity> get_shared_ptr() { return shared_from_this(); }
+
     public:
         static bool GetNoMixMultipart() { return mixmultipart; }
         static bool SetNoMixMultipart();
@@ -235,8 +237,7 @@ class FdEntity
         std::mutex* GetMutex() RETURN_CAPABILITY(fdent_lock);
 };
 
-typedef std::map<std::string, std::unique_ptr<FdEntity>> fdent_map_t;           // key=path, value=unique_ptr<FdEntity>
-typedef std::map<std::string, FdEntity*>                 fdent_direct_map_t;    // key=path, value=FdEntity*
+typedef std::map<std::string, std::shared_ptr<FdEntity>> fdent_map_t;           // key=path, value=FdEntity
 
 #endif // S3FS_FDCACHE_ENTITY_H_