SPIFFS.end() does not free memory

[Eszartek]

As per @petrkr: When do SPIFFS.begin() it will consume some like 2kB of memory, but SPIFFS.end() will not release it. That is kinda problem for low-memory environment as for my application these 2kB is difference between SSL handshake can be done later or not.

Tested SDK: 2.3.0, 2.4.1 from Arduino IDE
Tested ESP_12E

Test code:

// Filesystem
#include "FS.h"

void printHeap() {
  Serial.print(F("Heap size: "));
  Serial.println(ESP.getFreeHeap());
}

void setup() {
  Serial.begin(115200);
  delay(1000);
  Serial.println();
  Serial.println("Setup begin");
  Serial.print(F("SDK: ")); Serial.println(ESP.getSdkVersion());
  Serial.print(F("Core: ")); Serial.println(ESP.getCoreVersion());
  
  printHeap();
  
  Serial.println("SPIFF BEGIN");
  SPIFFS.begin();
  printHeap();

  Serial.println("SPIFF END");
  SPIFFS.end();
  printHeap();

  Serial.println("Setup end");
}

void loop() {
  Serial.println("Loooop");
  Serial.println("SPIFF BEGIN");
  SPIFFS.begin();
  printHeap();
  
  delay(1000);
  
  Serial.println("SPIFF END");
  SPIFFS.end();
  printHeap();

}

Sample output:

Setup begin
SDK: 1.5.3(aec24ac9)
Core: 2_3_0
Heap size: 47072
SPIFF BEGIN
Heap size: 44960
SPIFF END
Heap size: 44960
Setup end
Loooop
SPIFF BEGIN
Heap size: 44960

Setup begin
SDK: 2.2.1(cfd48f3)
Core: 2_4_1
Heap size: 47160
SPIFF BEGIN
Heap size: 44984
SPIFF END
Heap size: 44984
Setup end
Loooop
SPIFF BEGIN
Heap size: 44984
SPIFF END
Heap size: 44296
Loooop
SPIFF BEGIN
Heap size: 44296
SPIFF END
Heap size: 44224