From bab6699799911d90509fe8691d1602fe3912cd39 Mon Sep 17 00:00:00 2001
From: Christopher Haster <chaster@utexas.edu>
Date: Tue, 15 Aug 2017 17:04:11 -0500
Subject: [PATCH] Changed erase to just noop if erases are too small for erase
 command

Since it's an optimization, we should only send the command if the range
of bytes being erased fits. get_erase_size should still report 512, and
the erase should just noop with <SECTOR_SIZE bytes being erased. If
filesystems erase a larger range (at least spiffs does this), the
optimization can kick in.
---
 SDBlockDevice.cpp | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/SDBlockDevice.cpp b/SDBlockDevice.cpp
index d5b0f00db5..b2beece633 100644
--- a/SDBlockDevice.cpp
+++ b/SDBlockDevice.cpp
@@ -558,7 +558,15 @@ int SDBlockDevice::erase(bd_addr_t addr, bd_size_t size)
     }
     int status = BD_ERROR_OK;
 
-    size -= _block_size;
+    // Toss out erases that are too small, this is fine as the block device api
+    // doesn't garuntee the final state of erased bytes and a following program
+    // will still work fine.
+    if (size < _erase_size) {
+        _lock.unlock();
+        return status;
+    }
+
+    size -= _erase_size;
     // SDSC Card (CCS=0) uses byte unit address
     // SDHC and SDXC Cards (CCS=1) use block unit address (512 Bytes unit)
     if (SDCARD_V2HC == _card_type) {
@@ -594,7 +602,7 @@ bd_size_t SDBlockDevice::get_program_size() const
 
 bd_size_t SDBlockDevice::get_erase_size() const
 {
-    return _erase_size;
+    return _block_size;
 }
 
 bd_size_t SDBlockDevice::size() const