From ee44a75dbc2e03b51bbc498c682cc3620418b661 Mon Sep 17 00:00:00 2001
From: Brian Pugh <bnp117@gmail.com>
Date: Sun, 15 Nov 2020 09:43:30 -0800
Subject: [PATCH] Sync file upon opening to free storage when overwriting a
 file

---
 src/esp_littlefs.c       | 16 ++++++++++++++++
 src/test/test_littlefs.c | 30 ++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+)

diff --git a/src/esp_littlefs.c b/src/esp_littlefs.c
index f66c018..73c28af 100644
--- a/src/esp_littlefs.c
+++ b/src/esp_littlefs.c
@@ -896,6 +896,22 @@ static int vfs_littlefs_open(void* ctx, const char * path, int flags, int mode)
         return LFS_ERR_INVAL;
     }
 
+    /* Sync after opening. If we are overwriting a file, this will free that
+     * file's blocks in storage, prevent OOS errors.
+     * See TEST_CASE:
+     *     "Rewriting file frees space immediately (#7426)"
+     */
+    res = lfs_file_sync(efs->fs, &file->file);
+    if(res < 0){
+        errno = -res;
+#ifndef CONFIG_LITTLEFS_USE_ONLY_HASH
+        ESP_LOGV(TAG, "Failed to sync at opening file \"%s\". Error %s (%d)",
+                file->path, esp_littlefs_errno(res), res);
+#else
+        ESP_LOGV(TAG, "Failed to sync at opening file %d. Error %d", fd, res);
+#endif
+    }
+
     file->hash = compute_hash(path);
 #ifndef CONFIG_LITTLEFS_USE_ONLY_HASH
     memcpy(file->path, path, path_len);
diff --git a/src/test/test_littlefs.c b/src/test/test_littlefs.c
index 7c78a3f..0f0043a 100644
--- a/src/test/test_littlefs.c
+++ b/src/test/test_littlefs.c
@@ -972,7 +972,37 @@ TEST_CASE("SPIFFS COMPAT", "[littlefs]")
 }
 #endif  // CONFIG_LITTLEFS_SPIFFS_COMPAT
 
+TEST_CASE("Rewriting file frees space immediately (#7426)", "[littlefs]")
+{
+    /* modified from:
+     *     https://github.com/esp8266/Arduino/commit/c663c55926f205723c3d56dd7030bacbe7960f8e
+     */
+
+    test_setup();
+
+    size_t total = 0, used = 0;
+    TEST_ESP_OK(esp_littlefs_info(littlefs_test_partition_label, &total, &used));
+
+    // 2 block overhead
+    int kb_to_write = (total - used - (2*4096)) / 1024;
+
+    // Create and overwrite a file >50% of spaceA (48/64K)
+    uint8_t buf[1024];
+    memset(buf, 0xaa, 1024);
+    for (uint8_t x = 0; x < 2; x++) {
+        FILE *f = fopen(littlefs_base_path "/file1.bin", "w");
+        TEST_ASSERT_NOT_NULL(f);
+
+        for (size_t i = 0; i < kb_to_write; i++) {
+            TEST_ASSERT_EQUAL_INT(1024, fwrite(buf, 1, 1024, f));
+        }
+        fclose(f);
+    }
+    test_teardown();
+}
+
 static void test_setup() {
+    esp_littlefs_format(littlefs_test_partition_label);
     const esp_vfs_littlefs_conf_t conf = {
         .base_path = littlefs_base_path,
         .partition_label = littlefs_test_partition_label,