spiffs: make OBJ_META_LEN configurable, make mtime support optional

- SPIFFS_OBJ_META_LEN can be set in sdkconfig
- mtime support can be enabled in sdkconfig, if META_LENGTH is sufficient
- add test for mtime updates

components/spiffs/Kconfig

@@ -88,6 +88,25 @@ config SPIFFS_USE_MAGIC_LENGTH
         configured and formatted for 4 megabytes will not be accepted 
         for mounting with a configuration defining the filesystem as 2 megabytes.
 
+config SPIFFS_META_LENGTH
+    int "Size of per-file metadata field"
+    default 4
+    help
+        This option sets the number of extra bytes stored in the file header.
+        These bytes can be used in an application-specific manner.
+        Set this to at least 4 bytes to enable support for saving file
+        modification time.
+
+config SPIFFS_USE_MTIME
+    bool "Save file modification time"
+    default "y"
+    depends on SPIFFS_META_LENGTH >= 4
+    help
+        If enabled, then the first 4 bytes of per-file metadata will be used
+        to store file modification time (mtime), accessible through
+        stat/fstat functions.
+        Modification time is updated when the file is opened.
+
 menu "Debug Configuration"
 
 config SPIFFS_DBG

components/spiffs/esp_spiffs.c

@@ -33,6 +33,10 @@
 
 static const char * TAG = "SPIFFS";
 
+#ifdef CONFIG_SPIFFS_USE_MTIME
+_Static_assert(CONFIG_SPIFFS_META_LENGTH >= sizeof(time_t),
+        "SPIFFS_META_LENGTH size should be >= sizeof(time_t)");
+#endif //CONFIG_SPIFFS_USE_MTIME
 /**
  * @brief SPIFFS definition structure
  */
@@ -80,6 +84,8 @@ static long vfs_spiffs_telldir(void* ctx, DIR* pdir);
 static void vfs_spiffs_seekdir(void* ctx, DIR* pdir, long offset);
 static int vfs_spiffs_mkdir(void* ctx, const char* name, mode_t mode);
 static int vfs_spiffs_rmdir(void* ctx, const char* name);
+static void vfs_spiffs_update_mtime(spiffs *fs, spiffs_file f);
+static time_t vfs_spiffs_get_mtime(const spiffs_stat* s);
 
 static esp_spiffs_t * _efs[CONFIG_SPIFFS_MAX_PARTITIONS];
 
@@ -507,22 +513,16 @@ static int vfs_spiffs_open(void* ctx, const char * path, int flags, int mode)
 {
     assert(path);
     esp_spiffs_t * efs = (esp_spiffs_t *)ctx;
-    int fd = SPIFFS_open(efs->fs, path, spiffs_mode_conv(flags), mode);
+    int spiffs_flags = spiffs_mode_conv(flags);
+    int fd = SPIFFS_open(efs->fs, path, spiffs_flags, mode);
     if (fd < 0) {
         errno = spiffs_res_to_errno(SPIFFS_errno(efs->fs));
         SPIFFS_clearerr(efs->fs);
         return -1;
     }
-#if SPIFFS_OBJ_META_LEN > 0
-    if (!(spiffs_mode_conv(flags) & SPIFFS_O_RDONLY))
-        {
-            time_t t = time(NULL);
-            struct tm tmr;
-            localtime_r(&t, &tmr);
-            time_t meta = mktime(&tmr);
-            SPIFFS_fupdate_meta(efs->fs, fd, &meta);
-        }
-#endif
+    if (!(spiffs_flags & SPIFFS_RDONLY)) {
+        vfs_spiffs_update_mtime(efs->fs, fd);
+    }
     return fd;
 }
 
@@ -572,7 +572,6 @@ static off_t vfs_spiffs_lseek(void* ctx, int fd, off_t offset, int mode)
         return -1;
     }
     return res;
-
 }
 
 static int vfs_spiffs_fstat(void* ctx, int fd, struct stat * st)
@@ -588,7 +587,7 @@ static int vfs_spiffs_fstat(void* ctx, int fd, struct stat * st)
     }
     st->st_size = s.size;
     st->st_mode = S_IRWXU | S_IRWXG | S_IRWXO | S_IFREG;
-    st->st_mtime = 0;
+    st->st_mtime = vfs_spiffs_get_mtime(&s);
     st->st_atime = 0;
     st->st_ctime = 0;
     return res;
@@ -610,13 +609,7 @@ static int vfs_spiffs_stat(void* ctx, const char * path, struct stat * st)
     st->st_size = s.size;
     st->st_mode = S_IRWXU | S_IRWXG | S_IRWXO;
     st->st_mode |= (s.type == SPIFFS_TYPE_DIR)?S_IFDIR:S_IFREG;
-#if SPIFFS_OBJ_META_LEN > 0
-    time_t t =0;
-    memcpy(&t, s.meta, sizeof(time_t));
-    st->st_mtime = t;
-#else
-    st->st_mtime = 0;
-#endif
+    st->st_mtime = vfs_spiffs_get_mtime(&s);
     st->st_atime = 0;
     st->st_ctime = 0;
     return res;
@@ -786,3 +779,31 @@ static int vfs_spiffs_link(void* ctx, const char* n1, const char* n2)
     errno = ENOTSUP;
     return -1;
 }
+
+static void vfs_spiffs_update_mtime(spiffs *fs, spiffs_file fd)
+{
+#ifdef CONFIG_SPIFFS_USE_MTIME
+    time_t t = time(NULL);
+    spiffs_stat s;
+    int ret = SPIFFS_OK;
+    if (CONFIG_SPIFFS_META_LENGTH > sizeof(t)) {
+        ret = SPIFFS_fstat(fs, fd, &s);
+    }
+    if (ret == SPIFFS_OK) {
+        memcpy(s.meta, &t, sizeof(t));
+        ret = SPIFFS_fupdate_meta(fs, fd, s.meta);
+    }
+    if (ret != SPIFFS_OK) {
+        ESP_LOGW(TAG, "Failed to update mtime (%d)", ret);
+    }
+#endif //CONFIG_SPIFFS_USE_MTIME
+}
+
+static time_t vfs_spiffs_get_mtime(const spiffs_stat* s)
+{
+    time_t t = 0;
+#ifdef CONFIG_SPIFFS_USE_MTIME
+    memcpy(&t, s->meta, sizeof(t));
+#endif
+    return t;
+}

components/spiffs/include/spiffs_config.h

@@ -158,7 +158,7 @@ extern void spiffs_api_unlock(struct spiffs_t *fs);
 // This is derived from following:
 // logical_page_size - (SPIFFS_OBJ_NAME_LEN + sizeof(spiffs_page_header) +
 // spiffs_object_ix_header fields + at least some LUT entries)
-#define SPIFFS_OBJ_META_LEN             (4)
+#define SPIFFS_OBJ_META_LEN             (CONFIG_SPIFFS_META_LENGTH)
 
 // Size of buffer allocated on stack used when copying data.
 // Lower value generates more read/writes. No meaning having it bigger

components/spiffs/test/test_spiffs.c

@@ -505,3 +505,45 @@ TEST_CASE("multiple tasks can use same volume", "[spiffs]")
     test_spiffs_concurrent("/spiffs/f");
     test_teardown();
 }
+
+#ifdef CONFIG_SPIFFS_USE_MTIME
+TEST_CASE("mtime is updated when file is opened", "[spiffs]")
+{
+    /* Open a file, check that mtime is set correctly */
+    const char* filename = "/spiffs/time";
+    test_setup();
+    time_t t_before_create = time(NULL);
+    test_spiffs_create_file_with_text(filename, "\n");
+    time_t t_after_create = time(NULL);
+
+    struct stat st;
+    TEST_ASSERT_EQUAL(0, stat(filename, &st));
+    printf("mtime=%d\n", (int) st.st_mtime);
+    TEST_ASSERT(st.st_mtime >= t_before_create
+             && st.st_mtime <= t_after_create);
+
+    /* Wait a bit, open again, check that mtime is updated */
+    vTaskDelay(2000 / portTICK_PERIOD_MS);
+    time_t t_before_open = time(NULL);
+    FILE *f = fopen(filename, "a");
+    time_t t_after_open = time(NULL);
+    TEST_ASSERT_EQUAL(0, fstat(fileno(f), &st));
+    printf("mtime=%d\n", (int) st.st_mtime);
+    TEST_ASSERT(st.st_mtime >= t_before_open
+             && st.st_mtime <= t_after_open);
+    fclose(f);
+
+    /* Wait a bit, open for reading, check that mtime is not updated */
+    vTaskDelay(2000 / portTICK_PERIOD_MS);
+    time_t t_before_open_ro = time(NULL);
+    f = fopen(filename, "r");
+    TEST_ASSERT_EQUAL(0, fstat(fileno(f), &st));
+    printf("mtime=%d\n", (int) st.st_mtime);
+    TEST_ASSERT(t_before_open_ro > t_after_open
+             && st.st_mtime >= t_before_open
+             && st.st_mtime <= t_after_open);
+    fclose(f);
+
+    test_teardown();
+}
+#endif // CONFIG_SPIFFS_USE_MTIME