extmod/vfs_lfs: Add mtime support to littlefs files.

This commit adds support for modification time of files on littlefs v2
filesystems, using file attributes.  For some background see issue #6114.

Features/properties of this implementation:
- Only supported on littlefs2 (not littlefs1).
- Uses littlefs2's general file attributes to store the timestamp.
- The timestamp is 64-bits and stores nanoseconds since 1970/1/1 (if the
  range to the year 2554 is not enough then additional bits can be added to
  this timestamp by adding another file attribute).
- mtime is enabled by default but can be disabled in the constructor, eg:
  uos.mount(uos.VfsLfs2(bdev, mtime=False), '/flash')
- It's fully backwards compatible, existing littlefs2 filesystems will work
  without reformatting and timestamps will be added transparently to
  existing files (once they are opened for writing).
- Files without timestamps will open correctly, and stat will just return 0
  for their timestamp.
- mtime can be disabled or enabled each mount time and timestamps will only
  be updated if mtime is enabled (otherwise they will be untouched).

Signed-off-by: Damien George <damien@micropython.org>

3 files changed, 57 insertions, 7 deletions

diff --git a/extmod/vfs_lfs.c b/extmod/vfs_lfs.c
index 90a1996f9c..a53f66f2d6 100644
--- a/extmod/vfs_lfs.c
+++ b/extmod/vfs_lfs.c
@@ -3,7 +3,7 @@
  *
  * The MIT License (MIT)
  *
- * Copyright (c) 2019 Damien P. George
+ * Copyright (c) 2019-2020 Damien P. George
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -25,18 +25,20 @@
  */
 
 #include "py/runtime.h"
+#include "py/mphal.h"
 #include "extmod/vfs.h"
 #include "extmod/vfs_lfs.h"
 
 #if MICROPY_VFS && (MICROPY_VFS_LFS1 || MICROPY_VFS_LFS2)
 
-enum { LFS_MAKE_ARG_bdev, LFS_MAKE_ARG_readsize, LFS_MAKE_ARG_progsize, LFS_MAKE_ARG_lookahead };
+enum { LFS_MAKE_ARG_bdev, LFS_MAKE_ARG_readsize, LFS_MAKE_ARG_progsize, LFS_MAKE_ARG_lookahead, LFS_MAKE_ARG_mtime };
 
 static const mp_arg_t lfs_make_allowed_args[] = {
     { MP_QSTR_, MP_ARG_REQUIRED | MP_ARG_OBJ },
     { MP_QSTR_readsize, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 32} },
     { MP_QSTR_progsize, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 32} },
     { MP_QSTR_lookahead, MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 32} },
+    { MP_QSTR_mtime, MP_ARG_KW_ONLY | MP_ARG_BOOL, {.u_bool = true} },
 };
 
 #if MICROPY_VFS_LFS1
@@ -98,9 +100,13 @@ mp_obj_t mp_vfs_lfs1_file_open(mp_obj_t self_in, mp_obj_t path_in, mp_obj_t mode
 #define MP_TYPE_VFS_LFSx mp_type_vfs_lfs2
 #define MP_TYPE_VFS_LFSx_(s) mp_type_vfs_lfs2##s
 
+// Attribute ids for lfs2_attr.type.
+#define LFS_ATTR_MTIME (1) // 64-bit little endian, nanoseconds since 1970/1/1
+
 typedef struct _mp_obj_vfs_lfs2_t {
     mp_obj_base_t base;
     mp_vfs_blockdev_t blockdev;
+    bool enable_mtime;
     vstr_t cur_dir;
     struct lfs2_config config;
     lfs2_t lfs;
@@ -109,14 +115,25 @@ typedef struct _mp_obj_vfs_lfs2_t {
 typedef struct _mp_obj_vfs_lfs2_file_t {
     mp_obj_base_t base;
     mp_obj_vfs_lfs2_t *vfs;
+    uint8_t mtime[8];
     lfs2_file_t file;
     struct lfs2_file_config cfg;
+    struct lfs2_attr attrs[1];
     uint8_t file_buffer[0];
 } mp_obj_vfs_lfs2_file_t;
 
 const char *mp_vfs_lfs2_make_path(mp_obj_vfs_lfs2_t *self, mp_obj_t path_in);
 mp_obj_t mp_vfs_lfs2_file_open(mp_obj_t self_in, mp_obj_t path_in, mp_obj_t mode_in);
 
+STATIC void lfs_get_mtime(uint8_t buf[8]) {
+    uint64_t ns = mp_hal_time_ns();
+    // Store "ns" to "buf" in little-endian format (essentially htole64).
+    for (size_t i = 0; i < 8; ++i) {
+        buf[i] = ns;
+        ns >>= 8;
+    }
+}
+
 #include "extmod/vfs_lfsx.c"
 #include "extmod/vfs_lfsx_file.c"
 
diff --git a/extmod/vfs_lfsx.c b/extmod/vfs_lfsx.c
index 24816433be..511b741b0d 100644
--- a/extmod/vfs_lfsx.c
+++ b/extmod/vfs_lfsx.c
@@ -3,7 +3,7 @@
  *
  * The MIT License (MIT)
  *
- * Copyright (c) 2019 Damien P. George
+ * Copyright (c) 2019-2020 Damien P. George
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -34,6 +34,7 @@
 #include "py/objstr.h"
 #include "py/mperrno.h"
 #include "extmod/vfs.h"
+#include "lib/timeutils/timeutils.h"
 
 STATIC int MP_VFS_LFSx(dev_ioctl)(const struct LFSx_API (config) * c, int cmd, int arg, bool must_return_int) {
     mp_obj_t ret = mp_vfs_blockdev_ioctl(c->context, cmd, arg);
@@ -120,6 +121,9 @@ STATIC mp_obj_t MP_VFS_LFSx(make_new)(const mp_obj_type_t * type, size_t n_args,
     self->base.type = type;
     vstr_init(&self->cur_dir, 16);
     vstr_add_byte(&self->cur_dir, '/');
+    #if LFS_BUILD_VERSION == 2
+    self->enable_mtime = args[LFS_MAKE_ARG_mtime].u_bool;
+    #endif
     MP_VFS_LFSx(init_config)(self, args[LFS_MAKE_ARG_bdev].u_obj,
         args[LFS_MAKE_ARG_readsize].u_int, args[LFS_MAKE_ARG_progsize].u_int, args[LFS_MAKE_ARG_lookahead].u_int);
     int ret = LFSx_API(mount)(&self->lfs, &self->config);
@@ -352,6 +356,19 @@ STATIC mp_obj_t MP_VFS_LFSx(stat)(mp_obj_t self_in, mp_obj_t path_in) {
         mp_raise_OSError(-ret);
     }
 
+    mp_uint_t mtime = 0;
+    #if LFS_BUILD_VERSION == 2
+    uint8_t mtime_buf[8];
+    lfs2_ssize_t sz = lfs2_getattr(&self->lfs, path, LFS_ATTR_MTIME, &mtime_buf, sizeof(mtime_buf));
+    if (sz == sizeof(mtime_buf)) {
+        uint64_t ns = 0;
+        for (size_t i = sizeof(mtime_buf); i > 0; --i) {
+            ns = ns << 8 | mtime_buf[i - 1];
+        }
+        mtime = timeutils_seconds_since_2000_from_nanoseconds_since_1970(ns);
+    }
+    #endif
+
     mp_obj_tuple_t *t = MP_OBJ_TO_PTR(mp_obj_new_tuple(10, NULL));
     t->items[0] = MP_OBJ_NEW_SMALL_INT(info.type == LFSx_MACRO(_TYPE_REG) ? MP_S_IFREG : MP_S_IFDIR); // st_mode
     t->items[1] = MP_OBJ_NEW_SMALL_INT(0); // st_ino
@@ -360,9 +377,9 @@ STATIC mp_obj_t MP_VFS_LFSx(stat)(mp_obj_t self_in, mp_obj_t path_in) {
     t->items[4] = MP_OBJ_NEW_SMALL_INT(0); // st_uid
     t->items[5] = MP_OBJ_NEW_SMALL_INT(0); // st_gid
     t->items[6] = mp_obj_new_int_from_uint(info.size); // st_size
-    t->items[7] = MP_OBJ_NEW_SMALL_INT(0); // st_atime
-    t->items[8] = MP_OBJ_NEW_SMALL_INT(0); // st_mtime
-    t->items[9] = MP_OBJ_NEW_SMALL_INT(0); // st_ctime
+    t->items[7] = MP_OBJ_NEW_SMALL_INT(mtime); // st_atime
+    t->items[8] = MP_OBJ_NEW_SMALL_INT(mtime); // st_mtime
+    t->items[9] = MP_OBJ_NEW_SMALL_INT(mtime); // st_ctime
 
     return MP_OBJ_FROM_PTR(t);
 }
diff --git a/extmod/vfs_lfsx_file.c b/extmod/vfs_lfsx_file.c
index f74b41837d..bc1a37b90b 100644
--- a/extmod/vfs_lfsx_file.c
+++ b/extmod/vfs_lfsx_file.c
@@ -3,7 +3,7 @@
  *
  * The MIT License (MIT)
  *
- * Copyright (c) 2019 Damien P. George
+ * Copyright (c) 2019-2020 Damien P. George
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -101,6 +101,17 @@ mp_obj_t MP_VFS_LFSx(file_open)(mp_obj_t self_in, mp_obj_t path_in, mp_obj_t mod
     #endif
     o->cfg.buffer = &o->file_buffer[0];
 
+    #if LFS_BUILD_VERSION == 2
+    if (self->enable_mtime) {
+        lfs_get_mtime(&o->mtime[0]);
+        o->attrs[0].type = LFS_ATTR_MTIME;
+        o->attrs[0].buffer = &o->mtime[0];
+        o->attrs[0].size = sizeof(o->mtime);
+        o->cfg.attrs = &o->attrs[0];
+        o->cfg.attr_count = MP_ARRAY_SIZE(o->attrs);
+    }
+    #endif
+
     const char *path = MP_VFS_LFSx(make_path)(self, path_in);
     int ret = LFSx_API(file_opencfg)(&self->lfs, &o->file, path, flags, &o->cfg);
     if (ret < 0) {
@@ -131,6 +142,11 @@ STATIC mp_uint_t MP_VFS_LFSx(file_read)(mp_obj_t self_in, void *buf, mp_uint_t s
 STATIC mp_uint_t MP_VFS_LFSx(file_write)(mp_obj_t self_in, const void *buf, mp_uint_t size, int *errcode) {
     MP_OBJ_VFS_LFSx_FILE *self = MP_OBJ_TO_PTR(self_in);
     MP_VFS_LFSx(check_open)(self);
+    #if LFS_BUILD_VERSION == 2
+    if (self->vfs->enable_mtime) {
+        lfs_get_mtime(&self->mtime[0]);
+    }
+    #endif
     LFSx_API(ssize_t) sz = LFSx_API(file_write)(&self->vfs->lfs, &self->file, buf, size);
     if (sz < 0) {
         *errcode = -sz;