Question: is the attr size limited to the block size?

[dangfan]

When I set the block size to 512, and run the following code, it always stops after writing the first attr:

  for (int i = 0; i < 1000; ++i) {
    uint8_t buf[512];
    char path[10];
    sprintf(path, "%d\n", i);
    lfs_file_t file;
    if (lfs_file_open(&lfs, &file, path, LFS_O_CREAT | LFS_O_RDWR) < 0) {
      printf("Create file %s error\n", path);
      return 0;
    }
    if (lfs_file_write(&lfs, &file, NULL, 0) < 0) {
      printf("Write file %s error\n", path);
      return 0;
    }
    for (int j = 0; j < 256; ++j) {
      if ((ret = lfs_setattr(&lfs, path, j, buf, 486)) < 0) {
        printf("Set attr %d of %s error %d\n", j, path, ret);
        return 0;
      }
    }
    if (lfs_file_close(&lfs, &file) < 0) {
      printf("Close file %s error\n", path);
      return 0;
    }
  }

So is the attr size limited to the block size?

[geky]

Ah yes. Custom attributes contribute to the size of a file's metadata, and a limitation of littlefs is that the file's metadata must fit in a single block. This also includes the filename and pointer to the skiplist.

They are intended for small attributes such as timestamps, permission bitmasks, hashes, etc. I hadn't considered how larger attributes would interact with the block size.

Thanks for pointing this out, it should be documented, especially since it differs from traditional "extended attributes" which are effectively just multiple files attached to a single filename.