[LEDE-DEV] [RFC 3/3] config: ext4: use 1K blocks by default to support online resize2fs

[Jo-Philipp Wich]

Hi Michael,

> I can't see why adjusting the default partition size would have been necessary
> as genext2fs takes (or better: took) the following parameters:

The filesystem is generated okay but due to the total size : blocksize ratio there are not enough backup block group descriptor entries left to support online-resizing the rootfs partition, see http://lists.infradead.org/pipermail/lede-dev/2016-September/002518.html for a report that describes the problem.

I am fine with keeping 4k blocks but in this case we should increase the default image size to at least the minimum value being able to support resizing. The report mentions that 512M already work which would allow resizing up to 512GB (1024 times larger).

> Sorry, but I can only find the default value of 48 MB? Do I miss something?

See https://git.lede-project.org/?p=source.git;a=blob;f=config/Config-images.in#l263

> I don't like reverting to 1k because when you use the image on a real
> device, e.g. eMMC or SD card, then usually the internal blocksize is 4k,
> and internal erase block size is often even 4 MiB.
> Thus using 1k blocksize is not optimal when using a writeable filesystem.

I understand. As mentioned above, 4K blocks are fine for me too, but in this case I suggest to bump the rootfs part size to 2GB which would support 2TB rootfs partitions.


~ Jo