Re: [PATCHv3 4/8] zram: Introduce recompress sysfs knob

[Andrew Morton]

On Sun,  9 Oct 2022 18:07:16 +0900 Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx> wrote:

> Allow zram to recompress (using secondary compression streams)
> pages. We support three modes:
> 
> 1) IDLE pages recompression is activated by `idle` mode
> 
> 	echo idle > /sys/block/zram0/recompress
> 
> 2) Since there may be many idle pages user-space may pass a size
> watermark value and we will recompress IDLE pages only of equal
> or greater size:
> 
> 	echo 888 > /sys/block/zram0/recompress

It's helpful to describe the units ("bytes") here and in the
docmentation.

> 3) HUGE pages recompression is activated by `huge` mode
> 
> 	echo huge > /sys/block/zram0/recompress
> 
> 4) HUGE_IDLE pages recompression is activated by `huge_idle` mode
> 
> 	echo huge_idle > /sys/block/zram0/recompress
> 
> ...
>
> +	if (IS_ERR((void *)handle_next)) {

IS_ERR_VALUE() avoids castsing back and forth.