Re: [PATCH] zram: panic when use ext4 over zram

[Sergey Senozhatsky <senozhatsky@chromium.org>]

On (24/12/02 18:07), caiqingfu wrote:
> > What's your use-case, what apps you run and what data is stored
> > on zram disk?
> 
> The steps to reproduce are as follows:
> 
> 1. force slow path,then re-build kernel
> 
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 0ca6d55c9917..29ac52a4f2e7 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -1683,12 +1683,14 @@ static int zram_write_page(struct zram *zram, struct page *page, u32 index)
>          * if we have a 'non-null' handle here then we are coming
>          * from the slow path and handle has already been allocated.
>          */
> +    /*
>         if (IS_ERR_VALUE(handle))
>                 handle = zs_malloc(zram->mem_pool, comp_len,
>                                 __GFP_KSWAPD_RECLAIM |
>                                 __GFP_NOWARN |
>                                 __GFP_HIGHMEM |
>                                 __GFP_MOVABLE);
> +        */
>         if (IS_ERR_VALUE(handle)) {
>                 zcomp_stream_put(zram->comps[ZRAM_PRIMARY_COMP]);
>                 atomic64_inc(&zram->stats.writestall);
> 
> 2. create an arm64 virtual machine
> 
> qemu-system-aarch64 -M virt -cpu cortex-a57 -smp 4 -m 1024 -kernel kernel-build/arch/arm64/boot/Image \ 
>     -nographic -append "console=ttyAMA0,115200 root=/dev/vda rw" \ 
>     -drive file=$(IMGFILE),format=raw -nic user,hostfwd=tcp::60022-:22
> 
> 3. after the virtual machine is started, create zram
> 
> cat /sys/class/zram-control/hot_add
> echo 524288000 > /sys/devices/virtual/block/zram0/disksize
> echo 524288000 > /sys/devices/virtual/block/zram1/disksize
> mkfs.ext4 -O ^has_journal -b 4096 -F -L TEMP -m 0 /dev/zram0
> mkdir /tmp/zram
> mount -t ext4 -o errors=continue,nosuid,nodev,noatime /dev/zram0 /tmp/zram
> mkswap /dev/zram1
> swapon /dev/zram1
> echo 100 > /proc/sys/vm/swappiness
> mkdir -p /tmp/zram/stressTest
> 
> 
> 4. build demo app and run again and again
> 

I was more curious whether you have a real-world example/app
that does it.