Re: [PATCH V4 5/9] null_blk: free zones array on device power-off

[Zizhi Wo]

Hi Nilay!

在 2026/7/10 22:24, Nilay Shroff 写道:
> On 7/9/26 3:34 PM, Zizhi Wo wrote:
> > null_init_zoned_dev() allocates dev->zones when a zoned device is powered
> > on, but null_del_dev() never frees it on power-off; dev->zones is only
> > freed later in null_free_dev(), when the configfs directory is 
> > removed. If
> > the device is powered off and then on again, null_init_zoned_dev()
> > allocates a new array and overwrites the dev->zones pointer, leaking the
> > previous allocation each power cycle.
> >
> > Free dev->zones in null_del_dev() via null_free_zoned_dev() to solve it.
> > And calling null_del_dev() in null_free_dev() is no longer necessary
> > because every caller already invokes null_del_dev() first: via
> > nullb_group_drop_item() before nullb_device_release(), in the
> > null_add_dev() error path of null_create_dev(), and in 
> > null_destroy_dev().
> > Remove the redundant call.
>
> Looks good to me.
>
> Reviewed-by: Nilay Shroff <nilay@xxxxxxxxxxxxx>

Thanks for the review!

However, I just checked Sashiko and found that modifying it this way
directly would introduce a problem:

the caller of zone_cond_store() is lock-free, and internally it checks
whether dev->zones exists. This would then create a race with my patch.
The reason there was no problem before is that only
nullb_device_release() or null_exit() frees the dev->zones, which
guarantees that subsequent users won't access the configfs interface.
I'll address this issue in the next version by adding locking to them.

Thanks,
Zizhi Wo