linux-kernel - Re: [PATCH 1/6] zram: cond_resched() in writeback loop

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Message-Id: <20241210165456.288ed82b8a66a08ac36a4d15@linux-foundation.org>
Date: Tue, 10 Dec 2024 16:54:56 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Sergey Senozhatsky <senozhatsky@...omium.org>
Cc: Minchan Kim <minchan@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6] zram: cond_resched() in writeback loop

On Tue, 10 Dec 2024 19:53:55 +0900 Sergey Senozhatsky <senozhatsky@...omium.org> wrote:

> Writeback loop can run for quite a while (depending on
> wb device performance, compression algorithm and the
> number of entries we writeback), so we need to do
> cond_resched() there, similarly to what we do in
> recompress loop.
> 
> ...
>
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -889,6 +889,8 @@ static ssize_t writeback_store(struct device *dev,
>  next:
>  		zram_slot_unlock(zram, index);
>  		release_pp_slot(zram, pps);
> +
> +		cond_resched();
>  	}
>  
>  	if (blk_idx)

Should this be treated as a hotfix?  With a -stable backport?

If so, we'd need to explain our reasoning in the changelog.  "Fixes a
watchdog lockup splat when running <workload>".  And a Fixes: would be
nice if appropriate.