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Date: Thu, 19 Mar 2026 10:59:55 -0700
From: Minchan Kim <minchan@kernel.org>
To: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Brian Geffon <bgeffon@google.com>,
	Richard Chang <richardycc@google.com>, linux-block@vger.kernel.org,
	linux-mm@kvack.org
Subject: Re: [PATCH] zram: do not slot_free() written-back slots
Message-ID: <abw5m8Q5fFXGIweh@google.com>
References: <20260319034912.1894770-1-senozhatsky@chromium.org>
 <abt1dsjsT9826Ewy@google.com>
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In-Reply-To: <abt1dsjsT9826Ewy@google.com>

On Thu, Mar 19, 2026 at 01:05:55PM +0900, Sergey Senozhatsky wrote:
> As a side note:
> 
> On (26/03/19 12:44), Sergey Senozhatsky wrote:
> > -	slot_free(zram, index);
> [..]
> > -		if (huge)
> > -			set_slot_flag(zram, index, ZRAM_HUGE);
> 
> Original code had a bug.  slot_free() would decrement ->huge_pages,
> then writeback completion would restore the HUGE flag, so when slot
> would get freed for real slot_free() would decrement ->huge_pages
> again, leading to underflow.

This should also go into description of the patch.