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Date: Sun, 13 Sep 2026 00:48:31 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Baoquan He <hebaoquan@kylinos.cn>
Cc: hannes@cmpxchg.org, yosry@kernel.org, nphamcs@gmail.com,
 chengming.zhou@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org,
 kasong@tencent.com, chrisl@kernel.org
Subject: Re: [PATCH] mm: zswap: return -ENOENT when the swap device is gone
Message-Id: <20260913004831.884d37afd92249d763b7f1da@linux-foundation.org>
In-Reply-To: <20260913063031.1689420-1-hebaoquan@kylinos.cn>
References: <20260913063031.1689420-1-hebaoquan@kylinos.cn>
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On Sun, 13 Sep 2026 14:30:31 +0800 Baoquan He <hebaoquan@kylinos.cn> wrote:

> zswap_writeback_entry() returns -EEXIST when get_swap_device() finds no
> device.  -EEXIST is the shrinker's "page already in swap cache" signal,
> which makes zswap_shrinker_scan() stop shrinking entirely.  A NULL
> get_swap_device() instead means the device is being swapped off, so the
> entry is simply stale.
> 
> Return -ENOENT so the shrinker skips the stale entry and keeps scanning.
> Independent of xswap; affects all swap devices.

I'm struggling to understand the userspace-visible runtime effects of this.

I see that reclaim will prematurely abort, but is this a once-off thing
which will resolve on the next reclaim attempt, or will the reclaim
failure persist for a significant period?