linux-kernel - Re: [PATCH v2] mm: zswap: increase reject_compress_poor but not reject_compress

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Date: Sat, 17 Feb 2024 08:57:47 +0000
From: Yosry Ahmed <yosryahmed@...gle.com>
To: Barry Song <21cnbao@...il.com>
Cc: akpm@...ux-foundation.org, hannes@...xchg.org, linux-mm@...ck.org, 
	nphamcs@...il.com, zhouchengming@...edance.com, senozhatsky@...omium.org, 
	linux-kernel@...r.kernel.org, Barry Song <v-songbaohua@...o.com>
Subject: Re: [PATCH v2] mm: zswap: increase reject_compress_poor but not
 reject_compress_fail if compression returns ENOSPC

On Sat, Feb 17, 2024 at 06:36:42PM +1300, Barry Song wrote:
> From: Barry Song <v-songbaohua@...o.com>
> 
> We used to rely on the returned -ENOSPC of zpool_malloc() to increase
> reject_compress_poor. But the code wouldn't get to there after commit
> 744e1885922a ("crypto: scomp - fix req->dst buffer overflow") as the
> new code will goto out immediately after the special compression case
> happens. So there might be no longer a chance to execute zpool_malloc
> now. We are incorrectly increasing zswap_reject_compress_fail instead.
> Thus, we need to fix the counters handling right after compressions
> return ENOSPC. This patch also centralizes the counters handling for
> all of compress_poor, compress_fail and alloc_fail.
> 
> Fixes: 744e1885922a ("crypto: scomp - fix req->dst buffer overflow")
> Cc: Chengming Zhou <zhouchengming@...edance.com>
> Cc: Nhat Pham <nphamcs@...il.com>
> Cc: Sergey Senozhatsky <senozhatsky@...omium.org>
> Signed-off-by: Barry Song <v-songbaohua@...o.com>
> ---
>  -v2: 
>  * correct the fixes target according to Yosry, Chengming, Nhat's
>    comments;
>  * centralize the counters handling according to Yosry's comment

Yet Yosry is not CC'd :P

The patch LGTM, but it won't apply on top of mm-unstable given the
amount of zswap refactoring there. I would rebase on top of mm-unstable
if I were you (and if you did, add mm-unstable in the subject prefix).

Acked-by: Yosry Ahmed <yosryahmed@...gle.com>

Thanks!