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Tue, 28 Jul 2026 21:23:02 -0700 (PDT) Received: from google.com ([2a00:79e0:2031:6:65c1:52a3:f6d3:37dc]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-38f7f0ed140sm723275a91.1.2026.07.28.21.22.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Jul 2026 21:23:01 -0700 (PDT) Date: Wed, 29 Jul 2026 13:22:57 +0900 From: Sergey Senozhatsky To: haoqin huang Cc: Sergey Senozhatsky , Minchan Kim , Jens Axboe , Nick Terrell , David Sterba , Andrew Morton , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, Haoqin Huang , Rongwei Wang Subject: Re: [PATCH v2 3/5] zstd: move ZSTD_MAX_CLEVEL to zstd_lib.h Message-ID: References: <20260627070216.13511-1-haoqinhuang7@gmail.com> <20260728092935.31139-1-haoqinhuang7@gmail.com> <20260728092935.31139-3-haoqinhuang7@gmail.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On (26/07/29 12:16), haoqin huang wrote: > > On (26/07/28 17:29), Haoqin Huang wrote: > > [..] > > > #define ZSTD_MINMATCH_MAX 7 /* only for ZSTD_fast, other strategies are limited to 6 */ > > > #define ZSTD_MINMATCH_MIN 3 /* only for ZSTD_btopt+, faster strategies are limited to 4 */ > > > +#define ZSTD_MAX_CLEVEL 22 > > > #define ZSTD_TARGETLENGTH_MAX ZSTD_BLOCKSIZE_MAX > > > #define ZSTD_TARGETLENGTH_MIN 0 /* note : comparing this constant to an unsigned results in a tautological test */ > > > #define ZSTD_STRATEGY_MIN ZSTD_fast > > > diff --git a/lib/zstd/compress/clevels.h b/lib/zstd/compress/clevels.h > > > index 6ab8be6532ef..06565e064456 100644 > > > --- a/lib/zstd/compress/clevels.h > > > +++ b/lib/zstd/compress/clevels.h > > > @@ -17,8 +17,6 @@ > > > > > > /*-===== Pre-defined compression levels =====-*/ > > > > > > -#define ZSTD_MAX_CLEVEL 22 > > > - > > > __attribute__((__unused__)) > > > > Sashiko made a good point. Can we use zstd_max_clevel() instead? > > Good point, I'll drop this patch and use zstd_max_clevel() instead > in v3. > > Since it's a runtime function and can't be used for static struct > initialization, I plan to set backend_zstd's level_max to -1 as a > sentinel value, and query the actual maximum in > zcomp_validate_params(): > > s32 max = backend->level_max; > if (max < 0) > max = zstd_max_clevel(); > > Do you think this approach is feasible? Hmm, no, that doesn't look good. zcomp should not include zstd.h or any other libs directly. Should params validation be a per-backend callback then?