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[95.235.102.55]) by smtp.gmail.com with ESMTPSA id h8-20020adff4c8000000b0021d887f9468sm765579wrp.25.2022.07.14.00.46.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 14 Jul 2022 00:46:29 -0700 (PDT) From: "Fabio M. De Francesco" To: Wang Yugui Cc: Chris Mason , Josef Bacik , David Sterba , Nick Terrell , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, Filipe Manana , Ira Weiny Subject: Re: [PATCH] btrfs: Replace kmap() with kmap_local_page() in zstd.c Date: Thu, 14 Jul 2022 09:46:00 +0200 Message-ID: <8091114.T7Z3S40VBb@opensuse> In-Reply-To: <20220714082519.A7C9.409509F4@e16-tech.com> References: <20220611135203.27992-1-fmdefrancesco@gmail.com> <20220714082519.A7C9.409509F4@e16-tech.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On gioved=C3=AC 14 luglio 2022 02:25:20 CEST Wang Yugui wrote: > Hi, >=20 > Compiler warning: >=20 > fs/btrfs/zstd.c:478:55: warning: passing argument 1 of =E2=80=98__kunmap_= local=E2=80=99=20 discards =E2=80=98const=E2=80=99 qualifier from pointer target type [-Wdisc= arded- qualifiers] > 478 | kunmap_local(workspace->in_buf.src); > ./include/linux/highmem-internal.h:284:24: note: in definition of macro=20 =E2=80=98kunmap_local=E2=80=99 > 284 | __kunmap_local(__addr); \ > | ^~~~~~ > ./include/linux/highmem-internal.h:200:41: note: expected =E2=80=98void *= =E2=80=99 but=20 argument is of type =E2=80=98const void *=E2=80=99 > 200 | static inline void __kunmap_local(void *addr) > | ~~~~~~^~~~ >=20 > Best Regards > Wang Yugui (wangyugui@e16-tech.com) > 2022/07/14 Thanks for the build test, but you're a little late :) This patch is superseded by a series of two: please see [PATCH v6 0/2] btrfs: Replace kmap() with kmap_local_page() in zstd.c at https://lore.kernel.org/lkml/20220706111520.12858-1-fmdefrancesco@gmail.= com/ In that series, patch 1/2 changes __kunmap_{local,atomic}() prototypes to=20 take pointers to const void. Regards, =46abio > > The use of kmap() is being deprecated in favor of kmap_local_page().=20 With > > kmap_local_page(), the mapping is per thread, CPU local and not=20 globally > > visible. > >=20 > > Therefore, use kmap_local_page() / kunmap_local() in zstd.c because in > > this file the mappings are per thread and are not visible in other > > contexts; meanwhile refactor zstd_compress_pages() to comply with=20 nested > > local mapping / unmapping ordering rules. > >=20