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Miller" , Andreas Larsson , Richard Weinberger , Anton Ivanov , Johannes Berg , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Herbert Xu , Dan Williams , Chris Mason , David Sterba , Arnd Bergmann , Song Liu , Yu Kuai , Li Nan , linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, linux-crypto@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-arch@vger.kernel.org, linux-raid@vger.kernel.org Subject: [PATCH 21/25] xor: add a better public API Date: Thu, 26 Feb 2026 07:10:33 -0800 Message-ID: <20260226151106.144735-22-hch@lst.de> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260226151106.144735-1-hch@lst.de> References: <20260226151106.144735-1-hch@lst.de> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html xor_blocks is very annoying to use, because it is limited to 4 + 1 sources / destinations, has an odd argument order and is completely undocumented. Lift the code that loops around it from btrfs and async_tx/async_xor into common code under the name xor_gen and properly document it. Signed-off-by: Christoph Hellwig --- include/linux/raid/xor.h | 3 +++ lib/raid/xor/xor-core.c | 28 ++++++++++++++++++++++++++++ 2 files changed, 31 insertions(+) diff --git a/include/linux/raid/xor.h b/include/linux/raid/xor.h index 02bda8d99534..4735a4e960f9 100644 --- a/include/linux/raid/xor.h +++ b/include/linux/raid/xor.h @@ -7,4 +7,7 @@ extern void xor_blocks(unsigned int count, unsigned int bytes, void *dest, void **srcs); +void xor_gen(void *dest, void **srcss, unsigned int src_cnt, + unsigned int bytes); + #endif /* _XOR_H */ diff --git a/lib/raid/xor/xor-core.c b/lib/raid/xor/xor-core.c index 8dda4055ad09..b7c29ca931ec 100644 --- a/lib/raid/xor/xor-core.c +++ b/lib/raid/xor/xor-core.c @@ -46,6 +46,34 @@ xor_blocks(unsigned int src_count, unsigned int bytes, void *dest, void **srcs) } EXPORT_SYMBOL(xor_blocks); +/** + * xor_gen - generate RAID-style XOR information + * @dest: destination vector + * @srcs: source vectors + * @src_cnt: number of source vectors + * @bytes: length in bytes of each vector + * + * Performs bit-wise XOR operation into @dest for each of the @src_cnt vectors + * in @srcs for a length of @bytes bytes. + * + * Note: for typical RAID uses, @dest either needs to be zeroed, or filled with + * the first disk, which then needs to be removed from @srcs. + */ +void xor_gen(void *dest, void **srcs, unsigned int src_cnt, unsigned int bytes) +{ + unsigned int src_off = 0; + + while (src_cnt > 0) { + unsigned int this_cnt = min(src_cnt, MAX_XOR_BLOCKS); + + xor_blocks(this_cnt, bytes, dest, srcs + src_off); + + src_cnt -= this_cnt; + src_off += this_cnt; + } +} +EXPORT_SYMBOL(xor_gen); + /* Set of all registered templates. */ static struct xor_block_template *__initdata template_list; static int __initdata xor_forced = false; -- 2.47.3