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Wed, 11 Nov 2026 20:30:55 +0000 (UTC) Received: from dhowells-thinkpadp1gen8.rmtgb.csb (headnet04.pony-001.prod.iad2.dc.redhat.com [10.2.32.116]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id E133A30000D3; Wed, 11 Nov 2026 20:30:50 +0000 (UTC) From: David Howells To: Christian Brauner Cc: David Howells , Paulo Alcantara , Matthew Wilcox , Namjae Jeon , Marc Dionne , Stefan Metzmacher , Eric Van Hensbergen , Dominique Martinet , Ilya Dryomov , netfs@lists.linux.dev, linux-afs@lists.infradead.org, linux-cifs@vger.kernel.org, linux-nfs@vger.kernel.org, ceph-devel@vger.kernel.org, v9fs@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Jens Axboe , Christoph Hellwig , linux-block@vger.kernel.org Subject: [PATCH v17 02/17] Add a function to kmap one page of a multipage bio_vec Date: Wed, 11 Nov 2026 20:30:15 +0000 Message-ID: <20261111203034.2126314-3-dhowells@redhat.com> In-Reply-To: <20261111203034.2126314-1-dhowells@redhat.com> References: <20261111203034.2126314-1-dhowells@redhat.com> X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Add a function to kmap one page of a multipage bio_vec by offset (which is added to the offset in the bio_vec internally). The caller is responsible for calculating how much of the page is then available. Signed-off-by: David Howells Reviewed-by: Paulo Alcantara (Red Hat) cc: Matthew Wilcox cc: Jens Axboe cc: Christoph Hellwig cc: linux-block@vger.kernel.org cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org --- include/linux/bvec.h | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/include/linux/bvec.h b/include/linux/bvec.h index b63914ff56e3..7ea62643cfb7 100644 --- a/include/linux/bvec.h +++ b/include/linux/bvec.h @@ -344,4 +344,22 @@ static inline phys_addr_t bvec_phys(const struct bio_vec *bvec) return page_to_phys(bvec->bv_page) + bvec->bv_offset; } +/** + * bvec_kmap_partial - Map part of a bvec into the kernel virtual address space + * @bvec: bvec to map + * @offset: Offset into bvec + * + * Map the page containing the byte at @offset into the kernel virtual address + * space. The caller is responsible for making sure this doesn't overrun. + * + * Call kunmap_local on the returned address to unmap. + */ +static inline void *bvec_kmap_partial(const struct bio_vec *bvec, size_t offset) +{ + offset += bvec->bv_offset; + + return kmap_local_page(bvec->bv_page + (offset >> PAGE_SHIFT)) + + (offset & ~PAGE_MASK); +} + #endif /* __LINUX_BVEC_H */