From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 781E2409132 for ; Thu, 16 Jul 2026 10:31:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784197885; cv=none; b=SmFYK5+WjTGwMPnGJxfab4bK2hAxvyzu6udf6A7zS+UViT784S34d4O0CHiWDcE/orHCxbe6W6mnNVsawsms4Y3YWi7JSP+lrWlBcZk4mZLU28uCGTY14XgPhpl9f0YKbJFYdFTbZG0JMfNZf/++HRPbCUMfCeuLS1UQWfP/XU8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784197885; c=relaxed/simple; bh=W2r34cI+XaaQUdqCi3aOgKHvzlTyAT8XuHNk4YjX+HU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=aBhIThHCr8Zw5ds69cejP+L1FrsZ1B4fINkhvpG6dd7iVgU4s1pAL0+Hn2gN1f0jg+KTeGpgRzdu2m3474j+Wi+/vyyHSxhyr6+9lOcT9ExyTU4Fv94Z4YRXhJyl2/tzqCRitgZtr4DVU4J0Ccf/MEZEau2U2C3mBpIrKaD52n8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=Yu+unkyf; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Yu+unkyf" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1784197882; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=forfFVNHXdcKUrAO6tYWFvQxC3xkWQUr9XOJVlaCNVg=; b=Yu+unkyfKLfRUWG/yjHyxYLu4Z+CovrIEhz0cK8Mxb6kehaSt2Re0imro/bu82xnp5aHpu JsS2Cwm9D7ikJVgZqeyBM9h+BmJP6v5ezwzSmlFW7D3ViISqjGtRZgWnvsT7qPZ9pVADwz MrnS3q9ouRI0suCIW2jtRKIzhvl5i0U= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-572-CRMZ5cTANlyRJrFFM9ec3g-1; Thu, 16 Jul 2026 06:31:18 -0400 X-MC-Unique: CRMZ5cTANlyRJrFFM9ec3g-1 X-Mimecast-MFC-AGG-ID: CRMZ5cTANlyRJrFFM9ec3g_1784197875 Received: from mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.95]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 0BCA11800610; Thu, 16 Jul 2026 10:31:13 +0000 (UTC) Received: from warthog.procyon.org.com (unknown [10.44.33.159]) by mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 96F2C42C; Thu, 16 Jul 2026 10:31:05 +0000 (UTC) From: David Howells To: Christian Brauner , Matthew Wilcox , Christoph Hellwig Cc: David Howells , Paulo Alcantara , Jens Axboe , Leon Romanovsky , Steve French , ChenXiaoSong , 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-erofs@lists.ozlabs.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org Subject: [PATCH v6 03/24] Add a function to kmap one page of a multipage bio_vec Date: Thu, 16 Jul 2026 11:30:02 +0100 Message-ID: <20260716103030.3065561-4-dhowells@redhat.com> In-Reply-To: <20260716103030.3065561-1-dhowells@redhat.com> References: <20260716103030.3065561-1-dhowells@redhat.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.6 on 10.30.177.95 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 Acked-by: Paulo Alcantara (Red Hat) cc: Matthew Wilcox cc: Christoph Hellwig cc: Jens Axboe 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 92837e2743f1..53cf36e73967 100644 --- a/include/linux/bvec.h +++ b/include/linux/bvec.h @@ -343,4 +343,22 @@ 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(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 */