From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 DF76D448BB0 for ; Tue, 4 Aug 2026 10:03:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785837813; cv=none; b=dEMhfPVnzHPKmdDHQb+eaoxHBqyP49aHLPe89nL3bfBULea41P8SQfRuGcxz7M02URPW0YkiBbMKUCEI6StsSNw6zRQYccU3FqN5BnLXtGMvuDUqrcyFMB3uxzgOeeah8hAq5hy2FERNIUnc9TkXhcDgxqRA6kDbwchjtjvsj+s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785837813; c=relaxed/simple; bh=W2r34cI+XaaQUdqCi3aOgKHvzlTyAT8XuHNk4YjX+HU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:content-type; b=ly0E7m/gST3GISouMu9E0XwB05NpOMu1i8fMFUHIhutYhwDvxRI034rWXljSHm5Uorzak1r1rYsbdtTquEX/p6LAcXeNIIxS2crfVzvyKup5HqyGOCm4LrLtbLFEGAC741gWR5BVjnj2nvDxk0iqAc3RZiecV4Y8Z1IAhqcHYWk= 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=eB04paVr; arc=none smtp.client-ip=170.10.129.124 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="eB04paVr" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1785837811; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=forfFVNHXdcKUrAO6tYWFvQxC3xkWQUr9XOJVlaCNVg=; b=eB04paVrVghL5qxx1Ed3HWL3/l25698oQrjmpJ0dwzGmr2p3UBAlwVWalEp5t84/hPO87m ZIOcgjNpRKCHXQQSxIEtr37ZMk0eHcmxIrPlO0LigQ8h9yBqAN7goxYIH/PTxlDCzKevri iP6J9n/XkWVTrfEmq6revTk1AKz/kwM= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-295-D9vewdzqPTqtYuFKpPv8iQ-1; Tue, 04 Aug 2026 06:03:09 -0400 X-MC-Unique: D9vewdzqPTqtYuFKpPv8iQ-1 X-Mimecast-MFC-AGG-ID: D9vewdzqPTqtYuFKpPv8iQ_1785837786 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (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-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 247EA1956096; Tue, 4 Aug 2026 10:03:06 +0000 (UTC) Received: from warthog.procyon.org.com (unknown [10.44.32.44]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 514F430001B9; Tue, 4 Aug 2026 10:02:58 +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 v8 03/25] Add a function to kmap one page of a multipage bio_vec Date: Tue, 4 Aug 2026 11:01:58 +0100 Message-ID: <20260804100224.2748935-4-dhowells@redhat.com> In-Reply-To: <20260804100224.2748935-1-dhowells@redhat.com> References: <20260804100224.2748935-1-dhowells@redhat.com> Precedence: bulk X-Mailing-List: netfs@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 X-Mimecast-MFC-PROC-ID: 1kRbdPVoyv8YFDCoWH1N1YVTFRZwOC5bJKu_EEOT_bY_1785837786 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true 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 */