From nobody Thu Apr 2 23:53:31 2026 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 2A43238A73B for ; Thu, 26 Mar 2026 10:48:16 +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=1774522097; cv=none; b=nlenG5d5vClUrBGkDAPdKIgr8/+U5ZR/4QRK18V5vRh7/Fu1OHw54Cr5ltyfNeVAjM8ztclx/75mKtV3XAk8yM6F3sY1wiPuan3Gi6XEX/Nbu7o1O/BRLbvGE2NPqkqzyUIGK4PVrq+PEk8qO183HZjxAE1IeHbv3beXA6bDq/s= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774522097; c=relaxed/simple; bh=MTxqkqINhnmFwsYY0I5RGkHMRfSTiKvm3IE0AehnxE0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=D+Fru1Se+Vdd9cXtDWyZkzAX4hi2whcEX9/8aIicXUXtpuHXsa5sWYxbcQC7cSiepgBc4TzOq6zd3gQG5pwR/FyDOlgOHfnCg4pCDkHmtrG7kb6l5PkCF+hz9gPMRmM086XZ2WaL8XpOOcLA8yme8vhaWm55HCVbzH1121Iz61g= 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=TORcYEjj; 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="TORcYEjj" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1774522095; 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=0q3CSNpbXi5lOGrcvXbX8mvLw/thJvXIjpsnNa/bq6w=; b=TORcYEjjiXMIeWXLOD/kNKfxS4S1I0a8T8dEnEbGvFq8D2dM8brhiDM9tH8ki0mRm7i+Hs GlydInhZgclvF6FKVvsVZ6BszghbkdhXZXZ0SZ0fNu0SpRpgWqghJ10YyEUqrDU0A01KQc pMOzO9PK2QfWWcggAQKWQaB1wPjMMqM= 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-584-H2PjY8ChMyuS7rT40AhezQ-1; Thu, 26 Mar 2026 06:48:11 -0400 X-MC-Unique: H2PjY8ChMyuS7rT40AhezQ-1 X-Mimecast-MFC-AGG-ID: H2PjY8ChMyuS7rT40AhezQ_1774522089 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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 E6D89180034E; Thu, 26 Mar 2026 10:48:08 +0000 (UTC) Received: from warthog.procyon.org.com (unknown [10.44.33.121]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 783F11955F25; Thu, 26 Mar 2026 10:48:02 +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 , Eric Van Hensbergen , Dominique Martinet , Ilya Dryomov , Trond Myklebust , 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, Paulo Alcantara Subject: [PATCH 14/26] netfs: Add a function to extract from an iter into a bvecq Date: Thu, 26 Mar 2026 10:45:29 +0000 Message-ID: <20260326104544.509518-15-dhowells@redhat.com> In-Reply-To: <20260326104544.509518-1-dhowells@redhat.com> References: <20260326104544.509518-1-dhowells@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Content-Type: text/plain; charset="utf-8" Add a function to extract a slice of data from an iterator of any type into a bvec queue chain. Signed-off-by: David Howells cc: Paulo Alcantara cc: Matthew Wilcox cc: Christoph Hellwig cc: Steve French cc: linux-cifs@vger.kernel.org cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org --- fs/netfs/iterator.c | 123 ++++++++++++++++++++++++++++++++++++++++++ include/linux/netfs.h | 3 ++ 2 files changed, 126 insertions(+) diff --git a/fs/netfs/iterator.c b/fs/netfs/iterator.c index adca78747f23..e77fd39327c2 100644 --- a/fs/netfs/iterator.c +++ b/fs/netfs/iterator.c @@ -13,6 +13,129 @@ #include #include "internal.h" =20 +/** + * netfs_extract_iter - Extract the pages from an iterator into a bvecq + * @orig: The original iterator + * @orig_len: The amount of iterator to copy + * @max_segs: Maximum number of contiguous segments + * @fpos: Starting file position to label the bvecq with + * @_bvecq_head: Where to cache the bvec queue + * @extraction_flags: Flags to qualify the request + * + * Extract the page fragments from the given amount of the source iterator= and + * build bvec queue that refers to all of those bits. This allows the ori= ginal + * iterator to disposed of. + * + * @extraction_flags can have ITER_ALLOW_P2PDMA set to request peer-to-pee= r DMA be + * allowed on the pages extracted. + * + * On success, the amount of data in the bvec is returned, the original + * iterator will have been advanced by the amount extracted. + * + * The bvecq segments are marked with indications on how to get clean up t= he + * extracted fragments. + */ +ssize_t netfs_extract_iter(struct iov_iter *orig, size_t orig_len, size_t = max_segs, + unsigned long long fpos, struct bvecq **_bvecq_head, + iov_iter_extraction_t extraction_flags) +{ + struct bvecq *bq_tail =3D NULL; + ssize_t ret =3D 0; + size_t extracted =3D 0, nr_pages; + + _enter("{%u,%zx},%zx", orig->iter_type, orig->count, orig_len); + + WARN_ON_ONCE(orig_len > orig->count); + + nr_pages =3D iov_iter_npages(orig, max_segs ?: INT_MAX); + if (WARN_ON(nr_pages =3D=3D 0) || + WARN_ON(nr_pages > max_segs)) + nr_pages =3D max_segs; + max_segs =3D nr_pages; + + do { + struct bvecq *bq; + + if (WARN_ON(max_segs =3D=3D 0)) + break; + + bq =3D bvecq_alloc_one(max_segs, GFP_NOFS); + if (!bq) { + ret =3D -ENOMEM; + break; + } + bq->free =3D user_backed_iter(orig); + bq->unpin =3D iov_iter_extract_will_pin(orig); + bq->prev =3D bq_tail; + bq->fpos =3D fpos + extracted; + + if (bq_tail) + bq_tail->next =3D bq; + else + *_bvecq_head =3D bq; + bq_tail =3D bq; + + if (orig_len =3D=3D 0) + break; + + struct bio_vec *bv =3D bq->bv; + do { + struct page **pages; + ssize_t got; + size_t offset; + size_t space =3D bq->max_slots - bq->nr_slots; + size_t bv_size =3D array_size(bq->max_slots, sizeof(*bv)); + size_t pg_size =3D array_size(space, sizeof(*pages)); + + /* Put the page list at the end of the bvec list + * storage. bvec elements are larger than page + * pointers, so as long as we work 0->last, we should + * be fine. + */ + pages =3D (void *)bv + bv_size - pg_size; + + got =3D iov_iter_extract_pages(orig, &pages, orig_len, + space, extraction_flags, &offset); + if (got < 0) { + ret =3D got; + goto out; + } + + if (got =3D=3D 0) { + pr_err("extract_pages gave nothing from %zu, %zu\n", + extracted, orig_len); + ret =3D -EIO; + goto out; + } + + if (got > orig_len - extracted) { + pr_err("extract_pages rc=3D%zd more than %zu\n", + got, orig_len); + goto out; + } + + extracted +=3D got; + orig_len -=3D got; + + do { + size_t len =3D umin(got, PAGE_SIZE - offset); + + BUG_ON(bq->nr_slots >=3D bq->max_slots); + + bvec_set_page(&bq->bv[bq->nr_slots], + *pages++, len, offset); + bq->nr_slots++; + got -=3D len; + offset =3D 0; + } while (got > 0); + } while (orig_len > 0 && !bvecq_is_full(bq)); + } while (orig_len > 0 && max_segs > 0); + +out: + return extracted ?: ret; +} +EXPORT_SYMBOL_GPL(netfs_extract_iter); + /** * netfs_extract_user_iter - Extract the pages from a user iterator into a= bvec * @orig: The original iterator diff --git a/include/linux/netfs.h b/include/linux/netfs.h index 5bc48aacf7f6..b4602f7b6431 100644 --- a/include/linux/netfs.h +++ b/include/linux/netfs.h @@ -445,6 +445,9 @@ void netfs_get_subrequest(struct netfs_io_subrequest *s= ubreq, enum netfs_sreq_ref_trace what); void netfs_put_subrequest(struct netfs_io_subrequest *subreq, enum netfs_sreq_ref_trace what); +ssize_t netfs_extract_iter(struct iov_iter *orig, size_t orig_len, size_t = max_segs, + unsigned long long fpos, struct bvecq **_bvecq_head, + iov_iter_extraction_t extraction_flags); ssize_t netfs_extract_user_iter(struct iov_iter *orig, size_t orig_len, struct iov_iter *new, iov_iter_extraction_t extraction_flags);