From nobody Mon Nov 25 22:54:14 2024 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 CDA78157A72; Thu, 24 Oct 2024 05:00:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729746032; cv=none; b=J03gC5+XjIwMysAAcmaydm5whx08b5J2ktk5eod7WrVwdy+jkarYMhZQtj/kr7Qj3qPKRlPbUygoGPxfIKurcN6F2FYGVMsbVjtUM6rJCKntfgaqaMLvJtlJKg6S7wErWtwHh/mf4fjHNcvupoEJdWtJjyb3h7yk/6zFtxy/mvE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729746032; c=relaxed/simple; bh=vOZlOfvvHlHdcmizotR254p75Ian99uDLg8Ra3nRPIM=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=R6X+73q4f62OxlLnTMmCKD6eI/aj05F39MD2/P1Vpce/R2dXTGN0/YpnKdXrx3dlK73dSFDcrBwwKOX0BcUgISLYrkY+z9F8p/IiCYkHOrPUbOJcUDcNA3E3S6q4C1ryzWCJQEayP+1dIJydaG4MKrpP4VtIu0VXbUKZJBtAaRI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=Shq5lTT3; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="Shq5lTT3" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Content-Transfer-Encoding: MIME-Version:Message-ID:Date:Subject:Cc:To:From:Sender:Reply-To:Content-Type: Content-ID:Content-Description:In-Reply-To:References; bh=33dh5ptf7K7+w6J4b7L5weA0XvmksgkwCzeOBkeP89o=; b=Shq5lTT3Kj73IdrJUEXNEZbe8q pxY0v9rSHfd+OEG3Vap2aTUNBgBxskWnC4J7jKlA5g1vJP6S1wQF6tIMUfrKxfdIydJHzuRThmhMp uB9t8wYEbf5RMCd80lFrBetdCWjX0qQEVj61kR7n5vbaafwWn2r3dPLgZvTJgchQ6LJDXAqVJ9lHi mwLANL5lUqJnEO4+AXOjmSxXivxvGmk21S7FmYNB/oOOeQ5prndkpIdw9VEgnai+2ca9eOgWedQwN OwxZKwn5V8X6x0AkEId2jV9BngwV+rVC14NXPFS+D6+tn8ytr8ej4Dv2IU86+K/dHB/3ykAafxRs+ 99z8jOgg==; Received: from 2a02-8389-2341-5b80-fb3e-99eb-94f3-ec06.cable.dynamic.v6.surfer.at ([2a02:8389:2341:5b80:fb3e:99eb:94f3:ec06] helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1t3pxR-0000000Gkoz-3sPl; Thu, 24 Oct 2024 05:00:26 +0000 From: Christoph Hellwig To: axboe@kernel.dk Cc: akpm@linux-foundation.org, viro@zeniv.linux.org.uk, dhowells@redhat.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, ming.lei@redhat.com Subject: [PATCH] iov_iter: don't require contiguous pages in iov_iter_extract_bvec_pages Date: Thu, 24 Oct 2024 07:00:15 +0200 Message-ID: <20241024050021.627350-1-hch@lst.de> X-Mailer: git-send-email 2.45.2 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-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Content-Type: text/plain; charset="utf-8" From: Ming Lei The iov_iter_extract_pages interface allows to return physically discontiguous pages, as long as all but the first and last page in the array are page aligned and page size. Rewrite iov_iter_extract_bvec_pages to take advantage of that instead of only returning ranges of physically contiguous pages. Signed-off-by: Ming Lei [hch: minor cleanups, new commit log] Signed-off-by: Christoph Hellwig --- lib/iov_iter.c | 67 +++++++++++++++++++++++++++++++++----------------- 1 file changed, 45 insertions(+), 22 deletions(-) diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 1abb32c0da50..9fc06f5fb748 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -1677,8 +1677,8 @@ static ssize_t iov_iter_extract_xarray_pages(struct i= ov_iter *i, } =20 /* - * Extract a list of contiguous pages from an ITER_BVEC iterator. This do= es - * not get references on the pages, nor does it get a pin on them. + * Extract a list of virtually contiguous pages from an ITER_BVEC iterator. + * This does not get references on the pages, nor does it get a pin on the= m. */ static ssize_t iov_iter_extract_bvec_pages(struct iov_iter *i, struct page ***pages, size_t maxsize, @@ -1686,35 +1686,58 @@ static ssize_t iov_iter_extract_bvec_pages(struct i= ov_iter *i, iov_iter_extraction_t extraction_flags, size_t *offset0) { - struct page **p, *page; - size_t skip =3D i->iov_offset, offset, size; - int k; + size_t skip =3D i->iov_offset, size =3D 0; + struct bvec_iter bi; + int k =3D 0; =20 - for (;;) { - if (i->nr_segs =3D=3D 0) - return 0; - size =3D min(maxsize, i->bvec->bv_len - skip); - if (size) - break; + if (i->nr_segs =3D=3D 0) + return 0; + + if (i->iov_offset =3D=3D i->bvec->bv_len) { i->iov_offset =3D 0; i->nr_segs--; i->bvec++; skip =3D 0; } + bi.bi_size =3D maxsize + skip; + bi.bi_bvec_done =3D skip; + + maxpages =3D want_pages_array(pages, maxsize, skip, maxpages); + + while (bi.bi_size && bi.bi_idx < i->nr_segs) { + struct bio_vec bv =3D bvec_iter_bvec(i->bvec, bi); + + /* + * The iov_iter_extract_pages interface only allows an offset + * into the first page. Break out of the loop if we see an + * offset into subsequent pages, the caller will have to call + * iov_iter_extract_pages again for the reminder. + */ + if (k) { + if (bv.bv_offset) + break; + } else { + *offset0 =3D bv.bv_offset; + } =20 - skip +=3D i->bvec->bv_offset; - page =3D i->bvec->bv_page + skip / PAGE_SIZE; - offset =3D skip % PAGE_SIZE; - *offset0 =3D offset; + (*pages)[k++] =3D bv.bv_page; + size +=3D bv.bv_len; =20 - maxpages =3D want_pages_array(pages, size, offset, maxpages); - if (!maxpages) - return -ENOMEM; - p =3D *pages; - for (k =3D 0; k < maxpages; k++) - p[k] =3D page + k; + if (k >=3D maxpages) + break; + + /* + * We are done when the end of the bvec doesn't align to a page + * boundary as that would create a hole in the returned space. + * The caller will handle this with another call to + * iov_iter_extract_pages. + */ + if (bv.bv_offset + bv.bv_len !=3D PAGE_SIZE) + break; + + bvec_iter_advance_single(i->bvec, &bi, bv.bv_len); + } =20 - size =3D min_t(size_t, size, maxpages * PAGE_SIZE - offset); iov_iter_advance(i, size); return size; } --=20 2.45.2