From nobody Mon Nov 25 15:03:01 2024 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 309CB1DCB0D; Sun, 27 Oct 2024 14:23:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730038997; cv=none; b=vCVICtXpRCJn+HQ8Flg846RUiKtiB6BVBxGhsnFcxnltJTx2wzic+CXUNcM2bjfXuSf/lcHmthHSdT8wkBBfhGeyj25fDvbZIfTVJMwOdxVOxYePQ2xGN2OpHRaKxdKobuu6jEpZlMZoIO6azIXFnO1r1OXrZRn375UOC7HQTd8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730038997; c=relaxed/simple; bh=ZAkEvCDpOQpT4FqrkcEPmIofeDg0rb/b5+lEupSm25s=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=VC74ksCS/CoJ9Wx+FeY81aKcljslT/YyaDwtmUgG+4k2fCpHyI0+aCmLt7kQMEElPcFEfv3ofpF3b7fF02PFmw6E3N1W2t2ItC80aRSzI9BFQ1y2T+Dsgzpc5C6kCmJ0CMlNTbUZYO/gDy9kb6miICcLIsCBWDt9h70g7NNhHIw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=GU2WiE85; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="GU2WiE85" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 38793C4CEC3; Sun, 27 Oct 2024 14:23:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1730038997; bh=ZAkEvCDpOQpT4FqrkcEPmIofeDg0rb/b5+lEupSm25s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GU2WiE85QkyrGZabT77HMzH4RzcXBtUoK7DX8razab6E7GlTeZ2LQTeNI7ZRCEXcF +9yMHm9zDo08nuNcPNZNSsuaYkBUL9ipGLwLInfLmk0HejWEa8WPu1R8UqdKOsPV74 Z5wpY7UYyju99OwvD8w7GPbHNbCOK/zLgPk0s2GMr97M3wN8lKofvcDQjgjNlAIopH eIYUU6O634Ehr1WlX/W3GKJbeoFI2GpQCheDt+O+VjGAz5sar3RgcEymVxHQmnOdc4 uO+VYU+gZUk1F3VsP3juUi2vi+UCZ40ddUDVpK0TRukr1wrJIDD2IoyIOcFlFa0aTT I1l2OPb8MTV4g== From: Leon Romanovsky To: Jens Axboe , Jason Gunthorpe , Robin Murphy , Joerg Roedel , Will Deacon , Christoph Hellwig , Sagi Grimberg Cc: Keith Busch , Bjorn Helgaas , Logan Gunthorpe , Yishai Hadas , Shameer Kolothum , Kevin Tian , Alex Williamson , Marek Szyprowski , =?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?= , Andrew Morton , Jonathan Corbet , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-rdma@vger.kernel.org, iommu@lists.linux.dev, linux-nvme@lists.infradead.org, linux-pci@vger.kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org Subject: [RFC PATCH 3/7] blk-mq: add a dma mapping iterator Date: Sun, 27 Oct 2024 16:21:56 +0200 Message-ID: <9b7c6203fbbae90821f2220dba1bd600e3bd23ba.1730037261.git.leon@kernel.org> X-Mailer: git-send-email 2.46.2 In-Reply-To: References: 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 Content-Type: text/plain; charset="utf-8" From: Christoph Hellwig blk_rq_map_sg is maze of nested loops. Untangle it by creating an iterator that returns [paddr,len] tuples for DMA mapping, and then implement the DMA logic on top of this. This not only removes code at the source level, but also generates nicer binary code: $ size block/blk-merge.o.* text data bss dec hex filename 10001 432 0 10433 28c1 block/blk-merge.o.new 10317 468 0 10785 2a21 block/blk-merge.o.old Last but not least it will be used as a building block for a new DMA mapping helper that doesn't rely on struct scatterlist. Signed-off-by: Christoph Hellwig Signed-off-by: Leon Romanovsky --- block/blk-merge.c | 182 ++++++++++++++++++++-------------------------- 1 file changed, 77 insertions(+), 105 deletions(-) diff --git a/block/blk-merge.c b/block/blk-merge.c index ad763ec313b6..b63fd754a5de 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -451,137 +451,109 @@ unsigned int blk_recalc_rq_segments(struct request = *rq) return nr_phys_segs; } =20 -static inline struct scatterlist *blk_next_sg(struct scatterlist **sg, - struct scatterlist *sglist) +struct phys_vec { + phys_addr_t paddr; + u32 len; +}; + +static bool blk_map_iter_next(struct request *req, + struct req_iterator *iter, struct phys_vec *vec) { - if (!*sg) - return sglist; + unsigned int max_size; + struct bio_vec bv; =20 /* - * If the driver previously mapped a shorter list, we could see a - * termination bit prematurely unless it fully inits the sg table - * on each mapping. We KNOW that there must be more entries here - * or the driver would be buggy, so force clear the termination bit - * to avoid doing a full sg_init_table() in drivers for each command. + * For special payload requests there only is a single segment. Return + * it now and make sure blk_phys_iter_next stop iterating. */ - sg_unmark_end(*sg); - return sg_next(*sg); -} + if (req->rq_flags & RQF_SPECIAL_PAYLOAD) { + if (!iter->bio) + return false; + vec->paddr =3D bvec_phys(&req->special_vec); + vec->len =3D req->special_vec.bv_len; + iter->bio =3D NULL; + return true; + } =20 -static unsigned blk_bvec_map_sg(struct request_queue *q, - struct bio_vec *bvec, struct scatterlist *sglist, - struct scatterlist **sg) -{ - unsigned nbytes =3D bvec->bv_len; - unsigned nsegs =3D 0, total =3D 0; + if (!iter->iter.bi_size) + return false; =20 - while (nbytes > 0) { - unsigned offset =3D bvec->bv_offset + total; - unsigned len =3D get_max_segment_size(&q->limits, - bvec_phys(bvec) + total, nbytes); - struct page *page =3D bvec->bv_page; + bv =3D mp_bvec_iter_bvec(iter->bio->bi_io_vec, iter->iter); + vec->paddr =3D bvec_phys(&bv); + max_size =3D get_max_segment_size(&req->q->limits, vec->paddr, UINT_MAX); + bv.bv_len =3D min(bv.bv_len, max_size); + bio_advance_iter_single(iter->bio, &iter->iter, bv.bv_len); =20 - /* - * Unfortunately a fair number of drivers barf on scatterlists - * that have an offset larger than PAGE_SIZE, despite other - * subsystems dealing with that invariant just fine. For now - * stick to the legacy format where we never present those from - * the block layer, but the code below should be removed once - * these offenders (mostly MMC/SD drivers) are fixed. - */ - page +=3D (offset >> PAGE_SHIFT); - offset &=3D ~PAGE_MASK; + /* + * If we are entirely done with this bi_io_vec entry, check if the next + * one could be merged into it. This typically happens when moving to + * the next bio, but some callers also don't pack bvecs tight. + */ + while (!iter->iter.bi_size || !iter->iter.bi_bvec_done) { + struct bio_vec next; + + if (!iter->iter.bi_size) { + if (!iter->bio->bi_next) + break; + iter->bio =3D iter->bio->bi_next; + iter->iter =3D iter->bio->bi_iter; + } =20 - *sg =3D blk_next_sg(sg, sglist); - sg_set_page(*sg, page, len, offset); + next =3D mp_bvec_iter_bvec(iter->bio->bi_io_vec, iter->iter); + if (bv.bv_len + next.bv_len > max_size || + !biovec_phys_mergeable(req->q, &bv, &next)) + break; =20 - total +=3D len; - nbytes -=3D len; - nsegs++; + bv.bv_len +=3D next.bv_len; + bio_advance_iter_single(iter->bio, &iter->iter, next.bv_len); } =20 - return nsegs; + vec->len =3D bv.bv_len; + return true; } =20 -static inline int __blk_bvec_map_sg(struct bio_vec bv, - struct scatterlist *sglist, struct scatterlist **sg) -{ - *sg =3D blk_next_sg(sg, sglist); - sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset); - return 1; -} +#define blk_phys_to_page(_paddr) \ + (pfn_to_page(__phys_to_pfn(_paddr))) =20 -/* only try to merge bvecs into one sg if they are from two bios */ -static inline bool -__blk_segment_map_sg_merge(struct request_queue *q, struct bio_vec *bvec, - struct bio_vec *bvprv, struct scatterlist **sg) +static inline struct scatterlist *blk_next_sg(struct scatterlist **sg, + struct scatterlist *sglist) { - - int nbytes =3D bvec->bv_len; - if (!*sg) - return false; - - if ((*sg)->length + nbytes > queue_max_segment_size(q)) - return false; - - if (!biovec_phys_mergeable(q, bvprv, bvec)) - return false; - - (*sg)->length +=3D nbytes; - - return true; -} - -static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio, - struct scatterlist *sglist, - struct scatterlist **sg) -{ - struct bio_vec bvec, bvprv =3D { NULL }; - struct bvec_iter iter; - int nsegs =3D 0; - bool new_bio =3D false; - - for_each_bio(bio) { - bio_for_each_bvec(bvec, bio, iter) { - /* - * Only try to merge bvecs from two bios given we - * have done bio internal merge when adding pages - * to bio - */ - if (new_bio && - __blk_segment_map_sg_merge(q, &bvec, &bvprv, sg)) - goto next_bvec; - - if (bvec.bv_offset + bvec.bv_len <=3D PAGE_SIZE) - nsegs +=3D __blk_bvec_map_sg(bvec, sglist, sg); - else - nsegs +=3D blk_bvec_map_sg(q, &bvec, sglist, sg); - next_bvec: - new_bio =3D false; - } - if (likely(bio->bi_iter.bi_size)) { - bvprv =3D bvec; - new_bio =3D true; - } - } + return sglist; =20 - return nsegs; + /* + * If the driver previously mapped a shorter list, we could see a + * termination bit prematurely unless it fully inits the sg table + * on each mapping. We KNOW that there must be more entries here + * or the driver would be buggy, so force clear the termination bit + * to avoid doing a full sg_init_table() in drivers for each command. + */ + sg_unmark_end(*sg); + return sg_next(*sg); } =20 /* - * map a request to scatterlist, return number of sg entries setup. Caller - * must make sure sg can hold rq->nr_phys_segments entries + * Map a request to scatterlist, return number of sg entries setup. Caller + * must make sure sg can hold rq->nr_phys_segments entries. */ int __blk_rq_map_sg(struct request_queue *q, struct request *rq, struct scatterlist *sglist, struct scatterlist **last_sg) { + struct req_iterator iter =3D { + .bio =3D rq->bio, + .iter =3D rq->bio->bi_iter, + }; + struct phys_vec vec; int nsegs =3D 0; =20 - if (rq->rq_flags & RQF_SPECIAL_PAYLOAD) - nsegs =3D __blk_bvec_map_sg(rq->special_vec, sglist, last_sg); - else if (rq->bio) - nsegs =3D __blk_bios_map_sg(q, rq->bio, sglist, last_sg); + while (blk_map_iter_next(rq, &iter, &vec)) { + struct page *page =3D blk_phys_to_page(vec.paddr); + unsigned int offset =3D offset_in_page(vec.paddr); + + *last_sg =3D blk_next_sg(last_sg, sglist); + sg_set_page(*last_sg, page, vec.len, offset); + nsegs++; + } =20 if (*last_sg) sg_mark_end(*last_sg); --=20 2.46.2