From patchwork Tue Dec 3 22:00:07 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kent Overstreet X-Patchwork-Id: 3278981 X-Patchwork-Delegate: snitzer@redhat.com Return-Path: X-Original-To: patchwork-dm-devel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 9318A9F377 for ; Tue, 3 Dec 2013 22:04:43 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 164C020461 for ; Tue, 3 Dec 2013 22:04:42 +0000 (UTC) Received: from mx4-phx2.redhat.com (mx4-phx2.redhat.com [209.132.183.25]) by mail.kernel.org (Postfix) with ESMTP id 589CC20465 for ; Tue, 3 Dec 2013 22:04:40 +0000 (UTC) Received: from lists01.pubmisc.prod.ext.phx2.redhat.com (lists01.pubmisc.prod.ext.phx2.redhat.com [10.5.19.33]) by mx4-phx2.redhat.com (8.13.8/8.13.8) with ESMTP id rB3M0l3B011874; Tue, 3 Dec 2013 17:00:49 -0500 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by lists01.pubmisc.prod.ext.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id rB3M0jo4008197 for ; Tue, 3 Dec 2013 17:00:45 -0500 Received: from mx1.redhat.com (ext-mx14.extmail.prod.ext.phx2.redhat.com [10.5.110.19]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id rB3M0iCN009795 for ; Tue, 3 Dec 2013 17:00:45 -0500 Received: from mail-pb0-f54.google.com (mail-pb0-f54.google.com [209.85.160.54]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id rB3M0dSR014301 for ; Tue, 3 Dec 2013 17:00:40 -0500 Received: by mail-pb0-f54.google.com with SMTP id un15so22132937pbc.27 for ; Tue, 03 Dec 2013 14:00:39 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=+x4AC0blhZoKbs9/Js3W6Kb9srilEkWJECRwRVZg/l4=; b=XCpiaZsoYNuxQHTLUKK6HewaFnqsO+vYRm+cIE7QoS7WYAacFvw8JSrdZfzaOAo8vq SRZHh4H+8oefWWX2KQS9bsN0IJQAePRDVZ6V5ADn7WsHn0BT45DZukikDyvRU9H7tttd vbIdwqGaVVlAuk/BGGDAqmCDHPfbnfDAFwbGcDTfiBRUodcH904MDN/czMqLyugKpb/0 3M07jw2mG8VAoJEThJ/Ks1XqDagluFLUZNmLSx/JtK/ChLQPxAuIZ9GaNkJwSshYdliq aOVPXKGi0DgoQd3785dRuLpb/9XKEh7GEt6LTHV/ttmiffq4bEEi/xm9jtRIG8KLUcrb /rQg== X-Gm-Message-State: ALoCoQm+2GLQiZS2icGN7ps5CjEaRpnAxaFNW2InADUqvHlC0rJSwFiLYLy9ogEwdmX5gC/m2O7s X-Received: by 10.66.234.131 with SMTP id ue3mr76251731pac.35.1386108039209; Tue, 03 Dec 2013 14:00:39 -0800 (PST) Received: from kmo.daterainc.com ([157.22.22.146]) by mx.google.com with ESMTPSA id qw8sm132426211pbb.27.2013.12.03.14.00.37 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 03 Dec 2013 14:00:38 -0800 (PST) From: Kent Overstreet To: axboe@kernel.dk, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Date: Tue, 3 Dec 2013 14:00:07 -0800 Message-Id: <1386108017-27964-2-git-send-email-kmo@daterainc.com> In-Reply-To: <1386108017-27964-1-git-send-email-kmo@daterainc.com> References: <1386108017-27964-1-git-send-email-kmo@daterainc.com> X-RedHat-Spam-Score: -2.699 (BAYES_00, DCC_REPUT_13_19, RCVD_IN_DNSWL_LOW, URIBL_BLOCKED) X-Scanned-By: MIMEDefang 2.68 on 10.5.11.24 X-Scanned-By: MIMEDefang 2.68 on 10.5.110.19 X-loop: dm-devel@redhat.com Cc: shaggy@kernel.org, zab@redhat.com, dm-devel@redhat.com, hch@infradead.org, clm@fb.com, Kent Overstreet , viro@zeniv.linux.org.uk, Alasdair Kergon Subject: [dm-devel] [PATCH 01/11] block: Make generic_make_request handle arbitrary sized bios X-BeenThere: dm-devel@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk Reply-To: device-mapper development List-Id: device-mapper development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP The way the block layer is currently written, it goes to great lengths to avoid having to split bios; upper layer code (such as bio_add_page()) checks what the underlying device can handle and tries to always create bios that don't need to be split. But this approach becomes unwieldy and eventually breaks down with stacked devices and devices with dynamic limits, and it adds a lot of complexity. If the block layer could split bios as needed, we could eliminate a lot of complexity elsewhere - particularly in stacked drivers. Code that creates bios can then create whatever size bios are convenient, and more importantly stacked drivers don't have to deal with both their own bio size limitations and the limitations of the (potentially multiple) devices underneath them. In the future this will let us delete merge_bvec_fn and a bunch of other code. We do this by adding calls to blk_queue_split() to the various make_request functions that need it - a few can already handle arbitrary size bios. Note that we add the call _after_ any call to blk_queue_bounce(); this means that blk_queue_split() and blk_recalc_rq_segments() don't need to be concerned with bouncing affecting segment merging. Some make_request_fns were simple enough to audit and verify they don't need blk_queue_split() calls. The skipped ones are: * nfhd_make_request (arch/m68k/emu/nfblock.c) * axon_ram_make_request (arch/powerpc/sysdev/axonram.c) * simdisk_make_request (arch/xtensa/platforms/iss/simdisk.c) * brd_make_request (ramdisk - drivers/block/brd.c) * loop_make_request * null_queue_bio * bcache's make_request fns Some others are almost certainly safe to remove now, but will be left for future patches. Signed-off-by: Kent Overstreet Cc: Jens Axboe Cc: Neil Brown Cc: Alasdair Kergon Cc: dm-devel@redhat.com --- block/blk-core.c | 19 ++-- block/blk-merge.c | 150 ++++++++++++++++++++++++++-- block/blk-mq.c | 2 + drivers/block/drbd/drbd_req.c | 2 + drivers/block/mtip32xx/mtip32xx.c | 6 +- drivers/block/nvme-core.c | 2 + drivers/block/pktcdvd.c | 6 +- drivers/block/ps3vram.c | 2 + drivers/block/rsxx/dev.c | 2 + drivers/block/umem.c | 2 + drivers/md/dm.c | 2 + drivers/md/md.c | 2 + drivers/s390/block/dcssblk.c | 2 + drivers/s390/block/xpram.c | 2 + drivers/staging/lustre/lustre/llite/lloop.c | 2 + drivers/staging/zram/zram_drv.c | 2 + include/linux/blkdev.h | 3 + 17 files changed, 185 insertions(+), 23 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index 5da8e90..5cc7171 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -566,6 +566,10 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id) if (q->id < 0) goto fail_c; + q->bio_split = bioset_create(4, 0); + if (!q->bio_split) + goto fail_id; + q->backing_dev_info.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE; q->backing_dev_info.state = 0; @@ -575,7 +579,7 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id) err = bdi_init(&q->backing_dev_info); if (err) - goto fail_id; + goto fail_split; setup_timer(&q->backing_dev_info.laptop_mode_wb_timer, laptop_mode_timer_fn, (unsigned long) q); @@ -620,6 +624,8 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id) fail_bdi: bdi_destroy(&q->backing_dev_info); +fail_split: + bioset_free(q->bio_split); fail_id: ida_simple_remove(&blk_queue_ida, q->id); fail_c: @@ -1472,6 +1478,8 @@ void blk_queue_bio(struct request_queue *q, struct bio *bio) struct request *req; unsigned int request_count = 0; + blk_queue_split(q, &bio, q->bio_split); + /* * low level driver can indicate that it wants pages above a * certain limit bounced to low memory (ie for highmem, or even @@ -1694,15 +1702,6 @@ generic_make_request_checks(struct bio *bio) goto end_io; } - if (likely(bio_is_rw(bio) && - nr_sectors > queue_max_hw_sectors(q))) { - printk(KERN_ERR "bio too big device %s (%u > %u)\n", - bdevname(bio->bi_bdev, b), - bio_sectors(bio), - queue_max_hw_sectors(q)); - goto end_io; - } - part = bio->bi_bdev->bd_part; if (should_fail_request(part, bio->bi_iter.bi_size) || should_fail_request(&part_to_disk(part)->part0, diff --git a/block/blk-merge.c b/block/blk-merge.c index 8f8adaa..c1403ee 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -9,11 +9,149 @@ #include "blk.h" +static struct bio *blk_bio_discard_split(struct request_queue *q, + struct bio *bio, + struct bio_set *bs) +{ + unsigned int max_discard_sectors, granularity; + int alignment; + sector_t tmp; + unsigned split_sectors; + + /* Zero-sector (unknown) and one-sector granularities are the same. */ + granularity = max(q->limits.discard_granularity >> 9, 1U); + + max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9); + max_discard_sectors -= max_discard_sectors % granularity; + + if (unlikely(!max_discard_sectors)) { + /* XXX: warn */ + return NULL; + } + + if (bio_sectors(bio) <= max_discard_sectors) + return NULL; + + split_sectors = max_discard_sectors; + + /* + * If the next starting sector would be misaligned, stop the discard at + * the previous aligned sector. + */ + alignment = (q->limits.discard_alignment >> 9) % granularity; + + tmp = bio->bi_iter.bi_sector + split_sectors - alignment; + tmp = sector_div(tmp, granularity); + + if (split_sectors > tmp) + split_sectors -= tmp; + + return bio_split(bio, split_sectors, GFP_NOIO, bs); +} + +static struct bio *blk_bio_write_same_split(struct request_queue *q, + struct bio *bio, + struct bio_set *bs) +{ + if (!q->limits.max_write_same_sectors) + return NULL; + + if (bio_sectors(bio) <= q->limits.max_write_same_sectors) + return NULL; + + return bio_split(bio, q->limits.max_write_same_sectors, GFP_NOIO, bs); +} + +static struct bio *blk_bio_segment_split(struct request_queue *q, + struct bio *bio, + struct bio_set *bs) +{ + struct bio *split; + struct bio_vec bv, bvprv; + struct bvec_iter iter; + unsigned seg_size = 0, nsegs = 0; + int prev = 0; + + struct bvec_merge_data bvm = { + .bi_bdev = bio->bi_bdev, + .bi_sector = bio->bi_iter.bi_sector, + .bi_size = 0, + .bi_rw = bio->bi_rw, + }; + + bio_for_each_segment(bv, bio, iter) { + if (q->merge_bvec_fn && + q->merge_bvec_fn(q, &bvm, &bv) < (int) bv.bv_len) + goto split; + + bvm.bi_size += bv.bv_len; + + if (bvm.bi_size >> 9 > queue_max_sectors(q)) + goto split; + + if (prev && blk_queue_cluster(q)) { + if (seg_size + bv.bv_len > queue_max_segment_size(q)) + goto new_segment; + if (!BIOVEC_PHYS_MERGEABLE(&bvprv, &bv)) + goto new_segment; + if (!BIOVEC_SEG_BOUNDARY(q, &bvprv, &bv)) + goto new_segment; + + seg_size += bv.bv_len; + bvprv = bv; + prev = 1; + continue; + } +new_segment: + if (nsegs == queue_max_segments(q)) + goto split; + + nsegs++; + bvprv = bv; + prev = 1; + seg_size = bv.bv_len; + } + + return NULL; +split: + split = bio_clone_bioset(bio, GFP_NOIO, bs); + + split->bi_iter.bi_size -= iter.bi_size; + bio->bi_iter = iter; + + if (bio_integrity(bio)) { + bio_integrity_advance(bio, split->bi_iter.bi_size); + bio_integrity_trim(split, 0, bio_sectors(split)); + } + + return split; +} + +void blk_queue_split(struct request_queue *q, struct bio **bio, + struct bio_set *bs) +{ + struct bio *split; + + if ((*bio)->bi_rw & REQ_DISCARD) + split = blk_bio_discard_split(q, *bio, bs); + else if ((*bio)->bi_rw & REQ_WRITE_SAME) + split = blk_bio_write_same_split(q, *bio, bs); + else + split = blk_bio_segment_split(q, *bio, q->bio_split); + + if (split) { + bio_chain(split, *bio); + generic_make_request(*bio); + *bio = split; + } +} +EXPORT_SYMBOL(blk_queue_split); + static unsigned int __blk_recalc_rq_segments(struct request_queue *q, struct bio *bio) { struct bio_vec bv, bvprv = { NULL }; - int cluster, high, highprv = 1; + int cluster, prev = 0; unsigned int seg_size, nr_phys_segs; struct bio *fbio, *bbio; struct bvec_iter iter; @@ -27,13 +165,7 @@ static unsigned int __blk_recalc_rq_segments(struct request_queue *q, nr_phys_segs = 0; for_each_bio(bio) { bio_for_each_segment(bv, bio, iter) { - /* - * the trick here is making sure that a high page is - * never considered part of another segment, since that - * might change with the bounce page. - */ - high = page_to_pfn(bv.bv_page) > queue_bounce_pfn(q); - if (!high && !highprv && cluster) { + if (prev && cluster) { if (seg_size + bv.bv_len > queue_max_segment_size(q)) goto new_segment; @@ -53,8 +185,8 @@ new_segment: nr_phys_segs++; bvprv = bv; + prev = 1; seg_size = bv.bv_len; - highprv = high; } bbio = bio; } diff --git a/block/blk-mq.c b/block/blk-mq.c index e4fbcc3..d29be09 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -912,6 +912,8 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio) blk_queue_bounce(q, &bio); + blk_queue_split(q, &bio, q->bio_split); + if (use_plug && blk_attempt_plug_merge(q, bio, &request_count)) return; diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c index 104a040..941a69c 100644 --- a/drivers/block/drbd/drbd_req.c +++ b/drivers/block/drbd/drbd_req.c @@ -1275,6 +1275,8 @@ void drbd_make_request(struct request_queue *q, struct bio *bio) struct drbd_conf *mdev = (struct drbd_conf *) q->queuedata; unsigned long start_time; + blk_queue_split(q, &bio, q->bio_split); + start_time = jiffies; /* diff --git a/drivers/block/mtip32xx/mtip32xx.c b/drivers/block/mtip32xx/mtip32xx.c index 52b2f2a..3ff8120 100644 --- a/drivers/block/mtip32xx/mtip32xx.c +++ b/drivers/block/mtip32xx/mtip32xx.c @@ -3967,6 +3967,10 @@ static void mtip_make_request(struct request_queue *queue, struct bio *bio) int nents = 0; int tag = 0, unaligned = 0; + blk_queue_bounce(queue, &bio); + + blk_queue_split(queue, &bio, queue->bio_split); + if (unlikely(dd->dd_flag & MTIP_DDF_STOP_IO)) { if (unlikely(test_bit(MTIP_DDF_REMOVE_PENDING_BIT, &dd->dd_flag))) { @@ -4016,8 +4020,6 @@ static void mtip_make_request(struct request_queue *queue, struct bio *bio) sg = mtip_hw_get_scatterlist(dd, &tag, unaligned); if (likely(sg != NULL)) { - blk_queue_bounce(queue, &bio); - if (unlikely((bio)->bi_vcnt > MTIP_MAX_SG)) { dev_warn(&dd->pdev->dev, "Maximum number of SGL entries exceeded\n"); diff --git a/drivers/block/nvme-core.c b/drivers/block/nvme-core.c index 1f14ac4..cfb8f7b 100644 --- a/drivers/block/nvme-core.c +++ b/drivers/block/nvme-core.c @@ -707,6 +707,8 @@ static void nvme_make_request(struct request_queue *q, struct bio *bio) struct nvme_queue *nvmeq = get_nvmeq(ns->dev); int result = -EBUSY; + blk_queue_split(q, &bio, q->bio_split); + if (!nvmeq) { put_nvmeq(NULL); bio_endio(bio, -EIO); diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c index 3dda09a..38799f8 100644 --- a/drivers/block/pktcdvd.c +++ b/drivers/block/pktcdvd.c @@ -2442,6 +2442,10 @@ static void pkt_make_request(struct request_queue *q, struct bio *bio) char b[BDEVNAME_SIZE]; struct bio *split; + blk_queue_bounce(q, &bio); + + blk_queue_split(q, &bio, q->bio_split); + pd = q->queuedata; if (!pd) { pr_err("%s incorrect request queue\n", @@ -2472,8 +2476,6 @@ static void pkt_make_request(struct request_queue *q, struct bio *bio) goto end_io; } - blk_queue_bounce(q, &bio); - do { sector_t zone = get_zone(bio->bi_iter.bi_sector, pd); sector_t last_zone = get_zone(bio_end_sector(bio) - 1, pd); diff --git a/drivers/block/ps3vram.c b/drivers/block/ps3vram.c index ef45cfb..a995972 100644 --- a/drivers/block/ps3vram.c +++ b/drivers/block/ps3vram.c @@ -603,6 +603,8 @@ static void ps3vram_make_request(struct request_queue *q, struct bio *bio) struct ps3vram_priv *priv = ps3_system_bus_get_drvdata(dev); int busy; + blk_queue_split(q, &bio, q->bio_split); + dev_dbg(&dev->core, "%s\n", __func__); spin_lock_irq(&priv->lock); diff --git a/drivers/block/rsxx/dev.c b/drivers/block/rsxx/dev.c index 2839d37..ff074a3 100644 --- a/drivers/block/rsxx/dev.c +++ b/drivers/block/rsxx/dev.c @@ -169,6 +169,8 @@ static void rsxx_make_request(struct request_queue *q, struct bio *bio) struct rsxx_bio_meta *bio_meta; int st = -EINVAL; + blk_queue_split(q, &bio, q->bio_split); + might_sleep(); if (!card) diff --git a/drivers/block/umem.c b/drivers/block/umem.c index 4cf81b5..13d577c 100644 --- a/drivers/block/umem.c +++ b/drivers/block/umem.c @@ -531,6 +531,8 @@ static void mm_make_request(struct request_queue *q, struct bio *bio) (unsigned long long)bio->bi_iter.bi_sector, bio->bi_iter.bi_size); + blk_queue_split(q, &bio, q->bio_split); + spin_lock_irq(&card->lock); *card->biotail = bio; bio->bi_next = NULL; diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 44a2fa6..0bfb050 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -1500,6 +1500,8 @@ static void dm_request(struct request_queue *q, struct bio *bio) { struct mapped_device *md = q->queuedata; + blk_queue_split(q, &bio, q->bio_split); + if (dm_request_based(md)) blk_queue_bio(q, bio); else diff --git a/drivers/md/md.c b/drivers/md/md.c index b07fed3..de39a8a 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -256,6 +256,8 @@ static void md_make_request(struct request_queue *q, struct bio *bio) int cpu; unsigned int sectors; + blk_queue_split(q, &bio, q->bio_split); + if (mddev == NULL || mddev->pers == NULL || !mddev->ready) { bio_io_error(bio); diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c index ebf41e2..db33cd3 100644 --- a/drivers/s390/block/dcssblk.c +++ b/drivers/s390/block/dcssblk.c @@ -815,6 +815,8 @@ dcssblk_make_request(struct request_queue *q, struct bio *bio) unsigned long source_addr; unsigned long bytes_done; + blk_queue_split(q, &bio, q->bio_split); + bytes_done = 0; dev_info = bio->bi_bdev->bd_disk->private_data; if (dev_info == NULL) diff --git a/drivers/s390/block/xpram.c b/drivers/s390/block/xpram.c index 3e530f9..3ae29a0 100644 --- a/drivers/s390/block/xpram.c +++ b/drivers/s390/block/xpram.c @@ -190,6 +190,8 @@ static void xpram_make_request(struct request_queue *q, struct bio *bio) unsigned long page_addr; unsigned long bytes; + blk_queue_split(q, &bio, q->bio_split); + if ((bio->bi_iter.bi_sector & 7) != 0 || (bio->bi_iter.bi_size & 4095) != 0) /* Request is not page-aligned. */ diff --git a/drivers/staging/lustre/lustre/llite/lloop.c b/drivers/staging/lustre/lustre/llite/lloop.c index 581ff78..776d44c 100644 --- a/drivers/staging/lustre/lustre/llite/lloop.c +++ b/drivers/staging/lustre/lustre/llite/lloop.c @@ -344,6 +344,8 @@ static void loop_make_request(struct request_queue *q, struct bio *old_bio) int rw = bio_rw(old_bio); int inactive; + blk_queue_split(q, &old_bio, q->bio_split); + if (!lo) goto err; diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c index 6f98838..56eb09e 100644 --- a/drivers/staging/zram/zram_drv.c +++ b/drivers/staging/zram/zram_drv.c @@ -734,6 +734,8 @@ static void zram_make_request(struct request_queue *queue, struct bio *bio) { struct zram *zram = queue->queuedata; + blk_queue_split(queue, &bio, queue->bio_split); + down_read(&zram->init_lock); if (unlikely(!zram->init_done)) goto error; diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 02cb6f0..88d4e7b 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -476,6 +476,7 @@ struct request_queue { wait_queue_head_t mq_freeze_wq; struct percpu_counter mq_usage_counter; struct list_head all_q_node; + struct bio_set *bio_split; }; #define QUEUE_FLAG_QUEUED 1 /* uses generic tag queueing */ @@ -787,6 +788,8 @@ extern void blk_rq_unprep_clone(struct request *rq); extern int blk_insert_cloned_request(struct request_queue *q, struct request *rq); extern void blk_delay_queue(struct request_queue *, unsigned long); +extern void blk_queue_split(struct request_queue *, struct bio **, + struct bio_set *); extern void blk_recount_segments(struct request_queue *, struct bio *); extern int scsi_verify_blk_ioctl(struct block_device *, unsigned int); extern int scsi_cmd_blk_ioctl(struct block_device *, fmode_t,