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Message-ID: <CAFR8uefzG0+YzerogG=EZovdWyEXSV5jxBszN9y=eC_Sbf4a5A@mail.gmail.com>
Date: Sun, 2 Mar 2014 12:31:32 -0800
From: Muthu Kumar <muthu.lkml@...il.com>
To: Kent Overstreet <kmo@...erainc.com>
Cc: Jens Axboe <axboe@...nel.dk>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
linux-fsdevel <linux-fsdevel@...r.kernel.org>,
Neil Brown <neilb@...e.de>, Alasdair Kergon <agk@...hat.com>,
device-mapper development <dm-devel@...hat.com>,
Lars Ellenberg <drbd-dev@...ts.linbit.com>,
drbd-user@...ts.linbit.com,
Asai Thambi S P <asamymuthupa@...ron.com>,
Sam Bradshaw <sbradshaw@...ron.com>,
Matthew Wilcox <willy@...ux.intel.com>,
linux-nvme@...ts.infradead.org, Jiri Kosina <jkosina@...e.cz>,
Geoff Levand <geoff@...radead.org>, Jim Paris <jim@...n.com>,
Joshua Morris <josh.h.morris@...ibm.com>,
Philip Kelleher <pjk1939@...ux.vnet.ibm.com>,
Minchan Kim <minchan@...nel.org>,
Nitin Gupta <ngupta@...are.org>,
Martin Schwidefsky <schwidefsky@...ibm.com>,
Heiko Carstens <heiko.carstens@...ibm.com>,
Peng Tao <bergwolf@...il.com>
Subject: Re: [PATCH 1/9] block: Make generic_make_request handle arbitrary
sized bios
Kent,
The blk_queue_split(), splits a bio into at most two bios right? So,
if the original bio spans larger space than two bios can cover
(restriction by the lower driver in the stack), this might not work?
Am I reading it incorrectly?
Thanks!
Regards,
Muthu
On Wed, Feb 26, 2014 at 3:39 PM, Kent Overstreet <kmo@...erainc.com> wrote:
> 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 <kmo@...erainc.com>
> Cc: Jens Axboe <axboe@...nel.dk>
> Cc: Neil Brown <neilb@...e.de>
> Cc: Alasdair Kergon <agk@...hat.com>
> Cc: dm-devel@...hat.com
> Cc: Lars Ellenberg <drbd-dev@...ts.linbit.com>
> Cc: drbd-user@...ts.linbit.com
> Cc: Asai Thambi S P <asamymuthupa@...ron.com>
> Cc: Sam Bradshaw <sbradshaw@...ron.com>
> Cc: Matthew Wilcox <willy@...ux.intel.com>
> Cc: linux-nvme@...ts.infradead.org
> Cc: Jiri Kosina <jkosina@...e.cz>
> Cc: Geoff Levand <geoff@...radead.org>
> Cc: Jim Paris <jim@...n.com>
> Cc: Joshua Morris <josh.h.morris@...ibm.com>
> Cc: Philip Kelleher <pjk1939@...ux.vnet.ibm.com>
> Cc: Minchan Kim <minchan@...nel.org>
> Cc: Nitin Gupta <ngupta@...are.org>
> Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
> Cc: Heiko Carstens <heiko.carstens@...ibm.com>
> Cc: Peng Tao <bergwolf@...il.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/block/zram/zram_drv.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 +
> 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 853f927492..d3b0782ec3 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -581,6 +581,10 @@ 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;
> @@ -590,7 +594,7 @@ 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);
> @@ -635,6 +639,8 @@ 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:
> @@ -1501,6 +1507,8 @@ 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
> @@ -1723,15 +1731,6 @@ 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 6c583f9c5b..0afbe3f1c2 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;
> @@ -37,13 +175,7 @@ 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;
> @@ -63,8 +195,8 @@ 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 6468a715a0..7893e254d8 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -915,6 +915,8 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio)
> return;
> }
>
> + 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 104a040f24..941a69c50c 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 516026954b..df733ca685 100644
> --- a/drivers/block/mtip32xx/mtip32xx.c
> +++ b/drivers/block/mtip32xx/mtip32xx.c
> @@ -4033,6 +4033,10 @@ 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))) {
> @@ -4082,8 +4086,6 @@ 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 51824d1f23..e4376b9613 100644
> --- a/drivers/block/nvme-core.c
> +++ b/drivers/block/nvme-core.c
> @@ -737,6 +737,8 @@ 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 a2af73db18..a37acf722b 100644
> --- a/drivers/block/pktcdvd.c
> +++ b/drivers/block/pktcdvd.c
> @@ -2444,6 +2444,10 @@ 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",
> @@ -2474,8 +2478,6 @@ 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 ef45cfb98f..a995972961 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 2839d37e5a..ff074a3cd4 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 4cf81b5bf0..13d577cfbc 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/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 011e55d820..ecf9daa01c 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -733,6 +733,8 @@ 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/drivers/md/dm.c b/drivers/md/dm.c
> index 8c53b09b9a..97f70420f2 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 4ad5cc4e63..1421bc3f7b 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 ebf41e228e..db33cd3e4c 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 6969d39f1e..f03c103f13 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 0718905ade..a3f6dc930b 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/include/linux/blkdev.h b/include/linux/blkdev.h
> index 1e1fa3f93d..99e9955c4d 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -470,6 +470,7 @@ 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 */
> @@ -781,6 +782,8 @@ 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,
> --
> 1.9.0
>
> --
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