7 files changed, 647 insertions, 57 deletions

diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
index e67fa16e1938..5902bd006a9c 100644
--- a/drivers/block/Kconfig
+++ b/drivers/block/Kconfig
@@ -15,6 +15,9 @@ menuconfig BLK_DEV
 
 if BLK_DEV
 
+config BLK_DEV_NULL_BLK
+        tristate "Null test block driver"
+
 config BLK_DEV_FD
         tristate "Normal floppy disk support"
         depends on ARCH_MAY_HAVE_PC_FDC
diff --git a/drivers/block/Makefile b/drivers/block/Makefile
index ca07399a8d99..03b3b4a2bd8a 100644
--- a/drivers/block/Makefile
+++ b/drivers/block/Makefile
@@ -41,6 +41,7 @@ obj-$(CONFIG_BLK_DEV_RBD)     += rbd.o
 obj-$(CONFIG_BLK_DEV_PCIESSD_MTIP32XX)  += mtip32xx/
 
 obj-$(CONFIG_BLK_DEV_RSXX) += rsxx/
+obj-$(CONFIG_BLK_DEV_NULL_BLK)  += null_blk.o
 
 nvme-y          := nvme-core.o nvme-scsi.o
 swim_mod-y      := swim.o swim_asm.o
diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 9bf4371755f2..d91f1a56e861 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -545,7 +545,7 @@ static struct kobject *brd_probe(dev_t dev, int *part, void *data)
 
         mutex_lock(&brd_devices_mutex);
         brd = brd_init_one(MINOR(dev) >> part_shift);
-        kobj = brd ? get_disk(brd->brd_disk) : ERR_PTR(-ENOMEM);
+        kobj = brd ? get_disk(brd->brd_disk) : NULL;
         mutex_unlock(&brd_devices_mutex);
 
         *part = 0;
diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index 04ceb7e2fadd..000abe2f105c 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -2886,9 +2886,9 @@ static void do_fd_request(struct request_queue *q)
                 return;
 
         if (WARN(atomic_read(&usage_count) == 0,
-                 "warning: usage count=0, current_req=%p sect=%ld type=%x flags=%x\n",
+                 "warning: usage count=0, current_req=%p sect=%ld type=%x flags=%llx\n",
                  current_req, (long)blk_rq_pos(current_req), current_req->cmd_type,
-                 current_req->cmd_flags))
+                 (unsigned long long) current_req->cmd_flags))
                 return;
 
         if (test_and_set_bit(0, &fdc_busy)) {
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 40e715531aa6..dbdb88a4976c 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1633,7 +1633,7 @@ static int loop_add(struct loop_device **l, int i)
         err = -ENOMEM;
         lo->lo_queue = blk_alloc_queue(GFP_KERNEL);
         if (!lo->lo_queue)
-                goto out_free_dev;
+                goto out_free_idr;
 
         disk = lo->lo_disk = alloc_disk(1 << part_shift);
         if (!disk)
@@ -1678,6 +1678,8 @@ static int loop_add(struct loop_device **l, int i)
 
 out_free_queue:
         blk_cleanup_queue(lo->lo_queue);
+out_free_idr:
+        idr_remove(&loop_index_idr, i);
 out_free_dev:
         kfree(lo);
 out:
@@ -1741,7 +1743,7 @@ static struct kobject *loop_probe(dev_t dev, int *part, void *data)
         if (err < 0)
                 err = loop_add(&lo, MINOR(dev) >> part_shift);
         if (err < 0)
-                kobj = ERR_PTR(err);
+                kobj = NULL;
         else
                 kobj = get_disk(lo->lo_disk);
         mutex_unlock(&loop_index_mutex);
diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
new file mode 100644
index 000000000000..b5d842370cc9
--- /dev/null
+++ b/drivers/block/null_blk.c
@@ -0,0 +1,635 @@
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/sched.h>
+#include <linux/fs.h>
+#include <linux/blkdev.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/blk-mq.h>
+#include <linux/hrtimer.h>
+
+struct nullb_cmd {
+        struct list_head list;
+        struct llist_node ll_list;
+        struct call_single_data csd;
+        struct request *rq;
+        struct bio *bio;
+        unsigned int tag;
+        struct nullb_queue *nq;
+};
+
+struct nullb_queue {
+        unsigned long *tag_map;
+        wait_queue_head_t wait;
+        unsigned int queue_depth;
+
+        struct nullb_cmd *cmds;
+};
+
+struct nullb {
+        struct list_head list;
+        unsigned int index;
+        struct request_queue *q;
+        struct gendisk *disk;
+        struct hrtimer timer;
+        unsigned int queue_depth;
+        spinlock_t lock;
+
+        struct nullb_queue *queues;
+        unsigned int nr_queues;
+};
+
+static LIST_HEAD(nullb_list);
+static struct mutex lock;
+static int null_major;
+static int nullb_indexes;
+
+struct completion_queue {
+        struct llist_head list;
+        struct hrtimer timer;
+};
+
+/*
+ * These are per-cpu for now, they will need to be configured by the
+ * complete_queues parameter and appropriately mapped.
+ */
+static DEFINE_PER_CPU(struct completion_queue, completion_queues);
+
+enum {
+        NULL_IRQ_NONE           = 0,
+        NULL_IRQ_SOFTIRQ        = 1,
+        NULL_IRQ_TIMER          = 2,
+
+        NULL_Q_BIO              = 0,
+        NULL_Q_RQ               = 1,
+        NULL_Q_MQ               = 2,
+};
+
+static int submit_queues = 1;
+module_param(submit_queues, int, S_IRUGO);
+MODULE_PARM_DESC(submit_queues, "Number of submission queues");
+
+static int home_node = NUMA_NO_NODE;
+module_param(home_node, int, S_IRUGO);
+MODULE_PARM_DESC(home_node, "Home node for the device");
+
+static int queue_mode = NULL_Q_MQ;
+module_param(queue_mode, int, S_IRUGO);
+MODULE_PARM_DESC(use_mq, "Use blk-mq interface (0=bio,1=rq,2=multiqueue)");
+
+static int gb = 250;
+module_param(gb, int, S_IRUGO);
+MODULE_PARM_DESC(gb, "Size in GB");
+
+static int bs = 512;
+module_param(bs, int, S_IRUGO);
+MODULE_PARM_DESC(bs, "Block size (in bytes)");
+
+static int nr_devices = 2;
+module_param(nr_devices, int, S_IRUGO);
+MODULE_PARM_DESC(nr_devices, "Number of devices to register");
+
+static int irqmode = NULL_IRQ_SOFTIRQ;
+module_param(irqmode, int, S_IRUGO);
+MODULE_PARM_DESC(irqmode, "IRQ completion handler. 0-none, 1-softirq, 2-timer");
+
+static int completion_nsec = 10000;
+module_param(completion_nsec, int, S_IRUGO);
+MODULE_PARM_DESC(completion_nsec, "Time in ns to complete a request in hardware. Default: 10,000ns");
+
+static int hw_queue_depth = 64;
+module_param(hw_queue_depth, int, S_IRUGO);
+MODULE_PARM_DESC(hw_queue_depth, "Queue depth for each hardware queue. Default: 64");
+
+static bool use_per_node_hctx = true;
+module_param(use_per_node_hctx, bool, S_IRUGO);
+MODULE_PARM_DESC(use_per_node_hctx, "Use per-node allocation for hardware context queues. Default: true");
+
+static void put_tag(struct nullb_queue *nq, unsigned int tag)
+{
+        clear_bit_unlock(tag, nq->tag_map);
+
+        if (waitqueue_active(&nq->wait))
+                wake_up(&nq->wait);
+}
+
+static unsigned int get_tag(struct nullb_queue *nq)
+{
+        unsigned int tag;
+
+        do {
+                tag = find_first_zero_bit(nq->tag_map, nq->queue_depth);
+                if (tag >= nq->queue_depth)
+                        return -1U;
+        } while (test_and_set_bit_lock(tag, nq->tag_map));
+
+        return tag;
+}
+
+static void free_cmd(struct nullb_cmd *cmd)
+{
+        put_tag(cmd->nq, cmd->tag);
+}
+
+static struct nullb_cmd *__alloc_cmd(struct nullb_queue *nq)
+{
+        struct nullb_cmd *cmd;
+        unsigned int tag;
+
+        tag = get_tag(nq);
+        if (tag != -1U) {
+                cmd = &nq->cmds[tag];
+                cmd->tag = tag;
+                cmd->nq = nq;
+                return cmd;
+        }
+
+        return NULL;
+}
+
+static struct nullb_cmd *alloc_cmd(struct nullb_queue *nq, int can_wait)
+{
+        struct nullb_cmd *cmd;
+        DEFINE_WAIT(wait);
+
+        cmd = __alloc_cmd(nq);
+        if (cmd || !can_wait)
+                return cmd;
+
+        do {
+                prepare_to_wait(&nq->wait, &wait, TASK_UNINTERRUPTIBLE);
+                cmd = __alloc_cmd(nq);
+                if (cmd)
+                        break;
+
+                io_schedule();
+        } while (1);
+
+        finish_wait(&nq->wait, &wait);
+        return cmd;
+}
+
+static void end_cmd(struct nullb_cmd *cmd)
+{
+        if (cmd->rq) {
+                if (queue_mode == NULL_Q_MQ)
+                        blk_mq_end_io(cmd->rq, 0);
+                else {
+                        INIT_LIST_HEAD(&cmd->rq->queuelist);
+                        blk_end_request_all(cmd->rq, 0);
+                }
+        } else if (cmd->bio)
+                bio_endio(cmd->bio, 0);
+
+        if (queue_mode != NULL_Q_MQ)
+                free_cmd(cmd);
+}
+
+static enum hrtimer_restart null_cmd_timer_expired(struct hrtimer *timer)
+{
+        struct completion_queue *cq;
+        struct llist_node *entry;
+        struct nullb_cmd *cmd;
+
+        cq = &per_cpu(completion_queues, smp_processor_id());
+
+        while ((entry = llist_del_all(&cq->list)) != NULL) {
+                do {
+                        cmd = container_of(entry, struct nullb_cmd, ll_list);
+                        end_cmd(cmd);
+                        entry = entry->next;
+                } while (entry);
+        }
+
+        return HRTIMER_NORESTART;
+}
+
+static void null_cmd_end_timer(struct nullb_cmd *cmd)
+{
+        struct completion_queue *cq = &per_cpu(completion_queues, get_cpu());
+
+        cmd->ll_list.next = NULL;
+        if (llist_add(&cmd->ll_list, &cq->list)) {
+                ktime_t kt = ktime_set(0, completion_nsec);
+
+                hrtimer_start(&cq->timer, kt, HRTIMER_MODE_REL);
+        }
+
+        put_cpu();
+}
+
+static void null_softirq_done_fn(struct request *rq)
+{
+        blk_end_request_all(rq, 0);
+}
+
+#if defined(CONFIG_SMP) && defined(CONFIG_USE_GENERIC_SMP_HELPERS)
+
+static void null_ipi_cmd_end_io(void *data)
+{
+        struct completion_queue *cq;
+        struct llist_node *entry, *next;
+        struct nullb_cmd *cmd;
+
+        cq = &per_cpu(completion_queues, smp_processor_id());
+
+        entry = llist_del_all(&cq->list);
+
+        while (entry) {
+                next = entry->next;
+                cmd = llist_entry(entry, struct nullb_cmd, ll_list);
+                end_cmd(cmd);
+                entry = next;
+        }
+}
+
+static void null_cmd_end_ipi(struct nullb_cmd *cmd)
+{
+        struct call_single_data *data = &cmd->csd;
+        int cpu = get_cpu();
+        struct completion_queue *cq = &per_cpu(completion_queues, cpu);
+
+        cmd->ll_list.next = NULL;
+
+        if (llist_add(&cmd->ll_list, &cq->list)) {
+                data->func = null_ipi_cmd_end_io;
+                data->flags = 0;
+                __smp_call_function_single(cpu, data, 0);
+        }
+
+        put_cpu();
+}
+
+#endif /* CONFIG_SMP && CONFIG_USE_GENERIC_SMP_HELPERS */
+
+static inline void null_handle_cmd(struct nullb_cmd *cmd)
+{
+        /* Complete IO by inline, softirq or timer */
+        switch (irqmode) {
+        case NULL_IRQ_NONE:
+                end_cmd(cmd);
+                break;
+        case NULL_IRQ_SOFTIRQ:
+#if defined(CONFIG_SMP) && defined(CONFIG_USE_GENERIC_SMP_HELPERS)
+                null_cmd_end_ipi(cmd);
+#else
+                end_cmd(cmd);
+#endif
+                break;
+        case NULL_IRQ_TIMER:
+                null_cmd_end_timer(cmd);
+                break;
+        }
+}
+
+static struct nullb_queue *nullb_to_queue(struct nullb *nullb)
+{
+        int index = 0;
+
+        if (nullb->nr_queues != 1)
+                index = raw_smp_processor_id() / ((nr_cpu_ids + nullb->nr_queues - 1) / nullb->nr_queues);
+
+        return &nullb->queues[index];
+}
+
+static void null_queue_bio(struct request_queue *q, struct bio *bio)
+{
+        struct nullb *nullb = q->queuedata;
+        struct nullb_queue *nq = nullb_to_queue(nullb);
+        struct nullb_cmd *cmd;
+
+        cmd = alloc_cmd(nq, 1);
+        cmd->bio = bio;
+
+        null_handle_cmd(cmd);
+}
+
+static int null_rq_prep_fn(struct request_queue *q, struct request *req)
+{
+        struct nullb *nullb = q->queuedata;
+        struct nullb_queue *nq = nullb_to_queue(nullb);
+        struct nullb_cmd *cmd;
+
+        cmd = alloc_cmd(nq, 0);
+        if (cmd) {
+                cmd->rq = req;
+                req->special = cmd;
+                return BLKPREP_OK;
+        }
+
+        return BLKPREP_DEFER;
+}
+
+static void null_request_fn(struct request_queue *q)
+{
+        struct request *rq;
+
+        while ((rq = blk_fetch_request(q)) != NULL) {
+                struct nullb_cmd *cmd = rq->special;
+
+                spin_unlock_irq(q->queue_lock);
+                null_handle_cmd(cmd);
+                spin_lock_irq(q->queue_lock);
+        }
+}
+
+static int null_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *rq)
+{
+        struct nullb_cmd *cmd = rq->special;
+
+        cmd->rq = rq;
+        cmd->nq = hctx->driver_data;
+
+        null_handle_cmd(cmd);
+        return BLK_MQ_RQ_QUEUE_OK;
+}
+
+static struct blk_mq_hw_ctx *null_alloc_hctx(struct blk_mq_reg *reg, unsigned int hctx_index)
+{
+        return kzalloc_node(sizeof(struct blk_mq_hw_ctx), GFP_KERNEL,
+                                hctx_index);
+}
+
+static void null_free_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_index)
+{
+        kfree(hctx);
+}
+
+static int null_init_hctx(struct blk_mq_hw_ctx *hctx, void *data,
+                          unsigned int index)
+{
+        struct nullb *nullb = data;
+        struct nullb_queue *nq = &nullb->queues[index];
+
+        init_waitqueue_head(&nq->wait);
+        nq->queue_depth = nullb->queue_depth;
+        nullb->nr_queues++;
+        hctx->driver_data = nq;
+
+        return 0;
+}
+
+static struct blk_mq_ops null_mq_ops = {
+        .queue_rq       = null_queue_rq,
+        .map_queue      = blk_mq_map_queue,
+        .init_hctx      = null_init_hctx,
+};
+
+static struct blk_mq_reg null_mq_reg = {
+        .ops            = &null_mq_ops,
+        .queue_depth    = 64,
+        .cmd_size       = sizeof(struct nullb_cmd),
+        .flags          = BLK_MQ_F_SHOULD_MERGE,
+};
+
+static void null_del_dev(struct nullb *nullb)
+{
+        list_del_init(&nullb->list);
+
+        del_gendisk(nullb->disk);
+        if (queue_mode == NULL_Q_MQ)
+                blk_mq_free_queue(nullb->q);
+        else
+                blk_cleanup_queue(nullb->q);
+        put_disk(nullb->disk);
+        kfree(nullb);
+}
+
+static int null_open(struct block_device *bdev, fmode_t mode)
+{
+        return 0;
+}
+
+static void null_release(struct gendisk *disk, fmode_t mode)
+{
+}
+
+static const struct block_device_operations null_fops = {
+        .owner =        THIS_MODULE,
+        .open =         null_open,
+        .release =      null_release,
+};
+
+static int setup_commands(struct nullb_queue *nq)
+{
+        struct nullb_cmd *cmd;
+        int i, tag_size;
+
+        nq->cmds = kzalloc(nq->queue_depth * sizeof(*cmd), GFP_KERNEL);
+        if (!nq->cmds)
+                return 1;
+
+        tag_size = ALIGN(nq->queue_depth, BITS_PER_LONG) / BITS_PER_LONG;
+        nq->tag_map = kzalloc(tag_size * sizeof(unsigned long), GFP_KERNEL);
+        if (!nq->tag_map) {
+                kfree(nq->cmds);
+                return 1;
+        }
+
+        for (i = 0; i < nq->queue_depth; i++) {
+                cmd = &nq->cmds[i];
+                INIT_LIST_HEAD(&cmd->list);
+                cmd->ll_list.next = NULL;
+                cmd->tag = -1U;
+        }
+
+        return 0;
+}
+
+static void cleanup_queue(struct nullb_queue *nq)
+{
+        kfree(nq->tag_map);
+        kfree(nq->cmds);
+}
+
+static void cleanup_queues(struct nullb *nullb)
+{
+        int i;
+
+        for (i = 0; i < nullb->nr_queues; i++)
+                cleanup_queue(&nullb->queues[i]);
+
+        kfree(nullb->queues);
+}
+
+static int setup_queues(struct nullb *nullb)
+{
+        struct nullb_queue *nq;
+        int i;
+
+        nullb->queues = kzalloc(submit_queues * sizeof(*nq), GFP_KERNEL);
+        if (!nullb->queues)
+                return 1;
+
+        nullb->nr_queues = 0;
+        nullb->queue_depth = hw_queue_depth;
+
+        if (queue_mode == NULL_Q_MQ)
+                return 0;
+
+        for (i = 0; i < submit_queues; i++) {
+                nq = &nullb->queues[i];
+                init_waitqueue_head(&nq->wait);
+                nq->queue_depth = hw_queue_depth;
+                if (setup_commands(nq))
+                        break;
+                nullb->nr_queues++;
+        }
+
+        if (i == submit_queues)
+                return 0;
+
+        cleanup_queues(nullb);
+        return 1;
+}
+
+static int null_add_dev(void)
+{
+        struct gendisk *disk;
+        struct nullb *nullb;
+        sector_t size;
+
+        nullb = kzalloc_node(sizeof(*nullb), GFP_KERNEL, home_node);
+        if (!nullb)
+                return -ENOMEM;
+
+        spin_lock_init(&nullb->lock);
+
+        if (setup_queues(nullb))
+                goto err;
+
+        if (queue_mode == NULL_Q_MQ) {
+                null_mq_reg.numa_node = home_node;
+                null_mq_reg.queue_depth = hw_queue_depth;
+
+                if (use_per_node_hctx) {
+                        null_mq_reg.ops->alloc_hctx = null_alloc_hctx;
+                        null_mq_reg.ops->free_hctx = null_free_hctx;
+
+                        null_mq_reg.nr_hw_queues = nr_online_nodes;
+                } else {
+                        null_mq_reg.ops->alloc_hctx = blk_mq_alloc_single_hw_queue;
+                        null_mq_reg.ops->free_hctx = blk_mq_free_single_hw_queue;
+
+                        null_mq_reg.nr_hw_queues = submit_queues;
+                }
+
+                nullb->q = blk_mq_init_queue(&null_mq_reg, nullb);
+        } else if (queue_mode == NULL_Q_BIO) {
+                nullb->q = blk_alloc_queue_node(GFP_KERNEL, home_node);
+                blk_queue_make_request(nullb->q, null_queue_bio);
+        } else {
+                nullb->q = blk_init_queue_node(null_request_fn, &nullb->lock, home_node);
+                blk_queue_prep_rq(nullb->q, null_rq_prep_fn);
+                if (nullb->q)
+                        blk_queue_softirq_done(nullb->q, null_softirq_done_fn);
+        }
+
+        if (!nullb->q)
+                goto queue_fail;
+
+        nullb->q->queuedata = nullb;
+        queue_flag_set_unlocked(QUEUE_FLAG_NONROT, nullb->q);
+
+        disk = nullb->disk = alloc_disk_node(1, home_node);
+        if (!disk) {
+queue_fail:
+                if (queue_mode == NULL_Q_MQ)
+                        blk_mq_free_queue(nullb->q);
+                else
+                        blk_cleanup_queue(nullb->q);
+                cleanup_queues(nullb);
+err:
+                kfree(nullb);
+                return -ENOMEM;
+        }
+
+        mutex_lock(&lock);
+        list_add_tail(&nullb->list, &nullb_list);
+        nullb->index = nullb_indexes++;
+        mutex_unlock(&lock);
+
+        blk_queue_logical_block_size(nullb->q, bs);
+        blk_queue_physical_block_size(nullb->q, bs);
+
+        size = gb * 1024 * 1024 * 1024ULL;
+        sector_div(size, bs);
+        set_capacity(disk, size);
+
+        disk->flags |= GENHD_FL_EXT_DEVT;
+        disk->major             = null_major;
+        disk->first_minor       = nullb->index;
+        disk->fops              = &null_fops;
+        disk->private_data      = nullb;
+        disk->queue             = nullb->q;
+        sprintf(disk->disk_name, "nullb%d", nullb->index);
+        add_disk(disk);
+        return 0;
+}
+
+static int __init null_init(void)
+{
+        unsigned int i;
+
+#if !defined(CONFIG_SMP) || !defined(CONFIG_USE_GENERIC_SMP_HELPERS)
+        if (irqmode == NULL_IRQ_SOFTIRQ) {
+                pr_warn("null_blk: softirq completions not available.\n");
+                pr_warn("null_blk: using direct completions.\n");
+                irqmode = NULL_IRQ_NONE;
+        }
+#endif
+
+        if (submit_queues > nr_cpu_ids)
+                submit_queues = nr_cpu_ids;
+        else if (!submit_queues)
+                submit_queues = 1;
+
+        mutex_init(&lock);
+
+        /* Initialize a separate list for each CPU for issuing softirqs */
+        for_each_possible_cpu(i) {
+                struct completion_queue *cq = &per_cpu(completion_queues, i);
+
+                init_llist_head(&cq->list);
+
+                if (irqmode != NULL_IRQ_TIMER)
+                        continue;
+
+                hrtimer_init(&cq->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+                cq->timer.function = null_cmd_timer_expired;
+        }
+
+        null_major = register_blkdev(0, "nullb");
+        if (null_major < 0)
+                return null_major;
+
+        for (i = 0; i < nr_devices; i++) {
+                if (null_add_dev()) {
+                        unregister_blkdev(null_major, "nullb");
+                        return -EINVAL;
+                }
+        }
+
+        pr_info("null: module loaded\n");
+        return 0;
+}
+
+static void __exit null_exit(void)
+{
+        struct nullb *nullb;
+
+        unregister_blkdev(null_major, "nullb");
+
+        mutex_lock(&lock);
+        while (!list_empty(&nullb_list)) {
+                nullb = list_entry(nullb_list.next, struct nullb, list);
+                null_del_dev(nullb);
+        }
+        mutex_unlock(&lock);
+}
+
+module_init(null_init);
+module_exit(null_exit);
+
+MODULE_AUTHOR("Jens Axboe <jaxboe@fusionio.com>");
+MODULE_LICENSE("GPL");
diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index a4660bbee8a6..8d53ed293606 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -1336,57 +1336,6 @@ static int blkfront_probe(struct xenbus_device *dev,
         return 0;
 }
 
-/*
- * This is a clone of md_trim_bio, used to split a bio into smaller ones
- */
-static void trim_bio(struct bio *bio, int offset, int size)
-{
-        /* 'bio' is a cloned bio which we need to trim to match
-         * the given offset and size.
-         * This requires adjusting bi_sector, bi_size, and bi_io_vec
-         */
-        int i;
-        struct bio_vec *bvec;
-        int sofar = 0;
-
-        size <<= 9;
-        if (offset == 0 && size == bio->bi_size)
-                return;
-
-        bio->bi_sector += offset;
-        bio->bi_size = size;
-        offset <<= 9;
-        clear_bit(BIO_SEG_VALID, &bio->bi_flags);
-
-        while (bio->bi_idx < bio->bi_vcnt &&
-               bio->bi_io_vec[bio->bi_idx].bv_len <= offset) {
-                /* remove this whole bio_vec */
-                offset -= bio->bi_io_vec[bio->bi_idx].bv_len;
-                bio->bi_idx++;
-        }
-        if (bio->bi_idx < bio->bi_vcnt) {
-                bio->bi_io_vec[bio->bi_idx].bv_offset += offset;
-                bio->bi_io_vec[bio->bi_idx].bv_len -= offset;
-        }
-        /* avoid any complications with bi_idx being non-zero*/
-        if (bio->bi_idx) {
-                memmove(bio->bi_io_vec, bio->bi_io_vec+bio->bi_idx,
-                        (bio->bi_vcnt - bio->bi_idx) * sizeof(struct bio_vec));
-                bio->bi_vcnt -= bio->bi_idx;
-                bio->bi_idx = 0;
-        }
-        /* Make sure vcnt and last bv are not too big */
-        bio_for_each_segment(bvec, bio, i) {
-                if (sofar + bvec->bv_len > size)
-                        bvec->bv_len = size - sofar;
-                if (bvec->bv_len == 0) {
-                        bio->bi_vcnt = i;
-                        break;
-                }
-                sofar += bvec->bv_len;
-        }
-}
-
 static void split_bio_end(struct bio *bio, int error)
 {
         struct split_bio *split_bio = bio->bi_private;
@@ -1522,7 +1471,7 @@ static int blkif_recover(struct blkfront_info *info)
                                            (unsigned int)(bio->bi_size >> 9) - offset);
                                 cloned_bio = bio_clone(bio, GFP_NOIO);
                                 BUG_ON(cloned_bio == NULL);
-                                trim_bio(cloned_bio, offset, size);
+                                bio_trim(cloned_bio, offset, size);
                                 cloned_bio->bi_private = split_bio;
                                 cloned_bio->bi_end_io = split_bio_end;
                                 submit_bio(cloned_bio->bi_rw, cloned_bio);