Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

1 files changed, 678 insertions, 0 deletions

diff --git a/drivers/mtd/ubi/block.c b/drivers/mtd/ubi/block.c
new file mode 100644
index 000000000..29c0d6941
--- /dev/null
+++ b/drivers/mtd/ubi/block.c
@@ -0,0 +1,678 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2014 Ezequiel Garcia
+ * Copyright (c) 2011 Free Electrons
+ *
+ * Driver parameter handling strongly based on drivers/mtd/ubi/build.c
+ *   Copyright (c) International Business Machines Corp., 2006
+ *   Copyright (c) Nokia Corporation, 2007
+ *   Authors: Artem Bityutskiy, Frank Haverkamp
+ */
+
+/*
+ * Read-only block devices on top of UBI volumes
+ *
+ * A simple implementation to allow a block device to be layered on top of a
+ * UBI volume. The implementation is provided by creating a static 1-to-1
+ * mapping between the block device and the UBI volume.
+ *
+ * The addressed byte is obtained from the addressed block sector, which is
+ * mapped linearly into the corresponding LEB:
+ *
+ *   LEB number = addressed byte / LEB size
+ *
+ * This feature is compiled in the UBI core, and adds a 'block' parameter
+ * to allow early creation of block devices on top of UBI volumes. Runtime
+ * block creation/removal for UBI volumes is provided through two UBI ioctls:
+ * UBI_IOCVOLCRBLK and UBI_IOCVOLRMBLK.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/mtd/ubi.h>
+#include <linux/blkdev.h>
+#include <linux/blk-mq.h>
+#include <linux/hdreg.h>
+#include <linux/scatterlist.h>
+#include <linux/idr.h>
+#include <asm/div64.h>
+
+#include "ubi-media.h"
+#include "ubi.h"
+
+/* Maximum number of supported devices */
+#define UBIBLOCK_MAX_DEVICES 32
+
+/* Maximum length of the 'block=' parameter */
+#define UBIBLOCK_PARAM_LEN 63
+
+/* Maximum number of comma-separated items in the 'block=' parameter */
+#define UBIBLOCK_PARAM_COUNT 2
+
+struct ubiblock_param {
+	int ubi_num;
+	int vol_id;
+	char name[UBIBLOCK_PARAM_LEN+1];
+};
+
+struct ubiblock_pdu {
+	struct ubi_sgl usgl;
+};
+
+/* Numbers of elements set in the @ubiblock_param array */
+static int ubiblock_devs;
+
+/* MTD devices specification parameters */
+static struct ubiblock_param ubiblock_param[UBIBLOCK_MAX_DEVICES];
+
+struct ubiblock {
+	struct ubi_volume_desc *desc;
+	int ubi_num;
+	int vol_id;
+	int refcnt;
+	int leb_size;
+
+	struct gendisk *gd;
+	struct request_queue *rq;
+
+	struct mutex dev_mutex;
+	struct list_head list;
+	struct blk_mq_tag_set tag_set;
+};
+
+/* Linked list of all ubiblock instances */
+static LIST_HEAD(ubiblock_devices);
+static DEFINE_IDR(ubiblock_minor_idr);
+/* Protects ubiblock_devices and ubiblock_minor_idr */
+static DEFINE_MUTEX(devices_mutex);
+static int ubiblock_major;
+
+static int __init ubiblock_set_param(const char *val,
+				     const struct kernel_param *kp)
+{
+	int i, ret;
+	size_t len;
+	struct ubiblock_param *param;
+	char buf[UBIBLOCK_PARAM_LEN];
+	char *pbuf = &buf[0];
+	char *tokens[UBIBLOCK_PARAM_COUNT];
+
+	if (!val)
+		return -EINVAL;
+
+	len = strnlen(val, UBIBLOCK_PARAM_LEN);
+	if (len == 0) {
+		pr_warn("UBI: block: empty 'block=' parameter - ignored\n");
+		return 0;
+	}
+
+	if (len == UBIBLOCK_PARAM_LEN) {
+		pr_err("UBI: block: parameter \"%s\" is too long, max. is %d\n",
+		       val, UBIBLOCK_PARAM_LEN);
+		return -EINVAL;
+	}
+
+	strcpy(buf, val);
+
+	/* Get rid of the final newline */
+	if (buf[len - 1] == '\n')
+		buf[len - 1] = '\0';
+
+	for (i = 0; i < UBIBLOCK_PARAM_COUNT; i++)
+		tokens[i] = strsep(&pbuf, ",");
+
+	param = &ubiblock_param[ubiblock_devs];
+	if (tokens[1]) {
+		/* Two parameters: can be 'ubi, vol_id' or 'ubi, vol_name' */
+		ret = kstrtoint(tokens[0], 10, &param->ubi_num);
+		if (ret < 0)
+			return -EINVAL;
+
+		/* Second param can be a number or a name */
+		ret = kstrtoint(tokens[1], 10, &param->vol_id);
+		if (ret < 0) {
+			param->vol_id = -1;
+			strcpy(param->name, tokens[1]);
+		}
+
+	} else {
+		/* One parameter: must be device path */
+		strcpy(param->name, tokens[0]);
+		param->ubi_num = -1;
+		param->vol_id = -1;
+	}
+
+	ubiblock_devs++;
+
+	return 0;
+}
+
+static const struct kernel_param_ops ubiblock_param_ops = {
+	.set    = ubiblock_set_param,
+};
+module_param_cb(block, &ubiblock_param_ops, NULL, 0);
+MODULE_PARM_DESC(block, "Attach block devices to UBI volumes. Parameter format: block=<path|dev,num|dev,name>.\n"
+			"Multiple \"block\" parameters may be specified.\n"
+			"UBI volumes may be specified by their number, name, or path to the device node.\n"
+			"Examples\n"
+			"Using the UBI volume path:\n"
+			"ubi.block=/dev/ubi0_0\n"
+			"Using the UBI device, and the volume name:\n"
+			"ubi.block=0,rootfs\n"
+			"Using both UBI device number and UBI volume number:\n"
+			"ubi.block=0,0\n");
+
+static struct ubiblock *find_dev_nolock(int ubi_num, int vol_id)
+{
+	struct ubiblock *dev;
+
+	list_for_each_entry(dev, &ubiblock_devices, list)
+		if (dev->ubi_num == ubi_num && dev->vol_id == vol_id)
+			return dev;
+	return NULL;
+}
+
+static blk_status_t ubiblock_read(struct request *req)
+{
+	struct ubiblock_pdu *pdu = blk_mq_rq_to_pdu(req);
+	struct ubiblock *dev = req->q->queuedata;
+	u64 pos = blk_rq_pos(req) << 9;
+	int to_read = blk_rq_bytes(req);
+	int bytes_left = to_read;
+	/* Get LEB:offset address to read from */
+	int offset = do_div(pos, dev->leb_size);
+	int leb = pos;
+	struct req_iterator iter;
+	struct bio_vec bvec;
+	int ret;
+
+	blk_mq_start_request(req);
+
+	/*
+	 * It is safe to ignore the return value of blk_rq_map_sg() because
+	 * the number of sg entries is limited to UBI_MAX_SG_COUNT
+	 * and ubi_read_sg() will check that limit.
+	 */
+	ubi_sgl_init(&pdu->usgl);
+	blk_rq_map_sg(req, pdu->usgl.sg);
+
+	while (bytes_left) {
+		/*
+		 * We can only read one LEB at a time. Therefore if the read
+		 * length is larger than one LEB size, we split the operation.
+		 */
+		if (offset + to_read > dev->leb_size)
+			to_read = dev->leb_size - offset;
+
+		ret = ubi_read_sg(dev->desc, leb, &pdu->usgl, offset, to_read);
+		if (ret < 0)
+			break;
+
+		bytes_left -= to_read;
+		to_read = bytes_left;
+		leb += 1;
+		offset = 0;
+	}
+
+	rq_for_each_segment(bvec, req, iter)
+		flush_dcache_page(bvec.bv_page);
+
+	blk_mq_end_request(req, errno_to_blk_status(ret));
+
+	return BLK_STS_OK;
+}
+
+static int ubiblock_open(struct gendisk *disk, blk_mode_t mode)
+{
+	struct ubiblock *dev = disk->private_data;
+	int ret;
+
+	mutex_lock(&dev->dev_mutex);
+	if (dev->refcnt > 0) {
+		/*
+		 * The volume is already open, just increase the reference
+		 * counter.
+		 */
+		goto out_done;
+	}
+
+	/*
+	 * We want users to be aware they should only mount us as read-only.
+	 * It's just a paranoid check, as write requests will get rejected
+	 * in any case.
+	 */
+	if (mode & BLK_OPEN_WRITE) {
+		ret = -EROFS;
+		goto out_unlock;
+	}
+	dev->desc = ubi_open_volume(dev->ubi_num, dev->vol_id, UBI_READONLY);
+	if (IS_ERR(dev->desc)) {
+		dev_err(disk_to_dev(dev->gd), "failed to open ubi volume %d_%d",
+			dev->ubi_num, dev->vol_id);
+		ret = PTR_ERR(dev->desc);
+		dev->desc = NULL;
+		goto out_unlock;
+	}
+
+out_done:
+	dev->refcnt++;
+	mutex_unlock(&dev->dev_mutex);
+	return 0;
+
+out_unlock:
+	mutex_unlock(&dev->dev_mutex);
+	return ret;
+}
+
+static void ubiblock_release(struct gendisk *gd)
+{
+	struct ubiblock *dev = gd->private_data;
+
+	mutex_lock(&dev->dev_mutex);
+	dev->refcnt--;
+	if (dev->refcnt == 0) {
+		ubi_close_volume(dev->desc);
+		dev->desc = NULL;
+	}
+	mutex_unlock(&dev->dev_mutex);
+}
+
+static int ubiblock_getgeo(struct gendisk *disk, struct hd_geometry *geo)
+{
+	/* Some tools might require this information */
+	geo->heads = 1;
+	geo->cylinders = 1;
+	geo->sectors = get_capacity(disk);
+	geo->start = 0;
+	return 0;
+}
+
+static const struct block_device_operations ubiblock_ops = {
+	.owner = THIS_MODULE,
+	.open = ubiblock_open,
+	.release = ubiblock_release,
+	.getgeo	= ubiblock_getgeo,
+};
+
+static blk_status_t ubiblock_queue_rq(struct blk_mq_hw_ctx *hctx,
+			     const struct blk_mq_queue_data *bd)
+{
+	switch (req_op(bd->rq)) {
+	case REQ_OP_READ:
+		return ubiblock_read(bd->rq);
+	default:
+		return BLK_STS_IOERR;
+	}
+}
+
+static int ubiblock_init_request(struct blk_mq_tag_set *set,
+		struct request *req, unsigned int hctx_idx,
+		int numa_node)
+{
+	struct ubiblock_pdu *pdu = blk_mq_rq_to_pdu(req);
+
+	sg_init_table(pdu->usgl.sg, UBI_MAX_SG_COUNT);
+	return 0;
+}
+
+static const struct blk_mq_ops ubiblock_mq_ops = {
+	.queue_rq       = ubiblock_queue_rq,
+	.init_request	= ubiblock_init_request,
+};
+
+static int calc_disk_capacity(struct ubi_volume_info *vi, u64 *disk_capacity)
+{
+	u64 size = vi->used_bytes >> 9;
+
+	if (vi->used_bytes % 512) {
+		if (vi->vol_type == UBI_DYNAMIC_VOLUME)
+			pr_warn("UBI: block: volume size is not a multiple of 512, last %llu bytes are ignored!\n",
+				vi->used_bytes - (size << 9));
+		else
+			pr_info("UBI: block: volume size is not a multiple of 512, last %llu bytes are ignored!\n",
+				vi->used_bytes - (size << 9));
+	}
+
+	if ((sector_t)size != size)
+		return -EFBIG;
+
+	*disk_capacity = size;
+
+	return 0;
+}
+
+int ubiblock_create(struct ubi_volume_info *vi)
+{
+	struct queue_limits lim = {
+		.max_segments		= UBI_MAX_SG_COUNT,
+	};
+	struct ubiblock *dev;
+	struct gendisk *gd;
+	u64 disk_capacity;
+	int ret;
+
+	ret = calc_disk_capacity(vi, &disk_capacity);
+	if (ret) {
+		return ret;
+	}
+
+	/* Check that the volume isn't already handled */
+	mutex_lock(&devices_mutex);
+	if (find_dev_nolock(vi->ubi_num, vi->vol_id)) {
+		ret = -EEXIST;
+		goto out_unlock;
+	}
+
+	dev = kzalloc_obj(struct ubiblock);
+	if (!dev) {
+		ret = -ENOMEM;
+		goto out_unlock;
+	}
+
+	mutex_init(&dev->dev_mutex);
+
+	dev->ubi_num = vi->ubi_num;
+	dev->vol_id = vi->vol_id;
+	dev->leb_size = vi->usable_leb_size;
+
+	dev->tag_set.ops = &ubiblock_mq_ops;
+	dev->tag_set.queue_depth = 64;
+	dev->tag_set.numa_node = NUMA_NO_NODE;
+	dev->tag_set.flags = BLK_MQ_F_BLOCKING;
+	dev->tag_set.cmd_size = sizeof(struct ubiblock_pdu);
+	dev->tag_set.driver_data = dev;
+	dev->tag_set.nr_hw_queues = 1;
+
+	ret = blk_mq_alloc_tag_set(&dev->tag_set);
+	if (ret) {
+		pr_err("ubiblock%d_%d: blk_mq_alloc_tag_set failed\n",
+			dev->ubi_num, dev->vol_id);
+		goto out_free_dev;
+	}
+
+
+	/* Initialize the gendisk of this ubiblock device */
+	gd = blk_mq_alloc_disk(&dev->tag_set, &lim, dev);
+	if (IS_ERR(gd)) {
+		ret = PTR_ERR(gd);
+		goto out_free_tags;
+	}
+
+	gd->fops = &ubiblock_ops;
+	gd->major = ubiblock_major;
+	gd->minors = 1;
+	gd->first_minor = idr_alloc(&ubiblock_minor_idr, dev, 0, 0, GFP_KERNEL);
+	if (gd->first_minor < 0) {
+		pr_err("ubiblock%d_%d: block: dynamic minor allocation failed\n",
+			dev->ubi_num, dev->vol_id);
+		ret = -ENODEV;
+		goto out_cleanup_disk;
+	}
+	gd->flags |= GENHD_FL_NO_PART;
+	gd->private_data = dev;
+	sprintf(gd->disk_name, "ubiblock%d_%d", dev->ubi_num, dev->vol_id);
+	set_capacity(gd, disk_capacity);
+	dev->gd = gd;
+
+	dev->rq = gd->queue;
+
+	list_add_tail(&dev->list, &ubiblock_devices);
+
+	/* Must be the last step: anyone can call file ops from now on */
+	ret = device_add_disk(vi->dev, dev->gd, NULL);
+	if (ret)
+		goto out_remove_minor;
+
+	dev_info(disk_to_dev(dev->gd), "created from ubi%d:%d(%s)",
+		 dev->ubi_num, dev->vol_id, vi->name);
+	mutex_unlock(&devices_mutex);
+	return 0;
+
+out_remove_minor:
+	list_del(&dev->list);
+	idr_remove(&ubiblock_minor_idr, gd->first_minor);
+out_cleanup_disk:
+	put_disk(gd);
+out_free_tags:
+	blk_mq_free_tag_set(&dev->tag_set);
+out_free_dev:
+	kfree(dev);
+out_unlock:
+	mutex_unlock(&devices_mutex);
+
+	return ret;
+}
+
+static void ubiblock_cleanup(struct ubiblock *dev)
+{
+	int id = dev->gd->first_minor;
+
+	/* Stop new requests to arrive */
+	del_gendisk(dev->gd);
+	/* Finally destroy the blk queue */
+	dev_info(disk_to_dev(dev->gd), "released");
+	put_disk(dev->gd);
+	blk_mq_free_tag_set(&dev->tag_set);
+	idr_remove(&ubiblock_minor_idr, id);
+}
+
+int ubiblock_remove(struct ubi_volume_info *vi)
+{
+	struct ubiblock *dev;
+	int ret;
+
+	mutex_lock(&devices_mutex);
+	dev = find_dev_nolock(vi->ubi_num, vi->vol_id);
+	if (!dev) {
+		ret = -ENODEV;
+		goto out_unlock;
+	}
+
+	/* Found a device, let's lock it so we can check if it's busy */
+	mutex_lock(&dev->dev_mutex);
+	if (dev->refcnt > 0) {
+		ret = -EBUSY;
+		goto out_unlock_dev;
+	}
+
+	/* Remove from device list */
+	list_del(&dev->list);
+	ubiblock_cleanup(dev);
+	mutex_unlock(&dev->dev_mutex);
+	mutex_unlock(&devices_mutex);
+
+	kfree(dev);
+	return 0;
+
+out_unlock_dev:
+	mutex_unlock(&dev->dev_mutex);
+out_unlock:
+	mutex_unlock(&devices_mutex);
+	return ret;
+}
+
+static int ubiblock_resize(struct ubi_volume_info *vi)
+{
+	struct ubiblock *dev;
+	u64 disk_capacity;
+	int ret;
+
+	/*
+	 * Need to lock the device list until we stop using the device,
+	 * otherwise the device struct might get released in
+	 * 'ubiblock_remove()'.
+	 */
+	mutex_lock(&devices_mutex);
+	dev = find_dev_nolock(vi->ubi_num, vi->vol_id);
+	if (!dev) {
+		mutex_unlock(&devices_mutex);
+		return -ENODEV;
+	}
+
+	ret = calc_disk_capacity(vi, &disk_capacity);
+	if (ret) {
+		mutex_unlock(&devices_mutex);
+		if (ret == -EFBIG) {
+			dev_warn(disk_to_dev(dev->gd),
+				 "the volume is too big (%d LEBs), cannot resize",
+				 vi->size);
+		}
+		return ret;
+	}
+
+	mutex_lock(&dev->dev_mutex);
+
+	if (get_capacity(dev->gd) != disk_capacity) {
+		set_capacity(dev->gd, disk_capacity);
+		dev_info(disk_to_dev(dev->gd), "resized to %lld bytes",
+			 vi->used_bytes);
+	}
+	mutex_unlock(&dev->dev_mutex);
+	mutex_unlock(&devices_mutex);
+	return 0;
+}
+
+static bool
+match_volume_desc(struct ubi_volume_info *vi, const char *name, int ubi_num, int vol_id)
+{
+	int err, len, cur_ubi_num, cur_vol_id;
+
+	if (ubi_num == -1) {
+		/* No ubi num, name must be a vol device path */
+		err = ubi_get_num_by_path(name, &cur_ubi_num, &cur_vol_id);
+		if (err || vi->ubi_num != cur_ubi_num || vi->vol_id != cur_vol_id)
+			return false;
+
+		return true;
+	}
+
+	if (vol_id == -1) {
+		/* Got ubi_num, but no vol_id, name must be volume name */
+		if (vi->ubi_num != ubi_num)
+			return false;
+
+		len = strnlen(name, UBI_VOL_NAME_MAX + 1);
+		if (len < 1 || vi->name_len != len)
+			return false;
+
+		if (strcmp(name, vi->name))
+			return false;
+
+		return true;
+	}
+
+	if (vi->ubi_num != ubi_num)
+		return false;
+
+	if (vi->vol_id != vol_id)
+		return false;
+
+	return true;
+}
+
+static void
+ubiblock_create_from_param(struct ubi_volume_info *vi)
+{
+	int i, ret = 0;
+	struct ubiblock_param *p;
+
+	/*
+	 * Iterate over ubiblock cmdline parameters. If a parameter matches the
+	 * newly added volume create the ubiblock device for it.
+	 */
+	for (i = 0; i < ubiblock_devs; i++) {
+		p = &ubiblock_param[i];
+
+		if (!match_volume_desc(vi, p->name, p->ubi_num, p->vol_id))
+			continue;
+
+		ret = ubiblock_create(vi);
+		if (ret) {
+			pr_err(
+			       "UBI: block: can't add '%s' volume on ubi%d_%d, err=%d\n",
+			       vi->name, p->ubi_num, p->vol_id, ret);
+		}
+		break;
+	}
+}
+
+static int ubiblock_notify(struct notifier_block *nb,
+			 unsigned long notification_type, void *ns_ptr)
+{
+	struct ubi_notification *nt = ns_ptr;
+
+	switch (notification_type) {
+	case UBI_VOLUME_ADDED:
+		ubiblock_create_from_param(&nt->vi);
+		break;
+	case UBI_VOLUME_REMOVED:
+		ubiblock_remove(&nt->vi);
+		break;
+	case UBI_VOLUME_RESIZED:
+		ubiblock_resize(&nt->vi);
+		break;
+	case UBI_VOLUME_UPDATED:
+		/*
+		 * If the volume is static, a content update might mean the
+		 * size (i.e. used_bytes) was also changed.
+		 */
+		if (nt->vi.vol_type == UBI_STATIC_VOLUME)
+			ubiblock_resize(&nt->vi);
+		break;
+	default:
+		break;
+	}
+	return NOTIFY_OK;
+}
+
+static struct notifier_block ubiblock_notifier = {
+	.notifier_call = ubiblock_notify,
+};
+
+static void ubiblock_remove_all(void)
+{
+	struct ubiblock *next;
+	struct ubiblock *dev;
+
+	mutex_lock(&devices_mutex);
+	list_for_each_entry_safe(dev, next, &ubiblock_devices, list) {
+		/* The module is being forcefully removed */
+		WARN_ON(dev->desc);
+		/* Remove from device list */
+		list_del(&dev->list);
+		ubiblock_cleanup(dev);
+		kfree(dev);
+	}
+	mutex_unlock(&devices_mutex);
+}
+
+int __init ubiblock_init(void)
+{
+	int ret;
+
+	ubiblock_major = register_blkdev(0, "ubiblock");
+	if (ubiblock_major < 0)
+		return ubiblock_major;
+
+	ret = ubi_register_volume_notifier(&ubiblock_notifier, 0);
+	if (ret)
+		goto err_unreg;
+	return 0;
+
+err_unreg:
+	unregister_blkdev(ubiblock_major, "ubiblock");
+	ubiblock_remove_all();
+	return ret;
+}
+
+void ubiblock_exit(void)
+{
+	ubi_unregister_volume_notifier(&ubiblock_notifier);
+	ubiblock_remove_all();
+	unregister_blkdev(ubiblock_major, "ubiblock");
+}