Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 897 insertions, 0 deletions

diff --git a/drivers/mtd/mtdconcat.c b/drivers/mtd/mtdconcat.c
new file mode 100644
index 000000000..c97167d51
--- /dev/null
+++ b/drivers/mtd/mtdconcat.c
@@ -0,0 +1,897 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * MTD device concatenation layer
+ *
+ * Copyright © 2002 Robert Kaiser <rkaiser@sysgo.de>
+ * Copyright © 2002-2010 David Woodhouse <dwmw2@infradead.org>
+ *
+ * NAND support by Christian Gan <cgan@iders.ca>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
+#include <linux/types.h>
+#include <linux/backing-dev.h>
+
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/concat.h>
+
+#include <asm/div64.h>
+
+/*
+ * how to calculate the size required for the above structure,
+ * including the pointer array subdev points to:
+ */
+#define SIZEOF_STRUCT_MTD_CONCAT(num_subdev)	\
+	((sizeof(struct mtd_concat) + (num_subdev) * sizeof(struct mtd_info *)))
+
+/*
+ * Given a pointer to the MTD object in the mtd_concat structure,
+ * we can retrieve the pointer to that structure with this macro.
+ */
+#define CONCAT(x)  ((struct mtd_concat *)(x))
+
+/*
+ * MTD methods which look up the relevant subdevice, translate the
+ * effective address and pass through to the subdevice.
+ */
+
+static int
+concat_read(struct mtd_info *mtd, loff_t from, size_t len,
+	    size_t * retlen, u_char * buf)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	int ret = 0, err;
+	int i;
+
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+		size_t size, retsize;
+
+		if (from >= subdev->size) {
+			/* Not destined for this subdev */
+			size = 0;
+			from -= subdev->size;
+			continue;
+		}
+		if (from + len > subdev->size)
+			/* First part goes into this subdev */
+			size = subdev->size - from;
+		else
+			/* Entire transaction goes into this subdev */
+			size = len;
+
+		err = mtd_read(subdev, from, size, &retsize, buf);
+
+		/* Save information about bitflips! */
+		if (unlikely(err)) {
+			if (mtd_is_eccerr(err)) {
+				mtd->ecc_stats.failed++;
+				ret = err;
+			} else if (mtd_is_bitflip(err)) {
+				mtd->ecc_stats.corrected++;
+				/* Do not overwrite -EBADMSG !! */
+				if (!ret)
+					ret = err;
+			} else
+				return err;
+		}
+
+		*retlen += retsize;
+		len -= size;
+		if (len == 0)
+			return ret;
+
+		buf += size;
+		from = 0;
+	}
+	return -EINVAL;
+}
+
+static int
+concat_panic_write(struct mtd_info *mtd, loff_t to, size_t len,
+	     size_t * retlen, const u_char * buf)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	int err = -EINVAL;
+	int i;
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+		size_t size, retsize;
+
+		if (to >= subdev->size) {
+			to -= subdev->size;
+			continue;
+		}
+		if (to + len > subdev->size)
+			size = subdev->size - to;
+		else
+			size = len;
+
+		err = mtd_panic_write(subdev, to, size, &retsize, buf);
+		if (err == -EOPNOTSUPP) {
+			printk(KERN_ERR "mtdconcat: Cannot write from panic without panic_write\n");
+			return err;
+		}
+		if (err)
+			break;
+
+		*retlen += retsize;
+		len -= size;
+		if (len == 0)
+			break;
+
+		err = -EINVAL;
+		buf += size;
+		to = 0;
+	}
+	return err;
+}
+
+
+static int
+concat_write(struct mtd_info *mtd, loff_t to, size_t len,
+	     size_t * retlen, const u_char * buf)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	int err = -EINVAL;
+	int i;
+
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+		size_t size, retsize;
+
+		if (to >= subdev->size) {
+			size = 0;
+			to -= subdev->size;
+			continue;
+		}
+		if (to + len > subdev->size)
+			size = subdev->size - to;
+		else
+			size = len;
+
+		err = mtd_write(subdev, to, size, &retsize, buf);
+		if (err)
+			break;
+
+		*retlen += retsize;
+		len -= size;
+		if (len == 0)
+			break;
+
+		err = -EINVAL;
+		buf += size;
+		to = 0;
+	}
+	return err;
+}
+
+static int
+concat_writev(struct mtd_info *mtd, const struct kvec *vecs,
+		unsigned long count, loff_t to, size_t * retlen)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	struct kvec *vecs_copy;
+	unsigned long entry_low, entry_high;
+	size_t total_len = 0;
+	int i;
+	int err = -EINVAL;
+
+	/* Calculate total length of data */
+	for (i = 0; i < count; i++)
+		total_len += vecs[i].iov_len;
+
+	/* Check alignment */
+	if (mtd->writesize > 1) {
+		uint64_t __to = to;
+		if (do_div(__to, mtd->writesize) || (total_len % mtd->writesize))
+			return -EINVAL;
+	}
+
+	/* make a copy of vecs */
+	vecs_copy = kmemdup_array(vecs, count, sizeof(struct kvec), GFP_KERNEL);
+	if (!vecs_copy)
+		return -ENOMEM;
+
+	entry_low = 0;
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+		size_t size, wsize, retsize, old_iov_len;
+
+		if (to >= subdev->size) {
+			to -= subdev->size;
+			continue;
+		}
+
+		size = min_t(uint64_t, total_len, subdev->size - to);
+		wsize = size; /* store for future use */
+
+		entry_high = entry_low;
+		while (entry_high < count) {
+			if (size <= vecs_copy[entry_high].iov_len)
+				break;
+			size -= vecs_copy[entry_high++].iov_len;
+		}
+
+		old_iov_len = vecs_copy[entry_high].iov_len;
+		vecs_copy[entry_high].iov_len = size;
+
+		err = mtd_writev(subdev, &vecs_copy[entry_low],
+				 entry_high - entry_low + 1, to, &retsize);
+
+		vecs_copy[entry_high].iov_len = old_iov_len - size;
+		vecs_copy[entry_high].iov_base += size;
+
+		entry_low = entry_high;
+
+		if (err)
+			break;
+
+		*retlen += retsize;
+		total_len -= wsize;
+
+		if (total_len == 0)
+			break;
+
+		err = -EINVAL;
+		to = 0;
+	}
+
+	kfree(vecs_copy);
+	return err;
+}
+
+static int
+concat_read_oob(struct mtd_info *mtd, loff_t from, struct mtd_oob_ops *ops)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	struct mtd_oob_ops devops = *ops;
+	int i, err, ret = 0;
+
+	ops->retlen = ops->oobretlen = 0;
+
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+
+		if (from >= subdev->size) {
+			from -= subdev->size;
+			continue;
+		}
+
+		/* partial read ? */
+		if (from + devops.len > subdev->size)
+			devops.len = subdev->size - from;
+
+		err = mtd_read_oob(subdev, from, &devops);
+		ops->retlen += devops.retlen;
+		ops->oobretlen += devops.oobretlen;
+
+		/* Save information about bitflips! */
+		if (unlikely(err)) {
+			if (mtd_is_eccerr(err)) {
+				mtd->ecc_stats.failed++;
+				ret = err;
+			} else if (mtd_is_bitflip(err)) {
+				mtd->ecc_stats.corrected++;
+				/* Do not overwrite -EBADMSG !! */
+				if (!ret)
+					ret = err;
+			} else
+				return err;
+		}
+
+		if (devops.datbuf) {
+			devops.len = ops->len - ops->retlen;
+			if (!devops.len)
+				return ret;
+			devops.datbuf += devops.retlen;
+		}
+		if (devops.oobbuf) {
+			devops.ooblen = ops->ooblen - ops->oobretlen;
+			if (!devops.ooblen)
+				return ret;
+			devops.oobbuf += ops->oobretlen;
+		}
+
+		from = 0;
+	}
+	return -EINVAL;
+}
+
+static int
+concat_write_oob(struct mtd_info *mtd, loff_t to, struct mtd_oob_ops *ops)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	struct mtd_oob_ops devops = *ops;
+	int i, err;
+
+	if (!(mtd->flags & MTD_WRITEABLE))
+		return -EROFS;
+
+	ops->retlen = ops->oobretlen = 0;
+
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+
+		if (to >= subdev->size) {
+			to -= subdev->size;
+			continue;
+		}
+
+		/* partial write ? */
+		if (to + devops.len > subdev->size)
+			devops.len = subdev->size - to;
+
+		err = mtd_write_oob(subdev, to, &devops);
+		ops->retlen += devops.retlen;
+		ops->oobretlen += devops.oobretlen;
+		if (err)
+			return err;
+
+		if (devops.datbuf) {
+			devops.len = ops->len - ops->retlen;
+			if (!devops.len)
+				return 0;
+			devops.datbuf += devops.retlen;
+		}
+		if (devops.oobbuf) {
+			devops.ooblen = ops->ooblen - ops->oobretlen;
+			if (!devops.ooblen)
+				return 0;
+			devops.oobbuf += devops.oobretlen;
+		}
+		to = 0;
+	}
+	return -EINVAL;
+}
+
+static int concat_erase(struct mtd_info *mtd, struct erase_info *instr)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	struct mtd_info *subdev;
+	int i, err;
+	uint64_t length, offset = 0;
+	struct erase_info *erase;
+
+	/*
+	 * Check for proper erase block alignment of the to-be-erased area.
+	 * It is easier to do this based on the super device's erase
+	 * region info rather than looking at each particular sub-device
+	 * in turn.
+	 */
+	if (!concat->mtd.numeraseregions) {
+		/* the easy case: device has uniform erase block size */
+		if (instr->addr & (concat->mtd.erasesize - 1))
+			return -EINVAL;
+		if (instr->len & (concat->mtd.erasesize - 1))
+			return -EINVAL;
+	} else {
+		/* device has variable erase size */
+		struct mtd_erase_region_info *erase_regions =
+		    concat->mtd.eraseregions;
+
+		/*
+		 * Find the erase region where the to-be-erased area begins:
+		 */
+		for (i = 0; i < concat->mtd.numeraseregions &&
+		     instr->addr >= erase_regions[i].offset; i++) ;
+		--i;
+
+		/*
+		 * Now erase_regions[i] is the region in which the
+		 * to-be-erased area begins. Verify that the starting
+		 * offset is aligned to this region's erase size:
+		 */
+		if (i < 0 || instr->addr & (erase_regions[i].erasesize - 1))
+			return -EINVAL;
+
+		/*
+		 * now find the erase region where the to-be-erased area ends:
+		 */
+		for (; i < concat->mtd.numeraseregions &&
+		     (instr->addr + instr->len) >= erase_regions[i].offset;
+		     ++i) ;
+		--i;
+		/*
+		 * check if the ending offset is aligned to this region's erase size
+		 */
+		if (i < 0 || ((instr->addr + instr->len) &
+					(erase_regions[i].erasesize - 1)))
+			return -EINVAL;
+	}
+
+	/* make a local copy of instr to avoid modifying the caller's struct */
+	erase = kmalloc_obj(struct erase_info);
+
+	if (!erase)
+		return -ENOMEM;
+
+	*erase = *instr;
+	length = instr->len;
+
+	/*
+	 * find the subdevice where the to-be-erased area begins, adjust
+	 * starting offset to be relative to the subdevice start
+	 */
+	for (i = 0; i < concat->num_subdev; i++) {
+		subdev = concat->subdev[i];
+		if (subdev->size <= erase->addr) {
+			erase->addr -= subdev->size;
+			offset += subdev->size;
+		} else {
+			break;
+		}
+	}
+
+	/* must never happen since size limit has been verified above */
+	BUG_ON(i >= concat->num_subdev);
+
+	/* now do the erase: */
+	err = 0;
+	for (; length > 0; i++) {
+		/* loop for all subdevices affected by this request */
+		subdev = concat->subdev[i];	/* get current subdevice */
+
+		/* limit length to subdevice's size: */
+		if (erase->addr + length > subdev->size)
+			erase->len = subdev->size - erase->addr;
+		else
+			erase->len = length;
+
+		length -= erase->len;
+		if ((err = mtd_erase(subdev, erase))) {
+			/* sanity check: should never happen since
+			 * block alignment has been checked above */
+			BUG_ON(err == -EINVAL);
+			if (erase->fail_addr != MTD_FAIL_ADDR_UNKNOWN)
+				instr->fail_addr = erase->fail_addr + offset;
+			break;
+		}
+		/*
+		 * erase->addr specifies the offset of the area to be
+		 * erased *within the current subdevice*. It can be
+		 * non-zero only the first time through this loop, i.e.
+		 * for the first subdevice where blocks need to be erased.
+		 * All the following erases must begin at the start of the
+		 * current subdevice, i.e. at offset zero.
+		 */
+		erase->addr = 0;
+		offset += subdev->size;
+	}
+	kfree(erase);
+
+	return err;
+}
+
+static int concat_xxlock(struct mtd_info *mtd, loff_t ofs, uint64_t len,
+			 bool is_lock)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	int i, err = -EINVAL;
+
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+		uint64_t size;
+
+		if (ofs >= subdev->size) {
+			size = 0;
+			ofs -= subdev->size;
+			continue;
+		}
+		if (ofs + len > subdev->size)
+			size = subdev->size - ofs;
+		else
+			size = len;
+
+		if (is_lock)
+			err = mtd_lock(subdev, ofs, size);
+		else
+			err = mtd_unlock(subdev, ofs, size);
+		if (err)
+			break;
+
+		len -= size;
+		if (len == 0)
+			break;
+
+		err = -EINVAL;
+		ofs = 0;
+	}
+
+	return err;
+}
+
+static int concat_lock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
+{
+	return concat_xxlock(mtd, ofs, len, true);
+}
+
+static int concat_unlock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
+{
+	return concat_xxlock(mtd, ofs, len, false);
+}
+
+static int concat_is_locked(struct mtd_info *mtd, loff_t ofs, uint64_t len)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	int i, err = -EINVAL;
+
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+
+		if (ofs >= subdev->size) {
+			ofs -= subdev->size;
+			continue;
+		}
+
+		if (ofs + len > subdev->size)
+			break;
+
+		return mtd_is_locked(subdev, ofs, len);
+	}
+
+	return err;
+}
+
+static void concat_sync(struct mtd_info *mtd)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	int i;
+
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+		mtd_sync(subdev);
+	}
+}
+
+static int concat_suspend(struct mtd_info *mtd)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	int i, rc = 0;
+
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+		if ((rc = mtd_suspend(subdev)) < 0)
+			return rc;
+	}
+	return rc;
+}
+
+static void concat_resume(struct mtd_info *mtd)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	int i;
+
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+		mtd_resume(subdev);
+	}
+}
+
+static int concat_block_isbad(struct mtd_info *mtd, loff_t ofs)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	int i, res = 0;
+
+	if (!mtd_can_have_bb(concat->subdev[0]))
+		return res;
+
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+
+		if (ofs >= subdev->size) {
+			ofs -= subdev->size;
+			continue;
+		}
+
+		res = mtd_block_isbad(subdev, ofs);
+		break;
+	}
+
+	return res;
+}
+
+static int concat_block_markbad(struct mtd_info *mtd, loff_t ofs)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	int i, err = -EINVAL;
+
+	for (i = 0; i < concat->num_subdev; i++) {
+		struct mtd_info *subdev = concat->subdev[i];
+
+		if (ofs >= subdev->size) {
+			ofs -= subdev->size;
+			continue;
+		}
+
+		err = mtd_block_markbad(subdev, ofs);
+		if (!err)
+			mtd->ecc_stats.badblocks++;
+		break;
+	}
+
+	return err;
+}
+
+/*
+ * This function constructs a virtual MTD device by concatenating
+ * num_devs MTD devices. A pointer to the new device object is
+ * stored to *new_dev upon success. This function does _not_
+ * register any devices: this is the caller's responsibility.
+ */
+struct mtd_info *mtd_concat_create(struct mtd_info *subdev[],	/* subdevices to concatenate */
+				   int num_devs,	/* number of subdevices      */
+				   const char *name)
+{				/* name for the new device   */
+	int i;
+	struct mtd_concat *concat;
+	struct mtd_info *subdev_master = NULL;
+	uint32_t max_erasesize, curr_erasesize;
+	int num_erase_region;
+	int max_writebufsize = 0;
+
+	printk(KERN_NOTICE "Concatenating MTD devices:\n");
+	for (i = 0; i < num_devs; i++)
+		printk(KERN_NOTICE "(%d): \"%s\"\n", i, subdev[i]->name);
+	printk(KERN_NOTICE "into device \"%s\"\n", name);
+
+	/* allocate the device structure */
+	concat = kzalloc_flex(*concat, subdev, num_devs, GFP_KERNEL);
+	if (!concat) {
+		printk
+		    ("memory allocation error while creating concatenated device \"%s\"\n",
+		     name);
+		return NULL;
+	}
+
+	/*
+	 * Set up the new "super" device's MTD object structure, check for
+	 * incompatibilities between the subdevices.
+	 */
+	concat->mtd.type = subdev[0]->type;
+	concat->mtd.flags = subdev[0]->flags;
+	concat->mtd.size = subdev[0]->size;
+	concat->mtd.erasesize = subdev[0]->erasesize;
+	concat->mtd.writesize = subdev[0]->writesize;
+
+	for (i = 0; i < num_devs; i++)
+		if (max_writebufsize < subdev[i]->writebufsize)
+			max_writebufsize = subdev[i]->writebufsize;
+	concat->mtd.writebufsize = max_writebufsize;
+
+	concat->mtd.subpage_sft = subdev[0]->subpage_sft;
+	concat->mtd.oobsize = subdev[0]->oobsize;
+	concat->mtd.oobavail = subdev[0]->oobavail;
+
+	subdev_master = mtd_get_master(subdev[0]);
+	if (subdev_master->_writev)
+		concat->mtd._writev = concat_writev;
+	if (subdev_master->_read_oob)
+		concat->mtd._read_oob = concat_read_oob;
+	if (subdev_master->_write_oob)
+		concat->mtd._write_oob = concat_write_oob;
+	if (subdev_master->_block_isbad)
+		concat->mtd._block_isbad = concat_block_isbad;
+	if (subdev_master->_block_markbad)
+		concat->mtd._block_markbad = concat_block_markbad;
+	if (subdev_master->_panic_write)
+		concat->mtd._panic_write = concat_panic_write;
+	if (subdev_master->_read)
+		concat->mtd._read = concat_read;
+	if (subdev_master->_write)
+		concat->mtd._write = concat_write;
+
+	concat->mtd.ecc_stats.badblocks = subdev[0]->ecc_stats.badblocks;
+
+	concat->subdev[0] = subdev[0];
+
+	for (i = 1; i < num_devs; i++) {
+		if (concat->mtd.type != subdev[i]->type) {
+			kfree(concat);
+			printk("Incompatible device type on \"%s\"\n",
+			       subdev[i]->name);
+			return NULL;
+		}
+		if (concat->mtd.flags != subdev[i]->flags) {
+			/*
+			 * Expect all flags except MTD_WRITEABLE to be
+			 * equal on all subdevices.
+			 */
+			if ((concat->mtd.flags ^ subdev[i]->
+			     flags) & ~MTD_WRITEABLE) {
+				kfree(concat);
+				printk("Incompatible device flags on \"%s\"\n",
+				       subdev[i]->name);
+				return NULL;
+			} else
+				/* if writeable attribute differs,
+				   make super device writeable */
+				concat->mtd.flags |=
+				    subdev[i]->flags & MTD_WRITEABLE;
+		}
+
+		subdev_master = mtd_get_master(subdev[i]);
+		concat->mtd.size += subdev[i]->size;
+		concat->mtd.ecc_stats.badblocks +=
+			subdev[i]->ecc_stats.badblocks;
+		if (concat->mtd.writesize   !=  subdev[i]->writesize ||
+		    concat->mtd.subpage_sft != subdev[i]->subpage_sft ||
+		    concat->mtd.oobsize    !=  subdev[i]->oobsize ||
+		    !concat->mtd._read_oob  != !subdev_master->_read_oob ||
+		    !concat->mtd._write_oob != !subdev_master->_write_oob) {
+			/*
+			 * Check against subdev[i] for data members, because
+			 * subdev's attributes may be different from master
+			 * mtd device. Check against subdev's master mtd
+			 * device for callbacks, because the existence of
+			 * subdev's callbacks is decided by master mtd device.
+			 */
+			kfree(concat);
+			printk("Incompatible OOB or ECC data on \"%s\"\n",
+			       subdev[i]->name);
+			return NULL;
+		}
+		concat->subdev[i] = subdev[i];
+
+	}
+
+	mtd_set_ooblayout(&concat->mtd, subdev[0]->ooblayout);
+
+	concat->num_subdev = num_devs;
+	concat->mtd.name = name;
+
+	concat->mtd._erase = concat_erase;
+	concat->mtd._sync = concat_sync;
+	concat->mtd._lock = concat_lock;
+	concat->mtd._unlock = concat_unlock;
+	concat->mtd._is_locked = concat_is_locked;
+	concat->mtd._suspend = concat_suspend;
+	concat->mtd._resume = concat_resume;
+
+	/*
+	 * Combine the erase block size info of the subdevices:
+	 *
+	 * first, walk the map of the new device and see how
+	 * many changes in erase size we have
+	 */
+	max_erasesize = curr_erasesize = subdev[0]->erasesize;
+	num_erase_region = 1;
+	for (i = 0; i < num_devs; i++) {
+		if (subdev[i]->numeraseregions == 0) {
+			/* current subdevice has uniform erase size */
+			if (subdev[i]->erasesize != curr_erasesize) {
+				/* if it differs from the last subdevice's erase size, count it */
+				++num_erase_region;
+				curr_erasesize = subdev[i]->erasesize;
+				if (curr_erasesize > max_erasesize)
+					max_erasesize = curr_erasesize;
+			}
+		} else {
+			/* current subdevice has variable erase size */
+			int j;
+			for (j = 0; j < subdev[i]->numeraseregions; j++) {
+
+				/* walk the list of erase regions, count any changes */
+				if (subdev[i]->eraseregions[j].erasesize !=
+				    curr_erasesize) {
+					++num_erase_region;
+					curr_erasesize =
+					    subdev[i]->eraseregions[j].
+					    erasesize;
+					if (curr_erasesize > max_erasesize)
+						max_erasesize = curr_erasesize;
+				}
+			}
+		}
+	}
+
+	if (num_erase_region == 1) {
+		/*
+		 * All subdevices have the same uniform erase size.
+		 * This is easy:
+		 */
+		concat->mtd.erasesize = curr_erasesize;
+		concat->mtd.numeraseregions = 0;
+	} else {
+		uint64_t tmp64;
+
+		/*
+		 * erase block size varies across the subdevices: allocate
+		 * space to store the data describing the variable erase regions
+		 */
+		struct mtd_erase_region_info *erase_region_p;
+		uint64_t begin, position;
+
+		concat->mtd.erasesize = max_erasesize;
+		concat->mtd.numeraseregions = num_erase_region;
+		concat->mtd.eraseregions = erase_region_p =
+		    kmalloc_objs(struct mtd_erase_region_info, num_erase_region);
+		if (!erase_region_p) {
+			kfree(concat);
+			printk
+			    ("memory allocation error while creating erase region list"
+			     " for device \"%s\"\n", name);
+			return NULL;
+		}
+
+		/*
+		 * walk the map of the new device once more and fill in
+		 * erase region info:
+		 */
+		curr_erasesize = subdev[0]->erasesize;
+		begin = position = 0;
+		for (i = 0; i < num_devs; i++) {
+			if (subdev[i]->numeraseregions == 0) {
+				/* current subdevice has uniform erase size */
+				if (subdev[i]->erasesize != curr_erasesize) {
+					/*
+					 *  fill in an mtd_erase_region_info structure for the area
+					 *  we have walked so far:
+					 */
+					erase_region_p->offset = begin;
+					erase_region_p->erasesize =
+					    curr_erasesize;
+					tmp64 = position - begin;
+					do_div(tmp64, curr_erasesize);
+					erase_region_p->numblocks = tmp64;
+					begin = position;
+
+					curr_erasesize = subdev[i]->erasesize;
+					++erase_region_p;
+				}
+				position += subdev[i]->size;
+			} else {
+				/* current subdevice has variable erase size */
+				int j;
+				for (j = 0; j < subdev[i]->numeraseregions; j++) {
+					/* walk the list of erase regions, count any changes */
+					if (subdev[i]->eraseregions[j].
+					    erasesize != curr_erasesize) {
+						erase_region_p->offset = begin;
+						erase_region_p->erasesize =
+						    curr_erasesize;
+						tmp64 = position - begin;
+						do_div(tmp64, curr_erasesize);
+						erase_region_p->numblocks = tmp64;
+						begin = position;
+
+						curr_erasesize =
+						    subdev[i]->eraseregions[j].
+						    erasesize;
+						++erase_region_p;
+					}
+					position +=
+					    subdev[i]->eraseregions[j].
+					    numblocks * (uint64_t)curr_erasesize;
+				}
+			}
+		}
+		/* Now write the final entry */
+		erase_region_p->offset = begin;
+		erase_region_p->erasesize = curr_erasesize;
+		tmp64 = position - begin;
+		do_div(tmp64, curr_erasesize);
+		erase_region_p->numblocks = tmp64;
+	}
+
+	return &concat->mtd;
+}
+
+/* Cleans the context obtained from mtd_concat_create() */
+void mtd_concat_destroy(struct mtd_info *mtd)
+{
+	struct mtd_concat *concat = CONCAT(mtd);
+	if (concat->mtd.numeraseregions)
+		kfree(concat->mtd.eraseregions);
+	kfree(concat);
+}
+
+EXPORT_SYMBOL(mtd_concat_create);
+EXPORT_SYMBOL(mtd_concat_destroy);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Robert Kaiser <rkaiser@sysgo.de>");
+MODULE_DESCRIPTION("Generic support for concatenating of MTD devices");