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, 709 insertions, 0 deletions

diff --git a/drivers/md/dm-flakey.c b/drivers/md/dm-flakey.c
new file mode 100644
index 000000000..572225b0e
--- /dev/null
+++ b/drivers/md/dm-flakey.c
@@ -0,0 +1,709 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2003 Sistina Software (UK) Limited.
+ * Copyright (C) 2004, 2010-2011 Red Hat, Inc. All rights reserved.
+ *
+ * This file is released under the GPL.
+ */
+
+#include <linux/device-mapper.h>
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/blkdev.h>
+#include <linux/bio.h>
+#include <linux/slab.h>
+
+#define DM_MSG_PREFIX "flakey"
+
+#define PROBABILITY_BASE	1000000000
+
+#define all_corrupt_bio_flags_match(bio, fc)	\
+	(((bio)->bi_opf & (fc)->corrupt_bio_flags) == (fc)->corrupt_bio_flags)
+
+/*
+ * Flakey: Used for testing only, simulates intermittent,
+ * catastrophic device failure.
+ */
+struct flakey_c {
+	struct dm_dev *dev;
+	unsigned long start_time;
+	sector_t start;
+	unsigned int up_interval;
+	unsigned int down_interval;
+	unsigned long flags;
+	unsigned int corrupt_bio_byte;
+	unsigned int corrupt_bio_rw;
+	unsigned int corrupt_bio_value;
+	blk_opf_t corrupt_bio_flags;
+	unsigned int random_read_corrupt;
+	unsigned int random_write_corrupt;
+};
+
+enum feature_flag_bits {
+	ERROR_READS,
+	DROP_WRITES,
+	ERROR_WRITES
+};
+
+struct per_bio_data {
+	bool bio_can_corrupt;
+	struct bvec_iter saved_iter;
+};
+
+static int parse_features(struct dm_arg_set *as, struct flakey_c *fc,
+			  struct dm_target *ti)
+{
+	int r = 0;
+	unsigned int argc = 0;
+	const char *arg_name;
+
+	static const struct dm_arg _args[] = {
+		{0, 11, "Invalid number of feature args"},
+		{1, UINT_MAX, "Invalid corrupt bio byte"},
+		{0, 255, "Invalid corrupt value to write into bio byte (0-255)"},
+		{0, UINT_MAX, "Invalid corrupt bio flags mask"},
+		{0, PROBABILITY_BASE, "Invalid random corrupt argument"},
+	};
+
+	if (as->argc && (r = dm_read_arg_group(_args, as, &argc, &ti->error)))
+		return r;
+
+	/* No feature arguments supplied. */
+	if (!argc)
+		goto error_all_io;
+
+	while (argc) {
+		arg_name = dm_shift_arg(as);
+		argc--;
+
+		if (!arg_name) {
+			ti->error = "Insufficient feature arguments";
+			return -EINVAL;
+		}
+
+		/*
+		 * error_reads
+		 */
+		if (!strcasecmp(arg_name, "error_reads")) {
+			if (test_and_set_bit(ERROR_READS, &fc->flags)) {
+				ti->error = "Feature error_reads duplicated";
+				return -EINVAL;
+			}
+			continue;
+		}
+
+		/*
+		 * drop_writes
+		 */
+		if (!strcasecmp(arg_name, "drop_writes")) {
+			if (test_and_set_bit(DROP_WRITES, &fc->flags)) {
+				ti->error = "Feature drop_writes duplicated";
+				return -EINVAL;
+			} else if (test_bit(ERROR_WRITES, &fc->flags)) {
+				ti->error = "Feature drop_writes conflicts with feature error_writes";
+				return -EINVAL;
+			}
+
+			continue;
+		}
+
+		/*
+		 * error_writes
+		 */
+		if (!strcasecmp(arg_name, "error_writes")) {
+			if (test_and_set_bit(ERROR_WRITES, &fc->flags)) {
+				ti->error = "Feature error_writes duplicated";
+				return -EINVAL;
+
+			} else if (test_bit(DROP_WRITES, &fc->flags)) {
+				ti->error = "Feature error_writes conflicts with feature drop_writes";
+				return -EINVAL;
+			}
+
+			continue;
+		}
+
+		/*
+		 * corrupt_bio_byte <Nth_byte> <direction> <value> <bio_flags>
+		 */
+		if (!strcasecmp(arg_name, "corrupt_bio_byte")) {
+			if (fc->corrupt_bio_byte) {
+				ti->error = "Feature corrupt_bio_byte duplicated";
+				return -EINVAL;
+			} else if (argc < 4) {
+				ti->error = "Feature corrupt_bio_byte requires 4 parameters";
+				return -EINVAL;
+			}
+
+			r = dm_read_arg(_args + 1, as, &fc->corrupt_bio_byte, &ti->error);
+			if (r)
+				return r;
+			argc--;
+
+			/*
+			 * Direction r or w?
+			 */
+			arg_name = dm_shift_arg(as);
+			if (arg_name && !strcasecmp(arg_name, "w"))
+				fc->corrupt_bio_rw = WRITE;
+			else if (arg_name && !strcasecmp(arg_name, "r"))
+				fc->corrupt_bio_rw = READ;
+			else {
+				ti->error = "Invalid corrupt bio direction (r or w)";
+				return -EINVAL;
+			}
+			argc--;
+
+			/*
+			 * Value of byte (0-255) to write in place of correct one.
+			 */
+			r = dm_read_arg(_args + 2, as, &fc->corrupt_bio_value, &ti->error);
+			if (r)
+				return r;
+			argc--;
+
+			/*
+			 * Only corrupt bios with these flags set.
+			 */
+			BUILD_BUG_ON(sizeof(fc->corrupt_bio_flags) !=
+				     sizeof(unsigned int));
+			r = dm_read_arg(_args + 3, as,
+				(__force unsigned int *)&fc->corrupt_bio_flags,
+				&ti->error);
+			if (r)
+				return r;
+			argc--;
+
+			continue;
+		}
+
+		if (!strcasecmp(arg_name, "random_read_corrupt")) {
+			if (fc->random_read_corrupt) {
+				ti->error = "Feature random_read_corrupt duplicated";
+				return -EINVAL;
+			} else if (!argc) {
+				ti->error = "Feature random_read_corrupt requires a parameter";
+				return -EINVAL;
+			}
+			r = dm_read_arg(_args + 4, as, &fc->random_read_corrupt, &ti->error);
+			if (r)
+				return r;
+			argc--;
+
+			continue;
+		}
+
+		if (!strcasecmp(arg_name, "random_write_corrupt")) {
+			if (fc->random_write_corrupt) {
+				ti->error = "Feature random_write_corrupt duplicated";
+				return -EINVAL;
+			} else if (!argc) {
+				ti->error = "Feature random_write_corrupt requires a parameter";
+				return -EINVAL;
+			}
+			r = dm_read_arg(_args + 4, as, &fc->random_write_corrupt, &ti->error);
+			if (r)
+				return r;
+			argc--;
+
+			continue;
+		}
+
+		ti->error = "Unrecognised flakey feature requested";
+		return -EINVAL;
+	}
+
+	if (test_bit(DROP_WRITES, &fc->flags) &&
+	    ((fc->corrupt_bio_byte && fc->corrupt_bio_rw == WRITE) ||
+	     fc->random_write_corrupt)) {
+		ti->error = "drop_writes is incompatible with random_write_corrupt or corrupt_bio_byte with the WRITE flag set";
+		return -EINVAL;
+
+	} else if (test_bit(ERROR_WRITES, &fc->flags) &&
+		   ((fc->corrupt_bio_byte && fc->corrupt_bio_rw == WRITE) ||
+		    fc->random_write_corrupt)) {
+		ti->error = "error_writes is incompatible with random_write_corrupt or corrupt_bio_byte with the WRITE flag set";
+		return -EINVAL;
+	} else if (test_bit(ERROR_READS, &fc->flags) &&
+		   ((fc->corrupt_bio_byte && fc->corrupt_bio_rw == READ) ||
+		    fc->random_read_corrupt)) {
+		ti->error = "error_reads is incompatible with random_read_corrupt or corrupt_bio_byte with the READ flag set";
+		return -EINVAL;
+	}
+
+	if (!fc->corrupt_bio_byte && !test_bit(ERROR_READS, &fc->flags) &&
+	    !test_bit(DROP_WRITES, &fc->flags) && !test_bit(ERROR_WRITES, &fc->flags) &&
+	    !fc->random_read_corrupt && !fc->random_write_corrupt) {
+error_all_io:
+		set_bit(ERROR_WRITES, &fc->flags);
+		set_bit(ERROR_READS, &fc->flags);
+	}
+
+	return 0;
+}
+
+/*
+ * Construct a flakey mapping:
+ * <dev_path> <offset> <up interval> <down interval> [<#feature args> [<arg>]*]
+ *
+ *   Feature args:
+ *     [drop_writes]
+ *     [corrupt_bio_byte <Nth_byte> <direction> <value> <bio_flags>]
+ *
+ *   Nth_byte starts from 1 for the first byte.
+ *   Direction is r for READ or w for WRITE.
+ *   bio_flags is ignored if 0.
+ */
+static int flakey_ctr(struct dm_target *ti, unsigned int argc, char **argv)
+{
+	static const struct dm_arg _args[] = {
+		{0, UINT_MAX, "Invalid up interval"},
+		{0, UINT_MAX, "Invalid down interval"},
+	};
+
+	int r;
+	struct flakey_c *fc;
+	unsigned long long tmpll;
+	struct dm_arg_set as;
+	const char *devname;
+	char dummy;
+
+	as.argc = argc;
+	as.argv = argv;
+
+	if (argc < 4) {
+		ti->error = "Invalid argument count";
+		return -EINVAL;
+	}
+
+	fc = kzalloc_obj(*fc);
+	if (!fc) {
+		ti->error = "Cannot allocate context";
+		return -ENOMEM;
+	}
+	fc->start_time = jiffies;
+
+	devname = dm_shift_arg(&as);
+
+	r = -EINVAL;
+	if (sscanf(dm_shift_arg(&as), "%llu%c", &tmpll, &dummy) != 1 || tmpll != (sector_t)tmpll) {
+		ti->error = "Invalid device sector";
+		goto bad;
+	}
+	fc->start = tmpll;
+
+	r = dm_read_arg(_args, &as, &fc->up_interval, &ti->error);
+	if (r)
+		goto bad;
+
+	r = dm_read_arg(_args + 1, &as, &fc->down_interval, &ti->error);
+	if (r)
+		goto bad;
+
+	if (!(fc->up_interval + fc->down_interval)) {
+		ti->error = "Total (up + down) interval is zero";
+		r = -EINVAL;
+		goto bad;
+	}
+
+	if (fc->up_interval + fc->down_interval < fc->up_interval) {
+		ti->error = "Interval overflow";
+		r = -EINVAL;
+		goto bad;
+	}
+
+	r = parse_features(&as, fc, ti);
+	if (r)
+		goto bad;
+
+	r = dm_get_device(ti, devname, dm_table_get_mode(ti->table), &fc->dev);
+	if (r) {
+		ti->error = "Device lookup failed";
+		goto bad;
+	}
+
+	ti->num_flush_bios = 1;
+	ti->num_discard_bios = 1;
+	ti->per_io_data_size = sizeof(struct per_bio_data);
+	ti->private = fc;
+	return 0;
+
+bad:
+	kfree(fc);
+	return r;
+}
+
+static void flakey_dtr(struct dm_target *ti)
+{
+	struct flakey_c *fc = ti->private;
+
+	dm_put_device(ti, fc->dev);
+	kfree(fc);
+}
+
+static sector_t flakey_map_sector(struct dm_target *ti, sector_t bi_sector)
+{
+	struct flakey_c *fc = ti->private;
+
+	return fc->start + dm_target_offset(ti, bi_sector);
+}
+
+static void flakey_map_bio(struct dm_target *ti, struct bio *bio)
+{
+	struct flakey_c *fc = ti->private;
+
+	bio_set_dev(bio, fc->dev->bdev);
+	bio->bi_iter.bi_sector = flakey_map_sector(ti, bio->bi_iter.bi_sector);
+}
+
+static void corrupt_bio_common(struct bio *bio, unsigned int corrupt_bio_byte,
+			       unsigned char corrupt_bio_value,
+			       struct bvec_iter start)
+{
+	struct bvec_iter iter;
+	struct bio_vec bvec;
+
+	/*
+	 * Overwrite the Nth byte of the bio's data, on whichever page
+	 * it falls.
+	 */
+	__bio_for_each_segment(bvec, bio, iter, start) {
+		if (bio_iter_len(bio, iter) > corrupt_bio_byte) {
+			unsigned char *segment = bvec_kmap_local(&bvec);
+			segment[corrupt_bio_byte] = corrupt_bio_value;
+			kunmap_local(segment);
+			DMDEBUG("Corrupting data bio=%p by writing %u to byte %u "
+				"(rw=%c bi_opf=%u bi_sector=%llu size=%u)\n",
+				bio, corrupt_bio_value, corrupt_bio_byte,
+				(bio_data_dir(bio) == WRITE) ? 'w' : 'r', bio->bi_opf,
+				(unsigned long long)start.bi_sector,
+				start.bi_size);
+			break;
+		}
+		corrupt_bio_byte -= bio_iter_len(bio, iter);
+	}
+}
+
+static void corrupt_bio_data(struct bio *bio, struct flakey_c *fc,
+			     struct bvec_iter start)
+{
+	unsigned int corrupt_bio_byte = fc->corrupt_bio_byte - 1;
+
+	corrupt_bio_common(bio, corrupt_bio_byte, fc->corrupt_bio_value, start);
+}
+
+static void corrupt_bio_random(struct bio *bio, struct bvec_iter start)
+{
+	unsigned int corrupt_byte;
+	unsigned char corrupt_value;
+
+	corrupt_byte = get_random_u32() % start.bi_size;
+	corrupt_value = get_random_u8();
+
+	corrupt_bio_common(bio, corrupt_byte, corrupt_value, start);
+}
+
+static void clone_free(struct bio *clone)
+{
+	struct folio_iter fi;
+
+	if (clone->bi_vcnt > 0) { /* bio_for_each_folio_all crashes with an empty bio */
+		bio_for_each_folio_all(fi, clone)
+			folio_put(fi.folio);
+	}
+
+	bio_uninit(clone);
+	kfree(clone);
+}
+
+static void clone_endio(struct bio *clone)
+{
+	struct bio *bio = clone->bi_private;
+	bio->bi_status = clone->bi_status;
+	clone_free(clone);
+	bio_endio(bio);
+}
+
+static struct bio *clone_bio(struct dm_target *ti, struct flakey_c *fc, struct bio *bio)
+{
+	struct bio *clone;
+	unsigned size, remaining_size, nr_iovecs, order;
+	struct bvec_iter iter = bio->bi_iter;
+
+	if (unlikely(bio->bi_iter.bi_size > UIO_MAXIOV << PAGE_SHIFT))
+		dm_accept_partial_bio(bio, UIO_MAXIOV << PAGE_SHIFT >> SECTOR_SHIFT);
+
+	size = bio->bi_iter.bi_size;
+	nr_iovecs = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
+
+	clone = bio_kmalloc(nr_iovecs, GFP_NOIO | __GFP_NORETRY | __GFP_NOWARN);
+	if (!clone)
+		return NULL;
+
+	bio_init_inline(clone, fc->dev->bdev, nr_iovecs, bio->bi_opf);
+
+	clone->bi_iter.bi_sector = flakey_map_sector(ti, bio->bi_iter.bi_sector);
+	clone->bi_private = bio;
+	clone->bi_end_io = clone_endio;
+
+	remaining_size = size;
+
+	order = MAX_PAGE_ORDER;
+	while (remaining_size) {
+		struct page *pages;
+		unsigned size_to_add, to_copy;
+		unsigned char *virt;
+		unsigned remaining_order = __fls((remaining_size + PAGE_SIZE - 1) >> PAGE_SHIFT);
+		order = min(order, remaining_order);
+
+retry_alloc_pages:
+		pages = alloc_pages(GFP_NOIO | __GFP_NORETRY | __GFP_NOWARN | __GFP_COMP, order);
+		if (unlikely(!pages)) {
+			if (order) {
+				order--;
+				goto retry_alloc_pages;
+			}
+			clone_free(clone);
+			return NULL;
+		}
+		size_to_add = min((unsigned)PAGE_SIZE << order, remaining_size);
+
+		virt = page_to_virt(pages);
+		to_copy = size_to_add;
+		do {
+			struct bio_vec bvec = bvec_iter_bvec(bio->bi_io_vec, iter);
+			unsigned this_step = min(bvec.bv_len, to_copy);
+			void *map = bvec_kmap_local(&bvec);
+			memcpy(virt, map, this_step);
+			kunmap_local(map);
+
+			bvec_iter_advance(bio->bi_io_vec, &iter, this_step);
+			to_copy -= this_step;
+			virt += this_step;
+		} while (to_copy);
+
+		__bio_add_page(clone, pages, size_to_add, 0);
+		remaining_size -= size_to_add;
+	}
+
+	return clone;
+}
+
+static int flakey_map(struct dm_target *ti, struct bio *bio)
+{
+	struct flakey_c *fc = ti->private;
+	unsigned int elapsed;
+	struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
+
+	pb->bio_can_corrupt = false;
+
+	if (op_is_zone_mgmt(bio_op(bio)))
+		goto map_bio;
+
+	/* Are we alive ? */
+	elapsed = (jiffies - fc->start_time) / HZ;
+	if (elapsed % (fc->up_interval + fc->down_interval) >= fc->up_interval) {
+		bool corrupt_fixed, corrupt_random;
+
+		if (bio_has_data(bio)) {
+			pb->bio_can_corrupt = true;
+			pb->saved_iter = bio->bi_iter;
+		}
+
+		/*
+		 * If ERROR_READS isn't set flakey_end_io() will decide if the
+		 * reads should be modified.
+		 */
+		if (bio_data_dir(bio) == READ) {
+			if (test_bit(ERROR_READS, &fc->flags))
+				return DM_MAPIO_KILL;
+			goto map_bio;
+		}
+
+		/*
+		 * Drop or error writes?
+		 */
+		if (test_bit(DROP_WRITES, &fc->flags)) {
+			bio_endio(bio);
+			return DM_MAPIO_SUBMITTED;
+		} else if (test_bit(ERROR_WRITES, &fc->flags)) {
+			bio_io_error(bio);
+			return DM_MAPIO_SUBMITTED;
+		}
+
+		if (!pb->bio_can_corrupt)
+			goto map_bio;
+		/*
+		 * Corrupt matching writes.
+		 */
+		corrupt_fixed = false;
+		corrupt_random = false;
+		if (fc->corrupt_bio_byte && fc->corrupt_bio_rw == WRITE) {
+			if (all_corrupt_bio_flags_match(bio, fc))
+				corrupt_fixed = true;
+		}
+		if (fc->random_write_corrupt) {
+			u64 rnd = get_random_u64();
+			u32 rem = do_div(rnd, PROBABILITY_BASE);
+			if (rem < fc->random_write_corrupt)
+				corrupt_random = true;
+		}
+		if (corrupt_fixed || corrupt_random) {
+			struct bio *clone = clone_bio(ti, fc, bio);
+			if (clone) {
+				if (corrupt_fixed)
+					corrupt_bio_data(clone, fc,
+							 clone->bi_iter);
+				if (corrupt_random)
+					corrupt_bio_random(clone,
+							   clone->bi_iter);
+				submit_bio(clone);
+				return DM_MAPIO_SUBMITTED;
+			}
+		}
+	}
+
+map_bio:
+	flakey_map_bio(ti, bio);
+
+	return DM_MAPIO_REMAPPED;
+}
+
+static int flakey_end_io(struct dm_target *ti, struct bio *bio,
+			 blk_status_t *error)
+{
+	struct flakey_c *fc = ti->private;
+	struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
+
+	if (op_is_zone_mgmt(bio_op(bio)))
+		return DM_ENDIO_DONE;
+
+	if (!*error && pb->bio_can_corrupt && (bio_data_dir(bio) == READ)) {
+		if (fc->corrupt_bio_byte) {
+			if ((fc->corrupt_bio_rw == READ) &&
+			    all_corrupt_bio_flags_match(bio, fc)) {
+				/*
+				 * Corrupt successful matching READs while in down state.
+				 */
+				corrupt_bio_data(bio, fc, pb->saved_iter);
+			}
+		}
+		if (fc->random_read_corrupt) {
+			u64 rnd = get_random_u64();
+			u32 rem = do_div(rnd, PROBABILITY_BASE);
+			if (rem < fc->random_read_corrupt)
+				corrupt_bio_random(bio, pb->saved_iter);
+		}
+	}
+
+	return DM_ENDIO_DONE;
+}
+
+static void flakey_status(struct dm_target *ti, status_type_t type,
+			  unsigned int status_flags, char *result, unsigned int maxlen)
+{
+	unsigned int sz = 0;
+	struct flakey_c *fc = ti->private;
+	unsigned int error_reads, drop_writes, error_writes;
+
+	switch (type) {
+	case STATUSTYPE_INFO:
+		result[0] = '\0';
+		break;
+
+	case STATUSTYPE_TABLE:
+		DMEMIT("%s %llu %u %u", fc->dev->name,
+		       (unsigned long long)fc->start, fc->up_interval,
+		       fc->down_interval);
+
+		error_reads = test_bit(ERROR_READS, &fc->flags);
+		drop_writes = test_bit(DROP_WRITES, &fc->flags);
+		error_writes = test_bit(ERROR_WRITES, &fc->flags);
+		DMEMIT(" %u", error_reads + drop_writes + error_writes +
+			(fc->corrupt_bio_byte > 0) * 5 +
+			(fc->random_read_corrupt > 0) * 2 +
+			(fc->random_write_corrupt > 0) * 2);
+
+		if (error_reads)
+			DMEMIT(" error_reads");
+		if (drop_writes)
+			DMEMIT(" drop_writes");
+		else if (error_writes)
+			DMEMIT(" error_writes");
+
+		if (fc->corrupt_bio_byte)
+			DMEMIT(" corrupt_bio_byte %u %c %u %u",
+			       fc->corrupt_bio_byte,
+			       (fc->corrupt_bio_rw == WRITE) ? 'w' : 'r',
+			       fc->corrupt_bio_value, fc->corrupt_bio_flags);
+
+		if (fc->random_read_corrupt > 0)
+			DMEMIT(" random_read_corrupt %u", fc->random_read_corrupt);
+		if (fc->random_write_corrupt > 0)
+			DMEMIT(" random_write_corrupt %u", fc->random_write_corrupt);
+
+		break;
+
+	case STATUSTYPE_IMA:
+		result[0] = '\0';
+		break;
+	}
+}
+
+static int flakey_prepare_ioctl(struct dm_target *ti, struct block_device **bdev,
+				unsigned int cmd, unsigned long arg,
+				bool *forward)
+{
+	struct flakey_c *fc = ti->private;
+
+	*bdev = fc->dev->bdev;
+
+	/*
+	 * Only pass ioctls through if the device sizes match exactly.
+	 */
+	if (fc->start || ti->len != bdev_nr_sectors((*bdev)))
+		return 1;
+	return 0;
+}
+
+#ifdef CONFIG_BLK_DEV_ZONED
+static int flakey_report_zones(struct dm_target *ti,
+		struct dm_report_zones_args *args, unsigned int nr_zones)
+{
+	struct flakey_c *fc = ti->private;
+
+	return dm_report_zones(fc->dev->bdev, fc->start,
+			       flakey_map_sector(ti, args->next_sector),
+			       args, nr_zones);
+}
+#else
+#define flakey_report_zones NULL
+#endif
+
+static int flakey_iterate_devices(struct dm_target *ti, iterate_devices_callout_fn fn, void *data)
+{
+	struct flakey_c *fc = ti->private;
+
+	return fn(ti, fc->dev, fc->start, ti->len, data);
+}
+
+static struct target_type flakey_target = {
+	.name   = "flakey",
+	.version = {1, 5, 0},
+	.features = DM_TARGET_ZONED_HM | DM_TARGET_PASSES_CRYPTO,
+	.report_zones = flakey_report_zones,
+	.module = THIS_MODULE,
+	.ctr    = flakey_ctr,
+	.dtr    = flakey_dtr,
+	.map    = flakey_map,
+	.end_io = flakey_end_io,
+	.status = flakey_status,
+	.prepare_ioctl = flakey_prepare_ioctl,
+	.iterate_devices = flakey_iterate_devices,
+};
+module_dm(flakey);
+
+MODULE_DESCRIPTION(DM_NAME " flakey target");
+MODULE_AUTHOR("Joe Thornber <dm-devel@lists.linux.dev>");
+MODULE_LICENSE("GPL");