/*
   * 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 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 up_interval;
  	unsigned down_interval;

  	unsigned long flags;

  	unsigned corrupt_bio_byte;
  	unsigned corrupt_bio_rw;
  	unsigned corrupt_bio_value;
  	unsigned corrupt_bio_flags;

  };

  enum feature_flag_bits {

  	DROP_WRITES,
  	ERROR_WRITES

  };

  struct per_bio_data {
  	bool bio_submitted;
  };

  static int parse_features(struct dm_arg_set *as, struct flakey_c *fc,
  			  struct dm_target *ti)

  {
  	int r;
  	unsigned argc;
  	const char *arg_name;

  	static const struct dm_arg _args[] = {

  		{0, 6, "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"},

  	};
  
  	/* No feature arguments supplied. */
  	if (!as->argc)
  		return 0;
  
  	r = dm_read_arg_group(_args, as, &argc, &ti->error);
  	if (r)

  		return r;

  	while (argc) {

  		arg_name = dm_shift_arg(as);
  		argc--;

  		if (!arg_name) {
  			ti->error = "Insufficient feature arguments";
  			return -EINVAL;
  		}

  		/*
  		 * 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 (!argc) {

  				ti->error = "Feature corrupt_bio_byte requires 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 (!strcasecmp(arg_name, "w"))
  				fc->corrupt_bio_rw = WRITE;
  			else if (!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.
  			 */
  			r = dm_read_arg(_args + 3, as, &fc->corrupt_bio_flags, &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_rw == WRITE)) {
  		ti->error = "drop_writes is incompatible with corrupt_bio_byte with the WRITE flag set";
  		return -EINVAL;

  
  	} else if (test_bit(ERROR_WRITES, &fc->flags) && (fc->corrupt_bio_rw == WRITE)) {
  		ti->error = "error_writes is incompatible with corrupt_bio_byte with the WRITE flag set";
  		return -EINVAL;

  	}
  
  	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(sizeof(*fc), GFP_KERNEL);

  	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, &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);

  	if (bio_sectors(bio) || op_is_zone_mgmt(bio_op(bio)))

  		bio->bi_iter.bi_sector =
  			flakey_map_sector(ti, bio->bi_iter.bi_sector);

  }

  static void corrupt_bio_data(struct bio *bio, struct flakey_c *fc)
  {

  	unsigned int corrupt_bio_byte = fc->corrupt_bio_byte - 1;
  
  	struct bvec_iter iter;
  	struct bio_vec bvec;
  
  	if (!bio_has_data(bio))
  		return;

  
  	/*

  	 * Overwrite the Nth byte of the bio's data, on whichever page
  	 * it falls.

  	 */

  	bio_for_each_segment(bvec, bio, iter) {
  		if (bio_iter_len(bio, iter) > corrupt_bio_byte) {
  			char *segment = (page_address(bio_iter_page(bio, iter))
  					 + bio_iter_offset(bio, iter));
  			segment[corrupt_bio_byte] = fc->corrupt_bio_value;
  			DMDEBUG("Corrupting data bio=%p by writing %u to byte %u "
  				"(rw=%c bi_opf=%u bi_sector=%llu size=%u)
  ",
  				bio, fc->corrupt_bio_value, fc->corrupt_bio_byte,
  				(bio_data_dir(bio) == WRITE) ? 'w' : 'r', bio->bi_opf,
  				(unsigned long long)bio->bi_iter.bi_sector, bio->bi_iter.bi_size);
  			break;
  		}
  		corrupt_bio_byte -= bio_iter_len(bio, iter);

  	}
  }

  static int flakey_map(struct dm_target *ti, struct bio *bio)

  {
  	struct flakey_c *fc = ti->private;
  	unsigned elapsed;

  	struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
  	pb->bio_submitted = 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) {

  		/*
  		 * Flag this bio as submitted while down.
  		 */

  		pb->bio_submitted = true;

  
  		/*

  		 * Error reads if neither corrupt_bio_byte or drop_writes or error_writes are set.

  		 * Otherwise, flakey_end_io() will decide if the reads should be modified.

  		 */

  		if (bio_data_dir(bio) == READ) {

  			if (!fc->corrupt_bio_byte && !test_bit(DROP_WRITES, &fc->flags) &&
  			    !test_bit(ERROR_WRITES, &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;
  		}

  
  		/*
  		 * Corrupt matching writes.
  		 */
  		if (fc->corrupt_bio_byte && (fc->corrupt_bio_rw == WRITE)) {
  			if (all_corrupt_bio_flags_match(bio, fc))
  				corrupt_bio_data(bio, fc);

  			goto map_bio;
  		}
  
  		/*

  		 * By default, error all I/O.

  		 */

  		return DM_MAPIO_KILL;

  	}

  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_submitted && (bio_data_dir(bio) == READ)) {

  		if (fc->corrupt_bio_byte && (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);

  		} else if (!test_bit(DROP_WRITES, &fc->flags) &&
  			   !test_bit(ERROR_WRITES, &fc->flags)) {

  			/*
  			 * Error read during the down_interval if drop_writes

  			 * and error_writes were not configured.

  			 */

  			*error = BLK_STS_IOERR;

  		}

  	}

  	return DM_ENDIO_DONE;

  }

  static void flakey_status(struct dm_target *ti, status_type_t type,
  			  unsigned status_flags, char *result, unsigned maxlen)

  {

  	unsigned sz = 0;

  	struct flakey_c *fc = ti->private;

  	unsigned 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);
  
  		drop_writes = test_bit(DROP_WRITES, &fc->flags);

  		error_writes = test_bit(ERROR_WRITES, &fc->flags);
  		DMEMIT("%u ", drop_writes + error_writes + (fc->corrupt_bio_byte > 0) * 5);

  		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);

  		break;
  	}

  }

  static int flakey_prepare_ioctl(struct dm_target *ti, struct block_device **bdev)

  {
  	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 != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
  		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;

  	sector_t sector = flakey_map_sector(ti, args->next_sector);

  	args->start = fc->start;
  	return blkdev_report_zones(fc->dev->bdev, sector, nr_zones,
  				   dm_report_zones_cb, args);

  }
  #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},

  #ifdef CONFIG_BLK_DEV_ZONED

  	.features = DM_TARGET_ZONED_HM,

  	.report_zones = flakey_report_zones,

  #endif

  	.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,
  };
  
  static int __init dm_flakey_init(void)
  {
  	int r = dm_register_target(&flakey_target);
  
  	if (r < 0)
  		DMERR("register failed %d", r);
  
  	return r;
  }
  
  static void __exit dm_flakey_exit(void)
  {
  	dm_unregister_target(&flakey_target);
  }
  
  /* Module hooks */
  module_init(dm_flakey_init);
  module_exit(dm_flakey_exit);
  
  MODULE_DESCRIPTION(DM_NAME " flakey target");
  MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
  MODULE_LICENSE("GPL");