/*
   * faulty.c : Multiple Devices driver for Linux
   *
   * Copyright (C) 2004 Neil Brown
   *
   * fautly-device-simulator personality for md
   *
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2, or (at your option)
   * any later version.
   *
   * You should have received a copy of the GNU General Public License
   * (for example /usr/src/linux/COPYING); if not, write to the Free
   * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
   */
  
  
  /*
   * The "faulty" personality causes some requests to fail.
   *
   * Possible failure modes are:
   *   reads fail "randomly" but succeed on retry
   *   writes fail "randomly" but succeed on retry
   *   reads for some address fail and then persist until a write
   *   reads for some address fail and then persist irrespective of write
   *   writes for some address fail and persist
   *   all writes fail
   *
   * Different modes can be active at a time, but only
   * one can be set at array creation.  Others can be added later.
   * A mode can be one-shot or recurrent with the recurrance being
   * once in every N requests.
   * The bottom 5 bits of the "layout" indicate the mode.  The
   * remainder indicate a period, or 0 for one-shot.
   *
   * There is an implementation limit on the number of concurrently
   * persisting-faulty blocks. When a new fault is requested that would
   * exceed the limit, it is ignored.
   * All current faults can be clear using a layout of "0".
   *
   * Requests are always sent to the device.  If they are to fail,
   * we clone the bio and insert a new b_end_io into the chain.
   */
  
  #define	WriteTransient	0
  #define	ReadTransient	1
  #define	WritePersistent	2
  #define	ReadPersistent	3
  #define	WriteAll	4 /* doesn't go to device */
  #define	ReadFixable	5
  #define	Modes	6
  
  #define	ClearErrors	31
  #define	ClearFaults	30
  
  #define AllPersist	100 /* internal use only */
  #define	NoPersist	101
  
  #define	ModeMask	0x1f
  #define	ModeShift	5
  
  #define MaxFault	50
  #include <linux/raid/md.h>

  static void faulty_fail(struct bio *bio, int error)

  {
  	struct bio *b = bio->bi_private;
  
  	b->bi_size = bio->bi_size;
  	b->bi_sector = bio->bi_sector;

  	bio_put(bio);

  	bio_io_error(b);

  }
  
  typedef struct faulty_conf {
  	int period[Modes];
  	atomic_t counters[Modes];
  	sector_t faults[MaxFault];
  	int	modes[MaxFault];
  	int nfaults;
  	mdk_rdev_t *rdev;
  } conf_t;
  
  static int check_mode(conf_t *conf, int mode)
  {
  	if (conf->period[mode] == 0 &&
  	    atomic_read(&conf->counters[mode]) <= 0)
  		return 0; /* no failure, no decrement */
  
  
  	if (atomic_dec_and_test(&conf->counters[mode])) {
  		if (conf->period[mode])
  			atomic_set(&conf->counters[mode], conf->period[mode]);
  		return 1;
  	}
  	return 0;
  }
  
  static int check_sector(conf_t *conf, sector_t start, sector_t end, int dir)
  {
  	/* If we find a ReadFixable sector, we fix it ... */
  	int i;
  	for (i=0; i<conf->nfaults; i++)
  		if (conf->faults[i] >= start &&
  		    conf->faults[i] < end) {
  			/* found it ... */
  			switch (conf->modes[i] * 2 + dir) {
  			case WritePersistent*2+WRITE: return 1;
  			case ReadPersistent*2+READ: return 1;
  			case ReadFixable*2+READ: return 1;
  			case ReadFixable*2+WRITE:
  				conf->modes[i] = NoPersist;
  				return 0;
  			case AllPersist*2+READ:
  			case AllPersist*2+WRITE: return 1;
  			default:
  				return 0;
  			}
  		}
  	return 0;
  }
  
  static void add_sector(conf_t *conf, sector_t start, int mode)
  {
  	int i;
  	int n = conf->nfaults;
  	for (i=0; i<conf->nfaults; i++)
  		if (conf->faults[i] == start) {
  			switch(mode) {
  			case NoPersist: conf->modes[i] = mode; return;
  			case WritePersistent:
  				if (conf->modes[i] == ReadPersistent ||
  				    conf->modes[i] == ReadFixable)
  					conf->modes[i] = AllPersist;
  				else
  					conf->modes[i] = WritePersistent;
  				return;
  			case ReadPersistent:
  				if (conf->modes[i] == WritePersistent)
  					conf->modes[i] = AllPersist;
  				else
  					conf->modes[i] = ReadPersistent;
  				return;
  			case ReadFixable:
  				if (conf->modes[i] == WritePersistent ||
  				    conf->modes[i] == ReadPersistent)
  					conf->modes[i] = AllPersist;
  				else
  					conf->modes[i] = ReadFixable;
  				return;
  			}
  		} else if (conf->modes[i] == NoPersist)
  			n = i;
  
  	if (n >= MaxFault)
  		return;
  	conf->faults[n] = start;
  	conf->modes[n] = mode;
  	if (conf->nfaults == n)
  		conf->nfaults = n+1;
  }

  static int make_request(struct request_queue *q, struct bio *bio)

  {
  	mddev_t *mddev = q->queuedata;
  	conf_t *conf = (conf_t*)mddev->private;
  	int failit = 0;

  	if (bio_data_dir(bio) == WRITE) {

  		/* write request */
  		if (atomic_read(&conf->counters[WriteAll])) {
  			/* special case - don't decrement, don't generic_make_request,
  			 * just fail immediately
  			 */

  			bio_endio(bio, -EIO);

  			return 0;
  		}
  
  		if (check_sector(conf, bio->bi_sector, bio->bi_sector+(bio->bi_size>>9),
  				 WRITE))
  			failit = 1;
  		if (check_mode(conf, WritePersistent)) {
  			add_sector(conf, bio->bi_sector, WritePersistent);
  			failit = 1;
  		}
  		if (check_mode(conf, WriteTransient))
  			failit = 1;
  	} else {
  		/* read request */
  		if (check_sector(conf, bio->bi_sector, bio->bi_sector + (bio->bi_size>>9),
  				 READ))
  			failit = 1;
  		if (check_mode(conf, ReadTransient))
  			failit = 1;
  		if (check_mode(conf, ReadPersistent)) {
  			add_sector(conf, bio->bi_sector, ReadPersistent);
  			failit = 1;
  		}
  		if (check_mode(conf, ReadFixable)) {
  			add_sector(conf, bio->bi_sector, ReadFixable);
  			failit = 1;
  		}
  	}
  	if (failit) {
  		struct bio *b = bio_clone(bio, GFP_NOIO);
  		b->bi_bdev = conf->rdev->bdev;
  		b->bi_private = bio;
  		b->bi_end_io = faulty_fail;
  		generic_make_request(b);
  		return 0;
  	} else {
  		bio->bi_bdev = conf->rdev->bdev;
  		return 1;
  	}
  }
  
  static void status(struct seq_file *seq, mddev_t *mddev)
  {
  	conf_t *conf = (conf_t*)mddev->private;
  	int n;
  
  	if ((n=atomic_read(&conf->counters[WriteTransient])) != 0)
  		seq_printf(seq, " WriteTransient=%d(%d)",
  			   n, conf->period[WriteTransient]);
  
  	if ((n=atomic_read(&conf->counters[ReadTransient])) != 0)
  		seq_printf(seq, " ReadTransient=%d(%d)",
  			   n, conf->period[ReadTransient]);
  
  	if ((n=atomic_read(&conf->counters[WritePersistent])) != 0)
  		seq_printf(seq, " WritePersistent=%d(%d)",
  			   n, conf->period[WritePersistent]);
  
  	if ((n=atomic_read(&conf->counters[ReadPersistent])) != 0)
  		seq_printf(seq, " ReadPersistent=%d(%d)",
  			   n, conf->period[ReadPersistent]);
  
  
  	if ((n=atomic_read(&conf->counters[ReadFixable])) != 0)
  		seq_printf(seq, " ReadFixable=%d(%d)",
  			   n, conf->period[ReadFixable]);
  
  	if ((n=atomic_read(&conf->counters[WriteAll])) != 0)
  		seq_printf(seq, " WriteAll");
  
  	seq_printf(seq, " nfaults=%d", conf->nfaults);
  }
  
  
  static int reconfig(mddev_t *mddev, int layout, int chunk_size)
  {
  	int mode = layout & ModeMask;
  	int count = layout >> ModeShift;
  	conf_t *conf = mddev->private;
  
  	if (chunk_size != -1)
  		return -EINVAL;
  
  	/* new layout */
  	if (mode == ClearFaults)
  		conf->nfaults = 0;
  	else if (mode == ClearErrors) {
  		int i;
  		for (i=0 ; i < Modes ; i++) {
  			conf->period[i] = 0;
  			atomic_set(&conf->counters[i], 0);
  		}
  	} else if (mode < Modes) {
  		conf->period[mode] = count;
  		if (!count) count++;
  		atomic_set(&conf->counters[mode], count);
  	} else
  		return -EINVAL;
  	mddev->layout = -1; /* makes sure further changes come through */
  	return 0;
  }
  
  static int run(mddev_t *mddev)
  {
  	mdk_rdev_t *rdev;
  	struct list_head *tmp;
  	int i;
  
  	conf_t *conf = kmalloc(sizeof(*conf), GFP_KERNEL);
  
  	for (i=0; i<Modes; i++) {
  		atomic_set(&conf->counters[i], 0);
  		conf->period[i] = 0;
  	}
  	conf->nfaults = 0;

  	rdev_for_each(rdev, tmp, mddev)

  		conf->rdev = rdev;
  
  	mddev->array_size = mddev->size;
  	mddev->private = conf;
  
  	reconfig(mddev, mddev->layout, -1);
  
  	return 0;
  }
  
  static int stop(mddev_t *mddev)
  {
  	conf_t *conf = (conf_t *)mddev->private;
  
  	kfree(conf);
  	mddev->private = NULL;
  	return 0;
  }

  static struct mdk_personality faulty_personality =

  {
  	.name		= "faulty",

  	.level		= LEVEL_FAULTY,

  	.owner		= THIS_MODULE,
  	.make_request	= make_request,
  	.run		= run,
  	.stop		= stop,
  	.status		= status,
  	.reconfig	= reconfig,
  };
  
  static int __init raid_init(void)
  {

  	return register_md_personality(&faulty_personality);

  }
  
  static void raid_exit(void)
  {

  	unregister_md_personality(&faulty_personality);

  }
  
  module_init(raid_init);
  module_exit(raid_exit);
  MODULE_LICENSE("GPL");
  MODULE_ALIAS("md-personality-10"); /* faulty */

  MODULE_ALIAS("md-faulty");

  MODULE_ALIAS("md-level--5");