/*
   * Copyright (C) 2005, 2006

   * Avishay Traeger (avishay@gmail.com)

   * Copyright (C) 2008, 2009
   * Boaz Harrosh <bharrosh@panasas.com>
   *
   * This file is part of exofs.
   *
   * exofs 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.  Since it is based on ext2, and the only
   * valid version of GPL for the Linux kernel is version 2, the only valid
   * version of GPL for exofs is version 2.
   *
   * exofs is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with exofs; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
   */

  #include <linux/slab.h>

  #include <linux/module.h>

  #include <asm/div64.h>

  #include <linux/lcm.h>

  #include "ore_raid.h"

  MODULE_AUTHOR("Boaz Harrosh <bharrosh@panasas.com>");
  MODULE_DESCRIPTION("Objects Raid Engine ore.ko");
  MODULE_LICENSE("GPL");

  /* ore_verify_layout does a couple of things:
   * 1. Given a minimum number of needed parameters fixes up the rest of the
   *    members to be operatonals for the ore. The needed parameters are those
   *    that are defined by the pnfs-objects layout STD.
   * 2. Check to see if the current ore code actually supports these parameters
   *    for example stripe_unit must be a multple of the system PAGE_SIZE,
   *    and etc...
   * 3. Cache some havily used calculations that will be needed by users.
   */

  enum { BIO_MAX_PAGES_KMALLOC =
  		(PAGE_SIZE - sizeof(struct bio)) / sizeof(struct bio_vec),};
  
  int ore_verify_layout(unsigned total_comps, struct ore_layout *layout)
  {
  	u64 stripe_length;

  	switch (layout->raid_algorithm) {
  	case PNFS_OSD_RAID_0:
  		layout->parity = 0;
  		break;
  	case PNFS_OSD_RAID_5:
  		layout->parity = 1;
  		break;
  	case PNFS_OSD_RAID_PQ:
  	case PNFS_OSD_RAID_4:
  	default:
  		ORE_ERR("Only RAID_0/5 for now
  ");

  		return -EINVAL;
  	}
  	if (0 != (layout->stripe_unit & ~PAGE_MASK)) {
  		ORE_ERR("Stripe Unit(0x%llx)"
  			  " must be Multples of PAGE_SIZE(0x%lx)
  ",
  			  _LLU(layout->stripe_unit), PAGE_SIZE);
  		return -EINVAL;
  	}
  	if (layout->group_width) {
  		if (!layout->group_depth) {
  			ORE_ERR("group_depth == 0 && group_width != 0
  ");
  			return -EINVAL;
  		}
  		if (total_comps < (layout->group_width * layout->mirrors_p1)) {
  			ORE_ERR("Data Map wrong, "
  				"numdevs=%d < group_width=%d * mirrors=%d
  ",
  				total_comps, layout->group_width,
  				layout->mirrors_p1);
  			return -EINVAL;
  		}
  		layout->group_count = total_comps / layout->mirrors_p1 /
  						layout->group_width;
  	} else {
  		if (layout->group_depth) {
  			printk(KERN_NOTICE "Warning: group_depth ignored "
  				"group_width == 0 && group_depth == %lld
  ",
  				_LLU(layout->group_depth));
  		}
  		layout->group_width = total_comps / layout->mirrors_p1;
  		layout->group_depth = -1;
  		layout->group_count = 1;
  	}
  
  	stripe_length = (u64)layout->group_width * layout->stripe_unit;
  	if (stripe_length >= (1ULL << 32)) {
  		ORE_ERR("Stripe_length(0x%llx) >= 32bit is not supported
  ",
  			_LLU(stripe_length));
  		return -EINVAL;
  	}
  
  	layout->max_io_length =
  		(BIO_MAX_PAGES_KMALLOC * PAGE_SIZE - layout->stripe_unit) *
  							layout->group_width;

  	if (layout->parity) {
  		unsigned stripe_length =
  				(layout->group_width - layout->parity) *
  				layout->stripe_unit;
  
  		layout->max_io_length /= stripe_length;
  		layout->max_io_length *= stripe_length;
  	}

  	return 0;
  }
  EXPORT_SYMBOL(ore_verify_layout);

  static u8 *_ios_cred(struct ore_io_state *ios, unsigned index)

  {

  	return ios->oc->comps[index & ios->oc->single_comp].cred;

  }

  static struct osd_obj_id *_ios_obj(struct ore_io_state *ios, unsigned index)

  {

  	return &ios->oc->comps[index & ios->oc->single_comp].obj;

  }

  static struct osd_dev *_ios_od(struct ore_io_state *ios, unsigned index)

  {

  	ORE_DBGMSG2("oc->first_dev=%d oc->numdevs=%d i=%d oc->ods=%p
  ",
  		    ios->oc->first_dev, ios->oc->numdevs, index,
  		    ios->oc->ods);

  	return ore_comp_dev(ios->oc, index);

  }

  int  _ore_get_io_state(struct ore_layout *layout,

  			struct ore_components *oc, unsigned numdevs,
  			unsigned sgs_per_dev, unsigned num_par_pages,
  			struct ore_io_state **pios)

  {

  	struct ore_io_state *ios;

  	struct page **pages;
  	struct osd_sg_entry *sgilist;
  	struct __alloc_all_io_state {
  		struct ore_io_state ios;
  		struct ore_per_dev_state per_dev[numdevs];
  		union {
  			struct osd_sg_entry sglist[sgs_per_dev * numdevs];
  			struct page *pages[num_par_pages];
  		};
  	} *_aios;
  
  	if (likely(sizeof(*_aios) <= PAGE_SIZE)) {
  		_aios = kzalloc(sizeof(*_aios), GFP_KERNEL);
  		if (unlikely(!_aios)) {
  			ORE_DBGMSG("Failed kzalloc bytes=%zd
  ",
  				   sizeof(*_aios));
  			*pios = NULL;
  			return -ENOMEM;
  		}
  		pages = num_par_pages ? _aios->pages : NULL;
  		sgilist = sgs_per_dev ? _aios->sglist : NULL;
  		ios = &_aios->ios;
  	} else {
  		struct __alloc_small_io_state {
  			struct ore_io_state ios;
  			struct ore_per_dev_state per_dev[numdevs];
  		} *_aio_small;
  		union __extra_part {
  			struct osd_sg_entry sglist[sgs_per_dev * numdevs];
  			struct page *pages[num_par_pages];
  		} *extra_part;
  
  		_aio_small = kzalloc(sizeof(*_aio_small), GFP_KERNEL);
  		if (unlikely(!_aio_small)) {
  			ORE_DBGMSG("Failed alloc first part bytes=%zd
  ",
  				   sizeof(*_aio_small));
  			*pios = NULL;
  			return -ENOMEM;
  		}
  		extra_part = kzalloc(sizeof(*extra_part), GFP_KERNEL);
  		if (unlikely(!extra_part)) {
  			ORE_DBGMSG("Failed alloc second part bytes=%zd
  ",
  				   sizeof(*extra_part));
  			kfree(_aio_small);
  			*pios = NULL;
  			return -ENOMEM;
  		}

  		pages = num_par_pages ? extra_part->pages : NULL;
  		sgilist = sgs_per_dev ? extra_part->sglist : NULL;
  		/* In this case the per_dev[0].sgilist holds the pointer to
  		 * be freed
  		 */
  		ios = &_aio_small->ios;
  		ios->extra_part_alloc = true;
  	}
  
  	if (pages) {
  		ios->parity_pages = pages;
  		ios->max_par_pages = num_par_pages;
  	}
  	if (sgilist) {
  		unsigned d;
  
  		for (d = 0; d < numdevs; ++d) {
  			ios->per_dev[d].sglist = sgilist;
  			sgilist += sgs_per_dev;
  		}
  		ios->sgs_per_dev = sgs_per_dev;

  	}

  	ios->layout = layout;

  	ios->oc = oc;

  	*pios = ios;
  	return 0;
  }
  
  /* Allocate an io_state for only a single group of devices
   *
   * If a user needs to call ore_read/write() this version must be used becase it
   * allocates extra stuff for striping and raid.
   * The ore might decide to only IO less then @length bytes do to alignmets
   * and constrains as follows:
   * - The IO cannot cross group boundary.
   * - In raid5/6 The end of the IO must align at end of a stripe eg.
   *   (@offset + @length) % strip_size == 0. Or the complete range is within a
   *   single stripe.
   * - Memory condition only permitted a shorter IO. (A user can use @length=~0
   *   And check the returned ios->length for max_io_size.)
   *
   * The caller must check returned ios->length (and/or ios->nr_pages) and
   * re-issue these pages that fall outside of ios->length
   */
  int  ore_get_rw_state(struct ore_layout *layout, struct ore_components *oc,
  		      bool is_reading, u64 offset, u64 length,
  		      struct ore_io_state **pios)
  {
  	struct ore_io_state *ios;
  	unsigned numdevs = layout->group_width * layout->mirrors_p1;

  	unsigned sgs_per_dev = 0, max_par_pages = 0;

  	int ret;

  	if (layout->parity && length) {
  		unsigned data_devs = layout->group_width - layout->parity;
  		unsigned stripe_size = layout->stripe_unit * data_devs;
  		unsigned pages_in_unit = layout->stripe_unit / PAGE_SIZE;
  		u32 remainder;
  		u64 num_stripes;
  		u64 num_raid_units;
  
  		num_stripes = div_u64_rem(length, stripe_size, &remainder);
  		if (remainder)
  			++num_stripes;
  
  		num_raid_units =  num_stripes * layout->parity;
  
  		if (is_reading) {
  			/* For reads add per_dev sglist array */
  			/* TODO: Raid 6 we need twice more. Actually:
  			*         num_stripes / LCMdP(W,P);
  			*         if (W%P != 0) num_stripes *= parity;
  			*/
  
  			/* first/last seg is split */
  			num_raid_units += layout->group_width;

  			sgs_per_dev = div_u64(num_raid_units, data_devs) + 2;

  		} else {
  			/* For Writes add parity pages array. */
  			max_par_pages = num_raid_units * pages_in_unit *
  						sizeof(struct page *);
  		}
  	}
  
  	ret = _ore_get_io_state(layout, oc, numdevs, sgs_per_dev, max_par_pages,
  				pios);

  	if (unlikely(ret))
  		return ret;
  
  	ios = *pios;

  	ios->reading = is_reading;

  	ios->offset = offset;
  
  	if (length) {

  		ore_calc_stripe_info(layout, offset, length, &ios->si);
  		ios->length = ios->si.length;

  		ios->nr_pages = (ios->length + PAGE_SIZE - 1) / PAGE_SIZE;

  		if (layout->parity)
  			_ore_post_alloc_raid_stuff(ios);

  	}

  	return 0;

  }

  EXPORT_SYMBOL(ore_get_rw_state);

  /* Allocate an io_state for all the devices in the comps array
   *
   * This version of io_state allocation is used mostly by create/remove
   * and trunc where we currently need all the devices. The only wastful
   * bit is the read/write_attributes with no IO. Those sites should
   * be converted to use ore_get_rw_state() with length=0
   */

  int  ore_get_io_state(struct ore_layout *layout, struct ore_components *oc,

  		      struct ore_io_state **pios)

  {

  	return _ore_get_io_state(layout, oc, oc->numdevs, 0, 0, pios);

  }

  EXPORT_SYMBOL(ore_get_io_state);

  void ore_put_io_state(struct ore_io_state *ios)

  {

  	if (ios) {
  		unsigned i;

  		for (i = 0; i < ios->numdevs; i++) {

  			struct ore_per_dev_state *per_dev = &ios->per_dev[i];

  
  			if (per_dev->or)
  				osd_end_request(per_dev->or);
  			if (per_dev->bio)
  				bio_put(per_dev->bio);
  		}

  		_ore_free_raid_stuff(ios);

  		kfree(ios);

  	}

  }

  EXPORT_SYMBOL(ore_put_io_state);

  static void _sync_done(struct ore_io_state *ios, void *p)

  {
  	struct completion *waiting = p;

  	complete(waiting);
  }
  
  static void _last_io(struct kref *kref)
  {

  	struct ore_io_state *ios = container_of(
  					kref, struct ore_io_state, kref);

  
  	ios->done(ios, ios->private);
  }
  
  static void _done_io(struct osd_request *or, void *p)
  {

  	struct ore_io_state *ios = p;

  
  	kref_put(&ios->kref, _last_io);
  }

  int ore_io_execute(struct ore_io_state *ios)

  {
  	DECLARE_COMPLETION_ONSTACK(wait);
  	bool sync = (ios->done == NULL);
  	int i, ret;
  
  	if (sync) {
  		ios->done = _sync_done;
  		ios->private = &wait;
  	}
  
  	for (i = 0; i < ios->numdevs; i++) {
  		struct osd_request *or = ios->per_dev[i].or;
  		if (unlikely(!or))
  			continue;

  		ret = osd_finalize_request(or, 0, _ios_cred(ios, i), NULL);

  		if (unlikely(ret)) {

  			ORE_DBGMSG("Failed to osd_finalize_request() => %d
  ",

  				     ret);
  			return ret;
  		}
  	}
  
  	kref_init(&ios->kref);
  
  	for (i = 0; i < ios->numdevs; i++) {
  		struct osd_request *or = ios->per_dev[i].or;
  		if (unlikely(!or))
  			continue;
  
  		kref_get(&ios->kref);
  		osd_execute_request_async(or, _done_io, ios);
  	}
  
  	kref_put(&ios->kref, _last_io);
  	ret = 0;
  
  	if (sync) {
  		wait_for_completion(&wait);

  		ret = ore_check_io(ios, NULL);

  	}

  	return ret;
  }

  static void _clear_bio(struct bio *bio)
  {
  	struct bio_vec *bv;
  	unsigned i;
  
  	__bio_for_each_segment(bv, bio, i, 0) {
  		unsigned this_count = bv->bv_len;
  
  		if (likely(PAGE_SIZE == this_count))
  			clear_highpage(bv->bv_page);
  		else
  			zero_user(bv->bv_page, bv->bv_offset, this_count);
  	}
  }

  int ore_check_io(struct ore_io_state *ios, ore_on_dev_error on_dev_error)

  {

  	enum osd_err_priority acumulated_osd_err = 0;
  	int acumulated_lin_err = 0;
  	int i;

  	for (i = 0; i < ios->numdevs; i++) {
  		struct osd_sense_info osi;

  		struct ore_per_dev_state *per_dev = &ios->per_dev[i];
  		struct osd_request *or = per_dev->or;

  		int ret;
  
  		if (unlikely(!or))
  			continue;

  		ret = osd_req_decode_sense(or, &osi);

  		if (likely(!ret))
  			continue;

  		if (OSD_ERR_PRI_CLEAR_PAGES == osi.osd_err_pri) {
  			/* start read offset passed endof file */

  			_clear_bio(per_dev->bio);

  			ORE_DBGMSG("start read offset passed end of file "

  				"offset=0x%llx, length=0x%llx
  ",

  				_LLU(per_dev->offset),
  				_LLU(per_dev->length));

  
  			continue; /* we recovered */

  		}

  		if (on_dev_error) {
  			u64 residual = ios->reading ?
  					or->in.residual : or->out.residual;
  			u64 offset = (ios->offset + ios->length) - residual;

  			unsigned dev = per_dev->dev - ios->oc->first_dev;
  			struct ore_dev *od = ios->oc->ods[dev];

  			on_dev_error(ios, od, dev, osi.osd_err_pri,

  				     offset, residual);
  		}

  		if (osi.osd_err_pri >= acumulated_osd_err) {
  			acumulated_osd_err = osi.osd_err_pri;
  			acumulated_lin_err = ret;
  		}
  	}

  	return acumulated_lin_err;
  }

  EXPORT_SYMBOL(ore_check_io);

  /*
   * L - logical offset into the file
   *

   * D - number of Data devices
   *	D = group_width - parity

   *

   * U - The number of bytes in a stripe within a group
   *	U =  stripe_unit * D

   *

   * T - The number of bytes striped within a group of component objects
   *     (before advancing to the next group)

   *	T = U * group_depth

   *
   * S - The number of bytes striped across all component objects
   *     before the pattern repeats

   *	S = T * group_count

   *

   * M - The "major" (i.e., across all components) cycle number

   *	M = L / S
   *

   * G - Counts the groups from the beginning of the major cycle

   *	G = (L - (M * S)) / T	[or (L % S) / T]
   *
   * H - The byte offset within the group

   *	H = (L - (M * S)) % T	[or (L % S) % T]
   *
   * N - The "minor" (i.e., across the group) stripe number

   *	N = H / U

   *
   * C - The component index coresponding to L
   *

   *	C = (H - (N * U)) / stripe_unit + G * D
   *	[or (L % U) / stripe_unit + G * D]

   *
   * O - The component offset coresponding to L

   *	O = L % stripe_unit + N * stripe_unit + M * group_depth * stripe_unit

   *
   * LCMdP – Parity cycle: Lowest Common Multiple of group_width, parity
   *          divide by parity
   *	LCMdP = lcm(group_width, parity) / parity
   *
   * R - The parity Rotation stripe
   *     (Note parity cycle always starts at a group's boundary)
   *	R = N % LCMdP
   *
   * I = the first parity device index
   *	I = (group_width + group_width - R*parity - parity) % group_width
   *
   * Craid - The component index Rotated
   *	Craid = (group_width + C - R*parity) % group_width
   *      (We add the group_width to avoid negative numbers modulo math)

   */

  void ore_calc_stripe_info(struct ore_layout *layout, u64 file_offset,

  			  u64 length, struct ore_striping_info *si)

  {

  	u32	stripe_unit = layout->stripe_unit;
  	u32	group_width = layout->group_width;
  	u64	group_depth = layout->group_depth;

  	u32	parity      = layout->parity;

  	u32	D = group_width - parity;
  	u32	U = D * stripe_unit;

  	u64	T = U * group_depth;

  	u64	S = T * layout->group_count;

  	u64	M = div64_u64(file_offset, S);
  
  	/*
  	G = (L - (M * S)) / T
  	H = (L - (M * S)) % T
  	*/
  	u64	LmodS = file_offset - M * S;
  	u32	G = div64_u64(LmodS, T);
  	u64	H = LmodS - G * T;
  
  	u32	N = div_u64(H, U);
  
  	/* "H - (N * U)" is just "H % U" so it's bound to u32 */

  	u32	C = (u32)(H - (N * U)) / stripe_unit + G * group_width;

  	div_u64_rem(file_offset, stripe_unit, &si->unit_off);

  	si->obj_offset = si->unit_off + (N * stripe_unit) +
  				  (M * group_depth * stripe_unit);

  	if (parity) {
  		u32 LCMdP = lcm(group_width, parity) / parity;
  		/* R     = N % LCMdP; */
  		u32 RxP   = (N % LCMdP) * parity;
  		u32 first_dev = C - C % group_width;
  
  		si->par_dev = (group_width + group_width - parity - RxP) %
  			      group_width + first_dev;
  		si->dev = (group_width + C - RxP) % group_width + first_dev;
  		si->bytes_in_stripe = U;
  		si->first_stripe_start = M * S + G * T + N * U;
  	} else {
  		/* Make the math correct see _prepare_one_group */
  		si->par_dev = group_width;
  		si->dev = C;
  	}
  
  	si->dev *= layout->mirrors_p1;
  	si->par_dev *= layout->mirrors_p1;
  	si->offset = file_offset;
  	si->length = T - H;
  	if (si->length > length)
  		si->length = length;

  	si->M = M;

  }

  EXPORT_SYMBOL(ore_calc_stripe_info);

  int _ore_add_stripe_unit(struct ore_io_state *ios,  unsigned *cur_pg,
  			 unsigned pgbase, struct page **pages,
  			 struct ore_per_dev_state *per_dev, int cur_len)

  {

  	unsigned pg = *cur_pg;

  	struct request_queue *q =

  			osd_request_queue(_ios_od(ios, per_dev->dev));

  	unsigned len = cur_len;
  	int ret;

  
  	if (per_dev->bio == NULL) {
  		unsigned pages_in_stripe = ios->layout->group_width *
  					(ios->layout->stripe_unit / PAGE_SIZE);

  		unsigned nr_pages = ios->nr_pages * ios->layout->group_width /
  					(ios->layout->group_width -
  					 ios->layout->parity);
  		unsigned bio_size = (nr_pages + pages_in_stripe) /
  					ios->layout->group_width;

  
  		per_dev->bio = bio_kmalloc(GFP_KERNEL, bio_size);
  		if (unlikely(!per_dev->bio)) {

  			ORE_DBGMSG("Failed to allocate BIO size=%u
  ",

  				     bio_size);

  			ret = -ENOMEM;
  			goto out;

  		}
  	}
  
  	while (cur_len > 0) {

  		unsigned pglen = min_t(unsigned, PAGE_SIZE - pgbase, cur_len);
  		unsigned added_len;

  		cur_len -= pglen;

  		added_len = bio_add_pc_page(q, per_dev->bio, pages[pg],

  					    pglen, pgbase);

  		if (unlikely(pglen != added_len)) {

  			ORE_DBGMSG("Failed bio_add_pc_page bi_vcnt=%u
  ",
  				   per_dev->bio->bi_vcnt);

  			ret = -ENOMEM;
  			goto out;
  		}

  		_add_stripe_page(ios->sp2d, &ios->si, pages[pg]);

  		pgbase = 0;
  		++pg;

  	}
  	BUG_ON(cur_len);

  	per_dev->length += len;

  	*cur_pg = pg;

  	ret = 0;
  out:	/* we fail the complete unit on an error eg don't advance
  	 * per_dev->length and cur_pg. This means that we might have a bigger
  	 * bio than the CDB requested length (per_dev->length). That's fine
  	 * only the oposite is fatal.
  	 */
  	return ret;

  }

  static int _prepare_for_striping(struct ore_io_state *ios)

  {

  	struct ore_striping_info *si = &ios->si;

  	unsigned stripe_unit = ios->layout->stripe_unit;

  	unsigned mirrors_p1 = ios->layout->mirrors_p1;

  	unsigned group_width = ios->layout->group_width;
  	unsigned devs_in_group = group_width * mirrors_p1;

  	unsigned dev = si->dev;

  	unsigned first_dev = dev - (dev % devs_in_group);

  	unsigned dev_order;

  	unsigned cur_pg = ios->pages_consumed;

  	u64 length = ios->length;

  	int ret = 0;

  	if (!ios->pages) {

  		ios->numdevs = ios->layout->mirrors_p1;
  		return 0;
  	}

  	BUG_ON(length > si->length);
  
  	dev_order = _dev_order(devs_in_group, mirrors_p1, si->par_dev, dev);
  	si->cur_comp = dev_order;

  	si->cur_pg = si->unit_off / PAGE_SIZE;

  	while (length) {

  		unsigned comp = dev - first_dev;
  		struct ore_per_dev_state *per_dev = &ios->per_dev[comp];

  		unsigned cur_len, page_off = 0;

  
  		if (!per_dev->length) {

  			per_dev->dev = dev;

  			if (dev == si->dev) {
  				WARN_ON(dev == si->par_dev);

  				per_dev->offset = si->obj_offset;
  				cur_len = stripe_unit - si->unit_off;
  				page_off = si->unit_off & ~PAGE_MASK;
  				BUG_ON(page_off && (page_off != ios->pgbase));

  			} else {
  				if (si->cur_comp > dev_order)
  					per_dev->offset =
  						si->obj_offset - si->unit_off;
  				else /* si->cur_comp < dev_order */
  					per_dev->offset =
  						si->obj_offset + stripe_unit -
  								   si->unit_off;

  				cur_len = stripe_unit;
  			}

  		} else {

  			cur_len = stripe_unit;

  		}

  		if (cur_len >= length)
  			cur_len = length;

  		ret = _ore_add_stripe_unit(ios, &cur_pg, page_off, ios->pages,
  					   per_dev, cur_len);

  		if (unlikely(ret))
  			goto out;

  		dev += mirrors_p1;
  		dev = (dev % devs_in_group) + first_dev;

  
  		length -= cur_len;

  
  		si->cur_comp = (si->cur_comp + 1) % group_width;

  		if (unlikely((dev == si->par_dev) || (!length && ios->sp2d))) {
  			if (!length && ios->sp2d) {

  				/* If we are writing and this is the very last
  				 * stripe. then operate on parity dev.
  				 */
  				dev = si->par_dev;

  			}
  			if (ios->sp2d)

  				/* In writes cur_len just means if it's the
  				 * last one. See _ore_add_parity_unit.
  				 */
  				cur_len = length;
  			per_dev = &ios->per_dev[dev - first_dev];
  			if (!per_dev->length) {
  				/* Only/always the parity unit of the first
  				 * stripe will be empty. So this is a chance to
  				 * initialize the per_dev info.
  				 */
  				per_dev->dev = dev;
  				per_dev->offset = si->obj_offset - si->unit_off;
  			}
  
  			ret = _ore_add_parity_unit(ios, si, per_dev, cur_len);
  			if (unlikely(ret))
  					goto out;
  
  			/* Rotate next par_dev backwards with wraping */
  			si->par_dev = (devs_in_group + si->par_dev -
  				       ios->layout->parity * mirrors_p1) %
  				      devs_in_group + first_dev;
  			/* Next stripe, start fresh */
  			si->cur_comp = 0;

  			si->cur_pg = 0;

  		}

  	}
  out:

  	ios->numdevs = devs_in_group;

  	ios->pages_consumed = cur_pg;

  	if (unlikely(ret)) {
  		if (length == ios->length)
  			return ret;
  		else
  			ios->length -= length;
  	}
  	return 0;

  }

  int ore_create(struct ore_io_state *ios)

  {
  	int i, ret;

  	for (i = 0; i < ios->oc->numdevs; i++) {

  		struct osd_request *or;

  		or = osd_start_request(_ios_od(ios, i), GFP_KERNEL);

  		if (unlikely(!or)) {

  			ORE_ERR("%s: osd_start_request failed
  ", __func__);

  			ret = -ENOMEM;
  			goto out;
  		}
  		ios->per_dev[i].or = or;
  		ios->numdevs++;

  		osd_req_create_object(or, _ios_obj(ios, i));

  	}

  	ret = ore_io_execute(ios);

  
  out:
  	return ret;
  }

  EXPORT_SYMBOL(ore_create);

  int ore_remove(struct ore_io_state *ios)

  {
  	int i, ret;

  	for (i = 0; i < ios->oc->numdevs; i++) {

  		struct osd_request *or;

  		or = osd_start_request(_ios_od(ios, i), GFP_KERNEL);

  		if (unlikely(!or)) {

  			ORE_ERR("%s: osd_start_request failed
  ", __func__);

  			ret = -ENOMEM;
  			goto out;
  		}
  		ios->per_dev[i].or = or;
  		ios->numdevs++;

  		osd_req_remove_object(or, _ios_obj(ios, i));

  	}

  	ret = ore_io_execute(ios);

  
  out:
  	return ret;
  }

  EXPORT_SYMBOL(ore_remove);

  static int _write_mirror(struct ore_io_state *ios, int cur_comp)

  {

  	struct ore_per_dev_state *master_dev = &ios->per_dev[cur_comp];

  	unsigned dev = ios->per_dev[cur_comp].dev;
  	unsigned last_comp = cur_comp + ios->layout->mirrors_p1;
  	int ret = 0;

  	if (ios->pages && !master_dev->length)
  		return 0; /* Just an empty slot */

  	for (; cur_comp < last_comp; ++cur_comp, ++dev) {

  		struct ore_per_dev_state *per_dev = &ios->per_dev[cur_comp];

  		struct osd_request *or;

  		or = osd_start_request(_ios_od(ios, dev), GFP_KERNEL);

  		if (unlikely(!or)) {

  			ORE_ERR("%s: osd_start_request failed
  ", __func__);

  			ret = -ENOMEM;
  			goto out;
  		}

  		per_dev->or = or;

  		if (ios->pages) {

  			struct bio *bio;

  			if (per_dev != master_dev) {

  				bio = bio_kmalloc(GFP_KERNEL,

  						  master_dev->bio->bi_max_vecs);

  				if (unlikely(!bio)) {

  					ORE_DBGMSG(

  					      "Failed to allocate BIO size=%u
  ",

  					      master_dev->bio->bi_max_vecs);

  					ret = -ENOMEM;
  					goto out;
  				}

  				__bio_clone(bio, master_dev->bio);

  				bio->bi_bdev = NULL;
  				bio->bi_next = NULL;

  				per_dev->offset = master_dev->offset;

  				per_dev->length = master_dev->length;
  				per_dev->bio =  bio;
  				per_dev->dev = dev;

  			} else {

  				bio = master_dev->bio;
  				/* FIXME: bio_set_dir() */

  				bio->bi_rw |= REQ_WRITE;

  			}

  			osd_req_write(or, _ios_obj(ios, dev), per_dev->offset,
  				      bio, per_dev->length);

  			ORE_DBGMSG("write(0x%llx) offset=0x%llx "

  				      "length=0x%llx dev=%d
  ",

  				     _LLU(_ios_obj(ios, dev)->id),
  				     _LLU(per_dev->offset),

  				     _LLU(per_dev->length), dev);

  		} else if (ios->kern_buff) {

  			per_dev->offset = ios->si.obj_offset;
  			per_dev->dev = ios->si.dev + dev;
  
  			/* no cross device without page array */
  			BUG_ON((ios->layout->group_width > 1) &&
  			       (ios->si.unit_off + ios->length >
  				ios->layout->stripe_unit));
  
  			ret = osd_req_write_kern(or, _ios_obj(ios, per_dev->dev),

  						 per_dev->offset,
  						 ios->kern_buff, ios->length);

  			if (unlikely(ret))
  				goto out;

  			ORE_DBGMSG2("write_kern(0x%llx) offset=0x%llx "

  				      "length=0x%llx dev=%d
  ",

  				     _LLU(_ios_obj(ios, dev)->id),
  				     _LLU(per_dev->offset),

  				     _LLU(ios->length), per_dev->dev);

  		} else {

  			osd_req_set_attributes(or, _ios_obj(ios, dev));

  			ORE_DBGMSG2("obj(0x%llx) set_attributes=%d dev=%d
  ",

  				     _LLU(_ios_obj(ios, dev)->id),
  				     ios->out_attr_len, dev);

  		}
  
  		if (ios->out_attr)
  			osd_req_add_set_attr_list(or, ios->out_attr,
  						  ios->out_attr_len);
  
  		if (ios->in_attr)
  			osd_req_add_get_attr_list(or, ios->in_attr,
  						  ios->in_attr_len);

  	}

  
  out:
  	return ret;
  }

  int ore_write(struct ore_io_state *ios)

  {
  	int i;
  	int ret;

  	if (unlikely(ios->sp2d && !ios->r4w)) {
  		/* A library is attempting a RAID-write without providing
  		 * a pages lock interface.
  		 */
  		WARN_ON_ONCE(1);
  		return -ENOTSUPP;
  	}

  	ret = _prepare_for_striping(ios);
  	if (unlikely(ret))
  		return ret;
  
  	for (i = 0; i < ios->numdevs; i += ios->layout->mirrors_p1) {

  		ret = _write_mirror(ios, i);

  		if (unlikely(ret))
  			return ret;
  	}

  	ret = ore_io_execute(ios);

  	return ret;
  }

  EXPORT_SYMBOL(ore_write);

  int _ore_read_mirror(struct ore_io_state *ios, unsigned cur_comp)

  {

  	struct osd_request *or;

  	struct ore_per_dev_state *per_dev = &ios->per_dev[cur_comp];

  	struct osd_obj_id *obj = _ios_obj(ios, cur_comp);
  	unsigned first_dev = (unsigned)obj->id;

  	if (ios->pages && !per_dev->length)
  		return 0; /* Just an empty slot */

  	first_dev = per_dev->dev + first_dev % ios->layout->mirrors_p1;

  	or = osd_start_request(_ios_od(ios, first_dev), GFP_KERNEL);

  	if (unlikely(!or)) {

  		ORE_ERR("%s: osd_start_request failed
  ", __func__);

  		return -ENOMEM;
  	}
  	per_dev->or = or;

  	if (ios->pages) {

  		if (per_dev->cur_sg) {
  			/* finalize the last sg_entry */
  			_ore_add_sg_seg(per_dev, 0, false);
  			if (unlikely(!per_dev->cur_sg))
  				return 0; /* Skip parity only device */
  
  			osd_req_read_sg(or, obj, per_dev->bio,
  					per_dev->sglist, per_dev->cur_sg);
  		} else {
  			/* The no raid case */
  			osd_req_read(or, obj, per_dev->offset,
  				     per_dev->bio, per_dev->length);
  		}

  		ORE_DBGMSG("read(0x%llx) offset=0x%llx length=0x%llx"

  			     " dev=%d sg_len=%d
  ", _LLU(obj->id),

  			     _LLU(per_dev->offset), _LLU(per_dev->length),

  			     first_dev, per_dev->cur_sg);

  	} else {

  		BUG_ON(ios->kern_buff);

  		osd_req_get_attributes(or, obj);

  		ORE_DBGMSG2("obj(0x%llx) get_attributes=%d dev=%d
  ",

  			      _LLU(obj->id),
  			      ios->in_attr_len, first_dev);

  	}

  	if (ios->out_attr)
  		osd_req_add_set_attr_list(or, ios->out_attr, ios->out_attr_len);

  	if (ios->in_attr)
  		osd_req_add_get_attr_list(or, ios->in_attr, ios->in_attr_len);

  	return 0;
  }

  int ore_read(struct ore_io_state *ios)

  {
  	int i;
  	int ret;
  
  	ret = _prepare_for_striping(ios);
  	if (unlikely(ret))
  		return ret;
  
  	for (i = 0; i < ios->numdevs; i += ios->layout->mirrors_p1) {

  		ret = _ore_read_mirror(ios, i);

  		if (unlikely(ret))
  			return ret;
  	}

  	ret = ore_io_execute(ios);

  	return ret;

  }

  EXPORT_SYMBOL(ore_read);

  int extract_attr_from_ios(struct ore_io_state *ios, struct osd_attr *attr)

  {
  	struct osd_attr cur_attr = {.attr_page = 0}; /* start with zeros */
  	void *iter = NULL;
  	int nelem;
  
  	do {
  		nelem = 1;

  		osd_req_decode_get_attr_list(ios->per_dev[0].or,
  					     &cur_attr, &nelem, &iter);

  		if ((cur_attr.attr_page == attr->attr_page) &&
  		    (cur_attr.attr_id == attr->attr_id)) {
  			attr->len = cur_attr.len;
  			attr->val_ptr = cur_attr.val_ptr;
  			return 0;
  		}
  	} while (iter);
  
  	return -EIO;
  }

  EXPORT_SYMBOL(extract_attr_from_ios);

  static int _truncate_mirrors(struct ore_io_state *ios, unsigned cur_comp,

  			     struct osd_attr *attr)
  {
  	int last_comp = cur_comp + ios->layout->mirrors_p1;
  
  	for (; cur_comp < last_comp; ++cur_comp) {

  		struct ore_per_dev_state *per_dev = &ios->per_dev[cur_comp];

  		struct osd_request *or;

  		or = osd_start_request(_ios_od(ios, cur_comp), GFP_KERNEL);

  		if (unlikely(!or)) {

  			ORE_ERR("%s: osd_start_request failed
  ", __func__);

  			return -ENOMEM;
  		}
  		per_dev->or = or;

  		osd_req_set_attributes(or, _ios_obj(ios, cur_comp));

  		osd_req_add_set_attr_list(or, attr, 1);
  	}
  
  	return 0;
  }

  struct _trunc_info {

  	struct ore_striping_info si;

  	u64 prev_group_obj_off;
  	u64 next_group_obj_off;
  
  	unsigned first_group_dev;
  	unsigned nex_group_dev;

  };

  static void _calc_trunk_info(struct ore_layout *layout, u64 file_offset,
  			     struct _trunc_info *ti)

  {
  	unsigned stripe_unit = layout->stripe_unit;

  	ore_calc_stripe_info(layout, file_offset, 0, &ti->si);

  
  	ti->prev_group_obj_off = ti->si.M * stripe_unit;
  	ti->next_group_obj_off = ti->si.M ? (ti->si.M - 1) * stripe_unit : 0;
  
  	ti->first_group_dev = ti->si.dev - (ti->si.dev % layout->group_width);
  	ti->nex_group_dev = ti->first_group_dev + layout->group_width;

  }

  int ore_truncate(struct ore_layout *layout, struct ore_components *oc,

  		   u64 size)

  {

  	struct ore_io_state *ios;

  	struct exofs_trunc_attr {
  		struct osd_attr attr;
  		__be64 newsize;
  	} *size_attrs;

  	struct _trunc_info ti;

  	int i, ret;

  	ret = ore_get_io_state(layout, oc, &ios);

  	if (unlikely(ret))
  		return ret;

  	_calc_trunk_info(ios->layout, size, &ti);

  	size_attrs = kcalloc(ios->oc->numdevs, sizeof(*size_attrs),

  			     GFP_KERNEL);
  	if (unlikely(!size_attrs)) {
  		ret = -ENOMEM;
  		goto out;
  	}

  	ios->numdevs = ios->oc->numdevs;

  	for (i = 0; i < ios->numdevs; ++i) {

  		struct exofs_trunc_attr *size_attr = &size_attrs[i];
  		u64 obj_size;

  		if (i < ti.first_group_dev)
  			obj_size = ti.prev_group_obj_off;
  		else if (i >= ti.nex_group_dev)
  			obj_size = ti.next_group_obj_off;
  		else if (i < ti.si.dev) /* dev within this group */
  			obj_size = ti.si.obj_offset +
  				      ios->layout->stripe_unit - ti.si.unit_off;
  		else if (i == ti.si.dev)
  			obj_size = ti.si.obj_offset;
  		else /* i > ti.dev */
  			obj_size = ti.si.obj_offset - ti.si.unit_off;

  		size_attr->newsize = cpu_to_be64(obj_size);
  		size_attr->attr = g_attr_logical_length;
  		size_attr->attr.val_ptr = &size_attr->newsize;

  		ORE_DBGMSG("trunc(0x%llx) obj_offset=0x%llx dev=%d
  ",

  			     _LLU(oc->comps->obj.id), _LLU(obj_size), i);

  		ret = _truncate_mirrors(ios, i * ios->layout->mirrors_p1,
  					&size_attr->attr);
  		if (unlikely(ret))
  			goto out;

  	}

  	ret = ore_io_execute(ios);

  
  out:

  	kfree(size_attrs);

  	ore_put_io_state(ios);

  	return ret;
  }

  EXPORT_SYMBOL(ore_truncate);

  
  const struct osd_attr g_attr_logical_length = ATTR_DEF(
  	OSD_APAGE_OBJECT_INFORMATION, OSD_ATTR_OI_LOGICAL_LENGTH, 8);

  EXPORT_SYMBOL(g_attr_logical_length);