/*
   *  Module for the pnfs nfs4 file layout driver.
   *  Defines all I/O and Policy interface operations, plus code
   *  to register itself with the pNFS client.
   *
   *  Copyright (c) 2002
   *  The Regents of the University of Michigan
   *  All Rights Reserved
   *
   *  Dean Hildebrand <dhildebz@umich.edu>
   *
   *  Permission is granted to use, copy, create derivative works, and
   *  redistribute this software and such derivative works for any purpose,
   *  so long as the name of the University of Michigan is not used in
   *  any advertising or publicity pertaining to the use or distribution
   *  of this software without specific, written prior authorization. If
   *  the above copyright notice or any other identification of the
   *  University of Michigan is included in any copy of any portion of
   *  this software, then the disclaimer below must also be included.
   *
   *  This software is provided as is, without representation or warranty
   *  of any kind either express or implied, including without limitation
   *  the implied warranties of merchantability, fitness for a particular
   *  purpose, or noninfringement.  The Regents of the University of
   *  Michigan shall not be liable for any damages, including special,
   *  indirect, incidental, or consequential damages, with respect to any
   *  claim arising out of or in connection with the use of the software,
   *  even if it has been or is hereafter advised of the possibility of
   *  such damages.
   */
  
  #include <linux/nfs_fs.h>

  #include <linux/nfs_page.h>

  #include <linux/module.h>

  
  #include "internal.h"
  #include "nfs4filelayout.h"

  
  #define NFSDBG_FACILITY         NFSDBG_PNFS_LD
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Dean Hildebrand <dhildebz@umich.edu>");
  MODULE_DESCRIPTION("The NFSv4 file layout driver");

  #define FILELAYOUT_POLL_RETRY_MAX     (15*HZ)

  static loff_t
  filelayout_get_dense_offset(struct nfs4_filelayout_segment *flseg,
  			    loff_t offset)
  {
  	u32 stripe_width = flseg->stripe_unit * flseg->dsaddr->stripe_count;

  	u64 stripe_no;
  	u32 rem;

  
  	offset -= flseg->pattern_offset;

  	stripe_no = div_u64(offset, stripe_width);
  	div_u64_rem(offset, flseg->stripe_unit, &rem);

  	return stripe_no * flseg->stripe_unit + rem;

  }
  
  /* This function is used by the layout driver to calculate the
   * offset of the file on the dserver based on whether the
   * layout type is STRIPE_DENSE or STRIPE_SPARSE
   */
  static loff_t
  filelayout_get_dserver_offset(struct pnfs_layout_segment *lseg, loff_t offset)
  {
  	struct nfs4_filelayout_segment *flseg = FILELAYOUT_LSEG(lseg);
  
  	switch (flseg->stripe_type) {
  	case STRIPE_SPARSE:
  		return offset;
  
  	case STRIPE_DENSE:
  		return filelayout_get_dense_offset(flseg, offset);
  	}
  
  	BUG();
  }

  static int filelayout_async_handle_error(struct rpc_task *task,
  					 struct nfs4_state *state,
  					 struct nfs_client *clp,
  					 int *reset)
  {
  	if (task->tk_status >= 0)
  		return 0;
  
  	*reset = 0;
  
  	switch (task->tk_status) {
  	case -NFS4ERR_BADSESSION:
  	case -NFS4ERR_BADSLOT:
  	case -NFS4ERR_BAD_HIGH_SLOT:
  	case -NFS4ERR_DEADSESSION:
  	case -NFS4ERR_CONN_NOT_BOUND_TO_SESSION:
  	case -NFS4ERR_SEQ_FALSE_RETRY:
  	case -NFS4ERR_SEQ_MISORDERED:
  		dprintk("%s ERROR %d, Reset session. Exchangeid "
  			"flags 0x%x
  ", __func__, task->tk_status,
  			clp->cl_exchange_flags);
  		nfs4_schedule_session_recovery(clp->cl_session);
  		break;
  	case -NFS4ERR_DELAY:
  	case -NFS4ERR_GRACE:
  	case -EKEYEXPIRED:
  		rpc_delay(task, FILELAYOUT_POLL_RETRY_MAX);
  		break;

  	case -NFS4ERR_RETRY_UNCACHED_REP:
  		break;

  	default:
  		dprintk("%s DS error. Retry through MDS %d
  ", __func__,
  			task->tk_status);
  		*reset = 1;
  		break;
  	}
  	task->tk_status = 0;
  	return -EAGAIN;
  }
  
  /* NFS_PROTO call done callback routines */
  
  static int filelayout_read_done_cb(struct rpc_task *task,
  				struct nfs_read_data *data)
  {

  	int reset = 0;
  
  	dprintk("%s DS read
  ", __func__);
  
  	if (filelayout_async_handle_error(task, data->args.context->state,
  					  data->ds_clp, &reset) == -EAGAIN) {
  		dprintk("%s calling restart ds_clp %p ds_clp->cl_session %p
  ",
  			__func__, data->ds_clp, data->ds_clp->cl_session);
  		if (reset) {

  			pnfs_set_lo_fail(data->lseg);

  			nfs4_reset_read(task, data);

  		}

  		rpc_restart_call_prepare(task);

  		return -EAGAIN;
  	}
  
  	return 0;
  }

  /*

   * We reference the rpc_cred of the first WRITE that triggers the need for
   * a LAYOUTCOMMIT, and use it to send the layoutcommit compound.
   * rfc5661 is not clear about which credential should be used.
   */
  static void
  filelayout_set_layoutcommit(struct nfs_write_data *wdata)
  {
  	if (FILELAYOUT_LSEG(wdata->lseg)->commit_through_mds ||
  	    wdata->res.verf->committed == NFS_FILE_SYNC)
  		return;
  
  	pnfs_set_layoutcommit(wdata);
  	dprintk("%s ionde %lu pls_end_pos %lu
  ", __func__, wdata->inode->i_ino,

  		(unsigned long) NFS_I(wdata->inode)->layout->plh_lwb);

  }
  
  /*

   * Call ops for the async read/write cases
   * In the case of dense layouts, the offset needs to be reset to its
   * original value.
   */
  static void filelayout_read_prepare(struct rpc_task *task, void *data)
  {
  	struct nfs_read_data *rdata = (struct nfs_read_data *)data;

  	rdata->read_done_cb = filelayout_read_done_cb;

  	if (nfs41_setup_sequence(rdata->ds_clp->cl_session,
  				&rdata->args.seq_args, &rdata->res.seq_res,
  				0, task))
  		return;
  
  	rpc_call_start(task);
  }
  
  static void filelayout_read_call_done(struct rpc_task *task, void *data)
  {
  	struct nfs_read_data *rdata = (struct nfs_read_data *)data;
  
  	dprintk("--> %s task->tk_status %d
  ", __func__, task->tk_status);
  
  	/* Note this may cause RPC to be resent */
  	rdata->mds_ops->rpc_call_done(task, data);
  }
  
  static void filelayout_read_release(void *data)
  {
  	struct nfs_read_data *rdata = (struct nfs_read_data *)data;
  
  	rdata->mds_ops->rpc_release(data);
  }

  static int filelayout_write_done_cb(struct rpc_task *task,
  				struct nfs_write_data *data)
  {
  	int reset = 0;
  
  	if (filelayout_async_handle_error(task, data->args.context->state,
  					  data->ds_clp, &reset) == -EAGAIN) {

  		dprintk("%s calling restart ds_clp %p ds_clp->cl_session %p
  ",
  			__func__, data->ds_clp, data->ds_clp->cl_session);
  		if (reset) {

  			pnfs_set_lo_fail(data->lseg);

  			nfs4_reset_write(task, data);

  		}
  		rpc_restart_call_prepare(task);

  		return -EAGAIN;
  	}

  	filelayout_set_layoutcommit(data);

  	return 0;
  }

  /* Fake up some data that will cause nfs_commit_release to retry the writes. */
  static void prepare_to_resend_writes(struct nfs_write_data *data)
  {
  	struct nfs_page *first = nfs_list_entry(data->pages.next);
  
  	data->task.tk_status = 0;
  	memcpy(data->verf.verifier, first->wb_verf.verifier,
  	       sizeof(first->wb_verf.verifier));
  	data->verf.verifier[0]++; /* ensure verifier mismatch */
  }
  
  static int filelayout_commit_done_cb(struct rpc_task *task,
  				     struct nfs_write_data *data)
  {
  	int reset = 0;
  
  	if (filelayout_async_handle_error(task, data->args.context->state,
  					  data->ds_clp, &reset) == -EAGAIN) {
  		dprintk("%s calling restart ds_clp %p ds_clp->cl_session %p
  ",
  			__func__, data->ds_clp, data->ds_clp->cl_session);
  		if (reset) {
  			prepare_to_resend_writes(data);

  			pnfs_set_lo_fail(data->lseg);

  		} else

  			rpc_restart_call_prepare(task);

  		return -EAGAIN;
  	}
  
  	return 0;
  }

  static void filelayout_write_prepare(struct rpc_task *task, void *data)
  {
  	struct nfs_write_data *wdata = (struct nfs_write_data *)data;
  
  	if (nfs41_setup_sequence(wdata->ds_clp->cl_session,
  				&wdata->args.seq_args, &wdata->res.seq_res,
  				0, task))
  		return;
  
  	rpc_call_start(task);
  }
  
  static void filelayout_write_call_done(struct rpc_task *task, void *data)
  {
  	struct nfs_write_data *wdata = (struct nfs_write_data *)data;
  
  	/* Note this may cause RPC to be resent */
  	wdata->mds_ops->rpc_call_done(task, data);
  }
  
  static void filelayout_write_release(void *data)
  {
  	struct nfs_write_data *wdata = (struct nfs_write_data *)data;
  
  	wdata->mds_ops->rpc_release(data);
  }

  static void filelayout_commit_release(void *data)
  {
  	struct nfs_write_data *wdata = (struct nfs_write_data *)data;
  
  	nfs_commit_release_pages(wdata);
  	if (atomic_dec_and_test(&NFS_I(wdata->inode)->commits_outstanding))
  		nfs_commit_clear_lock(NFS_I(wdata->inode));
  	nfs_commitdata_release(wdata);
  }

  struct rpc_call_ops filelayout_read_call_ops = {
  	.rpc_call_prepare = filelayout_read_prepare,
  	.rpc_call_done = filelayout_read_call_done,
  	.rpc_release = filelayout_read_release,
  };

  struct rpc_call_ops filelayout_write_call_ops = {
  	.rpc_call_prepare = filelayout_write_prepare,
  	.rpc_call_done = filelayout_write_call_done,
  	.rpc_release = filelayout_write_release,
  };

  struct rpc_call_ops filelayout_commit_call_ops = {
  	.rpc_call_prepare = filelayout_write_prepare,
  	.rpc_call_done = filelayout_write_call_done,
  	.rpc_release = filelayout_commit_release,
  };

  static enum pnfs_try_status
  filelayout_read_pagelist(struct nfs_read_data *data)
  {
  	struct pnfs_layout_segment *lseg = data->lseg;
  	struct nfs4_pnfs_ds *ds;
  	loff_t offset = data->args.offset;
  	u32 j, idx;
  	struct nfs_fh *fh;
  	int status;
  
  	dprintk("--> %s ino %lu pgbase %u req %Zu@%llu
  ",
  		__func__, data->inode->i_ino,
  		data->args.pgbase, (size_t)data->args.count, offset);

  	if (test_bit(NFS_DEVICEID_INVALID, &FILELAYOUT_DEVID_NODE(lseg)->flags))
  		return PNFS_NOT_ATTEMPTED;

  	/* Retrieve the correct rpc_client for the byte range */
  	j = nfs4_fl_calc_j_index(lseg, offset);
  	idx = nfs4_fl_calc_ds_index(lseg, j);
  	ds = nfs4_fl_prepare_ds(lseg, idx);
  	if (!ds) {

  		/* Either layout fh index faulty, or ds connect failed */
  		set_bit(lo_fail_bit(IOMODE_RW), &lseg->pls_layout->plh_flags);
  		set_bit(lo_fail_bit(IOMODE_READ), &lseg->pls_layout->plh_flags);

  		return PNFS_NOT_ATTEMPTED;
  	}

  	dprintk("%s USE DS: %s
  ", __func__, ds->ds_remotestr);

  
  	/* No multipath support. Use first DS */
  	data->ds_clp = ds->ds_clp;
  	fh = nfs4_fl_select_ds_fh(lseg, j);
  	if (fh)
  		data->args.fh = fh;
  
  	data->args.offset = filelayout_get_dserver_offset(lseg, offset);
  	data->mds_offset = offset;
  
  	/* Perform an asynchronous read to ds */
  	status = nfs_initiate_read(data, ds->ds_clp->cl_rpcclient,
  				   &filelayout_read_call_ops);
  	BUG_ON(status != 0);
  	return PNFS_ATTEMPTED;
  }

  /* Perform async writes. */

  static enum pnfs_try_status
  filelayout_write_pagelist(struct nfs_write_data *data, int sync)
  {

  	struct pnfs_layout_segment *lseg = data->lseg;
  	struct nfs4_pnfs_ds *ds;
  	loff_t offset = data->args.offset;
  	u32 j, idx;
  	struct nfs_fh *fh;
  	int status;

  	if (test_bit(NFS_DEVICEID_INVALID, &FILELAYOUT_DEVID_NODE(lseg)->flags))
  		return PNFS_NOT_ATTEMPTED;

  	/* Retrieve the correct rpc_client for the byte range */
  	j = nfs4_fl_calc_j_index(lseg, offset);
  	idx = nfs4_fl_calc_ds_index(lseg, j);
  	ds = nfs4_fl_prepare_ds(lseg, idx);
  	if (!ds) {
  		printk(KERN_ERR "%s: prepare_ds failed, use MDS
  ", __func__);
  		set_bit(lo_fail_bit(IOMODE_RW), &lseg->pls_layout->plh_flags);
  		set_bit(lo_fail_bit(IOMODE_READ), &lseg->pls_layout->plh_flags);
  		return PNFS_NOT_ATTEMPTED;
  	}

  	dprintk("%s ino %lu sync %d req %Zu@%llu DS: %s
  ", __func__,

  		data->inode->i_ino, sync, (size_t) data->args.count, offset,

  		ds->ds_remotestr);

  	data->write_done_cb = filelayout_write_done_cb;
  	data->ds_clp = ds->ds_clp;
  	fh = nfs4_fl_select_ds_fh(lseg, j);
  	if (fh)
  		data->args.fh = fh;
  	/*
  	 * Get the file offset on the dserver. Set the write offset to
  	 * this offset and save the original offset.
  	 */
  	data->args.offset = filelayout_get_dserver_offset(lseg, offset);

  
  	/* Perform an asynchronous write */
  	status = nfs_initiate_write(data, ds->ds_clp->cl_rpcclient,
  				    &filelayout_write_call_ops, sync);
  	BUG_ON(status != 0);
  	return PNFS_ATTEMPTED;

  }

  /*

   * filelayout_check_layout()
   *
   * Make sure layout segment parameters are sane WRT the device.
   * At this point no generic layer initialization of the lseg has occurred,
   * and nothing has been added to the layout_hdr cache.
   *
   */
  static int
  filelayout_check_layout(struct pnfs_layout_hdr *lo,
  			struct nfs4_filelayout_segment *fl,
  			struct nfs4_layoutget_res *lgr,

  			struct nfs4_deviceid *id,
  			gfp_t gfp_flags)

  {

  	struct nfs4_deviceid_node *d;

  	struct nfs4_file_layout_dsaddr *dsaddr;
  	int status = -EINVAL;

  	struct nfs_server *nfss = NFS_SERVER(lo->plh_inode);

  
  	dprintk("--> %s
  ", __func__);

  	/* FIXME: remove this check when layout segment support is added */
  	if (lgr->range.offset != 0 ||
  	    lgr->range.length != NFS4_MAX_UINT64) {
  		dprintk("%s Only whole file layouts supported. Use MDS i/o
  ",
  			__func__);
  		goto out;
  	}

  	if (fl->pattern_offset > lgr->range.offset) {

  		dprintk("%s pattern_offset %lld too large
  ",

  				__func__, fl->pattern_offset);
  		goto out;
  	}

  	if (!fl->stripe_unit || fl->stripe_unit % PAGE_SIZE) {
  		dprintk("%s Invalid stripe unit (%u)
  ",

  			__func__, fl->stripe_unit);
  		goto out;
  	}
  
  	/* find and reference the deviceid */

  	d = nfs4_find_get_deviceid(NFS_SERVER(lo->plh_inode)->pnfs_curr_ld,
  				   NFS_SERVER(lo->plh_inode)->nfs_client, id);

  	if (d == NULL) {

  		dsaddr = get_device_info(lo->plh_inode, id, gfp_flags);

  		if (dsaddr == NULL)
  			goto out;

  	} else
  		dsaddr = container_of(d, struct nfs4_file_layout_dsaddr, id_node);

  	/* Found deviceid is being reaped */
  	if (test_bit(NFS_DEVICEID_INVALID, &dsaddr->id_node.flags))
  			goto out_put;

  	fl->dsaddr = dsaddr;

  	if (fl->first_stripe_index >= dsaddr->stripe_count) {
  		dprintk("%s Bad first_stripe_index %u
  ",

  				__func__, fl->first_stripe_index);
  		goto out_put;
  	}
  
  	if ((fl->stripe_type == STRIPE_SPARSE &&
  	    fl->num_fh > 1 && fl->num_fh != dsaddr->ds_num) ||
  	    (fl->stripe_type == STRIPE_DENSE &&
  	    fl->num_fh != dsaddr->stripe_count)) {
  		dprintk("%s num_fh %u not valid for given packing
  ",
  			__func__, fl->num_fh);
  		goto out_put;
  	}
  
  	if (fl->stripe_unit % nfss->rsize || fl->stripe_unit % nfss->wsize) {
  		dprintk("%s Stripe unit (%u) not aligned with rsize %u "
  			"wsize %u
  ", __func__, fl->stripe_unit, nfss->rsize,
  			nfss->wsize);
  	}
  
  	status = 0;
  out:
  	dprintk("--> %s returns %d
  ", __func__, status);
  	return status;
  out_put:

  	nfs4_fl_put_deviceid(dsaddr);

  	goto out;
  }
  
  static void filelayout_free_fh_array(struct nfs4_filelayout_segment *fl)
  {
  	int i;
  
  	for (i = 0; i < fl->num_fh; i++) {
  		if (!fl->fh_array[i])
  			break;
  		kfree(fl->fh_array[i]);
  	}
  	kfree(fl->fh_array);
  	fl->fh_array = NULL;
  }
  
  static void
  _filelayout_free_lseg(struct nfs4_filelayout_segment *fl)
  {
  	filelayout_free_fh_array(fl);
  	kfree(fl);
  }
  
  static int
  filelayout_decode_layout(struct pnfs_layout_hdr *flo,
  			 struct nfs4_filelayout_segment *fl,
  			 struct nfs4_layoutget_res *lgr,

  			 struct nfs4_deviceid *id,
  			 gfp_t gfp_flags)

  {

  	struct xdr_stream stream;

  	struct xdr_buf buf;

  	struct page *scratch;
  	__be32 *p;

  	uint32_t nfl_util;
  	int i;
  
  	dprintk("%s: set_layout_map Begin
  ", __func__);

  	scratch = alloc_page(gfp_flags);

  	if (!scratch)
  		return -ENOMEM;

  	xdr_init_decode_pages(&stream, &buf, lgr->layoutp->pages, lgr->layoutp->len);

  	xdr_set_scratch_buffer(&stream, page_address(scratch), PAGE_SIZE);
  
  	/* 20 = ufl_util (4), first_stripe_index (4), pattern_offset (8),
  	 * num_fh (4) */
  	p = xdr_inline_decode(&stream, NFS4_DEVICEID4_SIZE + 20);
  	if (unlikely(!p))
  		goto out_err;

  	memcpy(id, p, sizeof(*id));
  	p += XDR_QUADLEN(NFS4_DEVICEID4_SIZE);

  	nfs4_print_deviceid(id);

  
  	nfl_util = be32_to_cpup(p++);
  	if (nfl_util & NFL4_UFLG_COMMIT_THRU_MDS)
  		fl->commit_through_mds = 1;
  	if (nfl_util & NFL4_UFLG_DENSE)
  		fl->stripe_type = STRIPE_DENSE;
  	else
  		fl->stripe_type = STRIPE_SPARSE;
  	fl->stripe_unit = nfl_util & ~NFL4_UFLG_MASK;
  
  	fl->first_stripe_index = be32_to_cpup(p++);
  	p = xdr_decode_hyper(p, &fl->pattern_offset);
  	fl->num_fh = be32_to_cpup(p++);
  
  	dprintk("%s: nfl_util 0x%X num_fh %u fsi %u po %llu
  ",
  		__func__, nfl_util, fl->num_fh, fl->first_stripe_index,
  		fl->pattern_offset);

  	/* Note that a zero value for num_fh is legal for STRIPE_SPARSE.
  	 * Futher checking is done in filelayout_check_layout */

  	if (fl->num_fh >

  	    max(NFS4_PNFS_MAX_STRIPE_CNT, NFS4_PNFS_MAX_MULTI_CNT))

  		goto out_err;

  	if (fl->num_fh > 0) {
  		fl->fh_array = kzalloc(fl->num_fh * sizeof(struct nfs_fh *),
  				       gfp_flags);
  		if (!fl->fh_array)
  			goto out_err;
  	}

  
  	for (i = 0; i < fl->num_fh; i++) {
  		/* Do we want to use a mempool here? */

  		fl->fh_array[i] = kmalloc(sizeof(struct nfs_fh), gfp_flags);

  		if (!fl->fh_array[i])
  			goto out_err_free;
  
  		p = xdr_inline_decode(&stream, 4);
  		if (unlikely(!p))
  			goto out_err_free;

  		fl->fh_array[i]->size = be32_to_cpup(p++);
  		if (sizeof(struct nfs_fh) < fl->fh_array[i]->size) {
  			printk(KERN_ERR "Too big fh %d received %d
  ",
  			       i, fl->fh_array[i]->size);

  			goto out_err_free;

  		}

  
  		p = xdr_inline_decode(&stream, fl->fh_array[i]->size);
  		if (unlikely(!p))
  			goto out_err_free;

  		memcpy(fl->fh_array[i]->data, p, fl->fh_array[i]->size);

  		dprintk("DEBUG: %s: fh len %d
  ", __func__,
  			fl->fh_array[i]->size);
  	}

  	__free_page(scratch);

  	return 0;

  
  out_err_free:
  	filelayout_free_fh_array(fl);
  out_err:
  	__free_page(scratch);
  	return -EIO;

  }

  static void
  filelayout_free_lseg(struct pnfs_layout_segment *lseg)
  {
  	struct nfs4_filelayout_segment *fl = FILELAYOUT_LSEG(lseg);
  
  	dprintk("--> %s
  ", __func__);
  	nfs4_fl_put_deviceid(fl->dsaddr);

  	kfree(fl->commit_buckets);

  	_filelayout_free_lseg(fl);
  }

  static struct pnfs_layout_segment *
  filelayout_alloc_lseg(struct pnfs_layout_hdr *layoutid,

  		      struct nfs4_layoutget_res *lgr,
  		      gfp_t gfp_flags)

  {
  	struct nfs4_filelayout_segment *fl;
  	int rc;
  	struct nfs4_deviceid id;
  
  	dprintk("--> %s
  ", __func__);

  	fl = kzalloc(sizeof(*fl), gfp_flags);

  	if (!fl)
  		return NULL;

  	rc = filelayout_decode_layout(layoutid, fl, lgr, &id, gfp_flags);
  	if (rc != 0 || filelayout_check_layout(layoutid, fl, lgr, &id, gfp_flags)) {

  		_filelayout_free_lseg(fl);
  		return NULL;
  	}

  
  	/* This assumes there is only one IOMODE_RW lseg.  What
  	 * we really want to do is have a layout_hdr level
  	 * dictionary of <multipath_list4, fh> keys, each
  	 * associated with a struct list_head, populated by calls
  	 * to filelayout_write_pagelist().
  	 * */
  	if ((!fl->commit_through_mds) && (lgr->range.iomode == IOMODE_RW)) {
  		int i;
  		int size = (fl->stripe_type == STRIPE_SPARSE) ?
  			fl->dsaddr->ds_num : fl->dsaddr->stripe_count;

  		fl->commit_buckets = kcalloc(size, sizeof(struct list_head), gfp_flags);

  		if (!fl->commit_buckets) {
  			filelayout_free_lseg(&fl->generic_hdr);
  			return NULL;
  		}
  		fl->number_of_buckets = size;
  		for (i = 0; i < size; i++)
  			INIT_LIST_HEAD(&fl->commit_buckets[i]);
  	}

  	return &fl->generic_hdr;
  }

  /*
   * filelayout_pg_test(). Called by nfs_can_coalesce_requests()
   *

   * return true  : coalesce page
   * return false : don't coalesce page

   */

  static bool

  filelayout_pg_test(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
  		   struct nfs_page *req)
  {
  	u64 p_stripe, r_stripe;
  	u32 stripe_unit;

  	if (!pnfs_generic_pg_test(pgio, prev, req) ||
  	    !nfs_generic_pg_test(pgio, prev, req))
  		return false;

  	p_stripe = (u64)prev->wb_index << PAGE_CACHE_SHIFT;
  	r_stripe = (u64)req->wb_index << PAGE_CACHE_SHIFT;
  	stripe_unit = FILELAYOUT_LSEG(pgio->pg_lseg)->stripe_unit;
  
  	do_div(p_stripe, stripe_unit);
  	do_div(r_stripe, stripe_unit);
  
  	return (p_stripe == r_stripe);
  }

  void
  filelayout_pg_init_read(struct nfs_pageio_descriptor *pgio,
  			struct nfs_page *req)
  {
  	BUG_ON(pgio->pg_lseg != NULL);
  
  	pgio->pg_lseg = pnfs_update_layout(pgio->pg_inode,
  					   req->wb_context,
  					   0,
  					   NFS4_MAX_UINT64,
  					   IOMODE_READ,
  					   GFP_KERNEL);
  	/* If no lseg, fall back to read through mds */
  	if (pgio->pg_lseg == NULL)

  		nfs_pageio_reset_read_mds(pgio);

  }
  
  void
  filelayout_pg_init_write(struct nfs_pageio_descriptor *pgio,
  			 struct nfs_page *req)
  {
  	BUG_ON(pgio->pg_lseg != NULL);
  
  	pgio->pg_lseg = pnfs_update_layout(pgio->pg_inode,
  					   req->wb_context,
  					   0,
  					   NFS4_MAX_UINT64,
  					   IOMODE_RW,
  					   GFP_NOFS);
  	/* If no lseg, fall back to write through mds */
  	if (pgio->pg_lseg == NULL)

  		nfs_pageio_reset_write_mds(pgio);

  }

  static const struct nfs_pageio_ops filelayout_pg_read_ops = {

  	.pg_init = filelayout_pg_init_read,

  	.pg_test = filelayout_pg_test,

  	.pg_doio = pnfs_generic_pg_readpages,

  };
  
  static const struct nfs_pageio_ops filelayout_pg_write_ops = {

  	.pg_init = filelayout_pg_init_write,

  	.pg_test = filelayout_pg_test,

  	.pg_doio = pnfs_generic_pg_writepages,

  };

  static bool filelayout_mark_pnfs_commit(struct pnfs_layout_segment *lseg)
  {
  	return !FILELAYOUT_LSEG(lseg)->commit_through_mds;
  }
  
  static u32 select_bucket_index(struct nfs4_filelayout_segment *fl, u32 j)
  {
  	if (fl->stripe_type == STRIPE_SPARSE)
  		return nfs4_fl_calc_ds_index(&fl->generic_hdr, j);
  	else
  		return j;
  }
  
  struct list_head *filelayout_choose_commit_list(struct nfs_page *req)
  {
  	struct pnfs_layout_segment *lseg = req->wb_commit_lseg;
  	struct nfs4_filelayout_segment *fl = FILELAYOUT_LSEG(lseg);
  	u32 i, j;
  	struct list_head *list;
  
  	/* Note that we are calling nfs4_fl_calc_j_index on each page
  	 * that ends up being committed to a data server.  An attractive
  	 * alternative is to add a field to nfs_write_data and nfs_page
  	 * to store the value calculated in filelayout_write_pagelist
  	 * and just use that here.
  	 */
  	j = nfs4_fl_calc_j_index(lseg,
  				 (loff_t)req->wb_index << PAGE_CACHE_SHIFT);
  	i = select_bucket_index(fl, j);
  	list = &fl->commit_buckets[i];
  	if (list_empty(list)) {
  		/* Non-empty buckets hold a reference on the lseg */
  		get_lseg(lseg);
  	}
  	return list;
  }
  
  static u32 calc_ds_index_from_commit(struct pnfs_layout_segment *lseg, u32 i)
  {
  	struct nfs4_filelayout_segment *flseg = FILELAYOUT_LSEG(lseg);
  
  	if (flseg->stripe_type == STRIPE_SPARSE)
  		return i;
  	else
  		return nfs4_fl_calc_ds_index(lseg, i);
  }
  
  static struct nfs_fh *
  select_ds_fh_from_commit(struct pnfs_layout_segment *lseg, u32 i)
  {
  	struct nfs4_filelayout_segment *flseg = FILELAYOUT_LSEG(lseg);
  
  	if (flseg->stripe_type == STRIPE_SPARSE) {
  		if (flseg->num_fh == 1)
  			i = 0;
  		else if (flseg->num_fh == 0)
  			/* Use the MDS OPEN fh set in nfs_read_rpcsetup */
  			return NULL;
  	}
  	return flseg->fh_array[i];
  }
  
  static int filelayout_initiate_commit(struct nfs_write_data *data, int how)
  {
  	struct pnfs_layout_segment *lseg = data->lseg;
  	struct nfs4_pnfs_ds *ds;
  	u32 idx;
  	struct nfs_fh *fh;
  
  	idx = calc_ds_index_from_commit(lseg, data->ds_commit_index);
  	ds = nfs4_fl_prepare_ds(lseg, idx);
  	if (!ds) {
  		printk(KERN_ERR "%s: prepare_ds failed, use MDS
  ", __func__);
  		set_bit(lo_fail_bit(IOMODE_RW), &lseg->pls_layout->plh_flags);
  		set_bit(lo_fail_bit(IOMODE_READ), &lseg->pls_layout->plh_flags);
  		prepare_to_resend_writes(data);
  		data->mds_ops->rpc_release(data);
  		return -EAGAIN;
  	}
  	dprintk("%s ino %lu, how %d
  ", __func__, data->inode->i_ino, how);
  	data->write_done_cb = filelayout_commit_done_cb;
  	data->ds_clp = ds->ds_clp;
  	fh = select_ds_fh_from_commit(lseg, data->ds_commit_index);
  	if (fh)
  		data->args.fh = fh;
  	return nfs_initiate_commit(data, ds->ds_clp->cl_rpcclient,
  				   &filelayout_commit_call_ops, how);
  }
  
  /*
   * This is only useful while we are using whole file layouts.
   */
  static struct pnfs_layout_segment *find_only_write_lseg(struct inode *inode)
  {
  	struct pnfs_layout_segment *lseg, *rv = NULL;
  
  	spin_lock(&inode->i_lock);
  	list_for_each_entry(lseg, &NFS_I(inode)->layout->plh_segs, pls_list)
  		if (lseg->pls_range.iomode == IOMODE_RW)
  			rv = get_lseg(lseg);
  	spin_unlock(&inode->i_lock);
  	return rv;
  }
  
  static int alloc_ds_commits(struct inode *inode, struct list_head *list)
  {
  	struct pnfs_layout_segment *lseg;
  	struct nfs4_filelayout_segment *fl;
  	struct nfs_write_data *data;
  	int i, j;
  
  	/* Won't need this when non-whole file layout segments are supported
  	 * instead we will use a pnfs_layout_hdr structure */
  	lseg = find_only_write_lseg(inode);
  	if (!lseg)
  		return 0;
  	fl = FILELAYOUT_LSEG(lseg);
  	for (i = 0; i < fl->number_of_buckets; i++) {
  		if (list_empty(&fl->commit_buckets[i]))
  			continue;
  		data = nfs_commitdata_alloc();
  		if (!data)
  			goto out_bad;
  		data->ds_commit_index = i;
  		data->lseg = lseg;
  		list_add(&data->pages, list);
  	}
  	put_lseg(lseg);
  	return 0;
  
  out_bad:
  	for (j = i; j < fl->number_of_buckets; j++) {
  		if (list_empty(&fl->commit_buckets[i]))
  			continue;
  		nfs_retry_commit(&fl->commit_buckets[i], lseg);
  		put_lseg(lseg);  /* associated with emptying bucket */
  	}
  	put_lseg(lseg);
  	/* Caller will clean up entries put on list */
  	return -ENOMEM;
  }
  
  /* This follows nfs_commit_list pretty closely */
  static int
  filelayout_commit_pagelist(struct inode *inode, struct list_head *mds_pages,
  			   int how)
  {
  	struct nfs_write_data	*data, *tmp;
  	LIST_HEAD(list);
  
  	if (!list_empty(mds_pages)) {
  		data = nfs_commitdata_alloc();
  		if (!data)
  			goto out_bad;
  		data->lseg = NULL;
  		list_add(&data->pages, &list);
  	}
  
  	if (alloc_ds_commits(inode, &list))
  		goto out_bad;
  
  	list_for_each_entry_safe(data, tmp, &list, pages) {
  		list_del_init(&data->pages);
  		atomic_inc(&NFS_I(inode)->commits_outstanding);
  		if (!data->lseg) {
  			nfs_init_commit(data, mds_pages, NULL);
  			nfs_initiate_commit(data, NFS_CLIENT(inode),
  					    data->mds_ops, how);
  		} else {
  			nfs_init_commit(data, &FILELAYOUT_LSEG(data->lseg)->commit_buckets[data->ds_commit_index], data->lseg);
  			filelayout_initiate_commit(data, how);
  		}
  	}
  	return 0;
   out_bad:
  	list_for_each_entry_safe(data, tmp, &list, pages) {
  		nfs_retry_commit(&data->pages, data->lseg);
  		list_del_init(&data->pages);
  		nfs_commit_free(data);
  	}
  	nfs_retry_commit(mds_pages, NULL);
  	nfs_commit_clear_lock(NFS_I(inode));
  	return -ENOMEM;
  }

  static void
  filelayout_free_deveiceid_node(struct nfs4_deviceid_node *d)
  {
  	nfs4_fl_free_deviceid(container_of(d, struct nfs4_file_layout_dsaddr, id_node));
  }

  static struct pnfs_layoutdriver_type filelayout_type = {

  	.id			= LAYOUT_NFSV4_1_FILES,
  	.name			= "LAYOUT_NFSV4_1_FILES",
  	.owner			= THIS_MODULE,
  	.alloc_lseg		= filelayout_alloc_lseg,
  	.free_lseg		= filelayout_free_lseg,

  	.pg_read_ops		= &filelayout_pg_read_ops,
  	.pg_write_ops		= &filelayout_pg_write_ops,

  	.mark_pnfs_commit	= filelayout_mark_pnfs_commit,
  	.choose_commit_list	= filelayout_choose_commit_list,
  	.commit_pagelist	= filelayout_commit_pagelist,

  	.read_pagelist		= filelayout_read_pagelist,

  	.write_pagelist		= filelayout_write_pagelist,

  	.free_deviceid_node	= filelayout_free_deveiceid_node,

  };
  
  static int __init nfs4filelayout_init(void)
  {
  	printk(KERN_INFO "%s: NFSv4 File Layout Driver Registering...
  ",
  	       __func__);
  	return pnfs_register_layoutdriver(&filelayout_type);
  }
  
  static void __exit nfs4filelayout_exit(void)
  {
  	printk(KERN_INFO "%s: NFSv4 File Layout Driver Unregistering...
  ",
  	       __func__);
  	pnfs_unregister_layoutdriver(&filelayout_type);
  }

  MODULE_ALIAS("nfs-layouttype4-1");

  module_init(nfs4filelayout_init);
  module_exit(nfs4filelayout_exit);