/*
   *  pNFS functions to call and manage layout drivers.
   *
   *  Copyright (c) 2002 [year of first publication]
   *  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 "pnfs.h"

  #include "iostat.h"

  
  #define NFSDBG_FACILITY		NFSDBG_PNFS

  /* Locking:
   *
   * pnfs_spinlock:
   *      protects pnfs_modules_tbl.
   */
  static DEFINE_SPINLOCK(pnfs_spinlock);
  
  /*
   * pnfs_modules_tbl holds all pnfs modules
   */
  static LIST_HEAD(pnfs_modules_tbl);
  
  /* Return the registered pnfs layout driver module matching given id */
  static struct pnfs_layoutdriver_type *
  find_pnfs_driver_locked(u32 id)
  {
  	struct pnfs_layoutdriver_type *local;
  
  	list_for_each_entry(local, &pnfs_modules_tbl, pnfs_tblid)
  		if (local->id == id)
  			goto out;
  	local = NULL;
  out:
  	dprintk("%s: Searching for id %u, found %p
  ", __func__, id, local);
  	return local;
  }

  static struct pnfs_layoutdriver_type *
  find_pnfs_driver(u32 id)
  {

  	struct pnfs_layoutdriver_type *local;
  
  	spin_lock(&pnfs_spinlock);
  	local = find_pnfs_driver_locked(id);
  	spin_unlock(&pnfs_spinlock);
  	return local;

  }
  
  void
  unset_pnfs_layoutdriver(struct nfs_server *nfss)
  {

  	if (nfss->pnfs_curr_ld) {
  		if (nfss->pnfs_curr_ld->clear_layoutdriver)
  			nfss->pnfs_curr_ld->clear_layoutdriver(nfss);

  		module_put(nfss->pnfs_curr_ld->owner);

  	}

  	nfss->pnfs_curr_ld = NULL;
  }
  
  /*
   * Try to set the server's pnfs module to the pnfs layout type specified by id.
   * Currently only one pNFS layout driver per filesystem is supported.
   *
   * @id layout type. Zero (illegal layout type) indicates pNFS not in use.
   */
  void

  set_pnfs_layoutdriver(struct nfs_server *server, const struct nfs_fh *mntfh,
  		      u32 id)

  {
  	struct pnfs_layoutdriver_type *ld_type = NULL;
  
  	if (id == 0)
  		goto out_no_driver;
  	if (!(server->nfs_client->cl_exchange_flags &
  		 (EXCHGID4_FLAG_USE_NON_PNFS | EXCHGID4_FLAG_USE_PNFS_MDS))) {
  		printk(KERN_ERR "%s: id %u cl_exchange_flags 0x%x
  ", __func__,
  		       id, server->nfs_client->cl_exchange_flags);
  		goto out_no_driver;
  	}
  	ld_type = find_pnfs_driver(id);
  	if (!ld_type) {
  		request_module("%s-%u", LAYOUT_NFSV4_1_MODULE_PREFIX, id);
  		ld_type = find_pnfs_driver(id);
  		if (!ld_type) {
  			dprintk("%s: No pNFS module found for %u.
  ",
  				__func__, id);
  			goto out_no_driver;
  		}
  	}

  	if (!try_module_get(ld_type->owner)) {
  		dprintk("%s: Could not grab reference on module
  ", __func__);
  		goto out_no_driver;
  	}

  	server->pnfs_curr_ld = ld_type;

  	if (ld_type->set_layoutdriver
  	    && ld_type->set_layoutdriver(server, mntfh)) {
  		printk(KERN_ERR "%s: Error initializing pNFS layout driver %u.
  ",
  				__func__, id);
  		module_put(ld_type->owner);
  		goto out_no_driver;
  	}

  	dprintk("%s: pNFS module for %u set
  ", __func__, id);
  	return;
  
  out_no_driver:
  	dprintk("%s: Using NFSv4 I/O
  ", __func__);
  	server->pnfs_curr_ld = NULL;
  }

  
  int
  pnfs_register_layoutdriver(struct pnfs_layoutdriver_type *ld_type)
  {
  	int status = -EINVAL;
  	struct pnfs_layoutdriver_type *tmp;
  
  	if (ld_type->id == 0) {
  		printk(KERN_ERR "%s id 0 is reserved
  ", __func__);
  		return status;
  	}

  	if (!ld_type->alloc_lseg || !ld_type->free_lseg) {
  		printk(KERN_ERR "%s Layout driver must provide "
  		       "alloc_lseg and free_lseg.
  ", __func__);
  		return status;
  	}

  
  	spin_lock(&pnfs_spinlock);
  	tmp = find_pnfs_driver_locked(ld_type->id);
  	if (!tmp) {
  		list_add(&ld_type->pnfs_tblid, &pnfs_modules_tbl);
  		status = 0;
  		dprintk("%s Registering id:%u name:%s
  ", __func__, ld_type->id,
  			ld_type->name);
  	} else {
  		printk(KERN_ERR "%s Module with id %d already loaded!
  ",
  			__func__, ld_type->id);
  	}
  	spin_unlock(&pnfs_spinlock);
  
  	return status;
  }
  EXPORT_SYMBOL_GPL(pnfs_register_layoutdriver);
  
  void
  pnfs_unregister_layoutdriver(struct pnfs_layoutdriver_type *ld_type)
  {
  	dprintk("%s Deregistering id:%u
  ", __func__, ld_type->id);
  	spin_lock(&pnfs_spinlock);
  	list_del(&ld_type->pnfs_tblid);
  	spin_unlock(&pnfs_spinlock);
  }
  EXPORT_SYMBOL_GPL(pnfs_unregister_layoutdriver);

  /*
   * pNFS client layout cache
   */

  /* Need to hold i_lock if caller does not already hold reference */

  void

  get_layout_hdr(struct pnfs_layout_hdr *lo)

  {

  	atomic_inc(&lo->plh_refcount);

  }

  static struct pnfs_layout_hdr *
  pnfs_alloc_layout_hdr(struct inode *ino, gfp_t gfp_flags)
  {
  	struct pnfs_layoutdriver_type *ld = NFS_SERVER(ino)->pnfs_curr_ld;
  	return ld->alloc_layout_hdr ? ld->alloc_layout_hdr(ino, gfp_flags) :
  		kzalloc(sizeof(struct pnfs_layout_hdr), gfp_flags);
  }
  
  static void
  pnfs_free_layout_hdr(struct pnfs_layout_hdr *lo)
  {
  	struct pnfs_layoutdriver_type *ld = NFS_SERVER(lo->plh_inode)->pnfs_curr_ld;

  	put_rpccred(lo->plh_lc_cred);

  	return ld->alloc_layout_hdr ? ld->free_layout_hdr(lo) : kfree(lo);
  }

  static void

  destroy_layout_hdr(struct pnfs_layout_hdr *lo)

  {

  	dprintk("%s: freeing layout cache %p
  ", __func__, lo);
  	BUG_ON(!list_empty(&lo->plh_layouts));
  	NFS_I(lo->plh_inode)->layout = NULL;

  	pnfs_free_layout_hdr(lo);

  }

  static void
  put_layout_hdr_locked(struct pnfs_layout_hdr *lo)
  {
  	if (atomic_dec_and_test(&lo->plh_refcount))
  		destroy_layout_hdr(lo);

  }

  void

  put_layout_hdr(struct pnfs_layout_hdr *lo)

  {

  	struct inode *inode = lo->plh_inode;
  
  	if (atomic_dec_and_lock(&lo->plh_refcount, &inode->i_lock)) {
  		destroy_layout_hdr(lo);
  		spin_unlock(&inode->i_lock);
  	}

  }
  
  static void
  init_lseg(struct pnfs_layout_hdr *lo, struct pnfs_layout_segment *lseg)
  {

  	INIT_LIST_HEAD(&lseg->pls_list);

  	INIT_LIST_HEAD(&lseg->pls_lc_list);

  	atomic_set(&lseg->pls_refcount, 1);
  	smp_mb();
  	set_bit(NFS_LSEG_VALID, &lseg->pls_flags);

  	lseg->pls_layout = lo;

  }

  static void free_lseg(struct pnfs_layout_segment *lseg)

  {

  	struct inode *ino = lseg->pls_layout->plh_inode;

  	NFS_SERVER(ino)->pnfs_curr_ld->free_lseg(lseg);

  	/* Matched by get_layout_hdr in pnfs_insert_layout */

  	put_layout_hdr(NFS_I(ino)->layout);

  }

  static void
  put_lseg_common(struct pnfs_layout_segment *lseg)
  {
  	struct inode *inode = lseg->pls_layout->plh_inode;

  	WARN_ON(test_bit(NFS_LSEG_VALID, &lseg->pls_flags));

  	list_del_init(&lseg->pls_list);
  	if (list_empty(&lseg->pls_layout->plh_segs)) {
  		set_bit(NFS_LAYOUT_DESTROYED, &lseg->pls_layout->plh_flags);
  		/* Matched by initial refcount set in alloc_init_layout_hdr */
  		put_layout_hdr_locked(lseg->pls_layout);
  	}
  	rpc_wake_up(&NFS_SERVER(inode)->roc_rpcwaitq);
  }

  void

  put_lseg(struct pnfs_layout_segment *lseg)

  {

  	struct inode *inode;
  
  	if (!lseg)
  		return;

  	dprintk("%s: lseg %p ref %d valid %d
  ", __func__, lseg,
  		atomic_read(&lseg->pls_refcount),
  		test_bit(NFS_LSEG_VALID, &lseg->pls_flags));

  	inode = lseg->pls_layout->plh_inode;
  	if (atomic_dec_and_lock(&lseg->pls_refcount, &inode->i_lock)) {
  		LIST_HEAD(free_me);

  		put_lseg_common(lseg);
  		list_add(&lseg->pls_list, &free_me);
  		spin_unlock(&inode->i_lock);
  		pnfs_free_lseg_list(&free_me);

  	}

  }

  EXPORT_SYMBOL_GPL(put_lseg);

  static inline u64
  end_offset(u64 start, u64 len)
  {
  	u64 end;
  
  	end = start + len;
  	return end >= start ? end : NFS4_MAX_UINT64;
  }
  
  /* last octet in a range */
  static inline u64
  last_byte_offset(u64 start, u64 len)
  {
  	u64 end;
  
  	BUG_ON(!len);
  	end = start + len;
  	return end > start ? end - 1 : NFS4_MAX_UINT64;
  }
  
  /*
   * is l2 fully contained in l1?
   *   start1                             end1
   *   [----------------------------------)
   *           start2           end2
   *           [----------------)
   */
  static inline int
  lo_seg_contained(struct pnfs_layout_range *l1,
  		 struct pnfs_layout_range *l2)
  {
  	u64 start1 = l1->offset;
  	u64 end1 = end_offset(start1, l1->length);
  	u64 start2 = l2->offset;
  	u64 end2 = end_offset(start2, l2->length);
  
  	return (start1 <= start2) && (end1 >= end2);
  }
  
  /*
   * is l1 and l2 intersecting?
   *   start1                             end1
   *   [----------------------------------)
   *                              start2           end2
   *                              [----------------)
   */
  static inline int
  lo_seg_intersecting(struct pnfs_layout_range *l1,
  		    struct pnfs_layout_range *l2)
  {
  	u64 start1 = l1->offset;
  	u64 end1 = end_offset(start1, l1->length);
  	u64 start2 = l2->offset;
  	u64 end2 = end_offset(start2, l2->length);
  
  	return (end1 == NFS4_MAX_UINT64 || end1 > start2) &&
  	       (end2 == NFS4_MAX_UINT64 || end2 > start1);
  }

  static bool

  should_free_lseg(struct pnfs_layout_range *lseg_range,
  		 struct pnfs_layout_range *recall_range)

  {

  	return (recall_range->iomode == IOMODE_ANY ||
  		lseg_range->iomode == recall_range->iomode) &&
  	       lo_seg_intersecting(lseg_range, recall_range);

  }

  /* Returns 1 if lseg is removed from list, 0 otherwise */
  static int mark_lseg_invalid(struct pnfs_layout_segment *lseg,
  			     struct list_head *tmp_list)
  {
  	int rv = 0;
  
  	if (test_and_clear_bit(NFS_LSEG_VALID, &lseg->pls_flags)) {
  		/* Remove the reference keeping the lseg in the
  		 * list.  It will now be removed when all
  		 * outstanding io is finished.
  		 */

  		dprintk("%s: lseg %p ref %d
  ", __func__, lseg,
  			atomic_read(&lseg->pls_refcount));
  		if (atomic_dec_and_test(&lseg->pls_refcount)) {
  			put_lseg_common(lseg);
  			list_add(&lseg->pls_list, tmp_list);
  			rv = 1;
  		}

  	}
  	return rv;
  }
  
  /* Returns count of number of matching invalid lsegs remaining in list
   * after call.
   */

  int

  mark_matching_lsegs_invalid(struct pnfs_layout_hdr *lo,
  			    struct list_head *tmp_list,

  			    struct pnfs_layout_range *recall_range)

  {
  	struct pnfs_layout_segment *lseg, *next;

  	int invalid = 0, removed = 0;

  
  	dprintk("%s:Begin lo %p
  ", __func__, lo);

  	if (list_empty(&lo->plh_segs)) {
  		if (!test_and_set_bit(NFS_LAYOUT_DESTROYED, &lo->plh_flags))
  			put_layout_hdr_locked(lo);
  		return 0;
  	}

  	list_for_each_entry_safe(lseg, next, &lo->plh_segs, pls_list)

  		if (!recall_range ||
  		    should_free_lseg(&lseg->pls_range, recall_range)) {

  			dprintk("%s: freeing lseg %p iomode %d "
  				"offset %llu length %llu
  ", __func__,
  				lseg, lseg->pls_range.iomode, lseg->pls_range.offset,
  				lseg->pls_range.length);
  			invalid++;
  			removed += mark_lseg_invalid(lseg, tmp_list);
  		}
  	dprintk("%s:Return %i
  ", __func__, invalid - removed);
  	return invalid - removed;

  }

  /* note free_me must contain lsegs from a single layout_hdr */

  void

  pnfs_free_lseg_list(struct list_head *free_me)

  {

  	struct pnfs_layout_segment *lseg, *tmp;

  	struct pnfs_layout_hdr *lo;
  
  	if (list_empty(free_me))
  		return;
  
  	lo = list_first_entry(free_me, struct pnfs_layout_segment,
  			      pls_list)->pls_layout;

  	if (test_bit(NFS_LAYOUT_DESTROYED, &lo->plh_flags)) {
  		struct nfs_client *clp;
  
  		clp = NFS_SERVER(lo->plh_inode)->nfs_client;
  		spin_lock(&clp->cl_lock);
  		list_del_init(&lo->plh_layouts);
  		spin_unlock(&clp->cl_lock);
  	}

  	list_for_each_entry_safe(lseg, tmp, free_me, pls_list) {

  		list_del(&lseg->pls_list);

  		free_lseg(lseg);

  	}
  }

  void
  pnfs_destroy_layout(struct nfs_inode *nfsi)
  {
  	struct pnfs_layout_hdr *lo;

  	LIST_HEAD(tmp_list);

  
  	spin_lock(&nfsi->vfs_inode.i_lock);
  	lo = nfsi->layout;
  	if (lo) {

  		lo->plh_block_lgets++; /* permanently block new LAYOUTGETs */

  		mark_matching_lsegs_invalid(lo, &tmp_list, NULL);

  	}
  	spin_unlock(&nfsi->vfs_inode.i_lock);

  	pnfs_free_lseg_list(&tmp_list);
  }
  
  /*
   * Called by the state manger to remove all layouts established under an
   * expired lease.
   */
  void
  pnfs_destroy_all_layouts(struct nfs_client *clp)
  {

  	struct nfs_server *server;

  	struct pnfs_layout_hdr *lo;
  	LIST_HEAD(tmp_list);

  	nfs4_deviceid_mark_client_invalid(clp);
  	nfs4_deviceid_purge_client(clp);

  	spin_lock(&clp->cl_lock);

  	rcu_read_lock();
  	list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) {
  		if (!list_empty(&server->layouts))
  			list_splice_init(&server->layouts, &tmp_list);
  	}
  	rcu_read_unlock();

  	spin_unlock(&clp->cl_lock);
  
  	while (!list_empty(&tmp_list)) {
  		lo = list_entry(tmp_list.next, struct pnfs_layout_hdr,

  				plh_layouts);

  		dprintk("%s freeing layout for inode %lu
  ", __func__,

  			lo->plh_inode->i_ino);

  		list_del_init(&lo->plh_layouts);

  		pnfs_destroy_layout(NFS_I(lo->plh_inode));

  	}

  }

  /* update lo->plh_stateid with new if is more recent */

  void
  pnfs_set_layout_stateid(struct pnfs_layout_hdr *lo, const nfs4_stateid *new,
  			bool update_barrier)

  {

  	u32 oldseq, newseq;

  	oldseq = be32_to_cpu(lo->plh_stateid.stateid.seqid);
  	newseq = be32_to_cpu(new->stateid.seqid);

  	if ((int)(newseq - oldseq) > 0) {

  		memcpy(&lo->plh_stateid, &new->stateid, sizeof(new->stateid));

  		if (update_barrier) {
  			u32 new_barrier = be32_to_cpu(new->stateid.seqid);
  
  			if ((int)(new_barrier - lo->plh_barrier))
  				lo->plh_barrier = new_barrier;
  		} else {
  			/* Because of wraparound, we want to keep the barrier
  			 * "close" to the current seqids.  It needs to be
  			 * within 2**31 to count as "behind", so if it
  			 * gets too near that limit, give us a litle leeway
  			 * and bring it to within 2**30.
  			 * NOTE - and yes, this is all unsigned arithmetic.
  			 */
  			if (unlikely((newseq - lo->plh_barrier) > (3 << 29)))
  				lo->plh_barrier = newseq - (1 << 30);
  		}
  	}

  }

  /* lget is set to 1 if called from inside send_layoutget call chain */
  static bool

  pnfs_layoutgets_blocked(struct pnfs_layout_hdr *lo, nfs4_stateid *stateid,
  			int lget)
  {
  	if ((stateid) &&
  	    (int)(lo->plh_barrier - be32_to_cpu(stateid->stateid.seqid)) >= 0)
  		return true;

  	return lo->plh_block_lgets ||

  		test_bit(NFS_LAYOUT_DESTROYED, &lo->plh_flags) ||

  		test_bit(NFS_LAYOUT_BULK_RECALL, &lo->plh_flags) ||

  		(list_empty(&lo->plh_segs) &&

  		 (atomic_read(&lo->plh_outstanding) > lget));
  }

  int
  pnfs_choose_layoutget_stateid(nfs4_stateid *dst, struct pnfs_layout_hdr *lo,
  			      struct nfs4_state *open_state)

  {

  	int status = 0;

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

  	spin_lock(&lo->plh_inode->i_lock);

  	if (pnfs_layoutgets_blocked(lo, NULL, 1)) {

  		status = -EAGAIN;
  	} else if (list_empty(&lo->plh_segs)) {

  		int seq;
  
  		do {
  			seq = read_seqbegin(&open_state->seqlock);
  			memcpy(dst->data, open_state->stateid.data,
  			       sizeof(open_state->stateid.data));
  		} while (read_seqretry(&open_state->seqlock, seq));
  	} else
  		memcpy(dst->data, lo->plh_stateid.data, sizeof(lo->plh_stateid.data));
  	spin_unlock(&lo->plh_inode->i_lock);

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

  	return status;

  }
  
  /*
  * Get layout from server.
  *    for now, assume that whole file layouts are requested.
  *    arg->offset: 0
  *    arg->length: all ones
  */

  static struct pnfs_layout_segment *
  send_layoutget(struct pnfs_layout_hdr *lo,
  	   struct nfs_open_context *ctx,

  	   struct pnfs_layout_range *range,

  	   gfp_t gfp_flags)

  {

  	struct inode *ino = lo->plh_inode;

  	struct nfs_server *server = NFS_SERVER(ino);
  	struct nfs4_layoutget *lgp;
  	struct pnfs_layout_segment *lseg = NULL;

  	struct page **pages = NULL;
  	int i;
  	u32 max_resp_sz, max_pages;

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

  	BUG_ON(ctx == NULL);

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

  	if (lgp == NULL)

  		return NULL;

  
  	/* allocate pages for xdr post processing */
  	max_resp_sz = server->nfs_client->cl_session->fc_attrs.max_resp_sz;
  	max_pages = max_resp_sz >> PAGE_SHIFT;

  	pages = kzalloc(max_pages * sizeof(struct page *), gfp_flags);

  	if (!pages)
  		goto out_err_free;
  
  	for (i = 0; i < max_pages; i++) {

  		pages[i] = alloc_page(gfp_flags);

  		if (!pages[i])
  			goto out_err_free;
  	}

  	lgp->args.minlength = PAGE_CACHE_SIZE;
  	if (lgp->args.minlength > range->length)
  		lgp->args.minlength = range->length;

  	lgp->args.maxcount = PNFS_LAYOUT_MAXSIZE;

  	lgp->args.range = *range;

  	lgp->args.type = server->pnfs_curr_ld->id;
  	lgp->args.inode = ino;
  	lgp->args.ctx = get_nfs_open_context(ctx);

  	lgp->args.layout.pages = pages;
  	lgp->args.layout.pglen = max_pages * PAGE_SIZE;

  	lgp->lsegpp = &lseg;

  	lgp->gfp_flags = gfp_flags;

  
  	/* Synchronously retrieve layout information from server and
  	 * store in lseg.
  	 */
  	nfs4_proc_layoutget(lgp);

  	if (!lseg) {

  		/* remember that LAYOUTGET failed and suspend trying */

  		set_bit(lo_fail_bit(range->iomode), &lo->plh_flags);

  	}

  
  	/* free xdr pages */
  	for (i = 0; i < max_pages; i++)
  		__free_page(pages[i]);
  	kfree(pages);

  	return lseg;

  
  out_err_free:
  	/* free any allocated xdr pages, lgp as it's not used */
  	if (pages) {
  		for (i = 0; i < max_pages; i++) {
  			if (!pages[i])
  				break;
  			__free_page(pages[i]);
  		}
  		kfree(pages);
  	}
  	kfree(lgp);
  	return NULL;

  }

  /* Initiates a LAYOUTRETURN(FILE) */
  int
  _pnfs_return_layout(struct inode *ino)
  {
  	struct pnfs_layout_hdr *lo = NULL;
  	struct nfs_inode *nfsi = NFS_I(ino);
  	LIST_HEAD(tmp_list);
  	struct nfs4_layoutreturn *lrp;
  	nfs4_stateid stateid;
  	int status = 0;
  
  	dprintk("--> %s
  ", __func__);
  
  	spin_lock(&ino->i_lock);
  	lo = nfsi->layout;

  	if (!lo) {

  		spin_unlock(&ino->i_lock);

  		dprintk("%s: no layout to return
  ", __func__);
  		return status;

  	}
  	stateid = nfsi->layout->plh_stateid;
  	/* Reference matched in nfs4_layoutreturn_release */
  	get_layout_hdr(lo);

  	mark_matching_lsegs_invalid(lo, &tmp_list, NULL);
  	lo->plh_block_lgets++;

  	spin_unlock(&ino->i_lock);
  	pnfs_free_lseg_list(&tmp_list);
  
  	WARN_ON(test_bit(NFS_INO_LAYOUTCOMMIT, &nfsi->flags));
  
  	lrp = kzalloc(sizeof(*lrp), GFP_KERNEL);
  	if (unlikely(lrp == NULL)) {
  		status = -ENOMEM;

  		set_bit(NFS_LAYOUT_RW_FAILED, &lo->plh_flags);
  		set_bit(NFS_LAYOUT_RO_FAILED, &lo->plh_flags);

  		put_layout_hdr(lo);

  		goto out;
  	}
  
  	lrp->args.stateid = stateid;
  	lrp->args.layout_type = NFS_SERVER(ino)->pnfs_curr_ld->id;
  	lrp->args.inode = ino;

  	lrp->args.layout = lo;

  	lrp->clp = NFS_SERVER(ino)->nfs_client;
  
  	status = nfs4_proc_layoutreturn(lrp);
  out:
  	dprintk("<-- %s status: %d
  ", __func__, status);
  	return status;
  }

  bool pnfs_roc(struct inode *ino)
  {
  	struct pnfs_layout_hdr *lo;
  	struct pnfs_layout_segment *lseg, *tmp;
  	LIST_HEAD(tmp_list);
  	bool found = false;
  
  	spin_lock(&ino->i_lock);
  	lo = NFS_I(ino)->layout;
  	if (!lo || !test_and_clear_bit(NFS_LAYOUT_ROC, &lo->plh_flags) ||
  	    test_bit(NFS_LAYOUT_BULK_RECALL, &lo->plh_flags))
  		goto out_nolayout;
  	list_for_each_entry_safe(lseg, tmp, &lo->plh_segs, pls_list)
  		if (test_bit(NFS_LSEG_ROC, &lseg->pls_flags)) {
  			mark_lseg_invalid(lseg, &tmp_list);
  			found = true;
  		}
  	if (!found)
  		goto out_nolayout;
  	lo->plh_block_lgets++;
  	get_layout_hdr(lo); /* matched in pnfs_roc_release */
  	spin_unlock(&ino->i_lock);
  	pnfs_free_lseg_list(&tmp_list);
  	return true;
  
  out_nolayout:
  	spin_unlock(&ino->i_lock);
  	return false;
  }
  
  void pnfs_roc_release(struct inode *ino)
  {
  	struct pnfs_layout_hdr *lo;
  
  	spin_lock(&ino->i_lock);
  	lo = NFS_I(ino)->layout;
  	lo->plh_block_lgets--;
  	put_layout_hdr_locked(lo);
  	spin_unlock(&ino->i_lock);
  }
  
  void pnfs_roc_set_barrier(struct inode *ino, u32 barrier)
  {
  	struct pnfs_layout_hdr *lo;
  
  	spin_lock(&ino->i_lock);
  	lo = NFS_I(ino)->layout;
  	if ((int)(barrier - lo->plh_barrier) > 0)
  		lo->plh_barrier = barrier;
  	spin_unlock(&ino->i_lock);
  }
  
  bool pnfs_roc_drain(struct inode *ino, u32 *barrier)
  {
  	struct nfs_inode *nfsi = NFS_I(ino);
  	struct pnfs_layout_segment *lseg;
  	bool found = false;
  
  	spin_lock(&ino->i_lock);
  	list_for_each_entry(lseg, &nfsi->layout->plh_segs, pls_list)
  		if (test_bit(NFS_LSEG_ROC, &lseg->pls_flags)) {
  			found = true;
  			break;
  		}
  	if (!found) {
  		struct pnfs_layout_hdr *lo = nfsi->layout;
  		u32 current_seqid = be32_to_cpu(lo->plh_stateid.stateid.seqid);
  
  		/* Since close does not return a layout stateid for use as
  		 * a barrier, we choose the worst-case barrier.
  		 */
  		*barrier = current_seqid + atomic_read(&lo->plh_outstanding);
  	}
  	spin_unlock(&ino->i_lock);
  	return found;
  }

  /*
   * Compare two layout segments for sorting into layout cache.
   * We want to preferentially return RW over RO layouts, so ensure those
   * are seen first.
   */
  static s64

  cmp_layout(struct pnfs_layout_range *l1,
  	   struct pnfs_layout_range *l2)

  {

  	s64 d;
  
  	/* high offset > low offset */
  	d = l1->offset - l2->offset;
  	if (d)
  		return d;
  
  	/* short length > long length */
  	d = l2->length - l1->length;
  	if (d)
  		return d;

  	/* read > read/write */

  	return (int)(l1->iomode == IOMODE_READ) - (int)(l2->iomode == IOMODE_READ);

  }

  static void
  pnfs_insert_layout(struct pnfs_layout_hdr *lo,
  		   struct pnfs_layout_segment *lseg)
  {

  	struct pnfs_layout_segment *lp;

  	dprintk("%s:Begin
  ", __func__);

  	assert_spin_locked(&lo->plh_inode->i_lock);

  	list_for_each_entry(lp, &lo->plh_segs, pls_list) {

  		if (cmp_layout(&lseg->pls_range, &lp->pls_range) > 0)

  			continue;

  		list_add_tail(&lseg->pls_list, &lp->pls_list);

  		dprintk("%s: inserted lseg %p "
  			"iomode %d offset %llu length %llu before "
  			"lp %p iomode %d offset %llu length %llu
  ",

  			__func__, lseg, lseg->pls_range.iomode,
  			lseg->pls_range.offset, lseg->pls_range.length,
  			lp, lp->pls_range.iomode, lp->pls_range.offset,
  			lp->pls_range.length);

  		goto out;

  	}

  	list_add_tail(&lseg->pls_list, &lo->plh_segs);
  	dprintk("%s: inserted lseg %p "
  		"iomode %d offset %llu length %llu at tail
  ",
  		__func__, lseg, lseg->pls_range.iomode,
  		lseg->pls_range.offset, lseg->pls_range.length);
  out:

  	get_layout_hdr(lo);

  
  	dprintk("%s:Return
  ", __func__);

  }
  
  static struct pnfs_layout_hdr *

  alloc_init_layout_hdr(struct inode *ino,
  		      struct nfs_open_context *ctx,
  		      gfp_t gfp_flags)

  {
  	struct pnfs_layout_hdr *lo;

  	lo = pnfs_alloc_layout_hdr(ino, gfp_flags);

  	if (!lo)
  		return NULL;

  	atomic_set(&lo->plh_refcount, 1);

  	INIT_LIST_HEAD(&lo->plh_layouts);
  	INIT_LIST_HEAD(&lo->plh_segs);

  	INIT_LIST_HEAD(&lo->plh_bulk_recall);

  	lo->plh_inode = ino;

  	lo->plh_lc_cred = get_rpccred(ctx->state->owner->so_cred);

  	return lo;
  }
  
  static struct pnfs_layout_hdr *

  pnfs_find_alloc_layout(struct inode *ino,
  		       struct nfs_open_context *ctx,
  		       gfp_t gfp_flags)

  {
  	struct nfs_inode *nfsi = NFS_I(ino);
  	struct pnfs_layout_hdr *new = NULL;
  
  	dprintk("%s Begin ino=%p layout=%p
  ", __func__, ino, nfsi->layout);
  
  	assert_spin_locked(&ino->i_lock);

  	if (nfsi->layout) {
  		if (test_bit(NFS_LAYOUT_DESTROYED, &nfsi->layout->plh_flags))
  			return NULL;
  		else
  			return nfsi->layout;
  	}

  	spin_unlock(&ino->i_lock);

  	new = alloc_init_layout_hdr(ino, ctx, gfp_flags);

  	spin_lock(&ino->i_lock);
  
  	if (likely(nfsi->layout == NULL))	/* Won the race? */
  		nfsi->layout = new;
  	else

  		pnfs_free_layout_hdr(new);

  	return nfsi->layout;
  }

  /*
   * iomode matching rules:
   * iomode	lseg	match
   * -----	-----	-----
   * ANY		READ	true
   * ANY		RW	true
   * RW		READ	false
   * RW		RW	true
   * READ		READ	true
   * READ		RW	true
   */
  static int

  is_matching_lseg(struct pnfs_layout_range *ls_range,
  		 struct pnfs_layout_range *range)

  {

  	struct pnfs_layout_range range1;
  
  	if ((range->iomode == IOMODE_RW &&
  	     ls_range->iomode != IOMODE_RW) ||
  	    !lo_seg_intersecting(ls_range, range))
  		return 0;
  
  	/* range1 covers only the first byte in the range */
  	range1 = *range;
  	range1.length = 1;
  	return lo_seg_contained(ls_range, &range1);

  }
  
  /*
   * lookup range in layout
   */

  static struct pnfs_layout_segment *

  pnfs_find_lseg(struct pnfs_layout_hdr *lo,
  		struct pnfs_layout_range *range)

  {

  	struct pnfs_layout_segment *lseg, *ret = NULL;
  
  	dprintk("%s:Begin
  ", __func__);

  	assert_spin_locked(&lo->plh_inode->i_lock);
  	list_for_each_entry(lseg, &lo->plh_segs, pls_list) {

  		if (test_bit(NFS_LSEG_VALID, &lseg->pls_flags) &&

  		    is_matching_lseg(&lseg->pls_range, range)) {

  			ret = get_lseg(lseg);

  			break;
  		}

  		if (lseg->pls_range.offset > range->offset)

  			break;
  	}
  
  	dprintk("%s:Return lseg %p ref %d
  ",

  		__func__, ret, ret ? atomic_read(&ret->pls_refcount) : 0);

  	return ret;

  }
  
  /*
   * Layout segment is retreived from the server if not cached.
   * The appropriate layout segment is referenced and returned to the caller.
   */

  struct pnfs_layout_segment *

  pnfs_update_layout(struct inode *ino,
  		   struct nfs_open_context *ctx,

  		   loff_t pos,
  		   u64 count,

  		   enum pnfs_iomode iomode,
  		   gfp_t gfp_flags)

  {

  	struct pnfs_layout_range arg = {
  		.iomode = iomode,
  		.offset = pos,
  		.length = count,
  	};

  	unsigned pg_offset;

  	struct nfs_inode *nfsi = NFS_I(ino);

  	struct nfs_server *server = NFS_SERVER(ino);
  	struct nfs_client *clp = server->nfs_client;

  	struct pnfs_layout_hdr *lo;
  	struct pnfs_layout_segment *lseg = NULL;

  	bool first = false;

  
  	if (!pnfs_enabled_sb(NFS_SERVER(ino)))
  		return NULL;
  	spin_lock(&ino->i_lock);

  	lo = pnfs_find_alloc_layout(ino, ctx, gfp_flags);

  	if (lo == NULL) {
  		dprintk("%s ERROR: can't get pnfs_layout_hdr
  ", __func__);
  		goto out_unlock;
  	}

  	/* Do we even need to bother with this? */
  	if (test_bit(NFS4CLNT_LAYOUTRECALL, &clp->cl_state) ||
  	    test_bit(NFS_LAYOUT_BULK_RECALL, &lo->plh_flags)) {
  		dprintk("%s matches recall, use MDS
  ", __func__);

  		goto out_unlock;
  	}
  
  	/* if LAYOUTGET already failed once we don't try again */

  	if (test_bit(lo_fail_bit(iomode), &nfsi->layout->plh_flags))

  		goto out_unlock;

  	/* Check to see if the layout for the given range already exists */

  	lseg = pnfs_find_lseg(lo, &arg);

  	if (lseg)
  		goto out_unlock;

  	if (pnfs_layoutgets_blocked(lo, NULL, 0))

  		goto out_unlock;
  	atomic_inc(&lo->plh_outstanding);

  	get_layout_hdr(lo);

  	if (list_empty(&lo->plh_segs))
  		first = true;
  	spin_unlock(&ino->i_lock);
  	if (first) {

  		/* The lo must be on the clp list if there is any
  		 * chance of a CB_LAYOUTRECALL(FILE) coming in.
  		 */
  		spin_lock(&clp->cl_lock);
  		BUG_ON(!list_empty(&lo->plh_layouts));

  		list_add_tail(&lo->plh_layouts, &server->layouts);

  		spin_unlock(&clp->cl_lock);
  	}

  	pg_offset = arg.offset & ~PAGE_CACHE_MASK;
  	if (pg_offset) {
  		arg.offset -= pg_offset;
  		arg.length += pg_offset;
  	}

  	if (arg.length != NFS4_MAX_UINT64)
  		arg.length = PAGE_CACHE_ALIGN(arg.length);

  	lseg = send_layoutget(lo, ctx, &arg, gfp_flags);

  	if (!lseg && first) {
  		spin_lock(&clp->cl_lock);
  		list_del_init(&lo->plh_layouts);
  		spin_unlock(&clp->cl_lock);

  	}

  	atomic_dec(&lo->plh_outstanding);

  	put_layout_hdr(lo);

  out:
  	dprintk("%s end, state 0x%lx lseg %p
  ", __func__,

  		nfsi->layout ? nfsi->layout->plh_flags : -1, lseg);

  	return lseg;
  out_unlock:
  	spin_unlock(&ino->i_lock);
  	goto out;
  }

  EXPORT_SYMBOL_GPL(pnfs_update_layout);

  
  int
  pnfs_layout_process(struct nfs4_layoutget *lgp)
  {
  	struct pnfs_layout_hdr *lo = NFS_I(lgp->args.inode)->layout;
  	struct nfs4_layoutget_res *res = &lgp->res;
  	struct pnfs_layout_segment *lseg;

  	struct inode *ino = lo->plh_inode;

  	struct nfs_client *clp = NFS_SERVER(ino)->nfs_client;

  	int status = 0;
  
  	/* Inject layout blob into I/O device driver */

  	lseg = NFS_SERVER(ino)->pnfs_curr_ld->alloc_lseg(lo, res, lgp->gfp_flags);

  	if (!lseg || IS_ERR(lseg)) {
  		if (!lseg)
  			status = -ENOMEM;
  		else
  			status = PTR_ERR(lseg);
  		dprintk("%s: Could not allocate layout: error %d
  ",
  		       __func__, status);
  		goto out;
  	}
  
  	spin_lock(&ino->i_lock);

  	if (test_bit(NFS4CLNT_LAYOUTRECALL, &clp->cl_state) ||
  	    test_bit(NFS_LAYOUT_BULK_RECALL, &lo->plh_flags)) {
  		dprintk("%s forget reply due to recall
  ", __func__);
  		goto out_forget_reply;
  	}
  
  	if (pnfs_layoutgets_blocked(lo, &res->stateid, 1)) {
  		dprintk("%s forget reply due to state
  ", __func__);
  		goto out_forget_reply;
  	}

  	init_lseg(lo, lseg);

  	lseg->pls_range = res->range;

  	*lgp->lsegpp = get_lseg(lseg);

  	pnfs_insert_layout(lo, lseg);

  	if (res->return_on_close) {
  		set_bit(NFS_LSEG_ROC, &lseg->pls_flags);
  		set_bit(NFS_LAYOUT_ROC, &lo->plh_flags);
  	}

  	/* Done processing layoutget. Set the layout stateid */

  	pnfs_set_layout_stateid(lo, &res->stateid, false);

  	spin_unlock(&ino->i_lock);
  out:
  	return status;

  
  out_forget_reply:
  	spin_unlock(&ino->i_lock);
  	lseg->pls_layout = lo;
  	NFS_SERVER(ino)->pnfs_curr_ld->free_lseg(lseg);
  	goto out;

  }

  void
  pnfs_generic_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,
  					   req_offset(req),
  					   req->wb_bytes,
  					   IOMODE_READ,
  					   GFP_KERNEL);

  	/* If no lseg, fall back to read through mds */
  	if (pgio->pg_lseg == NULL)

  		nfs_pageio_reset_read_mds(pgio);

  }
  EXPORT_SYMBOL_GPL(pnfs_generic_pg_init_read);
  
  void
  pnfs_generic_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,
  					   req_offset(req),
  					   req->wb_bytes,
  					   IOMODE_RW,
  					   GFP_NOFS);

  	/* If no lseg, fall back to write through mds */
  	if (pgio->pg_lseg == NULL)

  		nfs_pageio_reset_write_mds(pgio);

  }
  EXPORT_SYMBOL_GPL(pnfs_generic_pg_init_write);

  bool

  pnfs_pageio_init_read(struct nfs_pageio_descriptor *pgio, struct inode *inode)
  {
  	struct nfs_server *server = NFS_SERVER(inode);
  	struct pnfs_layoutdriver_type *ld = server->pnfs_curr_ld;
  
  	if (ld == NULL)
  		return false;
  	nfs_pageio_init(pgio, inode, ld->pg_read_ops, server->rsize, 0);
  	return true;
  }
  
  bool
  pnfs_pageio_init_write(struct nfs_pageio_descriptor *pgio, struct inode *inode, int ioflags)
  {
  	struct nfs_server *server = NFS_SERVER(inode);
  	struct pnfs_layoutdriver_type *ld = server->pnfs_curr_ld;
  
  	if (ld == NULL)
  		return false;
  	nfs_pageio_init(pgio, inode, ld->pg_write_ops, server->wsize, ioflags);
  	return true;
  }
  
  bool

  pnfs_generic_pg_test(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
  		     struct nfs_page *req)

  {

  	if (pgio->pg_lseg == NULL)
  		return nfs_generic_pg_test(pgio, prev, req);

  	/*
  	 * Test if a nfs_page is fully contained in the pnfs_layout_range.
  	 * Note that this test makes several assumptions:
  	 * - that the previous nfs_page in the struct nfs_pageio_descriptor
  	 *   is known to lie within the range.
  	 *   - that the nfs_page being tested is known to be contiguous with the
  	 *   previous nfs_page.
  	 *   - Layout ranges are page aligned, so we only have to test the
  	 *   start offset of the request.
  	 *
  	 * Please also note that 'end_offset' is actually the offset of the
  	 * first byte that lies outside the pnfs_layout_range. FIXME?
  	 *
  	 */
  	return req_offset(req) < end_offset(pgio->pg_lseg->pls_range.offset,
  					 pgio->pg_lseg->pls_range.length);

  }

  EXPORT_SYMBOL_GPL(pnfs_generic_pg_test);

  static int pnfs_write_done_resend_to_mds(struct inode *inode, struct list_head *head)
  {
  	struct nfs_pageio_descriptor pgio;
  	LIST_HEAD(failed);
  
  	/* Resend all requests through the MDS */
  	nfs_pageio_init_write_mds(&pgio, inode, FLUSH_STABLE);
  	while (!list_empty(head)) {
  		struct nfs_page *req = nfs_list_entry(head->next);
  
  		nfs_list_remove_request(req);
  		if (!nfs_pageio_add_request(&pgio, req))
  			nfs_list_add_request(req, &failed);
  	}
  	nfs_pageio_complete(&pgio);
  
  	if (!list_empty(&failed)) {
  		/* For some reason our attempt to resend pages. Mark the
  		 * overall send request as having failed, and let
  		 * nfs_writeback_release_full deal with the error.
  		 */
  		list_move(&failed, head);
  		return -EIO;
  	}
  	return 0;
  }

  /*
   * Called by non rpc-based layout drivers
   */

  void pnfs_ld_write_done(struct nfs_write_data *data)

  {

  	if (likely(!data->pnfs_error)) {

  		pnfs_set_layoutcommit(data);
  		data->mds_ops->rpc_call_done(&data->task, data);

  	} else {

  		dprintk("pnfs write error = %d
  ", data->pnfs_error);

  		if (NFS_SERVER(data->inode)->pnfs_curr_ld->flags &
  						PNFS_LAYOUTRET_ON_ERROR) {
  			/* Don't lo_commit on error, Server will needs to
  			 * preform a file recovery.
  			 */
  			clear_bit(NFS_INO_LAYOUTCOMMIT,
  				  &NFS_I(data->inode)->flags);
  			pnfs_return_layout(data->inode);
  		}

  		data->task.tk_status = pnfs_write_done_resend_to_mds(data->inode, &data->pages);

  	}

  	data->mds_ops->rpc_release(data);

  }

  EXPORT_SYMBOL_GPL(pnfs_ld_write_done);

  static void
  pnfs_write_through_mds(struct nfs_pageio_descriptor *desc,
  		struct nfs_write_data *data)
  {
  	list_splice_tail_init(&data->pages, &desc->pg_list);
  	if (data->req && list_empty(&data->req->wb_list))
  		nfs_list_add_request(data->req, &desc->pg_list);
  	nfs_pageio_reset_write_mds(desc);
  	desc->pg_recoalesce = 1;
  	nfs_writedata_release(data);
  }
  
  static enum pnfs_try_status

  pnfs_try_to_write_data(struct nfs_write_data *wdata,

  			const struct rpc_call_ops *call_ops,
  			struct pnfs_layout_segment *lseg,
  			int how)

  {
  	struct inode *inode = wdata->inode;
  	enum pnfs_try_status trypnfs;
  	struct nfs_server *nfss = NFS_SERVER(inode);
  
  	wdata->mds_ops = call_ops;

  	wdata->lseg = get_lseg(lseg);

  
  	dprintk("%s: Writing ino:%lu %u@%llu (how %d)
  ", __func__,
  		inode->i_ino, wdata->args.count, wdata->args.offset, how);
  
  	trypnfs = nfss->pnfs_curr_ld->write_pagelist(wdata, how);
  	if (trypnfs == PNFS_NOT_ATTEMPTED) {
  		put_lseg(wdata->lseg);
  		wdata->lseg = NULL;
  	} else
  		nfs_inc_stats(inode, NFSIOS_PNFS_WRITE);
  
  	dprintk("%s End (trypnfs:%d)
  ", __func__, trypnfs);
  	return trypnfs;
  }

  static void
  pnfs_do_multiple_writes(struct nfs_pageio_descriptor *desc, struct list_head *head, int how)
  {
  	struct nfs_write_data *data;
  	const struct rpc_call_ops *call_ops = desc->pg_rpc_callops;
  	struct pnfs_layout_segment *lseg = desc->pg_lseg;
  
  	desc->pg_lseg = NULL;
  	while (!list_empty(head)) {
  		enum pnfs_try_status trypnfs;
  
  		data = list_entry(head->next, struct nfs_write_data, list);
  		list_del_init(&data->list);
  
  		trypnfs = pnfs_try_to_write_data(data, call_ops, lseg, how);
  		if (trypnfs == PNFS_NOT_ATTEMPTED)
  			pnfs_write_through_mds(desc, data);
  	}
  	put_lseg(lseg);
  }
  
  int
  pnfs_generic_pg_writepages(struct nfs_pageio_descriptor *desc)
  {
  	LIST_HEAD(head);
  	int ret;
  
  	ret = nfs_generic_flush(desc, &head);
  	if (ret != 0) {
  		put_lseg(desc->pg_lseg);
  		desc->pg_lseg = NULL;
  		return ret;
  	}
  	pnfs_do_multiple_writes(desc, &head, desc->pg_ioflags);
  	return 0;
  }
  EXPORT_SYMBOL_GPL(pnfs_generic_pg_writepages);

  static void pnfs_ld_handle_read_error(struct nfs_read_data *data)
  {
  	struct nfs_pageio_descriptor pgio;
  
  	put_lseg(data->lseg);
  	data->lseg = NULL;
  	dprintk("pnfs write error = %d
  ", data->pnfs_error);

  	if (NFS_SERVER(data->inode)->pnfs_curr_ld->flags &
  						PNFS_LAYOUTRET_ON_ERROR)
  		pnfs_return_layout(data->inode);

  
  	nfs_pageio_init_read_mds(&pgio, data->inode);
  
  	while (!list_empty(&data->pages)) {
  		struct nfs_page *req = nfs_list_entry(data->pages.next);
  
  		nfs_list_remove_request(req);
  		nfs_pageio_add_request(&pgio, req);
  	}
  	nfs_pageio_complete(&pgio);
  }

  /*

   * Called by non rpc-based layout drivers
   */

  void pnfs_ld_read_done(struct nfs_read_data *data)

  {

  	if (likely(!data->pnfs_error)) {

  		__nfs4_read_done_cb(data);
  		data->mds_ops->rpc_call_done(&data->task, data);

  	} else
  		pnfs_ld_handle_read_error(data);

  	data->mds_ops->rpc_release(data);

  }
  EXPORT_SYMBOL_GPL(pnfs_ld_read_done);

  static void
  pnfs_read_through_mds(struct nfs_pageio_descriptor *desc,
  		struct nfs_read_data *data)
  {
  	list_splice_tail_init(&data->pages, &desc->pg_list);
  	if (data->req && list_empty(&data->req->wb_list))
  		nfs_list_add_request(data->req, &desc->pg_list);
  	nfs_pageio_reset_read_mds(desc);
  	desc->pg_recoalesce = 1;
  	nfs_readdata_release(data);
  }

  /*

   * Call the appropriate parallel I/O subsystem read function.
   */

  static enum pnfs_try_status

  pnfs_try_to_read_data(struct nfs_read_data *rdata,

  		       const struct rpc_call_ops *call_ops,
  		       struct pnfs_layout_segment *lseg)

  {
  	struct inode *inode = rdata->inode;
  	struct nfs_server *nfss = NFS_SERVER(inode);
  	enum pnfs_try_status trypnfs;
  
  	rdata->mds_ops = call_ops;

  	rdata->lseg = get_lseg(lseg);

  
  	dprintk("%s: Reading ino:%lu %u@%llu
  ",
  		__func__, inode->i_ino, rdata->args.count, rdata->args.offset);
  
  	trypnfs = nfss->pnfs_curr_ld->read_pagelist(rdata);
  	if (trypnfs == PNFS_NOT_ATTEMPTED) {
  		put_lseg(rdata->lseg);
  		rdata->lseg = NULL;
  	} else {
  		nfs_inc_stats(inode, NFSIOS_PNFS_READ);
  	}
  	dprintk("%s End (trypnfs:%d)
  ", __func__, trypnfs);
  	return trypnfs;
  }

  static void
  pnfs_do_multiple_reads(struct nfs_pageio_descriptor *desc, struct list_head *head)
  {
  	struct nfs_read_data *data;
  	const struct rpc_call_ops *call_ops = desc->pg_rpc_callops;
  	struct pnfs_layout_segment *lseg = desc->pg_lseg;
  
  	desc->pg_lseg = NULL;
  	while (!list_empty(head)) {
  		enum pnfs_try_status trypnfs;
  
  		data = list_entry(head->next, struct nfs_read_data, list);
  		list_del_init(&data->list);
  
  		trypnfs = pnfs_try_to_read_data(data, call_ops, lseg);
  		if (trypnfs == PNFS_NOT_ATTEMPTED)
  			pnfs_read_through_mds(desc, data);
  	}
  	put_lseg(lseg);
  }
  
  int
  pnfs_generic_pg_readpages(struct nfs_pageio_descriptor *desc)
  {
  	LIST_HEAD(head);
  	int ret;
  
  	ret = nfs_generic_pagein(desc, &head);
  	if (ret != 0) {
  		put_lseg(desc->pg_lseg);
  		desc->pg_lseg = NULL;
  		return ret;
  	}
  	pnfs_do_multiple_reads(desc, &head);
  	return 0;
  }
  EXPORT_SYMBOL_GPL(pnfs_generic_pg_readpages);

  /*

   * There can be multiple RW segments.

   */

  static void pnfs_list_write_lseg(struct inode *inode, struct list_head *listp)

  {

  	struct pnfs_layout_segment *lseg;

  	list_for_each_entry(lseg, &NFS_I(inode)->layout->plh_segs, pls_list) {
  		if (lseg->pls_range.iomode == IOMODE_RW &&
  		    test_bit(NFS_LSEG_LAYOUTCOMMIT, &lseg->pls_flags))
  			list_add(&lseg->pls_lc_list, listp);
  	}

  }

  void pnfs_set_lo_fail(struct pnfs_layout_segment *lseg)
  {
  	if (lseg->pls_range.iomode == IOMODE_RW) {
  		dprintk("%s Setting layout IOMODE_RW fail bit
  ", __func__);
  		set_bit(lo_fail_bit(IOMODE_RW), &lseg->pls_layout->plh_flags);
  	} else {
  		dprintk("%s Setting layout IOMODE_READ fail bit
  ", __func__);
  		set_bit(lo_fail_bit(IOMODE_READ), &lseg->pls_layout->plh_flags);
  	}
  }
  EXPORT_SYMBOL_GPL(pnfs_set_lo_fail);

  void
  pnfs_set_layoutcommit(struct nfs_write_data *wdata)
  {
  	struct nfs_inode *nfsi = NFS_I(wdata->inode);

  	loff_t end_pos = wdata->mds_offset + wdata->res.count;

  	bool mark_as_dirty = false;

  
  	spin_lock(&nfsi->vfs_inode.i_lock);
  	if (!test_and_set_bit(NFS_INO_LAYOUTCOMMIT, &nfsi->flags)) {

  		mark_as_dirty = true;

  		dprintk("%s: Set layoutcommit for inode %lu ",
  			__func__, wdata->inode->i_ino);
  	}

  	if (!test_and_set_bit(NFS_LSEG_LAYOUTCOMMIT, &wdata->lseg->pls_flags)) {
  		/* references matched in nfs4_layoutcommit_release */
  		get_lseg(wdata->lseg);
  	}

  	if (end_pos > nfsi->layout->plh_lwb)
  		nfsi->layout->plh_lwb = end_pos;

  	spin_unlock(&nfsi->vfs_inode.i_lock);

  	dprintk("%s: lseg %p end_pos %llu
  ",
  		__func__, wdata->lseg, nfsi->layout->plh_lwb);

  
  	/* if pnfs_layoutcommit_inode() runs between inode locks, the next one
  	 * will be a noop because NFS_INO_LAYOUTCOMMIT will not be set */
  	if (mark_as_dirty)
  		mark_inode_dirty_sync(wdata->inode);

  }
  EXPORT_SYMBOL_GPL(pnfs_set_layoutcommit);

  void pnfs_cleanup_layoutcommit(struct nfs4_layoutcommit_data *data)
  {
  	struct nfs_server *nfss = NFS_SERVER(data->args.inode);
  
  	if (nfss->pnfs_curr_ld->cleanup_layoutcommit)
  		nfss->pnfs_curr_ld->cleanup_layoutcommit(data);
  }

  /*
   * For the LAYOUT4_NFSV4_1_FILES layout type, NFS_DATA_SYNC WRITEs and
   * NFS_UNSTABLE WRITEs with a COMMIT to data servers must store enough
   * data to disk to allow the server to recover the data if it crashes.
   * LAYOUTCOMMIT is only needed when the NFL4_UFLG_COMMIT_THRU_MDS flag
   * is off, and a COMMIT is sent to a data server, or
   * if WRITEs to a data server return NFS_DATA_SYNC.
   */

  int

  pnfs_layoutcommit_inode(struct inode *inode, bool sync)

  {
  	struct nfs4_layoutcommit_data *data;
  	struct nfs_inode *nfsi = NFS_I(inode);

  	loff_t end_pos;
  	int status = 0;
  
  	dprintk("--> %s inode %lu
  ", __func__, inode->i_ino);

  	if (!test_bit(NFS_INO_LAYOUTCOMMIT, &nfsi->flags))
  		return 0;

  	/* Note kzalloc ensures data->res.seq_res.sr_slot == NULL */
  	data = kzalloc(sizeof(*data), GFP_NOFS);

  	if (!data) {

  		status = -ENOMEM;
  		goto out;
  	}

  	if (!test_bit(NFS_INO_LAYOUTCOMMIT, &nfsi->flags))
  		goto out_free;
  
  	if (test_and_set_bit(NFS_INO_LAYOUTCOMMITTING, &nfsi->flags)) {
  		if (!sync) {
  			status = -EAGAIN;
  			goto out_free;
  		}
  		status = wait_on_bit_lock(&nfsi->flags, NFS_INO_LAYOUTCOMMITTING,
  					nfs_wait_bit_killable, TASK_KILLABLE);
  		if (status)
  			goto out_free;
  	}

  	INIT_LIST_HEAD(&data->lseg_list);

  	spin_lock(&inode->i_lock);

  	if (!test_and_clear_bit(NFS_INO_LAYOUTCOMMIT, &nfsi->flags)) {

  		clear_bit(NFS_INO_LAYOUTCOMMITTING, &nfsi->flags);

  		spin_unlock(&inode->i_lock);

  		wake_up_bit(&nfsi->flags, NFS_INO_LAYOUTCOMMITTING);
  		goto out_free;

  	}

  
  	pnfs_list_write_lseg(inode, &data->lseg_list);

  	end_pos = nfsi->layout->plh_lwb;

  	nfsi->layout->plh_lwb = 0;

  	memcpy(&data->args.stateid.data, nfsi->layout->plh_stateid.data,
  		sizeof(nfsi->layout->plh_stateid.data));

  	spin_unlock(&inode->i_lock);
  
  	data->args.inode = inode;

  	data->cred = get_rpccred(nfsi->layout->plh_lc_cred);

  	nfs_fattr_init(&data->fattr);
  	data->args.bitmask = NFS_SERVER(inode)->cache_consistency_bitmask;
  	data->res.fattr = &data->fattr;
  	data->args.lastbytewritten = end_pos - 1;
  	data->res.server = NFS_SERVER(inode);
  
  	status = nfs4_proc_layoutcommit(data, sync);
  out:

  	if (status)
  		mark_inode_dirty_sync(inode);

  	dprintk("<-- %s status %d
  ", __func__, status);
  	return status;

  out_free:
  	kfree(data);
  	goto out;

  }