text: /*
   *  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 <linux/backing-dev.h>
  
  #include <linux/sunrpc/metrics.h>
  
  #include "../nfs4session.h"
  #include "../internal.h"
  #include "../delegation.h"
  #include "filelayout.h"
  #include "../nfs4trace.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 void filelayout_reset_write(struct nfs_pgio_header *hdr)
  {
  	struct rpc_task *task = &hdr->task;
  
  	if (!test_and_set_bit(NFS_IOHDR_REDO, &hdr->flags)) {
  		dprintk("%s Reset task %5u for i/o through MDS "
  			"(req %s/%llu, %u bytes @ offset %llu)\n", __func__,
  			hdr->task.tk_pid,
  			hdr->inode->i_sb->s_id,
  			(unsigned long long)NFS_FILEID(hdr->inode),
  			hdr->args.count,
  			(unsigned long long)hdr->args.offset);
  
  		task->tk_status = pnfs_write_done_resend_to_mds(hdr);
  	}
  }
  
  static void filelayout_reset_read(struct nfs_pgio_header *hdr)
  {
  	struct rpc_task *task = &hdr->task;
  
  	if (!test_and_set_bit(NFS_IOHDR_REDO, &hdr->flags)) {
  		dprintk("%s Reset task %5u for i/o through MDS "
  			"(req %s/%llu, %u bytes @ offset %llu)\n", __func__,
  			hdr->task.tk_pid,
  			hdr->inode->i_sb->s_id,
  			(unsigned long long)NFS_FILEID(hdr->inode),
  			hdr->args.count,
  			(unsigned long long)hdr->args.offset);
  
  		task->tk_status = pnfs_read_done_resend_to_mds(hdr);
  	}
  }
  
  static int filelayout_async_handle_error(struct rpc_task *task,
  					 struct nfs4_state *state,
  					 struct nfs_client *clp,
  					 struct pnfs_layout_segment *lseg)
  {
  	struct pnfs_layout_hdr *lo = lseg->pls_layout;
  	struct inode *inode = lo->plh_inode;
  	struct nfs4_deviceid_node *devid = FILELAYOUT_DEVID_NODE(lseg);
  	struct nfs4_slot_table *tbl = &clp->cl_session->fc_slot_table;
  
  	if (task->tk_status >= 0)
  		return 0;
  
  	switch (task->tk_status) {
  	/* DS session errors */
  	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\n", __func__, task->tk_status,
  			clp->cl_exchange_flags);
  		nfs4_schedule_session_recovery(clp->cl_session, task->tk_status);
  		break;
  	case -NFS4ERR_DELAY:
  	case -NFS4ERR_GRACE:
  		rpc_delay(task, FILELAYOUT_POLL_RETRY_MAX);
  		break;
  	case -NFS4ERR_RETRY_UNCACHED_REP:
  		break;
  	/* Invalidate Layout errors */
  	case -NFS4ERR_ACCESS:
  	case -NFS4ERR_PNFS_NO_LAYOUT:
  	case -ESTALE:           /* mapped NFS4ERR_STALE */
  	case -EBADHANDLE:       /* mapped NFS4ERR_BADHANDLE */
  	case -EISDIR:           /* mapped NFS4ERR_ISDIR */
  	case -NFS4ERR_FHEXPIRED:
  	case -NFS4ERR_WRONG_TYPE:
  		dprintk("%s Invalid layout error %d\n", __func__,
  			task->tk_status);
  		/*
  		 * Destroy layout so new i/o will get a new layout.
  		 * Layout will not be destroyed until all current lseg
  		 * references are put. Mark layout as invalid to resend failed
  		 * i/o and all i/o waiting on the slot table to the MDS until
  		 * layout is destroyed and a new valid layout is obtained.
  		 */
  		pnfs_destroy_layout(NFS_I(inode));
  		rpc_wake_up(&tbl->slot_tbl_waitq);
  		goto reset;
  	/* RPC connection errors */
  	case -ECONNREFUSED:
  	case -EHOSTDOWN:
  	case -EHOSTUNREACH:
  	case -ENETUNREACH:
  	case -EIO:
  	case -ETIMEDOUT:
  	case -EPIPE:
  		dprintk("%s DS connection error %d\n", __func__,
  			task->tk_status);
  		nfs4_mark_deviceid_unavailable(devid);
  		pnfs_error_mark_layout_for_return(inode, lseg);
  		pnfs_set_lo_fail(lseg);
  		rpc_wake_up(&tbl->slot_tbl_waitq);
  		/* fall through */
  	default:
  reset:
  		dprintk("%s Retry through MDS. Error %d\n", __func__,
  			task->tk_status);
  		return -NFS4ERR_RESET_TO_MDS;
  	}
  	task->tk_status = 0;
  	return -EAGAIN;
  }
  
  /* NFS_PROTO call done callback routines */
  
  static int filelayout_read_done_cb(struct rpc_task *task,
  				struct nfs_pgio_header *hdr)
  {
  	int err;
  
  	trace_nfs4_pnfs_read(hdr, task->tk_status);
  	err = filelayout_async_handle_error(task, hdr->args.context->state,
  					    hdr->ds_clp, hdr->lseg);
  
  	switch (err) {
  	case -NFS4ERR_RESET_TO_MDS:
  		filelayout_reset_read(hdr);
  		return task->tk_status;
  	case -EAGAIN:
  		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_pgio_header *hdr)
  {
  	loff_t end_offs = 0;
  
  	if (FILELAYOUT_LSEG(hdr->lseg)->commit_through_mds ||
  	    hdr->res.verf->committed == NFS_FILE_SYNC)
  		return;
  	if (hdr->res.verf->committed == NFS_DATA_SYNC)
  		end_offs = hdr->mds_offset + (loff_t)hdr->res.count;
  
  	/* Note: if the write is unstable, don't set end_offs until commit */
  	pnfs_set_layoutcommit(hdr->inode, hdr->lseg, end_offs);
  	dprintk("%s inode %lu pls_end_pos %lu\n", __func__, hdr->inode->i_ino,
  		(unsigned long) NFS_I(hdr->inode)->layout->plh_lwb);
  }
  
  bool
  filelayout_test_devid_unavailable(struct nfs4_deviceid_node *node)
  {
  	return filelayout_test_devid_invalid(node) ||
  		nfs4_test_deviceid_unavailable(node);
  }
  
  static bool
  filelayout_reset_to_mds(struct pnfs_layout_segment *lseg)
  {
  	struct nfs4_deviceid_node *node = FILELAYOUT_DEVID_NODE(lseg);
  
  	return filelayout_test_devid_unavailable(node);
  }
  
  /*
   * 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_pgio_header *hdr = data;
  
  	if (unlikely(test_bit(NFS_CONTEXT_BAD, &hdr->args.context->flags))) {
  		rpc_exit(task, -EIO);
  		return;
  	}
  	if (filelayout_reset_to_mds(hdr->lseg)) {
  		dprintk("%s task %u reset io to MDS\n", __func__, task->tk_pid);
  		filelayout_reset_read(hdr);
  		rpc_exit(task, 0);
  		return;
  	}
  	hdr->pgio_done_cb = filelayout_read_done_cb;
  
  	if (nfs4_setup_sequence(hdr->ds_clp,
  			&hdr->args.seq_args,
  			&hdr->res.seq_res,
  			task))
  		return;
  	if (nfs4_set_rw_stateid(&hdr->args.stateid, hdr->args.context,
  			hdr->args.lock_context, FMODE_READ) == -EIO)
  		rpc_exit(task, -EIO); /* lost lock, terminate I/O */
  }
  
  static void filelayout_read_call_done(struct rpc_task *task, void *data)
  {
  	struct nfs_pgio_header *hdr = data;
  
  	dprintk("--> %s task->tk_status %d\n", __func__, task->tk_status);
  
  	if (test_bit(NFS_IOHDR_REDO, &hdr->flags) &&
  	    task->tk_status == 0) {
  		nfs41_sequence_done(task, &hdr->res.seq_res);
  		return;
  	}
  
  	/* Note this may cause RPC to be resent */
  	hdr->mds_ops->rpc_call_done(task, data);
  }
  
  static void filelayout_read_count_stats(struct rpc_task *task, void *data)
  {
  	struct nfs_pgio_header *hdr = data;
  
  	rpc_count_iostats(task, NFS_SERVER(hdr->inode)->client->cl_metrics);
  }
  
  static int filelayout_write_done_cb(struct rpc_task *task,
  				struct nfs_pgio_header *hdr)
  {
  	int err;
  
  	trace_nfs4_pnfs_write(hdr, task->tk_status);
  	err = filelayout_async_handle_error(task, hdr->args.context->state,
  					    hdr->ds_clp, hdr->lseg);
  
  	switch (err) {
  	case -NFS4ERR_RESET_TO_MDS:
  		filelayout_reset_write(hdr);
  		return task->tk_status;
  	case -EAGAIN:
  		rpc_restart_call_prepare(task);
  		return -EAGAIN;
  	}
  
  	filelayout_set_layoutcommit(hdr);
  
  	/* zero out the fattr */
  	hdr->fattr.valid = 0;
  	if (task->tk_status >= 0)
  		nfs_writeback_update_inode(hdr);
  
  	return 0;
  }
  
  static int filelayout_commit_done_cb(struct rpc_task *task,
  				     struct nfs_commit_data *data)
  {
  	int err;
  
  	trace_nfs4_pnfs_commit_ds(data, task->tk_status);
  	err = filelayout_async_handle_error(task, NULL, data->ds_clp,
  					    data->lseg);
  
  	switch (err) {
  	case -NFS4ERR_RESET_TO_MDS:
  		pnfs_generic_prepare_to_resend_writes(data);
  		return -EAGAIN;
  	case -EAGAIN:
  		rpc_restart_call_prepare(task);
  		return -EAGAIN;
  	}
  
  	pnfs_set_layoutcommit(data->inode, data->lseg, data->lwb);
  
  	return 0;
  }
  
  static void filelayout_write_prepare(struct rpc_task *task, void *data)
  {
  	struct nfs_pgio_header *hdr = data;
  
  	if (unlikely(test_bit(NFS_CONTEXT_BAD, &hdr->args.context->flags))) {
  		rpc_exit(task, -EIO);
  		return;
  	}
  	if (filelayout_reset_to_mds(hdr->lseg)) {
  		dprintk("%s task %u reset io to MDS\n", __func__, task->tk_pid);
  		filelayout_reset_write(hdr);
  		rpc_exit(task, 0);
  		return;
  	}
  	if (nfs4_setup_sequence(hdr->ds_clp,
  			&hdr->args.seq_args,
  			&hdr->res.seq_res,
  			task))
  		return;
  	if (nfs4_set_rw_stateid(&hdr->args.stateid, hdr->args.context,
  			hdr->args.lock_context, FMODE_WRITE) == -EIO)
  		rpc_exit(task, -EIO); /* lost lock, terminate I/O */
  }
  
  static void filelayout_write_call_done(struct rpc_task *task, void *data)
  {
  	struct nfs_pgio_header *hdr = data;
  
  	if (test_bit(NFS_IOHDR_REDO, &hdr->flags) &&
  	    task->tk_status == 0) {
  		nfs41_sequence_done(task, &hdr->res.seq_res);
  		return;
  	}
  
  	/* Note this may cause RPC to be resent */
  	hdr->mds_ops->rpc_call_done(task, data);
  }
  
  static void filelayout_write_count_stats(struct rpc_task *task, void *data)
  {
  	struct nfs_pgio_header *hdr = data;
  
  	rpc_count_iostats(task, NFS_SERVER(hdr->inode)->client->cl_metrics);
  }
  
  static void filelayout_commit_prepare(struct rpc_task *task, void *data)
  {
  	struct nfs_commit_data *wdata = data;
  
  	nfs4_setup_sequence(wdata->ds_clp,
  			&wdata->args.seq_args,
  			&wdata->res.seq_res,
  			task);
  }
  
  static void filelayout_commit_count_stats(struct rpc_task *task, void *data)
  {
  	struct nfs_commit_data *cdata = data;
  
  	rpc_count_iostats(task, NFS_SERVER(cdata->inode)->client->cl_metrics);
  }
  
  static const struct rpc_call_ops filelayout_read_call_ops = {
  	.rpc_call_prepare = filelayout_read_prepare,
  	.rpc_call_done = filelayout_read_call_done,
  	.rpc_count_stats = filelayout_read_count_stats,
  	.rpc_release = pnfs_generic_rw_release,
  };
  
  static const struct rpc_call_ops filelayout_write_call_ops = {
  	.rpc_call_prepare = filelayout_write_prepare,
  	.rpc_call_done = filelayout_write_call_done,
  	.rpc_count_stats = filelayout_write_count_stats,
  	.rpc_release = pnfs_generic_rw_release,
  };
  
  static const struct rpc_call_ops filelayout_commit_call_ops = {
  	.rpc_call_prepare = filelayout_commit_prepare,
  	.rpc_call_done = pnfs_generic_write_commit_done,
  	.rpc_count_stats = filelayout_commit_count_stats,
  	.rpc_release = pnfs_generic_commit_release,
  };
  
  static enum pnfs_try_status
  filelayout_read_pagelist(struct nfs_pgio_header *hdr)
  {
  	struct pnfs_layout_segment *lseg = hdr->lseg;
  	struct nfs4_pnfs_ds *ds;
  	struct rpc_clnt *ds_clnt;
  	loff_t offset = hdr->args.offset;
  	u32 j, idx;
  	struct nfs_fh *fh;
  
  	dprintk("--> %s ino %lu pgbase %u req %zu@%llu\n",
  		__func__, hdr->inode->i_ino,
  		hdr->args.pgbase, (size_t)hdr->args.count, offset);
  
  	/* 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)
  		return PNFS_NOT_ATTEMPTED;
  
  	ds_clnt = nfs4_find_or_create_ds_client(ds->ds_clp, hdr->inode);
  	if (IS_ERR(ds_clnt))
  		return PNFS_NOT_ATTEMPTED;
  
  	dprintk("%s USE DS: %s cl_count %d\n", __func__,
  		ds->ds_remotestr, atomic_read(&ds->ds_clp->cl_count));
  
  	/* No multipath support. Use first DS */
  	atomic_inc(&ds->ds_clp->cl_count);
  	hdr->ds_clp = ds->ds_clp;
  	hdr->ds_commit_idx = idx;
  	fh = nfs4_fl_select_ds_fh(lseg, j);
  	if (fh)
  		hdr->args.fh = fh;
  
  	hdr->args.offset = filelayout_get_dserver_offset(lseg, offset);
  	hdr->mds_offset = offset;
  
  	/* Perform an asynchronous read to ds */
  	nfs_initiate_pgio(ds_clnt, hdr, hdr->cred,
  			  NFS_PROTO(hdr->inode), &filelayout_read_call_ops,
  			  0, RPC_TASK_SOFTCONN);
  	return PNFS_ATTEMPTED;
  }
  
  /* Perform async writes. */
  static enum pnfs_try_status
  filelayout_write_pagelist(struct nfs_pgio_header *hdr, int sync)
  {
  	struct pnfs_layout_segment *lseg = hdr->lseg;
  	struct nfs4_pnfs_ds *ds;
  	struct rpc_clnt *ds_clnt;
  	loff_t offset = hdr->args.offset;
  	u32 j, idx;
  	struct nfs_fh *fh;
  
  	/* 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)
  		return PNFS_NOT_ATTEMPTED;
  
  	ds_clnt = nfs4_find_or_create_ds_client(ds->ds_clp, hdr->inode);
  	if (IS_ERR(ds_clnt))
  		return PNFS_NOT_ATTEMPTED;
  
  	dprintk("%s ino %lu sync %d req %zu@%llu DS: %s cl_count %d\n",
  		__func__, hdr->inode->i_ino, sync, (size_t) hdr->args.count,
  		offset, ds->ds_remotestr, atomic_read(&ds->ds_clp->cl_count));
  
  	hdr->pgio_done_cb = filelayout_write_done_cb;
  	atomic_inc(&ds->ds_clp->cl_count);
  	hdr->ds_clp = ds->ds_clp;
  	hdr->ds_commit_idx = idx;
  	fh = nfs4_fl_select_ds_fh(lseg, j);
  	if (fh)
  		hdr->args.fh = fh;
  	hdr->args.offset = filelayout_get_dserver_offset(lseg, offset);
  
  	/* Perform an asynchronous write */
  	nfs_initiate_pgio(ds_clnt, hdr, hdr->cred,
  			  NFS_PROTO(hdr->inode), &filelayout_write_call_ops,
  			  sync, RPC_TASK_SOFTCONN);
  	return PNFS_ATTEMPTED;
  }
  
  static int
  filelayout_check_deviceid(struct pnfs_layout_hdr *lo,
  			  struct nfs4_filelayout_segment *fl,
  			  gfp_t gfp_flags)
  {
  	struct nfs4_deviceid_node *d;
  	struct nfs4_file_layout_dsaddr *dsaddr;
  	int status = -EINVAL;
  
  	/* Is the deviceid already set? If so, we're good. */
  	if (fl->dsaddr != NULL)
  		return 0;
  
  	/* find and reference the deviceid */
  	d = nfs4_find_get_deviceid(NFS_SERVER(lo->plh_inode), &fl->deviceid,
  			lo->plh_lc_cred, gfp_flags);
  	if (d == NULL)
  		goto out;
  
  	dsaddr = container_of(d, struct nfs4_file_layout_dsaddr, id_node);
  	/* Found deviceid is unavailable */
  	if (filelayout_test_devid_unavailable(&dsaddr->id_node))
  		goto out_put;
  
  	if (fl->first_stripe_index >= dsaddr->stripe_count) {
  		dprintk("%s Bad first_stripe_index %u\n",
  				__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\n",
  			__func__, fl->num_fh);
  		goto out_put;
  	}
  	status = 0;
  
  	/*
  	 * Atomic compare and xchange to ensure we don't scribble
  	 * over a non-NULL pointer.
  	 */
  	if (cmpxchg(&fl->dsaddr, NULL, dsaddr) != NULL)
  		goto out_put;
  out:
  	return status;
  out_put:
  	nfs4_fl_put_deviceid(dsaddr);
  	goto out;
  }
  
  /*
   * 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,
  			gfp_t gfp_flags)
  {
  	int status = -EINVAL;
  
  	dprintk("--> %s\n", __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\n",
  			__func__);
  		goto out;
  	}
  
  	if (fl->pattern_offset > lgr->range.offset) {
  		dprintk("%s pattern_offset %lld too large\n",
  				__func__, fl->pattern_offset);
  		goto out;
  	}
  
  	if (!fl->stripe_unit) {
  		dprintk("%s Invalid stripe unit (%u)\n",
  			__func__, fl->stripe_unit);
  		goto out;
  	}
  
  	status = 0;
  out:
  	dprintk("--> %s returns %d\n", __func__, status);
  	return status;
  }
  
  static void _filelayout_free_lseg(struct nfs4_filelayout_segment *fl)
  {
  	int i;
  
  	if (fl->fh_array) {
  		for (i = 0; i < fl->num_fh; i++) {
  			if (!fl->fh_array[i])
  				break;
  			kfree(fl->fh_array[i]);
  		}
  		kfree(fl->fh_array);
  	}
  	kfree(fl);
  }
  
  static int
  filelayout_decode_layout(struct pnfs_layout_hdr *flo,
  			 struct nfs4_filelayout_segment *fl,
  			 struct nfs4_layoutget_res *lgr,
  			 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\n", __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(&fl->deviceid, p, sizeof(fl->deviceid));
  	p += XDR_QUADLEN(NFS4_DEVICEID4_SIZE);
  	nfs4_print_deviceid(&fl->deviceid);
  
  	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\n",
  		__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 = kcalloc(fl->num_fh, sizeof(fl->fh_array[0]),
  				       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;
  
  		p = xdr_inline_decode(&stream, 4);
  		if (unlikely(!p))
  			goto out_err;
  		fl->fh_array[i]->size = be32_to_cpup(p++);
  		if (sizeof(struct nfs_fh) < fl->fh_array[i]->size) {
  			printk(KERN_ERR "NFS: Too big fh %d received %d\n",
  			       i, fl->fh_array[i]->size);
  			goto out_err;
  		}
  
  		p = xdr_inline_decode(&stream, fl->fh_array[i]->size);
  		if (unlikely(!p))
  			goto out_err;
  		memcpy(fl->fh_array[i]->data, p, fl->fh_array[i]->size);
  		dprintk("DEBUG: %s: fh len %d\n", __func__,
  			fl->fh_array[i]->size);
  	}
  
  	__free_page(scratch);
  	return 0;
  
  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\n", __func__);
  	nfs4_fl_put_deviceid(fl->dsaddr);
  	/* This assumes a single RW lseg */
  	if (lseg->pls_range.iomode == IOMODE_RW) {
  		struct nfs4_filelayout *flo;
  
  		flo = FILELAYOUT_FROM_HDR(lseg->pls_layout);
  		flo->commit_info.nbuckets = 0;
  		kfree(flo->commit_info.buckets);
  		flo->commit_info.buckets = NULL;
  	}
  	_filelayout_free_lseg(fl);
  }
  
  static int
  filelayout_alloc_commit_info(struct pnfs_layout_segment *lseg,
  			     struct nfs_commit_info *cinfo,
  			     gfp_t gfp_flags)
  {
  	struct nfs4_filelayout_segment *fl = FILELAYOUT_LSEG(lseg);
  	struct pnfs_commit_bucket *buckets;
  	int size, i;
  
  	if (fl->commit_through_mds)
  		return 0;
  
  	size = (fl->stripe_type == STRIPE_SPARSE) ?
  		fl->dsaddr->ds_num : fl->dsaddr->stripe_count;
  
  	if (cinfo->ds->nbuckets >= size) {
  		/* 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().
  		 * */
  		return 0;
  	}
  
  	buckets = kcalloc(size, sizeof(struct pnfs_commit_bucket),
  			  gfp_flags);
  	if (!buckets)
  		return -ENOMEM;
  	for (i = 0; i < size; i++) {
  		INIT_LIST_HEAD(&buckets[i].written);
  		INIT_LIST_HEAD(&buckets[i].committing);
  		/* mark direct verifier as unset */
  		buckets[i].direct_verf.committed = NFS_INVALID_STABLE_HOW;
  	}
  
  	spin_lock(&cinfo->inode->i_lock);
  	if (cinfo->ds->nbuckets >= size)
  		goto out;
  	for (i = 0; i < cinfo->ds->nbuckets; i++) {
  		list_splice(&cinfo->ds->buckets[i].written,
  			    &buckets[i].written);
  		list_splice(&cinfo->ds->buckets[i].committing,
  			    &buckets[i].committing);
  		buckets[i].direct_verf.committed =
  			cinfo->ds->buckets[i].direct_verf.committed;
  		buckets[i].wlseg = cinfo->ds->buckets[i].wlseg;
  		buckets[i].clseg = cinfo->ds->buckets[i].clseg;
  	}
  	swap(cinfo->ds->buckets, buckets);
  	cinfo->ds->nbuckets = size;
  out:
  	spin_unlock(&cinfo->inode->i_lock);
  	kfree(buckets);
  	return 0;
  }
  
  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;
  
  	dprintk("--> %s\n", __func__);
  	fl = kzalloc(sizeof(*fl), gfp_flags);
  	if (!fl)
  		return NULL;
  
  	rc = filelayout_decode_layout(layoutid, fl, lgr, gfp_flags);
  	if (rc != 0 || filelayout_check_layout(layoutid, fl, lgr, gfp_flags)) {
  		_filelayout_free_lseg(fl);
  		return NULL;
  	}
  	return &fl->generic_hdr;
  }
  
  /*
   * filelayout_pg_test(). Called by nfs_can_coalesce_requests()
   *
   * Return 0 if @req cannot be coalesced into @pgio, otherwise return the number
   * of bytes (maximum @req->wb_bytes) that can be coalesced.
   */
  static size_t
  filelayout_pg_test(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
  		   struct nfs_page *req)
  {
  	unsigned int size;
  	u64 p_stripe, r_stripe;
  	u32 stripe_offset;
  	u64 segment_offset = pgio->pg_lseg->pls_range.offset;
  	u32 stripe_unit = FILELAYOUT_LSEG(pgio->pg_lseg)->stripe_unit;
  
  	/* calls nfs_generic_pg_test */
  	size = pnfs_generic_pg_test(pgio, prev, req);
  	if (!size)
  		return 0;
  
  	/* see if req and prev are in the same stripe */
  	if (prev) {
  		p_stripe = (u64)req_offset(prev) - segment_offset;
  		r_stripe = (u64)req_offset(req) - segment_offset;
  		do_div(p_stripe, stripe_unit);
  		do_div(r_stripe, stripe_unit);
  
  		if (p_stripe != r_stripe)
  			return 0;
  	}
  
  	/* calculate remaining bytes in the current stripe */
  	div_u64_rem((u64)req_offset(req) - segment_offset,
  			stripe_unit,
  			&stripe_offset);
  	WARN_ON_ONCE(stripe_offset > stripe_unit);
  	if (stripe_offset >= stripe_unit)
  		return 0;
  	return min(stripe_unit - (unsigned int)stripe_offset, size);
  }
  
  static struct pnfs_layout_segment *
  fl_pnfs_update_layout(struct inode *ino,
  		      struct nfs_open_context *ctx,
  		      loff_t pos,
  		      u64 count,
  		      enum pnfs_iomode iomode,
  		      bool strict_iomode,
  		      gfp_t gfp_flags)
  {
  	struct pnfs_layout_segment *lseg = NULL;
  	struct pnfs_layout_hdr *lo;
  	struct nfs4_filelayout_segment *fl;
  	int status;
  
  	lseg = pnfs_update_layout(ino, ctx, pos, count, iomode, strict_iomode,
  				  gfp_flags);
  	if (!lseg)
  		lseg = ERR_PTR(-ENOMEM);
  	if (IS_ERR(lseg))
  		goto out;
  
  	lo = NFS_I(ino)->layout;
  	fl = FILELAYOUT_LSEG(lseg);
  
  	status = filelayout_check_deviceid(lo, fl, gfp_flags);
  	if (status) {
  		pnfs_put_lseg(lseg);
  		lseg = ERR_PTR(status);
  	}
  out:
  	return lseg;
  }
  
  static void
  filelayout_pg_init_read(struct nfs_pageio_descriptor *pgio,
  			struct nfs_page *req)
  {
  	pnfs_generic_pg_check_layout(pgio);
  	if (!pgio->pg_lseg) {
  		pgio->pg_lseg = fl_pnfs_update_layout(pgio->pg_inode,
  						      req->wb_context,
  						      0,
  						      NFS4_MAX_UINT64,
  						      IOMODE_READ,
  						      false,
  						      GFP_KERNEL);
  		if (IS_ERR(pgio->pg_lseg)) {
  			pgio->pg_error = PTR_ERR(pgio->pg_lseg);
  			pgio->pg_lseg = NULL;
  			return;
  		}
  	}
  	/* If no lseg, fall back to read through mds */
  	if (pgio->pg_lseg == NULL)
  		nfs_pageio_reset_read_mds(pgio);
  }
  
  static void
  filelayout_pg_init_write(struct nfs_pageio_descriptor *pgio,
  			 struct nfs_page *req)
  {
  	struct nfs_commit_info cinfo;
  	int status;
  
  	pnfs_generic_pg_check_layout(pgio);
  	if (!pgio->pg_lseg) {
  		pgio->pg_lseg = fl_pnfs_update_layout(pgio->pg_inode,
  						      req->wb_context,
  						      0,
  						      NFS4_MAX_UINT64,
  						      IOMODE_RW,
  						      false,
  						      GFP_NOFS);
  		if (IS_ERR(pgio->pg_lseg)) {
  			pgio->pg_error = PTR_ERR(pgio->pg_lseg);
  			pgio->pg_lseg = NULL;
  			return;
  		}
  	}
  
  	/* If no lseg, fall back to write through mds */
  	if (pgio->pg_lseg == NULL)
  		goto out_mds;
  	nfs_init_cinfo(&cinfo, pgio->pg_inode, pgio->pg_dreq);
  	status = filelayout_alloc_commit_info(pgio->pg_lseg, &cinfo, GFP_NOFS);
  	if (status < 0) {
  		pnfs_put_lseg(pgio->pg_lseg);
  		pgio->pg_lseg = NULL;
  		goto out_mds;
  	}
  	return;
  out_mds:
  	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,
  	.pg_cleanup = pnfs_generic_pg_cleanup,
  };
  
  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,
  	.pg_cleanup = pnfs_generic_pg_cleanup,
  };
  
  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;
  }
  
  static void
  filelayout_mark_request_commit(struct nfs_page *req,
  			       struct pnfs_layout_segment *lseg,
  			       struct nfs_commit_info *cinfo,
  			       u32 ds_commit_idx)
  
  {
  	struct nfs4_filelayout_segment *fl = FILELAYOUT_LSEG(lseg);
  	u32 i, j;
  
  	if (fl->commit_through_mds) {
  		nfs_request_add_commit_list(req, cinfo);
  	} else {
  		/* 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, req_offset(req));
  		i = select_bucket_index(fl, j);
  		pnfs_layout_mark_request_commit(req, lseg, cinfo, i);
  	}
  }
  
  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_commit_data *data, int how)
  {
  	struct pnfs_layout_segment *lseg = data->lseg;
  	struct nfs4_pnfs_ds *ds;
  	struct rpc_clnt *ds_clnt;
  	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)
  		goto out_err;
  
  	ds_clnt = nfs4_find_or_create_ds_client(ds->ds_clp, data->inode);
  	if (IS_ERR(ds_clnt))
  		goto out_err;
  
  	dprintk("%s ino %lu, how %d cl_count %d\n", __func__,
  		data->inode->i_ino, how, atomic_read(&ds->ds_clp->cl_count));
  	data->commit_done_cb = filelayout_commit_done_cb;
  	atomic_inc(&ds->ds_clp->cl_count);
  	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(ds_clnt, data, NFS_PROTO(data->inode),
  				   &filelayout_commit_call_ops, how,
  				   RPC_TASK_SOFTCONN);
  out_err:
  	pnfs_generic_prepare_to_resend_writes(data);
  	pnfs_generic_commit_release(data);
  	return -EAGAIN;
  }
  
  /* filelayout_search_commit_reqs - Search lists in @cinfo for the head reqest
   *				   for @page
   * @cinfo - commit info for current inode
   * @page - page to search for matching head request
   *
   * Returns a the head request if one is found, otherwise returns NULL.
   */
  static struct nfs_page *
  filelayout_search_commit_reqs(struct nfs_commit_info *cinfo, struct page *page)
  {
  	struct nfs_page *freq, *t;
  	struct pnfs_commit_bucket *b;
  	int i;
  
  	/* Linearly search the commit lists for each bucket until a matching
  	 * request is found */
  	for (i = 0, b = cinfo->ds->buckets; i < cinfo->ds->nbuckets; i++, b++) {
  		list_for_each_entry_safe(freq, t, &b->written, wb_list) {
  			if (freq->wb_page == page)
  				return freq->wb_head;
  		}
  		list_for_each_entry_safe(freq, t, &b->committing, wb_list) {
  			if (freq->wb_page == page)
  				return freq->wb_head;
  		}
  	}
  
  	return NULL;
  }
  
  static int
  filelayout_commit_pagelist(struct inode *inode, struct list_head *mds_pages,
  			   int how, struct nfs_commit_info *cinfo)
  {
  	return pnfs_generic_commit_pagelist(inode, mds_pages, how, cinfo,
  					    filelayout_initiate_commit);
  }
  
  static struct nfs4_deviceid_node *
  filelayout_alloc_deviceid_node(struct nfs_server *server,
  		struct pnfs_device *pdev, gfp_t gfp_flags)
  {
  	struct nfs4_file_layout_dsaddr *dsaddr;
  
  	dsaddr = nfs4_fl_alloc_deviceid_node(server, pdev, gfp_flags);
  	if (!dsaddr)
  		return NULL;
  	return &dsaddr->id_node;
  }
  
  static void
  filelayout_free_deviceid_node(struct nfs4_deviceid_node *d)
  {
  	nfs4_fl_free_deviceid(container_of(d, struct nfs4_file_layout_dsaddr, id_node));
  }
  
  static struct pnfs_layout_hdr *
  filelayout_alloc_layout_hdr(struct inode *inode, gfp_t gfp_flags)
  {
  	struct nfs4_filelayout *flo;
  
  	flo = kzalloc(sizeof(*flo), gfp_flags);
  	return flo != NULL ? &flo->generic_hdr : NULL;
  }
  
  static void
  filelayout_free_layout_hdr(struct pnfs_layout_hdr *lo)
  {
  	kfree(FILELAYOUT_FROM_HDR(lo));
  }
  
  static struct pnfs_ds_commit_info *
  filelayout_get_ds_info(struct inode *inode)
  {
  	struct pnfs_layout_hdr *layout = NFS_I(inode)->layout;
  
  	if (layout == NULL)
  		return NULL;
  	else
  		return &FILELAYOUT_FROM_HDR(layout)->commit_info;
  }
  
  static struct pnfs_layoutdriver_type filelayout_type = {
  	.id			= LAYOUT_NFSV4_1_FILES,
  	.name			= "LAYOUT_NFSV4_1_FILES",
  	.owner			= THIS_MODULE,
  	.alloc_layout_hdr	= filelayout_alloc_layout_hdr,
  	.free_layout_hdr	= filelayout_free_layout_hdr,
  	.alloc_lseg		= filelayout_alloc_lseg,
  	.free_lseg		= filelayout_free_lseg,
  	.pg_read_ops		= &filelayout_pg_read_ops,
  	.pg_write_ops		= &filelayout_pg_write_ops,
  	.get_ds_info		= &filelayout_get_ds_info,
  	.mark_request_commit	= filelayout_mark_request_commit,
  	.clear_request_commit	= pnfs_generic_clear_request_commit,
  	.scan_commit_lists	= pnfs_generic_scan_commit_lists,
  	.recover_commit_reqs	= pnfs_generic_recover_commit_reqs,
  	.search_commit_reqs	= filelayout_search_commit_reqs,
  	.commit_pagelist	= filelayout_commit_pagelist,
  	.read_pagelist		= filelayout_read_pagelist,
  	.write_pagelist		= filelayout_write_pagelist,
  	.alloc_deviceid_node	= filelayout_alloc_deviceid_node,
  	.free_deviceid_node	= filelayout_free_deviceid_node,
  	.sync			= pnfs_nfs_generic_sync,
  };
  
  static int __init nfs4filelayout_init(void)
  {
  	printk(KERN_INFO "%s: NFSv4 File Layout Driver Registering...\n",
  	       __func__);
  	return pnfs_register_layoutdriver(&filelayout_type);
  }
  
  static void __exit nfs4filelayout_exit(void)
  {
  	printk(KERN_INFO "%s: NFSv4 File Layout Driver Unregistering...\n",
  	       __func__);
  	pnfs_unregister_layoutdriver(&filelayout_type);
  }
  
  MODULE_ALIAS("nfs-layouttype4-1");
  
  module_init(nfs4filelayout_init);
  module_exit(nfs4filelayout_exit);
  