fs/nfs/blocklayout/blocklayoutdev.c - pub/scm/linux/kernel/git/cjb/mmc - Git at Google

 /*
  *  linux/fs/nfs/blocklayout/blocklayoutdev.c
  *
  *  Device operations for the pnfs nfs4 file layout driver.
  *
  *  Copyright (c) 2006 The Regents of the University of Michigan.
  *  All rights reserved.
  *
  *  Andy Adamson <andros@citi.umich.edu>
  *  Fred Isaman <iisaman@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 from the
  * university of michigan as to its fitness for any purpose, and without
  * warranty by the university of michigan of any kind, either express
  * or implied, including without limitation the implied warranties of
  * merchantability and fitness for a particular purpose.  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 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/module.h>
 #include <linux/buffer_head.h> /* __bread */

 #include <linux/genhd.h>
 #include <linux/blkdev.h>
 #include <linux/hash.h>

 #include "blocklayout.h"

 #define NFSDBG_FACILITY         NFSDBG_PNFS_LD

 static int decode_sector_number(__be32 **rp, sector_t *sp)
 {
 	uint64_t s;

 	*rp = xdr_decode_hyper(*rp, &s);
 	if (s & 0x1ff) {
 		printk(KERN_WARNING "NFS: %s: sector not aligned\n", __func__);
 		return -1;
 	}
 	*sp = s >> SECTOR_SHIFT;
 	return 0;
 }

 /*
  * Release the block device
  */
 void nfs4_blkdev_put(struct block_device *bdev)
 {
 	dprintk("%s for device %d:%d\n", __func__, MAJOR(bdev->bd_dev),
 			MINOR(bdev->bd_dev));
 	blkdev_put(bdev, FMODE_READ);
 }

 ssize_t bl_pipe_downcall(struct file *filp, const char __user *src,
 			 size_t mlen)
 {
 	struct nfs_net *nn = net_generic(filp->f_dentry->d_sb->s_fs_info,
 					 nfs_net_id);

 	if (mlen != sizeof (struct bl_dev_msg))
 		return -EINVAL;

 	if (copy_from_user(&nn->bl_mount_reply, src, mlen) != 0)
 		return -EFAULT;

 	wake_up(&nn->bl_wq);

 	return mlen;
 }

 void bl_pipe_destroy_msg(struct rpc_pipe_msg *msg)
 {
 	struct bl_pipe_msg *bl_pipe_msg = container_of(msg, struct bl_pipe_msg, msg);

 	if (msg->errno >= 0)
 		return;
 	wake_up(bl_pipe_msg->bl_wq);
 }

 /*
  * Decodes pnfs_block_deviceaddr4 which is XDR encoded in dev->dev_addr_buf.
  */
 struct pnfs_block_dev *
 nfs4_blk_decode_device(struct nfs_server *server,
 		       struct pnfs_device *dev)
 {
 	struct pnfs_block_dev *rv;
 	struct block_device *bd = NULL;
 	struct bl_pipe_msg bl_pipe_msg;
 	struct rpc_pipe_msg *msg = &bl_pipe_msg.msg;
 	struct bl_msg_hdr bl_msg = {
 		.type = BL_DEVICE_MOUNT,
 		.totallen = dev->mincount,
 	};
 	uint8_t *dataptr;
 	DECLARE_WAITQUEUE(wq, current);
 	int offset, len, i, rc;
 	struct net *net = server->nfs_client->cl_net;
 	struct nfs_net *nn = net_generic(net, nfs_net_id);
 	struct bl_dev_msg *reply = &nn->bl_mount_reply;

 	dprintk("%s CREATING PIPEFS MESSAGE\n", __func__);
 	dprintk("%s: deviceid: %s, mincount: %d\n", __func__, dev->dev_id.data,
 		dev->mincount);

 	bl_pipe_msg.bl_wq = &nn->bl_wq;
 	memset(msg, 0, sizeof(*msg));
 	msg->data = kzalloc(sizeof(bl_msg) + dev->mincount, GFP_NOFS);
 	if (!msg->data) {
 		rv = ERR_PTR(-ENOMEM);
 		goto out;
 	}

 	memcpy(msg->data, &bl_msg, sizeof(bl_msg));
 	dataptr = (uint8_t *) msg->data;
 	len = dev->mincount;
 	offset = sizeof(bl_msg);
 	for (i = 0; len > 0; i++) {
 		memcpy(&dataptr[offset], page_address(dev->pages[i]),
 				len < PAGE_CACHE_SIZE ? len : PAGE_CACHE_SIZE);
 		len -= PAGE_CACHE_SIZE;
 		offset += PAGE_CACHE_SIZE;
 	}
 	msg->len = sizeof(bl_msg) + dev->mincount;

 	dprintk("%s CALLING USERSPACE DAEMON\n", __func__);
 	add_wait_queue(&nn->bl_wq, &wq);
 	rc = rpc_queue_upcall(nn->bl_device_pipe, msg);
 	if (rc < 0) {
 		remove_wait_queue(&nn->bl_wq, &wq);
 		rv = ERR_PTR(rc);
 		goto out;
 	}

 	set_current_state(TASK_UNINTERRUPTIBLE);
 	schedule();
 	__set_current_state(TASK_RUNNING);
 	remove_wait_queue(&nn->bl_wq, &wq);

 	if (reply->status != BL_DEVICE_REQUEST_PROC) {
 		dprintk("%s failed to open device: %d\n",
 			__func__, reply->status);
 		rv = ERR_PTR(-EINVAL);
 		goto out;
 	}

 	bd = blkdev_get_by_dev(MKDEV(reply->major, reply->minor),
 			       FMODE_READ, NULL);
 	if (IS_ERR(bd)) {
 		dprintk("%s failed to open device : %ld\n", __func__,
 			PTR_ERR(bd));
 		rv = ERR_CAST(bd);
 		goto out;
 	}

 	rv = kzalloc(sizeof(*rv), GFP_NOFS);
 	if (!rv) {
 		rv = ERR_PTR(-ENOMEM);
 		goto out;
 	}

 	rv->bm_mdev = bd;
 	memcpy(&rv->bm_mdevid, &dev->dev_id, sizeof(struct nfs4_deviceid));
 	rv->net = net;
 	dprintk("%s Created device %s with bd_block_size %u\n",
 		__func__,
 		bd->bd_disk->disk_name,
 		bd->bd_block_size);

 out:
 	kfree(msg->data);
 	return rv;
 }

 /* Map deviceid returned by the server to constructed block_device */
 static struct block_device *translate_devid(struct pnfs_layout_hdr *lo,
 					    struct nfs4_deviceid *id)
 {
 	struct block_device *rv = NULL;
 	struct block_mount_id *mid;
 	struct pnfs_block_dev *dev;

 	dprintk("%s enter, lo=%p, id=%p\n", __func__, lo, id);
 	mid = BLK_ID(lo);
 	spin_lock(&mid->bm_lock);
 	list_for_each_entry(dev, &mid->bm_devlist, bm_node) {
 		if (memcmp(id->data, dev->bm_mdevid.data,
 			   NFS4_DEVICEID4_SIZE) == 0) {
 			rv = dev->bm_mdev;
 			goto out;
 		}
 	}
  out:
 	spin_unlock(&mid->bm_lock);
 	dprintk("%s returning %p\n", __func__, rv);
 	return rv;
 }

 /* Tracks info needed to ensure extents in layout obey constraints of spec */
 struct layout_verification {
 	u32 mode;	/* R or RW */
 	u64 start;	/* Expected start of next non-COW extent */
 	u64 inval;	/* Start of INVAL coverage */
 	u64 cowread;	/* End of COW read coverage */
 };

 /* Verify the extent meets the layout requirements of the pnfs-block draft,
  * section 2.3.1.
  */
 static int verify_extent(struct pnfs_block_extent *be,
 			 struct layout_verification *lv)
 {
 	if (lv->mode == IOMODE_READ) {
 		if (be->be_state == PNFS_BLOCK_READWRITE_DATA ||
 		    be->be_state == PNFS_BLOCK_INVALID_DATA)
 			return -EIO;
 		if (be->be_f_offset != lv->start)
 			return -EIO;
 		lv->start += be->be_length;
 		return 0;
 	}
 	/* lv->mode == IOMODE_RW */
 	if (be->be_state == PNFS_BLOCK_READWRITE_DATA) {
 		if (be->be_f_offset != lv->start)
 			return -EIO;
 		if (lv->cowread > lv->start)
 			return -EIO;
 		lv->start += be->be_length;
 		lv->inval = lv->start;
 		return 0;
 	} else if (be->be_state == PNFS_BLOCK_INVALID_DATA) {
 		if (be->be_f_offset != lv->start)
 			return -EIO;
 		lv->start += be->be_length;
 		return 0;
 	} else if (be->be_state == PNFS_BLOCK_READ_DATA) {
 		if (be->be_f_offset > lv->start)
 			return -EIO;
 		if (be->be_f_offset < lv->inval)
 			return -EIO;
 		if (be->be_f_offset < lv->cowread)
 			return -EIO;
 		/* It looks like you might want to min this with lv->start,
 		 * but you really don't.
 		 */
 		lv->inval = lv->inval + be->be_length;
 		lv->cowread = be->be_f_offset + be->be_length;
 		return 0;
 	} else
 		return -EIO;
 }

 /* XDR decode pnfs_block_layout4 structure */
 int
 nfs4_blk_process_layoutget(struct pnfs_layout_hdr *lo,
 			   struct nfs4_layoutget_res *lgr, gfp_t gfp_flags)
 {
 	struct pnfs_block_layout *bl = BLK_LO2EXT(lo);
 	int i, status = -EIO;
 	uint32_t count;
 	struct pnfs_block_extent *be = NULL, *save;
 	struct xdr_stream stream;
 	struct xdr_buf buf;
 	struct page *scratch;
 	__be32 *p;
 	struct layout_verification lv = {
 		.mode = lgr->range.iomode,
 		.start = lgr->range.offset >> SECTOR_SHIFT,
 		.inval = lgr->range.offset >> SECTOR_SHIFT,
 		.cowread = lgr->range.offset >> SECTOR_SHIFT,
 	};
 	LIST_HEAD(extents);

 	dprintk("---> %s\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);

 	p = xdr_inline_decode(&stream, 4);
 	if (unlikely(!p))
 		goto out_err;

 	count = be32_to_cpup(p++);

 	dprintk("%s enter, number of extents %i\n", __func__, count);
 	p = xdr_inline_decode(&stream, (28 + NFS4_DEVICEID4_SIZE) * count);
 	if (unlikely(!p))
 		goto out_err;

 	/* Decode individual extents, putting them in temporary
 	 * staging area until whole layout is decoded to make error
 	 * recovery easier.
 	 */
 	for (i = 0; i < count; i++) {
 		be = bl_alloc_extent();
 		if (!be) {
 			status = -ENOMEM;
 			goto out_err;
 		}
 		memcpy(&be->be_devid, p, NFS4_DEVICEID4_SIZE);
 		p += XDR_QUADLEN(NFS4_DEVICEID4_SIZE);
 		be->be_mdev = translate_devid(lo, &be->be_devid);
 		if (!be->be_mdev)
 			goto out_err;

 		/* The next three values are read in as bytes,
 		 * but stored as 512-byte sector lengths
 		 */
 		if (decode_sector_number(&p, &be->be_f_offset) < 0)
 			goto out_err;
 		if (decode_sector_number(&p, &be->be_length) < 0)
 			goto out_err;
 		if (decode_sector_number(&p, &be->be_v_offset) < 0)
 			goto out_err;
 		be->be_state = be32_to_cpup(p++);
 		if (be->be_state == PNFS_BLOCK_INVALID_DATA)
 			be->be_inval = &bl->bl_inval;
 		if (verify_extent(be, &lv)) {
 			dprintk("%s verify failed\n", __func__);
 			goto out_err;
 		}
 		list_add_tail(&be->be_node, &extents);
 	}
 	if (lgr->range.offset + lgr->range.length !=
 			lv.start << SECTOR_SHIFT) {
 		dprintk("%s Final length mismatch\n", __func__);
 		be = NULL;
 		goto out_err;
 	}
 	if (lv.start < lv.cowread) {
 		dprintk("%s Final uncovered COW extent\n", __func__);
 		be = NULL;
 		goto out_err;
 	}
 	/* Extents decoded properly, now try to merge them in to
 	 * existing layout extents.
 	 */
 	spin_lock(&bl->bl_ext_lock);
 	list_for_each_entry_safe(be, save, &extents, be_node) {
 		list_del(&be->be_node);
 		status = bl_add_merge_extent(bl, be);
 		if (status) {
 			spin_unlock(&bl->bl_ext_lock);
 			/* This is a fairly catastrophic error, as the
 			 * entire layout extent lists are now corrupted.
 			 * We should have some way to distinguish this.
 			 */
 			be = NULL;
 			goto out_err;
 		}
 	}
 	spin_unlock(&bl->bl_ext_lock);
 	status = 0;
  out:
 	__free_page(scratch);
 	dprintk("%s returns %i\n", __func__, status);
 	return status;

  out_err:
 	bl_put_extent(be);
 	while (!list_empty(&extents)) {
 		be = list_first_entry(&extents, struct pnfs_block_extent,
 				      be_node);
 		list_del(&be->be_node);
 		bl_put_extent(be);
 	}
 	goto out;
 }
	/*
	* linux/fs/nfs/blocklayout/blocklayoutdev.c
	*
	* Device operations for the pnfs nfs4 file layout driver.
	*
	* Copyright (c) 2006 The Regents of the University of Michigan.
	* All rights reserved.
	*
	* Andy Adamson <andros@citi.umich.edu>
	* Fred Isaman <iisaman@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 from the
	* university of michigan as to its fitness for any purpose, and without
	* warranty by the university of michigan of any kind, either express
	* or implied, including without limitation the implied warranties of
	* merchantability and fitness for a particular purpose. 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 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/module.h>
	#include <linux/buffer_head.h> /* __bread */

	#include <linux/genhd.h>
	#include <linux/blkdev.h>
	#include <linux/hash.h>

	#include "blocklayout.h"

	#define NFSDBG_FACILITY NFSDBG_PNFS_LD

	static int decode_sector_number(__be32 *rp, sector_t sp)
	{
	uint64_t s;

	rp = xdr_decode_hyper(rp, &s);
	if (s & 0x1ff) {
	printk(KERN_WARNING "NFS: %s: sector not aligned\n", __func__);
	return -1;
	}
	*sp = s >> SECTOR_SHIFT;
	return 0;
	}

	/*
	* Release the block device
	*/
	void nfs4_blkdev_put(struct block_device *bdev)
	{
	dprintk("%s for device %d:%d\n", __func__, MAJOR(bdev->bd_dev),
	MINOR(bdev->bd_dev));
	blkdev_put(bdev, FMODE_READ);
	}

	ssize_t bl_pipe_downcall(struct file filp, const char __user src,
	size_t mlen)
	{
	struct nfs_net *nn = net_generic(filp->f_dentry->d_sb->s_fs_info,
	nfs_net_id);

	if (mlen != sizeof (struct bl_dev_msg))
	return -EINVAL;

	if (copy_from_user(&nn->bl_mount_reply, src, mlen) != 0)
	return -EFAULT;

	wake_up(&nn->bl_wq);

	return mlen;
	}

	void bl_pipe_destroy_msg(struct rpc_pipe_msg *msg)
	{
	struct bl_pipe_msg *bl_pipe_msg = container_of(msg, struct bl_pipe_msg, msg);

	if (msg->errno >= 0)
	return;
	wake_up(bl_pipe_msg->bl_wq);
	}

	/*
	* Decodes pnfs_block_deviceaddr4 which is XDR encoded in dev->dev_addr_buf.
	*/
	struct pnfs_block_dev *
	nfs4_blk_decode_device(struct nfs_server *server,
	struct pnfs_device *dev)
	{
	struct pnfs_block_dev *rv;
	struct block_device *bd = NULL;
	struct bl_pipe_msg bl_pipe_msg;
	struct rpc_pipe_msg *msg = &bl_pipe_msg.msg;
	struct bl_msg_hdr bl_msg = {
	.type = BL_DEVICE_MOUNT,
	.totallen = dev->mincount,
	};
	uint8_t *dataptr;
	DECLARE_WAITQUEUE(wq, current);
	int offset, len, i, rc;
	struct net *net = server->nfs_client->cl_net;
	struct nfs_net *nn = net_generic(net, nfs_net_id);
	struct bl_dev_msg *reply = &nn->bl_mount_reply;

	dprintk("%s CREATING PIPEFS MESSAGE\n", __func__);
	dprintk("%s: deviceid: %s, mincount: %d\n", __func__, dev->dev_id.data,
	dev->mincount);

	bl_pipe_msg.bl_wq = &nn->bl_wq;
	memset(msg, 0, sizeof(*msg));
	msg->data = kzalloc(sizeof(bl_msg) + dev->mincount, GFP_NOFS);
	if (!msg->data) {
	rv = ERR_PTR(-ENOMEM);
	goto out;
	}

	memcpy(msg->data, &bl_msg, sizeof(bl_msg));
	dataptr = (uint8_t *) msg->data;
	len = dev->mincount;
	offset = sizeof(bl_msg);
	for (i = 0; len > 0; i++) {
	memcpy(&dataptr[offset], page_address(dev->pages[i]),
	len < PAGE_CACHE_SIZE ? len : PAGE_CACHE_SIZE);
	len -= PAGE_CACHE_SIZE;
	offset += PAGE_CACHE_SIZE;
	}
	msg->len = sizeof(bl_msg) + dev->mincount;

	dprintk("%s CALLING USERSPACE DAEMON\n", __func__);
	add_wait_queue(&nn->bl_wq, &wq);
	rc = rpc_queue_upcall(nn->bl_device_pipe, msg);
	if (rc < 0) {
	remove_wait_queue(&nn->bl_wq, &wq);
	rv = ERR_PTR(rc);
	goto out;
	}

	set_current_state(TASK_UNINTERRUPTIBLE);
	schedule();
	__set_current_state(TASK_RUNNING);
	remove_wait_queue(&nn->bl_wq, &wq);

	if (reply->status != BL_DEVICE_REQUEST_PROC) {
	dprintk("%s failed to open device: %d\n",
	__func__, reply->status);
	rv = ERR_PTR(-EINVAL);
	goto out;
	}

	bd = blkdev_get_by_dev(MKDEV(reply->major, reply->minor),
	FMODE_READ, NULL);
	if (IS_ERR(bd)) {
	dprintk("%s failed to open device : %ld\n", __func__,
	PTR_ERR(bd));
	rv = ERR_CAST(bd);
	goto out;
	}

	rv = kzalloc(sizeof(*rv), GFP_NOFS);
	if (!rv) {
	rv = ERR_PTR(-ENOMEM);
	goto out;
	}

	rv->bm_mdev = bd;
	memcpy(&rv->bm_mdevid, &dev->dev_id, sizeof(struct nfs4_deviceid));
	rv->net = net;
	dprintk("%s Created device %s with bd_block_size %u\n",
	__func__,
	bd->bd_disk->disk_name,
	bd->bd_block_size);

	out:
	kfree(msg->data);
	return rv;
	}

	/* Map deviceid returned by the server to constructed block_device */
	static struct block_device translate_devid(struct pnfs_layout_hdr lo,
	struct nfs4_deviceid *id)
	{
	struct block_device *rv = NULL;
	struct block_mount_id *mid;
	struct pnfs_block_dev *dev;

	dprintk("%s enter, lo=%p, id=%p\n", __func__, lo, id);
	mid = BLK_ID(lo);
	spin_lock(&mid->bm_lock);
	list_for_each_entry(dev, &mid->bm_devlist, bm_node) {
	if (memcmp(id->data, dev->bm_mdevid.data,
	NFS4_DEVICEID4_SIZE) == 0) {
	rv = dev->bm_mdev;
	goto out;
	}
	}
	out:
	spin_unlock(&mid->bm_lock);
	dprintk("%s returning %p\n", __func__, rv);
	return rv;
	}

	/* Tracks info needed to ensure extents in layout obey constraints of spec */
	struct layout_verification {
	u32 mode; /* R or RW */
	u64 start; /* Expected start of next non-COW extent */
	u64 inval; /* Start of INVAL coverage */
	u64 cowread; /* End of COW read coverage */
	};

	/* Verify the extent meets the layout requirements of the pnfs-block draft,
	* section 2.3.1.
	*/
	static int verify_extent(struct pnfs_block_extent *be,
	struct layout_verification *lv)
	{
	if (lv->mode == IOMODE_READ) {
	if (be->be_state == PNFS_BLOCK_READWRITE_DATA \|\|
	be->be_state == PNFS_BLOCK_INVALID_DATA)
	return -EIO;
	if (be->be_f_offset != lv->start)
	return -EIO;
	lv->start += be->be_length;
	return 0;
	}
	/* lv->mode == IOMODE_RW */
	if (be->be_state == PNFS_BLOCK_READWRITE_DATA) {
	if (be->be_f_offset != lv->start)
	return -EIO;
	if (lv->cowread > lv->start)
	return -EIO;
	lv->start += be->be_length;
	lv->inval = lv->start;
	return 0;
	} else if (be->be_state == PNFS_BLOCK_INVALID_DATA) {
	if (be->be_f_offset != lv->start)
	return -EIO;
	lv->start += be->be_length;
	return 0;
	} else if (be->be_state == PNFS_BLOCK_READ_DATA) {
	if (be->be_f_offset > lv->start)
	return -EIO;
	if (be->be_f_offset < lv->inval)
	return -EIO;
	if (be->be_f_offset < lv->cowread)
	return -EIO;
	/* It looks like you might want to min this with lv->start,
	* but you really don't.
	*/
	lv->inval = lv->inval + be->be_length;
	lv->cowread = be->be_f_offset + be->be_length;
	return 0;
	} else
	return -EIO;
	}

	/* XDR decode pnfs_block_layout4 structure */
	int
	nfs4_blk_process_layoutget(struct pnfs_layout_hdr *lo,
	struct nfs4_layoutget_res *lgr, gfp_t gfp_flags)
	{
	struct pnfs_block_layout *bl = BLK_LO2EXT(lo);
	int i, status = -EIO;
	uint32_t count;
	struct pnfs_block_extent be = NULL, save;
	struct xdr_stream stream;
	struct xdr_buf buf;
	struct page *scratch;
	__be32 *p;
	struct layout_verification lv = {
	.mode = lgr->range.iomode,
	.start = lgr->range.offset >> SECTOR_SHIFT,
	.inval = lgr->range.offset >> SECTOR_SHIFT,
	.cowread = lgr->range.offset >> SECTOR_SHIFT,
	};
	LIST_HEAD(extents);

	dprintk("---> %s\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);

	p = xdr_inline_decode(&stream, 4);
	if (unlikely(!p))
	goto out_err;

	count = be32_to_cpup(p++);

	dprintk("%s enter, number of extents %i\n", __func__, count);
	p = xdr_inline_decode(&stream, (28 + NFS4_DEVICEID4_SIZE) * count);
	if (unlikely(!p))
	goto out_err;

	/* Decode individual extents, putting them in temporary
	* staging area until whole layout is decoded to make error
	* recovery easier.
	*/
	for (i = 0; i < count; i++) {
	be = bl_alloc_extent();
	if (!be) {
	status = -ENOMEM;
	goto out_err;
	}
	memcpy(&be->be_devid, p, NFS4_DEVICEID4_SIZE);
	p += XDR_QUADLEN(NFS4_DEVICEID4_SIZE);
	be->be_mdev = translate_devid(lo, &be->be_devid);
	if (!be->be_mdev)
	goto out_err;

	/* The next three values are read in as bytes,
	* but stored as 512-byte sector lengths
	*/
	if (decode_sector_number(&p, &be->be_f_offset) < 0)
	goto out_err;
	if (decode_sector_number(&p, &be->be_length) < 0)
	goto out_err;
	if (decode_sector_number(&p, &be->be_v_offset) < 0)
	goto out_err;
	be->be_state = be32_to_cpup(p++);
	if (be->be_state == PNFS_BLOCK_INVALID_DATA)
	be->be_inval = &bl->bl_inval;
	if (verify_extent(be, &lv)) {
	dprintk("%s verify failed\n", __func__);
	goto out_err;
	}
	list_add_tail(&be->be_node, &extents);
	}
	if (lgr->range.offset + lgr->range.length !=
	lv.start << SECTOR_SHIFT) {
	dprintk("%s Final length mismatch\n", __func__);
	be = NULL;
	goto out_err;
	}
	if (lv.start < lv.cowread) {
	dprintk("%s Final uncovered COW extent\n", __func__);
	be = NULL;
	goto out_err;
	}
	/* Extents decoded properly, now try to merge them in to
	* existing layout extents.
	*/
	spin_lock(&bl->bl_ext_lock);
	list_for_each_entry_safe(be, save, &extents, be_node) {
	list_del(&be->be_node);
	status = bl_add_merge_extent(bl, be);
	if (status) {
	spin_unlock(&bl->bl_ext_lock);
	/* This is a fairly catastrophic error, as the
	* entire layout extent lists are now corrupted.
	* We should have some way to distinguish this.
	*/
	be = NULL;
	goto out_err;
	}
	}
	spin_unlock(&bl->bl_ext_lock);
	status = 0;
	out:
	__free_page(scratch);
	dprintk("%s returns %i\n", __func__, status);
	return status;

	out_err:
	bl_put_extent(be);
	while (!list_empty(&extents)) {
	be = list_first_entry(&extents, struct pnfs_block_extent,
	be_node);
	list_del(&be->be_node);
	bl_put_extent(be);
	}
	goto out;
	}