/*
 *  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 "%s: sector not aligned\n", __func__);
		return -1;
	}
	*sp = s >> SECTOR_SHIFT;
	return 0;
}

/* Open a block_device by device number. */
struct block_device *nfs4_blkdev_get(dev_t dev)
{
	struct block_device *bd;

	dprintk("%s enter\n", __func__);
	bd = blkdev_get_by_dev(dev, FMODE_READ, NULL);
	if (IS_ERR(bd))
		goto fail;
	return bd;
fail:
	dprintk("%s failed to open device : %ld\n",
			__func__, PTR_ERR(bd));
	return NULL;
}

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

/*
 * Shouldn't there be a rpc_generic_upcall() to do this for us?
 */
ssize_t bl_pipe_upcall(struct file *filp, struct rpc_pipe_msg *msg,
		       char __user *dst, size_t buflen)
{
	char *data = (char *)msg->data + msg->copied;
	size_t mlen = min(msg->len - msg->copied, buflen);
	unsigned long left;

	left = copy_to_user(dst, data, mlen);
	if (left == mlen) {
		msg->errno = -EFAULT;
		return -EFAULT;
	}

	mlen -= left;
	msg->copied += mlen;
	msg->errno = 0;
	return mlen;
}

static struct bl_dev_msg bl_mount_reply;

ssize_t bl_pipe_downcall(struct file *filp, const char __user *src,
			 size_t mlen)
{
	if (mlen != sizeof (struct bl_dev_msg))
		return -EINVAL;

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

	wake_up(&bl_wq);

	return mlen;
}

void bl_pipe_destroy_msg(struct rpc_pipe_msg *msg)
{
	if (msg->errno >= 0)
		return;
	wake_up(&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 = NULL;
	struct block_device *bd = NULL;
	struct rpc_pipe_msg msg;
	struct bl_msg_hdr bl_msg = {
		.type = BL_DEVICE_MOUNT,
		.totallen = dev->mincount,
	};
	uint8_t *dataptr;
	DECLARE_WAITQUEUE(wq, current);
	struct bl_dev_msg *reply = &bl_mount_reply;
	int offset, len, i;

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

	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(&bl_wq, &wq);
	if (rpc_queue_upcall(bl_device_pipe->d_inode, &msg) < 0) {
		remove_wait_queue(&bl_wq, &wq);
		goto out;
	}

	set_current_state(TASK_UNINTERRUPTIBLE);
	schedule();
	__set_current_state(TASK_RUNNING);
	remove_wait_queue(&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 = nfs4_blkdev_get(MKDEV(reply->major, reply->minor));
	if (IS_ERR(bd)) {
		dprintk("%s failed to open device : %ld\n",
			__func__, PTR_ERR(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));
	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;
}