/*
   *  linux/fs/nfs/blocklayout/blocklayout.c
   *
   *  Module for the NFSv4.1 pNFS block 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/init.h>
  #include <linux/mount.h>
  #include <linux/namei.h>
  #include <linux/bio.h>		/* struct bio */
  #include <linux/prefetch.h>
  #include <linux/pagevec.h>
  
  #include "../pnfs.h"
  #include "../nfs4session.h"
  #include "../internal.h"
  #include "blocklayout.h"
  
  #define NFSDBG_FACILITY	NFSDBG_PNFS_LD
  
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Andy Adamson <andros@citi.umich.edu>");
  MODULE_DESCRIPTION("The NFSv4.1 pNFS Block layout driver");
  
  static bool is_hole(struct pnfs_block_extent *be)
  {
  	switch (be->be_state) {
  	case PNFS_BLOCK_NONE_DATA:
  		return true;
  	case PNFS_BLOCK_INVALID_DATA:
  		return be->be_tag ? false : true;
  	default:
  		return false;
  	}
  }
  
  /* The data we are handed might be spread across several bios.  We need
   * to track when the last one is finished.
   */
  struct parallel_io {
  	struct kref refcnt;
  	void (*pnfs_callback) (void *data);
  	void *data;
  };
  
  static inline struct parallel_io *alloc_parallel(void *data)
  {
  	struct parallel_io *rv;
  
  	rv  = kmalloc(sizeof(*rv), GFP_NOFS);
  	if (rv) {
  		rv->data = data;
  		kref_init(&rv->refcnt);
  	}
  	return rv;
  }
  
  static inline void get_parallel(struct parallel_io *p)
  {
  	kref_get(&p->refcnt);
  }
  
  static void destroy_parallel(struct kref *kref)
  {
  	struct parallel_io *p = container_of(kref, struct parallel_io, refcnt);
  
  	dprintk("%s enter
  ", __func__);
  	p->pnfs_callback(p->data);
  	kfree(p);
  }
  
  static inline void put_parallel(struct parallel_io *p)
  {
  	kref_put(&p->refcnt, destroy_parallel);
  }
  
  static struct bio *
  bl_submit_bio(int rw, struct bio *bio)
  {
  	if (bio) {
  		get_parallel(bio->bi_private);
  		dprintk("%s submitting %s bio %u@%llu
  ", __func__,
  			rw == READ ? "read" : "write", bio->bi_iter.bi_size,
  			(unsigned long long)bio->bi_iter.bi_sector);
  		submit_bio(rw, bio);
  	}
  	return NULL;
  }
  
  static struct bio *
  bl_alloc_init_bio(int npg, struct block_device *bdev, sector_t disk_sector,
  		bio_end_io_t end_io, struct parallel_io *par)
  {
  	struct bio *bio;
  
  	npg = min(npg, BIO_MAX_PAGES);
  	bio = bio_alloc(GFP_NOIO, npg);
  	if (!bio && (current->flags & PF_MEMALLOC)) {
  		while (!bio && (npg /= 2))
  			bio = bio_alloc(GFP_NOIO, npg);
  	}
  
  	if (bio) {
  		bio->bi_iter.bi_sector = disk_sector;
  		bio->bi_bdev = bdev;
  		bio->bi_end_io = end_io;
  		bio->bi_private = par;
  	}
  	return bio;
  }
  
  static struct bio *
  do_add_page_to_bio(struct bio *bio, int npg, int rw, sector_t isect,
  		struct page *page, struct pnfs_block_dev_map *map,
  		struct pnfs_block_extent *be, bio_end_io_t end_io,
  		struct parallel_io *par, unsigned int offset, int *len)
  {
  	struct pnfs_block_dev *dev =
  		container_of(be->be_device, struct pnfs_block_dev, node);
  	u64 disk_addr, end;
  
  	dprintk("%s: npg %d rw %d isect %llu offset %u len %d
  ", __func__,
  		npg, rw, (unsigned long long)isect, offset, *len);
  
  	/* translate to device offset */
  	isect += be->be_v_offset;
  	isect -= be->be_f_offset;
  
  	/* translate to physical disk offset */
  	disk_addr = (u64)isect << SECTOR_SHIFT;
  	if (disk_addr < map->start || disk_addr >= map->start + map->len) {
  		if (!dev->map(dev, disk_addr, map))
  			return ERR_PTR(-EIO);
  		bio = bl_submit_bio(rw, bio);
  	}
  	disk_addr += map->disk_offset;
  	disk_addr -= map->start;
  
  	/* limit length to what the device mapping allows */
  	end = disk_addr + *len;
  	if (end >= map->start + map->len)
  		*len = map->start + map->len - disk_addr;
  
  retry:
  	if (!bio) {
  		bio = bl_alloc_init_bio(npg, map->bdev,
  				disk_addr >> SECTOR_SHIFT, end_io, par);
  		if (!bio)
  			return ERR_PTR(-ENOMEM);
  	}
  	if (bio_add_page(bio, page, *len, offset) < *len) {
  		bio = bl_submit_bio(rw, bio);
  		goto retry;
  	}
  	return bio;
  }
  
  static void bl_end_io_read(struct bio *bio)
  {
  	struct parallel_io *par = bio->bi_private;
  
  	if (bio->bi_error) {
  		struct nfs_pgio_header *header = par->data;
  
  		if (!header->pnfs_error)
  			header->pnfs_error = -EIO;
  		pnfs_set_lo_fail(header->lseg);
  	}
  
  	bio_put(bio);
  	put_parallel(par);
  }
  
  static void bl_read_cleanup(struct work_struct *work)
  {
  	struct rpc_task *task;
  	struct nfs_pgio_header *hdr;
  	dprintk("%s enter
  ", __func__);
  	task = container_of(work, struct rpc_task, u.tk_work);
  	hdr = container_of(task, struct nfs_pgio_header, task);
  	pnfs_ld_read_done(hdr);
  }
  
  static void
  bl_end_par_io_read(void *data)
  {
  	struct nfs_pgio_header *hdr = data;
  
  	hdr->task.tk_status = hdr->pnfs_error;
  	INIT_WORK(&hdr->task.u.tk_work, bl_read_cleanup);
  	schedule_work(&hdr->task.u.tk_work);
  }
  
  static enum pnfs_try_status
  bl_read_pagelist(struct nfs_pgio_header *header)
  {
  	struct pnfs_block_layout *bl = BLK_LSEG2EXT(header->lseg);
  	struct pnfs_block_dev_map map = { .start = NFS4_MAX_UINT64 };
  	struct bio *bio = NULL;
  	struct pnfs_block_extent be;
  	sector_t isect, extent_length = 0;
  	struct parallel_io *par;
  	loff_t f_offset = header->args.offset;
  	size_t bytes_left = header->args.count;
  	unsigned int pg_offset = header->args.pgbase, pg_len;
  	struct page **pages = header->args.pages;
  	int pg_index = header->args.pgbase >> PAGE_CACHE_SHIFT;
  	const bool is_dio = (header->dreq != NULL);
  	struct blk_plug plug;
  	int i;
  
  	dprintk("%s enter nr_pages %u offset %lld count %u
  ", __func__,
  		header->page_array.npages, f_offset,
  		(unsigned int)header->args.count);
  
  	par = alloc_parallel(header);
  	if (!par)
  		return PNFS_NOT_ATTEMPTED;
  	par->pnfs_callback = bl_end_par_io_read;
  
  	blk_start_plug(&plug);
  
  	isect = (sector_t) (f_offset >> SECTOR_SHIFT);
  	/* Code assumes extents are page-aligned */
  	for (i = pg_index; i < header->page_array.npages; i++) {
  		if (extent_length <= 0) {
  			/* We've used up the previous extent */
  			bio = bl_submit_bio(READ, bio);
  
  			/* Get the next one */
  			if (!ext_tree_lookup(bl, isect, &be, false)) {
  				header->pnfs_error = -EIO;
  				goto out;
  			}
  			extent_length = be.be_length - (isect - be.be_f_offset);
  		}
  
  		if (is_dio) {
  			if (pg_offset + bytes_left > PAGE_CACHE_SIZE)
  				pg_len = PAGE_CACHE_SIZE - pg_offset;
  			else
  				pg_len = bytes_left;
  		} else {
  			BUG_ON(pg_offset != 0);
  			pg_len = PAGE_CACHE_SIZE;
  		}
  
  		if (is_hole(&be)) {
  			bio = bl_submit_bio(READ, bio);
  			/* Fill hole w/ zeroes w/o accessing device */
  			dprintk("%s Zeroing page for hole
  ", __func__);
  			zero_user_segment(pages[i], pg_offset, pg_len);
  
  			/* invalidate map */
  			map.start = NFS4_MAX_UINT64;
  		} else {
  			bio = do_add_page_to_bio(bio,
  						 header->page_array.npages - i,
  						 READ,
  						 isect, pages[i], &map, &be,
  						 bl_end_io_read, par,
  						 pg_offset, &pg_len);
  			if (IS_ERR(bio)) {
  				header->pnfs_error = PTR_ERR(bio);
  				bio = NULL;
  				goto out;
  			}
  		}
  		isect += (pg_len >> SECTOR_SHIFT);
  		extent_length -= (pg_len >> SECTOR_SHIFT);
  		f_offset += pg_len;
  		bytes_left -= pg_len;
  		pg_offset = 0;
  	}
  	if ((isect << SECTOR_SHIFT) >= header->inode->i_size) {
  		header->res.eof = 1;
  		header->res.count = header->inode->i_size - header->args.offset;
  	} else {
  		header->res.count = (isect << SECTOR_SHIFT) - header->args.offset;
  	}
  out:
  	bl_submit_bio(READ, bio);
  	blk_finish_plug(&plug);
  	put_parallel(par);
  	return PNFS_ATTEMPTED;
  }
  
  static void bl_end_io_write(struct bio *bio)
  {
  	struct parallel_io *par = bio->bi_private;
  	struct nfs_pgio_header *header = par->data;
  
  	if (bio->bi_error) {
  		if (!header->pnfs_error)
  			header->pnfs_error = -EIO;
  		pnfs_set_lo_fail(header->lseg);
  	}
  	bio_put(bio);
  	put_parallel(par);
  }
  
  /* Function scheduled for call during bl_end_par_io_write,
   * it marks sectors as written and extends the commitlist.
   */
  static void bl_write_cleanup(struct work_struct *work)
  {
  	struct rpc_task *task = container_of(work, struct rpc_task, u.tk_work);
  	struct nfs_pgio_header *hdr =
  			container_of(task, struct nfs_pgio_header, task);
  
  	dprintk("%s enter
  ", __func__);
  
  	if (likely(!hdr->pnfs_error)) {
  		struct pnfs_block_layout *bl = BLK_LSEG2EXT(hdr->lseg);
  		u64 start = hdr->args.offset & (loff_t)PAGE_CACHE_MASK;
  		u64 end = (hdr->args.offset + hdr->args.count +
  			PAGE_CACHE_SIZE - 1) & (loff_t)PAGE_CACHE_MASK;
  
  		ext_tree_mark_written(bl, start >> SECTOR_SHIFT,
  					(end - start) >> SECTOR_SHIFT);
  	}
  
  	pnfs_ld_write_done(hdr);
  }
  
  /* Called when last of bios associated with a bl_write_pagelist call finishes */
  static void bl_end_par_io_write(void *data)
  {
  	struct nfs_pgio_header *hdr = data;
  
  	hdr->task.tk_status = hdr->pnfs_error;
  	hdr->verf.committed = NFS_FILE_SYNC;
  	INIT_WORK(&hdr->task.u.tk_work, bl_write_cleanup);
  	schedule_work(&hdr->task.u.tk_work);
  }
  
  static enum pnfs_try_status
  bl_write_pagelist(struct nfs_pgio_header *header, int sync)
  {
  	struct pnfs_block_layout *bl = BLK_LSEG2EXT(header->lseg);
  	struct pnfs_block_dev_map map = { .start = NFS4_MAX_UINT64 };
  	struct bio *bio = NULL;
  	struct pnfs_block_extent be;
  	sector_t isect, extent_length = 0;
  	struct parallel_io *par = NULL;
  	loff_t offset = header->args.offset;
  	size_t count = header->args.count;
  	struct page **pages = header->args.pages;
  	int pg_index = header->args.pgbase >> PAGE_CACHE_SHIFT;
  	unsigned int pg_len;
  	struct blk_plug plug;
  	int i;
  
  	dprintk("%s enter, %Zu@%lld
  ", __func__, count, offset);
  
  	/* At this point, header->page_aray is a (sequential) list of nfs_pages.
  	 * We want to write each, and if there is an error set pnfs_error
  	 * to have it redone using nfs.
  	 */
  	par = alloc_parallel(header);
  	if (!par)
  		return PNFS_NOT_ATTEMPTED;
  	par->pnfs_callback = bl_end_par_io_write;
  
  	blk_start_plug(&plug);
  
  	/* we always write out the whole page */
  	offset = offset & (loff_t)PAGE_CACHE_MASK;
  	isect = offset >> SECTOR_SHIFT;
  
  	for (i = pg_index; i < header->page_array.npages; i++) {
  		if (extent_length <= 0) {
  			/* We've used up the previous extent */
  			bio = bl_submit_bio(WRITE, bio);
  			/* Get the next one */
  			if (!ext_tree_lookup(bl, isect, &be, true)) {
  				header->pnfs_error = -EINVAL;
  				goto out;
  			}
  
  			extent_length = be.be_length - (isect - be.be_f_offset);
  		}
  
  		pg_len = PAGE_CACHE_SIZE;
  		bio = do_add_page_to_bio(bio, header->page_array.npages - i,
  					 WRITE, isect, pages[i], &map, &be,
  					 bl_end_io_write, par,
  					 0, &pg_len);
  		if (IS_ERR(bio)) {
  			header->pnfs_error = PTR_ERR(bio);
  			bio = NULL;
  			goto out;
  		}
  
  		offset += pg_len;
  		count -= pg_len;
  		isect += (pg_len >> SECTOR_SHIFT);
  		extent_length -= (pg_len >> SECTOR_SHIFT);
  	}
  
  	header->res.count = header->args.count;
  out:
  	bl_submit_bio(WRITE, bio);
  	blk_finish_plug(&plug);
  	put_parallel(par);
  	return PNFS_ATTEMPTED;
  }
  
  static void bl_free_layout_hdr(struct pnfs_layout_hdr *lo)
  {
  	struct pnfs_block_layout *bl = BLK_LO2EXT(lo);
  	int err;
  
  	dprintk("%s enter
  ", __func__);
  
  	err = ext_tree_remove(bl, true, 0, LLONG_MAX);
  	WARN_ON(err);
  
  	kfree(bl);
  }
  
  static struct pnfs_layout_hdr *bl_alloc_layout_hdr(struct inode *inode,
  						   gfp_t gfp_flags)
  {
  	struct pnfs_block_layout *bl;
  
  	dprintk("%s enter
  ", __func__);
  	bl = kzalloc(sizeof(*bl), gfp_flags);
  	if (!bl)
  		return NULL;
  
  	bl->bl_ext_rw = RB_ROOT;
  	bl->bl_ext_ro = RB_ROOT;
  	spin_lock_init(&bl->bl_ext_lock);
  
  	return &bl->bl_layout;
  }
  
  static void bl_free_lseg(struct pnfs_layout_segment *lseg)
  {
  	dprintk("%s enter
  ", __func__);
  	kfree(lseg);
  }
  
  /* 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;
  }
  
  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
  ", __func__);
  		return -1;
  	}
  	*sp = s >> SECTOR_SHIFT;
  	return 0;
  }
  
  static int
  bl_alloc_extent(struct xdr_stream *xdr, struct pnfs_layout_hdr *lo,
  		struct layout_verification *lv, struct list_head *extents,
  		gfp_t gfp_mask)
  {
  	struct pnfs_block_extent *be;
  	struct nfs4_deviceid id;
  	int error;
  	__be32 *p;
  
  	p = xdr_inline_decode(xdr, 28 + NFS4_DEVICEID4_SIZE);
  	if (!p)
  		return -EIO;
  
  	be = kzalloc(sizeof(*be), GFP_NOFS);
  	if (!be)
  		return -ENOMEM;
  
  	memcpy(&id, p, NFS4_DEVICEID4_SIZE);
  	p += XDR_QUADLEN(NFS4_DEVICEID4_SIZE);
  
  	error = -EIO;
  	be->be_device = nfs4_find_get_deviceid(NFS_SERVER(lo->plh_inode), &id,
  						lo->plh_lc_cred, gfp_mask);
  	if (!be->be_device)
  		goto out_free_be;
  
  	/*
  	 * The next three values are read in as bytes, but stored in the
  	 * extent structure in 512-byte granularity.
  	 */
  	if (decode_sector_number(&p, &be->be_f_offset) < 0)
  		goto out_put_deviceid;
  	if (decode_sector_number(&p, &be->be_length) < 0)
  		goto out_put_deviceid;
  	if (decode_sector_number(&p, &be->be_v_offset) < 0)
  		goto out_put_deviceid;
  	be->be_state = be32_to_cpup(p++);
  
  	error = verify_extent(be, lv);
  	if (error) {
  		dprintk("%s: extent verification failed
  ", __func__);
  		goto out_put_deviceid;
  	}
  
  	list_add_tail(&be->be_list, extents);
  	return 0;
  
  out_put_deviceid:
  	nfs4_put_deviceid_node(be->be_device);
  out_free_be:
  	kfree(be);
  	return error;
  }
  
  static struct pnfs_layout_segment *
  bl_alloc_lseg(struct pnfs_layout_hdr *lo, struct nfs4_layoutget_res *lgr,
  		gfp_t gfp_mask)
  {
  	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,
  	};
  	struct pnfs_block_layout *bl = BLK_LO2EXT(lo);
  	struct pnfs_layout_segment *lseg;
  	struct xdr_buf buf;
  	struct xdr_stream xdr;
  	struct page *scratch;
  	int status, i;
  	uint32_t count;
  	__be32 *p;
  	LIST_HEAD(extents);
  
  	dprintk("---> %s
  ", __func__);
  
  	lseg = kzalloc(sizeof(*lseg), gfp_mask);
  	if (!lseg)
  		return ERR_PTR(-ENOMEM);
  
  	status = -ENOMEM;
  	scratch = alloc_page(gfp_mask);
  	if (!scratch)
  		goto out;
  
  	xdr_init_decode_pages(&xdr, &buf,
  			lgr->layoutp->pages, lgr->layoutp->len);
  	xdr_set_scratch_buffer(&xdr, page_address(scratch), PAGE_SIZE);
  
  	status = -EIO;
  	p = xdr_inline_decode(&xdr, 4);
  	if (unlikely(!p))
  		goto out_free_scratch;
  
  	count = be32_to_cpup(p++);
  	dprintk("%s: number of extents %d
  ", __func__, count);
  
  	/*
  	 * 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++) {
  		status = bl_alloc_extent(&xdr, lo, &lv, &extents, gfp_mask);
  		if (status)
  			goto process_extents;
  	}
  
  	if (lgr->range.offset + lgr->range.length !=
  			lv.start << SECTOR_SHIFT) {
  		dprintk("%s Final length mismatch
  ", __func__);
  		status = -EIO;
  		goto process_extents;
  	}
  
  	if (lv.start < lv.cowread) {
  		dprintk("%s Final uncovered COW extent
  ", __func__);
  		status = -EIO;
  	}
  
  process_extents:
  	while (!list_empty(&extents)) {
  		struct pnfs_block_extent *be =
  			list_first_entry(&extents, struct pnfs_block_extent,
  					 be_list);
  		list_del(&be->be_list);
  
  		if (!status)
  			status = ext_tree_insert(bl, be);
  
  		if (status) {
  			nfs4_put_deviceid_node(be->be_device);
  			kfree(be);
  		}
  	}
  
  out_free_scratch:
  	__free_page(scratch);
  out:
  	dprintk("%s returns %d
  ", __func__, status);
  	if (status) {
  		kfree(lseg);
  		return ERR_PTR(status);
  	}
  	return lseg;
  }
  
  static void
  bl_return_range(struct pnfs_layout_hdr *lo,
  		struct pnfs_layout_range *range)
  {
  	struct pnfs_block_layout *bl = BLK_LO2EXT(lo);
  	sector_t offset = range->offset >> SECTOR_SHIFT, end;
  
  	if (range->offset % 8) {
  		dprintk("%s: offset %lld not block size aligned
  ",
  			__func__, range->offset);
  		return;
  	}
  
  	if (range->length != NFS4_MAX_UINT64) {
  		if (range->length % 8) {
  			dprintk("%s: length %lld not block size aligned
  ",
  				__func__, range->length);
  			return;
  		}
  
  		end = offset + (range->length >> SECTOR_SHIFT);
  	} else {
  		end = round_down(NFS4_MAX_UINT64, PAGE_SIZE);
  	}
  
  	ext_tree_remove(bl, range->iomode & IOMODE_RW, offset, end);
  }
  
  static int
  bl_prepare_layoutcommit(struct nfs4_layoutcommit_args *arg)
  {
  	return ext_tree_prepare_commit(arg);
  }
  
  static void
  bl_cleanup_layoutcommit(struct nfs4_layoutcommit_data *lcdata)
  {
  	ext_tree_mark_committed(&lcdata->args, lcdata->res.status);
  }
  
  static int
  bl_set_layoutdriver(struct nfs_server *server, const struct nfs_fh *fh)
  {
  	dprintk("%s enter
  ", __func__);
  
  	if (server->pnfs_blksize == 0) {
  		dprintk("%s Server did not return blksize
  ", __func__);
  		return -EINVAL;
  	}
  	if (server->pnfs_blksize > PAGE_SIZE) {
  		printk(KERN_ERR "%s: pNFS blksize %d not supported.
  ",
  			__func__, server->pnfs_blksize);
  		return -EINVAL;
  	}
  
  	return 0;
  }
  
  static bool
  is_aligned_req(struct nfs_pageio_descriptor *pgio,
  		struct nfs_page *req, unsigned int alignment)
  {
  	/*
  	 * Always accept buffered writes, higher layers take care of the
  	 * right alignment.
  	 */
  	if (pgio->pg_dreq == NULL)
  		return true;
  
  	if (!IS_ALIGNED(req->wb_offset, alignment))
  		return false;
  
  	if (IS_ALIGNED(req->wb_bytes, alignment))
  		return true;
  
  	if (req_offset(req) + req->wb_bytes == i_size_read(pgio->pg_inode)) {
  		/*
  		 * If the write goes up to the inode size, just write
  		 * the full page.  Data past the inode size is
  		 * guaranteed to be zeroed by the higher level client
  		 * code, and this behaviour is mandated by RFC 5663
  		 * section 2.3.2.
  		 */
  		return true;
  	}
  
  	return false;
  }
  
  static void
  bl_pg_init_read(struct nfs_pageio_descriptor *pgio, struct nfs_page *req)
  {
  	if (!is_aligned_req(pgio, req, SECTOR_SIZE)) {
  		nfs_pageio_reset_read_mds(pgio);
  		return;
  	}
  
  	pnfs_generic_pg_init_read(pgio, req);
  }
  
  /*
   * 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
  bl_pg_test_read(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
  		struct nfs_page *req)
  {
  	if (!is_aligned_req(pgio, req, SECTOR_SIZE))
  		return 0;
  	return pnfs_generic_pg_test(pgio, prev, req);
  }
  
  /*
   * Return the number of contiguous bytes for a given inode
   * starting at page frame idx.
   */
  static u64 pnfs_num_cont_bytes(struct inode *inode, pgoff_t idx)
  {
  	struct address_space *mapping = inode->i_mapping;
  	pgoff_t end;
  
  	/* Optimize common case that writes from 0 to end of file */
  	end = DIV_ROUND_UP(i_size_read(inode), PAGE_CACHE_SIZE);
  	if (end != inode->i_mapping->nrpages) {
  		rcu_read_lock();
  		end = page_cache_next_hole(mapping, idx + 1, ULONG_MAX);
  		rcu_read_unlock();
  	}
  
  	if (!end)
  		return i_size_read(inode) - (idx << PAGE_CACHE_SHIFT);
  	else
  		return (end - idx) << PAGE_CACHE_SHIFT;
  }
  
  static void
  bl_pg_init_write(struct nfs_pageio_descriptor *pgio, struct nfs_page *req)
  {
  	u64 wb_size;
  
  	if (!is_aligned_req(pgio, req, PAGE_SIZE)) {
  		nfs_pageio_reset_write_mds(pgio);
  		return;
  	}
  
  	if (pgio->pg_dreq == NULL)
  		wb_size = pnfs_num_cont_bytes(pgio->pg_inode,
  					      req->wb_index);
  	else
  		wb_size = nfs_dreq_bytes_left(pgio->pg_dreq);
  
  	pnfs_generic_pg_init_write(pgio, req, wb_size);
  }
  
  /*
   * 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
  bl_pg_test_write(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
  		 struct nfs_page *req)
  {
  	if (!is_aligned_req(pgio, req, PAGE_SIZE))
  		return 0;
  	return pnfs_generic_pg_test(pgio, prev, req);
  }
  
  static const struct nfs_pageio_ops bl_pg_read_ops = {
  	.pg_init = bl_pg_init_read,
  	.pg_test = bl_pg_test_read,
  	.pg_doio = pnfs_generic_pg_readpages,
  	.pg_cleanup = pnfs_generic_pg_cleanup,
  };
  
  static const struct nfs_pageio_ops bl_pg_write_ops = {
  	.pg_init = bl_pg_init_write,
  	.pg_test = bl_pg_test_write,
  	.pg_doio = pnfs_generic_pg_writepages,
  	.pg_cleanup = pnfs_generic_pg_cleanup,
  };
  
  static struct pnfs_layoutdriver_type blocklayout_type = {
  	.id				= LAYOUT_BLOCK_VOLUME,
  	.name				= "LAYOUT_BLOCK_VOLUME",
  	.owner				= THIS_MODULE,
  	.flags				= PNFS_LAYOUTRET_ON_SETATTR |
  					  PNFS_READ_WHOLE_PAGE,
  	.read_pagelist			= bl_read_pagelist,
  	.write_pagelist			= bl_write_pagelist,
  	.alloc_layout_hdr		= bl_alloc_layout_hdr,
  	.free_layout_hdr		= bl_free_layout_hdr,
  	.alloc_lseg			= bl_alloc_lseg,
  	.free_lseg			= bl_free_lseg,
  	.return_range			= bl_return_range,
  	.prepare_layoutcommit		= bl_prepare_layoutcommit,
  	.cleanup_layoutcommit		= bl_cleanup_layoutcommit,
  	.set_layoutdriver		= bl_set_layoutdriver,
  	.alloc_deviceid_node		= bl_alloc_deviceid_node,
  	.free_deviceid_node		= bl_free_deviceid_node,
  	.pg_read_ops			= &bl_pg_read_ops,
  	.pg_write_ops			= &bl_pg_write_ops,
  	.sync				= pnfs_generic_sync,
  };
  
  static int __init nfs4blocklayout_init(void)
  {
  	int ret;
  
  	dprintk("%s: NFSv4 Block Layout Driver Registering...
  ", __func__);
  
  	ret = pnfs_register_layoutdriver(&blocklayout_type);
  	if (ret)
  		goto out;
  	ret = bl_init_pipefs();
  	if (ret)
  		goto out_unregister;
  	return 0;
  
  out_unregister:
  	pnfs_unregister_layoutdriver(&blocklayout_type);
  out:
  	return ret;
  }
  
  static void __exit nfs4blocklayout_exit(void)
  {
  	dprintk("%s: NFSv4 Block Layout Driver Unregistering...
  ",
  	       __func__);
  
  	bl_cleanup_pipefs();
  	pnfs_unregister_layoutdriver(&blocklayout_type);
  }
  
  MODULE_ALIAS("nfs-layouttype4-3");
  
  module_init(nfs4blocklayout_init);
  module_exit(nfs4blocklayout_exit);