/*
 *  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\n", __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\n", __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\n", __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\n", __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_SHIFT;
        const bool is_dio = (header->dreq != NULL);
        struct blk_plug plug;
        int i;

        dprintk("%s enter nr_pages %u offset %lld count %u\n", __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_SIZE)
                                pg_len = PAGE_SIZE - pg_offset;
                        else
                                pg_len = bytes_left;
                } else {
                        BUG_ON(pg_offset != 0);
                        pg_len = PAGE_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\n", __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\n", __func__);

        if (likely(!hdr->pnfs_error)) {
                struct pnfs_block_layout *bl = BLK_LSEG2EXT(hdr->lseg);
                u64 start = hdr->args.offset & (loff_t)PAGE_MASK;
                u64 end = (hdr->args.offset + hdr->args.count +
                        PAGE_SIZE - 1) & (loff_t)PAGE_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_SHIFT;
        unsigned int pg_len;
        struct blk_plug plug;
        int i;

        dprintk("%s enter, %Zu@%lld\n", __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_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_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\n", __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, bool is_scsi_layout)
{
        struct pnfs_block_layout *bl;

        dprintk("%s enter\n", __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);

        bl->bl_scsi_layout = is_scsi_layout;
        return &bl->bl_layout;
}

static struct pnfs_layout_hdr *bl_alloc_layout_hdr(struct inode *inode,
                                                   gfp_t gfp_flags)
{
        return __bl_alloc_layout_hdr(inode, gfp_flags, false);
}

static struct pnfs_layout_hdr *sl_alloc_layout_hdr(struct inode *inode,
                                                   gfp_t gfp_flags)
{
        return __bl_alloc_layout_hdr(inode, gfp_flags, true);
}

static void bl_free_lseg(struct pnfs_layout_segment *lseg)
{
        dprintk("%s enter\n", __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\n", __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\n", __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\n", __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\n", __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\n", __func__);
                status = -EIO;
                goto process_extents;
        }

        if (lv.start < lv.cowread) {
                dprintk("%s Final uncovered COW extent\n", __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\n", __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\n",
                        __func__, range->offset);
                return;
        }

        if (range->length != NFS4_MAX_UINT64) {
                if (range->length % 8) {
                        dprintk("%s: length %lld not block size aligned\n",
                                __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\n", __func__);

        if (server->pnfs_blksize == 0) {
                dprintk("%s Server did not return blksize\n", __func__);
                return -EINVAL;
        }
        if (server->pnfs_blksize > PAGE_SIZE) {
                printk(KERN_ERR "%s: pNFS blksize %d not supported.\n",
                        __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, bool is_write)
{
        /*
         * 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 (is_write &&
            (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, false)) {
                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, false))
                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_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_SHIFT);
        else
                return (end - idx) << PAGE_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, true)) {
                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, true))
                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 struct pnfs_layoutdriver_type scsilayout_type = {
        .id                             = LAYOUT_SCSI,
        .name                           = "LAYOUT_SCSI",
        .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               = sl_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...\n", __func__);

        ret = bl_init_pipefs();
        if (ret)
                goto out;

        ret = pnfs_register_layoutdriver(&blocklayout_type);
        if (ret)
                goto out_cleanup_pipe;

        ret = pnfs_register_layoutdriver(&scsilayout_type);
        if (ret)
                goto out_unregister_block;
        return 0;

out_unregister_block:
        pnfs_unregister_layoutdriver(&blocklayout_type);
out_cleanup_pipe:
        bl_cleanup_pipefs();
out:
        return ret;
}

static void __exit nfs4blocklayout_exit(void)
{
        dprintk("%s: NFSv4 Block Layout Driver Unregistering...\n",
               __func__);

        pnfs_unregister_layoutdriver(&scsilayout_type);
        pnfs_unregister_layoutdriver(&blocklayout_type);
        bl_cleanup_pipefs();
}

MODULE_ALIAS("nfs-layouttype4-3");

module_init(nfs4blocklayout_init);
module_exit(nfs4blocklayout_exit);