Merge tag 'for-v3.8-part2' of git://git.infradead.org/battery-2.6

[mirror_ubuntu-artful-kernel.git] / fs / nfs / blocklayout / blocklayout.c

/*
 *  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/buffer_head.h>  /* various write calls */
#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 void print_page(struct page *page)
{
        dprintk("PRINTPAGE page %p\n", page);
        dprintk("       PagePrivate %d\n", PagePrivate(page));
        dprintk("       PageUptodate %d\n", PageUptodate(page));
        dprintk("       PageError %d\n", PageError(page));
        dprintk("       PageDirty %d\n", PageDirty(page));
        dprintk("       PageReferenced %d\n", PageReferenced(page));
        dprintk("       PageLocked %d\n", PageLocked(page));
        dprintk("       PageWriteback %d\n", PageWriteback(page));
        dprintk("       PageMappedToDisk %d\n", PageMappedToDisk(page));
        dprintk("\n");
}

/* Given the be associated with isect, determine if page data needs to be
 * initialized.
 */
static int is_hole(struct pnfs_block_extent *be, sector_t isect)
{
        if (be->be_state == PNFS_BLOCK_NONE_DATA)
                return 1;
        else if (be->be_state != PNFS_BLOCK_INVALID_DATA)
                return 0;
        else
                return !bl_is_sector_init(be->be_inval, isect);
}

/* Given the be associated with isect, determine if page data can be
 * written to disk.
 */
static int is_writable(struct pnfs_block_extent *be, sector_t isect)
{
        return (be->be_state == PNFS_BLOCK_READWRITE_DATA ||
                be->be_state == PNFS_BLOCK_INVALID_DATA);
}

/* 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, int num_se);
        void *data;
        int bse_count;
};

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);
                rv->bse_count = 0;
        }
        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, p->bse_count);
        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_size, (unsigned long long)bio->bi_sector);
                submit_bio(rw, bio);
        }
        return NULL;
}

static struct bio *bl_alloc_init_bio(int npg, sector_t isect,
                                     struct pnfs_block_extent *be,
                                     void (*end_io)(struct bio *, int err),
                                     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_sector = isect - be->be_f_offset + be->be_v_offset;
                bio->bi_bdev = be->be_mdev;
                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_extent *be,
                                      void (*end_io)(struct bio *, int err),
                                      struct parallel_io *par,
                                      unsigned int offset, int len)
{
        isect = isect + (offset >> SECTOR_SHIFT);
        dprintk("%s: npg %d rw %d isect %llu offset %u len %d\n", __func__,
                npg, rw, (unsigned long long)isect, offset, len);
retry:
        if (!bio) {
                bio = bl_alloc_init_bio(npg, isect, be, 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 struct bio *bl_add_page_to_bio(struct bio *bio, int npg, int rw,
                                      sector_t isect, struct page *page,
                                      struct pnfs_block_extent *be,
                                      void (*end_io)(struct bio *, int err),
                                      struct parallel_io *par)
{
        return do_add_page_to_bio(bio, npg, rw, isect, page, be,
                                  end_io, par, 0, PAGE_CACHE_SIZE);
}

/* This is basically copied from mpage_end_io_read */
static void bl_end_io_read(struct bio *bio, int err)
{
        struct parallel_io *par = bio->bi_private;
        const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
        struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;

        do {
                struct page *page = bvec->bv_page;

                if (--bvec >= bio->bi_io_vec)
                        prefetchw(&bvec->bv_page->flags);
                if (uptodate)
                        SetPageUptodate(page);
        } while (bvec >= bio->bi_io_vec);
        if (!uptodate) {
                struct nfs_read_data *rdata = par->data;
                struct nfs_pgio_header *header = rdata->header;

                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_read_data *rdata;
        dprintk("%s enter\n", __func__);
        task = container_of(work, struct rpc_task, u.tk_work);
        rdata = container_of(task, struct nfs_read_data, task);
        pnfs_ld_read_done(rdata);
}

static void
bl_end_par_io_read(void *data, int unused)
{
        struct nfs_read_data *rdata = data;

        rdata->task.tk_status = rdata->header->pnfs_error;
        INIT_WORK(&rdata->task.u.tk_work, bl_read_cleanup);
        schedule_work(&rdata->task.u.tk_work);
}

static enum pnfs_try_status
bl_read_pagelist(struct nfs_read_data *rdata)
{
        struct nfs_pgio_header *header = rdata->header;
        int i, hole;
        struct bio *bio = NULL;
        struct pnfs_block_extent *be = NULL, *cow_read = NULL;
        sector_t isect, extent_length = 0;
        struct parallel_io *par;
        loff_t f_offset = rdata->args.offset;
        size_t bytes_left = rdata->args.count;
        unsigned int pg_offset, pg_len;
        struct page **pages = rdata->args.pages;
        int pg_index = rdata->args.pgbase >> PAGE_CACHE_SHIFT;
        const bool is_dio = (header->dreq != NULL);

        dprintk("%s enter nr_pages %u offset %lld count %u\n", __func__,
               rdata->pages.npages, f_offset, (unsigned int)rdata->args.count);

        par = alloc_parallel(rdata);
        if (!par)
                goto use_mds;
        par->pnfs_callback = bl_end_par_io_read;
        /* At this point, we can no longer jump to use_mds */

        isect = (sector_t) (f_offset >> SECTOR_SHIFT);
        /* Code assumes extents are page-aligned */
        for (i = pg_index; i < rdata->pages.npages; i++) {
                if (!extent_length) {
                        /* We've used up the previous extent */
                        bl_put_extent(be);
                        bl_put_extent(cow_read);
                        bio = bl_submit_bio(READ, bio);
                        /* Get the next one */
                        be = bl_find_get_extent(BLK_LSEG2EXT(header->lseg),
                                             isect, &cow_read);
                        if (!be) {
                                header->pnfs_error = -EIO;
                                goto out;
                        }
                        extent_length = be->be_length -
                                (isect - be->be_f_offset);
                        if (cow_read) {
                                sector_t cow_length = cow_read->be_length -
                                        (isect - cow_read->be_f_offset);
                                extent_length = min(extent_length, cow_length);
                        }
                }

                if (is_dio) {
                        pg_offset = f_offset & ~PAGE_CACHE_MASK;
                        if (pg_offset + bytes_left > PAGE_CACHE_SIZE)
                                pg_len = PAGE_CACHE_SIZE - pg_offset;
                        else
                                pg_len = bytes_left;

                        f_offset += pg_len;
                        bytes_left -= pg_len;
                        isect += (pg_offset >> SECTOR_SHIFT);
                } else {
                        pg_offset = 0;
                        pg_len = PAGE_CACHE_SIZE;
                }

                hole = is_hole(be, isect);
                if (hole && !cow_read) {
                        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);
                        print_page(pages[i]);
                        SetPageUptodate(pages[i]);
                } else {
                        struct pnfs_block_extent *be_read;

                        be_read = (hole && cow_read) ? cow_read : be;
                        bio = do_add_page_to_bio(bio, rdata->pages.npages - i,
                                                 READ,
                                                 isect, pages[i], be_read,
                                                 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 -= PAGE_CACHE_SECTORS;
        }
        if ((isect << SECTOR_SHIFT) >= header->inode->i_size) {
                rdata->res.eof = 1;
                rdata->res.count = header->inode->i_size - rdata->args.offset;
        } else {
                rdata->res.count = (isect << SECTOR_SHIFT) - rdata->args.offset;
        }
out:
        bl_put_extent(be);
        bl_put_extent(cow_read);
        bl_submit_bio(READ, bio);
        put_parallel(par);
        return PNFS_ATTEMPTED;

 use_mds:
        dprintk("Giving up and using normal NFS\n");
        return PNFS_NOT_ATTEMPTED;
}

static void mark_extents_written(struct pnfs_block_layout *bl,
                                 __u64 offset, __u32 count)
{
        sector_t isect, end;
        struct pnfs_block_extent *be;
        struct pnfs_block_short_extent *se;

        dprintk("%s(%llu, %u)\n", __func__, offset, count);
        if (count == 0)
                return;
        isect = (offset & (long)(PAGE_CACHE_MASK)) >> SECTOR_SHIFT;
        end = (offset + count + PAGE_CACHE_SIZE - 1) & (long)(PAGE_CACHE_MASK);
        end >>= SECTOR_SHIFT;
        while (isect < end) {
                sector_t len;
                be = bl_find_get_extent(bl, isect, NULL);
                BUG_ON(!be); /* FIXME */
                len = min(end, be->be_f_offset + be->be_length) - isect;
                if (be->be_state == PNFS_BLOCK_INVALID_DATA) {
                        se = bl_pop_one_short_extent(be->be_inval);
                        BUG_ON(!se);
                        bl_mark_for_commit(be, isect, len, se);
                }
                isect += len;
                bl_put_extent(be);
        }
}

static void bl_end_io_write_zero(struct bio *bio, int err)
{
        struct parallel_io *par = bio->bi_private;
        const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
        struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;

        do {
                struct page *page = bvec->bv_page;

                if (--bvec >= bio->bi_io_vec)
                        prefetchw(&bvec->bv_page->flags);
                /* This is the zeroing page we added */
                end_page_writeback(page);
                page_cache_release(page);
        } while (bvec >= bio->bi_io_vec);

        if (unlikely(!uptodate)) {
                struct nfs_write_data *data = par->data;
                struct nfs_pgio_header *header = data->header;

                if (!header->pnfs_error)
                        header->pnfs_error = -EIO;
                pnfs_set_lo_fail(header->lseg);
        }
        bio_put(bio);
        put_parallel(par);
}

static void bl_end_io_write(struct bio *bio, int err)
{
        struct parallel_io *par = bio->bi_private;
        const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
        struct nfs_write_data *data = par->data;
        struct nfs_pgio_header *header = data->header;

        if (!uptodate) {
                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;
        struct nfs_write_data *wdata;
        dprintk("%s enter\n", __func__);
        task = container_of(work, struct rpc_task, u.tk_work);
        wdata = container_of(task, struct nfs_write_data, task);
        if (likely(!wdata->header->pnfs_error)) {
                /* Marks for LAYOUTCOMMIT */
                mark_extents_written(BLK_LSEG2EXT(wdata->header->lseg),
                                     wdata->args.offset, wdata->args.count);
        }
        pnfs_ld_write_done(wdata);
}

/* Called when last of bios associated with a bl_write_pagelist call finishes */
static void bl_end_par_io_write(void *data, int num_se)
{
        struct nfs_write_data *wdata = data;

        if (unlikely(wdata->header->pnfs_error)) {
                bl_free_short_extents(&BLK_LSEG2EXT(wdata->header->lseg)->bl_inval,
                                        num_se);
        }

        wdata->task.tk_status = wdata->header->pnfs_error;
        wdata->verf.committed = NFS_FILE_SYNC;
        INIT_WORK(&wdata->task.u.tk_work, bl_write_cleanup);
        schedule_work(&wdata->task.u.tk_work);
}

/* FIXME STUB - mark intersection of layout and page as bad, so is not
 * used again.
 */
static void mark_bad_read(void)
{
        return;
}

/*
 * map_block:  map a requested I/0 block (isect) into an offset in the LVM
 * block_device
 */
static void
map_block(struct buffer_head *bh, sector_t isect, struct pnfs_block_extent *be)
{
        dprintk("%s enter be=%p\n", __func__, be);

        set_buffer_mapped(bh);
        bh->b_bdev = be->be_mdev;
        bh->b_blocknr = (isect - be->be_f_offset + be->be_v_offset) >>
            (be->be_mdev->bd_inode->i_blkbits - SECTOR_SHIFT);

        dprintk("%s isect %llu, bh->b_blocknr %ld, using bsize %Zd\n",
                __func__, (unsigned long long)isect, (long)bh->b_blocknr,
                bh->b_size);
        return;
}

static void
bl_read_single_end_io(struct bio *bio, int error)
{
        struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
        struct page *page = bvec->bv_page;

        /* Only one page in bvec */
        unlock_page(page);
}

static int
bl_do_readpage_sync(struct page *page, struct pnfs_block_extent *be,
                    unsigned int offset, unsigned int len)
{
        struct bio *bio;
        struct page *shadow_page;
        sector_t isect;
        char *kaddr, *kshadow_addr;
        int ret = 0;

        dprintk("%s: offset %u len %u\n", __func__, offset, len);

        shadow_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
        if (shadow_page == NULL)
                return -ENOMEM;

        bio = bio_alloc(GFP_NOIO, 1);
        if (bio == NULL)
                return -ENOMEM;

        isect = (page->index << PAGE_CACHE_SECTOR_SHIFT) +
                (offset / SECTOR_SIZE);

        bio->bi_sector = isect - be->be_f_offset + be->be_v_offset;
        bio->bi_bdev = be->be_mdev;
        bio->bi_end_io = bl_read_single_end_io;

        lock_page(shadow_page);
        if (bio_add_page(bio, shadow_page,
                         SECTOR_SIZE, round_down(offset, SECTOR_SIZE)) == 0) {
                unlock_page(shadow_page);
                bio_put(bio);
                return -EIO;
        }

        submit_bio(READ, bio);
        wait_on_page_locked(shadow_page);
        if (unlikely(!test_bit(BIO_UPTODATE, &bio->bi_flags))) {
                ret = -EIO;
        } else {
                kaddr = kmap_atomic(page);
                kshadow_addr = kmap_atomic(shadow_page);
                memcpy(kaddr + offset, kshadow_addr + offset, len);
                kunmap_atomic(kshadow_addr);
                kunmap_atomic(kaddr);
        }
        __free_page(shadow_page);
        bio_put(bio);

        return ret;
}

static int
bl_read_partial_page_sync(struct page *page, struct pnfs_block_extent *be,
                          unsigned int dirty_offset, unsigned int dirty_len,
                          bool full_page)
{
        int ret = 0;
        unsigned int start, end;

        if (full_page) {
                start = 0;
                end = PAGE_CACHE_SIZE;
        } else {
                start = round_down(dirty_offset, SECTOR_SIZE);
                end = round_up(dirty_offset + dirty_len, SECTOR_SIZE);
        }

        dprintk("%s: offset %u len %d\n", __func__, dirty_offset, dirty_len);
        if (!be) {
                zero_user_segments(page, start, dirty_offset,
                                   dirty_offset + dirty_len, end);
                if (start == 0 && end == PAGE_CACHE_SIZE &&
                    trylock_page(page)) {
                        SetPageUptodate(page);
                        unlock_page(page);
                }
                return ret;
        }

        if (start != dirty_offset)
                ret = bl_do_readpage_sync(page, be, start, dirty_offset - start);

        if (!ret && (dirty_offset + dirty_len < end))
                ret = bl_do_readpage_sync(page, be, dirty_offset + dirty_len,
                                          end - dirty_offset - dirty_len);

        return ret;
}

/* Given an unmapped page, zero it or read in page for COW, page is locked
 * by caller.
 */
static int
init_page_for_write(struct page *page, struct pnfs_block_extent *cow_read)
{
        struct buffer_head *bh = NULL;
        int ret = 0;
        sector_t isect;

        dprintk("%s enter, %p\n", __func__, page);
        BUG_ON(PageUptodate(page));
        if (!cow_read) {
                zero_user_segment(page, 0, PAGE_SIZE);
                SetPageUptodate(page);
                goto cleanup;
        }

        bh = alloc_page_buffers(page, PAGE_CACHE_SIZE, 0);
        if (!bh) {
                ret = -ENOMEM;
                goto cleanup;
        }

        isect = (sector_t) page->index << PAGE_CACHE_SECTOR_SHIFT;
        map_block(bh, isect, cow_read);
        if (!bh_uptodate_or_lock(bh))
                ret = bh_submit_read(bh);
        if (ret)
                goto cleanup;
        SetPageUptodate(page);

cleanup:
        if (bh)
                free_buffer_head(bh);
        if (ret) {
                /* Need to mark layout with bad read...should now
                 * just use nfs4 for reads and writes.
                 */
                mark_bad_read();
        }
        return ret;
}

/* Find or create a zeroing page marked being writeback.
 * Return ERR_PTR on error, NULL to indicate skip this page and page itself
 * to indicate write out.
 */
static struct page *
bl_find_get_zeroing_page(struct inode *inode, pgoff_t index,
                        struct pnfs_block_extent *cow_read)
{
        struct page *page;
        int locked = 0;
        page = find_get_page(inode->i_mapping, index);
        if (page)
                goto check_page;

        page = find_or_create_page(inode->i_mapping, index, GFP_NOFS);
        if (unlikely(!page)) {
                dprintk("%s oom\n", __func__);
                return ERR_PTR(-ENOMEM);
        }
        locked = 1;

check_page:
        /* PageDirty: Other will write this out
         * PageWriteback: Other is writing this out
         * PageUptodate: It was read before
         */
        if (PageDirty(page) || PageWriteback(page)) {
                print_page(page);
                if (locked)
                        unlock_page(page);
                page_cache_release(page);
                return NULL;
        }

        if (!locked) {
                lock_page(page);
                locked = 1;
                goto check_page;
        }
        if (!PageUptodate(page)) {
                /* New page, readin or zero it */
                init_page_for_write(page, cow_read);
        }
        set_page_writeback(page);
        unlock_page(page);

        return page;
}

static enum pnfs_try_status
bl_write_pagelist(struct nfs_write_data *wdata, int sync)
{
        struct nfs_pgio_header *header = wdata->header;
        int i, ret, npg_zero, pg_index, last = 0;
        struct bio *bio = NULL;
        struct pnfs_block_extent *be = NULL, *cow_read = NULL;
        sector_t isect, last_isect = 0, extent_length = 0;
        struct parallel_io *par = NULL;
        loff_t offset = wdata->args.offset;
        size_t count = wdata->args.count;
        unsigned int pg_offset, pg_len, saved_len;
        struct page **pages = wdata->args.pages;
        struct page *page;
        pgoff_t index;
        u64 temp;
        int npg_per_block =
            NFS_SERVER(header->inode)->pnfs_blksize >> PAGE_CACHE_SHIFT;

        dprintk("%s enter, %Zu@%lld\n", __func__, count, offset);

        if (header->dreq != NULL &&
            (!IS_ALIGNED(offset, NFS_SERVER(header->inode)->pnfs_blksize) ||
             !IS_ALIGNED(count, NFS_SERVER(header->inode)->pnfs_blksize))) {
                dprintk("pnfsblock nonblock aligned DIO writes. Resend MDS\n");
                goto out_mds;
        }
        /* At this point, wdata->pages 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(wdata);
        if (!par)
                goto out_mds;
        par->pnfs_callback = bl_end_par_io_write;
        /* At this point, have to be more careful with error handling */

        isect = (sector_t) ((offset & (long)PAGE_CACHE_MASK) >> SECTOR_SHIFT);
        be = bl_find_get_extent(BLK_LSEG2EXT(header->lseg), isect, &cow_read);
        if (!be || !is_writable(be, isect)) {
                dprintk("%s no matching extents!\n", __func__);
                goto out_mds;
        }

        /* First page inside INVALID extent */
        if (be->be_state == PNFS_BLOCK_INVALID_DATA) {
                if (likely(!bl_push_one_short_extent(be->be_inval)))
                        par->bse_count++;
                else
                        goto out_mds;
                temp = offset >> PAGE_CACHE_SHIFT;
                npg_zero = do_div(temp, npg_per_block);
                isect = (sector_t) (((offset - npg_zero * PAGE_CACHE_SIZE) &
                                     (long)PAGE_CACHE_MASK) >> SECTOR_SHIFT);
                extent_length = be->be_length - (isect - be->be_f_offset);

fill_invalid_ext:
                dprintk("%s need to zero %d pages\n", __func__, npg_zero);
                for (;npg_zero > 0; npg_zero--) {
                        if (bl_is_sector_init(be->be_inval, isect)) {
                                dprintk("isect %llu already init\n",
                                        (unsigned long long)isect);
                                goto next_page;
                        }
                        /* page ref released in bl_end_io_write_zero */
                        index = isect >> PAGE_CACHE_SECTOR_SHIFT;
                        dprintk("%s zero %dth page: index %lu isect %llu\n",
                                __func__, npg_zero, index,
                                (unsigned long long)isect);
                        page = bl_find_get_zeroing_page(header->inode, index,
                                                        cow_read);
                        if (unlikely(IS_ERR(page))) {
                                header->pnfs_error = PTR_ERR(page);
                                goto out;
                        } else if (page == NULL)
                                goto next_page;

                        ret = bl_mark_sectors_init(be->be_inval, isect,
                                                       PAGE_CACHE_SECTORS);
                        if (unlikely(ret)) {
                                dprintk("%s bl_mark_sectors_init fail %d\n",
                                        __func__, ret);
                                end_page_writeback(page);
                                page_cache_release(page);
                                header->pnfs_error = ret;
                                goto out;
                        }
                        if (likely(!bl_push_one_short_extent(be->be_inval)))
                                par->bse_count++;
                        else {
                                end_page_writeback(page);
                                page_cache_release(page);
                                header->pnfs_error = -ENOMEM;
                                goto out;
                        }
                        /* FIXME: This should be done in bi_end_io */
                        mark_extents_written(BLK_LSEG2EXT(header->lseg),
                                             page->index << PAGE_CACHE_SHIFT,
                                             PAGE_CACHE_SIZE);

                        bio = bl_add_page_to_bio(bio, npg_zero, WRITE,
                                                 isect, page, be,
                                                 bl_end_io_write_zero, par);
                        if (IS_ERR(bio)) {
                                header->pnfs_error = PTR_ERR(bio);
                                bio = NULL;
                                goto out;
                        }
next_page:
                        isect += PAGE_CACHE_SECTORS;
                        extent_length -= PAGE_CACHE_SECTORS;
                }
                if (last)
                        goto write_done;
        }
        bio = bl_submit_bio(WRITE, bio);

        /* Middle pages */
        pg_index = wdata->args.pgbase >> PAGE_CACHE_SHIFT;
        for (i = pg_index; i < wdata->pages.npages; i++) {
                if (!extent_length) {
                        /* We've used up the previous extent */
                        bl_put_extent(be);
                        bl_put_extent(cow_read);
                        bio = bl_submit_bio(WRITE, bio);
                        /* Get the next one */
                        be = bl_find_get_extent(BLK_LSEG2EXT(header->lseg),
                                             isect, &cow_read);
                        if (!be || !is_writable(be, isect)) {
                                header->pnfs_error = -EINVAL;
                                goto out;
                        }
                        if (be->be_state == PNFS_BLOCK_INVALID_DATA) {
                                if (likely(!bl_push_one_short_extent(
                                                                be->be_inval)))
                                        par->bse_count++;
                                else {
                                        header->pnfs_error = -ENOMEM;
                                        goto out;
                                }
                        }
                        extent_length = be->be_length -
                            (isect - be->be_f_offset);
                }

                dprintk("%s offset %lld count %Zu\n", __func__, offset, count);
                pg_offset = offset & ~PAGE_CACHE_MASK;
                if (pg_offset + count > PAGE_CACHE_SIZE)
                        pg_len = PAGE_CACHE_SIZE - pg_offset;
                else
                        pg_len = count;

                saved_len = pg_len;
                if (be->be_state == PNFS_BLOCK_INVALID_DATA &&
                    !bl_is_sector_init(be->be_inval, isect)) {
                        ret = bl_read_partial_page_sync(pages[i], cow_read,
                                                        pg_offset, pg_len, true);
                        if (ret) {
                                dprintk("%s bl_read_partial_page_sync fail %d\n",
                                        __func__, ret);
                                header->pnfs_error = ret;
                                goto out;
                        }

                        ret = bl_mark_sectors_init(be->be_inval, isect,
                                                       PAGE_CACHE_SECTORS);
                        if (unlikely(ret)) {
                                dprintk("%s bl_mark_sectors_init fail %d\n",
                                        __func__, ret);
                                header->pnfs_error = ret;
                                goto out;
                        }

                        /* Expand to full page write */
                        pg_offset = 0;
                        pg_len = PAGE_CACHE_SIZE;
                } else if  ((pg_offset & (SECTOR_SIZE - 1)) ||
                            (pg_len & (SECTOR_SIZE - 1))){
                        /* ahh, nasty case. We have to do sync full sector
                         * read-modify-write cycles.
                         */
                        unsigned int saved_offset = pg_offset;
                        ret = bl_read_partial_page_sync(pages[i], be, pg_offset,
                                                        pg_len, false);
                        pg_offset = round_down(pg_offset, SECTOR_SIZE);
                        pg_len = round_up(saved_offset + pg_len, SECTOR_SIZE)
                                 - pg_offset;
                }


                bio = do_add_page_to_bio(bio, wdata->pages.npages - i, WRITE,
                                         isect, pages[i], be,
                                         bl_end_io_write, par,
                                         pg_offset, pg_len);
                if (IS_ERR(bio)) {
                        header->pnfs_error = PTR_ERR(bio);
                        bio = NULL;
                        goto out;
                }
                offset += saved_len;
                count -= saved_len;
                isect += PAGE_CACHE_SECTORS;
                last_isect = isect;
                extent_length -= PAGE_CACHE_SECTORS;
        }

        /* Last page inside INVALID extent */
        if (be->be_state == PNFS_BLOCK_INVALID_DATA) {
                bio = bl_submit_bio(WRITE, bio);
                temp = last_isect >> PAGE_CACHE_SECTOR_SHIFT;
                npg_zero = npg_per_block - do_div(temp, npg_per_block);
                if (npg_zero < npg_per_block) {
                        last = 1;
                        goto fill_invalid_ext;
                }
        }

write_done:
        wdata->res.count = wdata->args.count;
out:
        bl_put_extent(be);
        bl_put_extent(cow_read);
        bl_submit_bio(WRITE, bio);
        put_parallel(par);
        return PNFS_ATTEMPTED;
out_mds:
        bl_put_extent(be);
        bl_put_extent(cow_read);
        kfree(par);
        return PNFS_NOT_ATTEMPTED;
}

/* FIXME - range ignored */
static void
release_extents(struct pnfs_block_layout *bl, struct pnfs_layout_range *range)
{
        int i;
        struct pnfs_block_extent *be;

        spin_lock(&bl->bl_ext_lock);
        for (i = 0; i < EXTENT_LISTS; i++) {
                while (!list_empty(&bl->bl_extents[i])) {
                        be = list_first_entry(&bl->bl_extents[i],
                                              struct pnfs_block_extent,
                                              be_node);
                        list_del(&be->be_node);
                        bl_put_extent(be);
                }
        }
        spin_unlock(&bl->bl_ext_lock);
}

static void
release_inval_marks(struct pnfs_inval_markings *marks)
{
        struct pnfs_inval_tracking *pos, *temp;
        struct pnfs_block_short_extent *se, *stemp;

        list_for_each_entry_safe(pos, temp, &marks->im_tree.mtt_stub, it_link) {
                list_del(&pos->it_link);
                kfree(pos);
        }

        list_for_each_entry_safe(se, stemp, &marks->im_extents, bse_node) {
                list_del(&se->bse_node);
                kfree(se);
        }
        return;
}

static void bl_free_layout_hdr(struct pnfs_layout_hdr *lo)
{
        struct pnfs_block_layout *bl = BLK_LO2EXT(lo);

        dprintk("%s enter\n", __func__);
        release_extents(bl, NULL);
        release_inval_marks(&bl->bl_inval);
        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\n", __func__);
        bl = kzalloc(sizeof(*bl), gfp_flags);
        if (!bl)
                return NULL;
        spin_lock_init(&bl->bl_ext_lock);
        INIT_LIST_HEAD(&bl->bl_extents[0]);
        INIT_LIST_HEAD(&bl->bl_extents[1]);
        INIT_LIST_HEAD(&bl->bl_commit);
        INIT_LIST_HEAD(&bl->bl_committing);
        bl->bl_count = 0;
        bl->bl_blocksize = NFS_SERVER(inode)->pnfs_blksize >> SECTOR_SHIFT;
        BL_INIT_INVAL_MARKS(&bl->bl_inval, bl->bl_blocksize);
        return &bl->bl_layout;
}

static void bl_free_lseg(struct pnfs_layout_segment *lseg)
{
        dprintk("%s enter\n", __func__);
        kfree(lseg);
}

/* We pretty much ignore lseg, and store all data layout wide, so we
 * can correctly merge.
 */
static struct pnfs_layout_segment *bl_alloc_lseg(struct pnfs_layout_hdr *lo,
                                                 struct nfs4_layoutget_res *lgr,
                                                 gfp_t gfp_flags)
{
        struct pnfs_layout_segment *lseg;
        int status;

        dprintk("%s enter\n", __func__);
        lseg = kzalloc(sizeof(*lseg), gfp_flags);
        if (!lseg)
                return ERR_PTR(-ENOMEM);
        status = nfs4_blk_process_layoutget(lo, lgr, gfp_flags);
        if (status) {
                /* We don't want to call the full-blown bl_free_lseg,
                 * since on error extents were not touched.
                 */
                kfree(lseg);
                return ERR_PTR(status);
        }
        return lseg;
}

static void
bl_encode_layoutcommit(struct pnfs_layout_hdr *lo, struct xdr_stream *xdr,
                       const struct nfs4_layoutcommit_args *arg)
{
        dprintk("%s enter\n", __func__);
        encode_pnfs_block_layoutupdate(BLK_LO2EXT(lo), xdr, arg);
}

static void
bl_cleanup_layoutcommit(struct nfs4_layoutcommit_data *lcdata)
{
        struct pnfs_layout_hdr *lo = NFS_I(lcdata->args.inode)->layout;

        dprintk("%s enter\n", __func__);
        clean_pnfs_block_layoutupdate(BLK_LO2EXT(lo), &lcdata->args, lcdata->res.status);
}

static void free_blk_mountid(struct block_mount_id *mid)
{
        if (mid) {
                struct pnfs_block_dev *dev, *tmp;

                /* No need to take bm_lock as we are last user freeing bm_devlist */
                list_for_each_entry_safe(dev, tmp, &mid->bm_devlist, bm_node) {
                        list_del(&dev->bm_node);
                        bl_free_block_dev(dev);
                }
                kfree(mid);
        }
}

/* This is mostly copied from the filelayout_get_device_info function.
 * It seems much of this should be at the generic pnfs level.
 */
static struct pnfs_block_dev *
nfs4_blk_get_deviceinfo(struct nfs_server *server, const struct nfs_fh *fh,
                        struct nfs4_deviceid *d_id)
{
        struct pnfs_device *dev;
        struct pnfs_block_dev *rv;
        u32 max_resp_sz;
        int max_pages;
        struct page **pages = NULL;
        int i, rc;

        /*
         * Use the session max response size as the basis for setting
         * GETDEVICEINFO's maxcount
         */
        max_resp_sz = server->nfs_client->cl_session->fc_attrs.max_resp_sz;
        max_pages = nfs_page_array_len(0, max_resp_sz);
        dprintk("%s max_resp_sz %u max_pages %d\n",
                __func__, max_resp_sz, max_pages);

        dev = kmalloc(sizeof(*dev), GFP_NOFS);
        if (!dev) {
                dprintk("%s kmalloc failed\n", __func__);
                return ERR_PTR(-ENOMEM);
        }

        pages = kzalloc(max_pages * sizeof(struct page *), GFP_NOFS);
        if (pages == NULL) {
                kfree(dev);
                return ERR_PTR(-ENOMEM);
        }
        for (i = 0; i < max_pages; i++) {
                pages[i] = alloc_page(GFP_NOFS);
                if (!pages[i]) {
                        rv = ERR_PTR(-ENOMEM);
                        goto out_free;
                }
        }

        memcpy(&dev->dev_id, d_id, sizeof(*d_id));
        dev->layout_type = LAYOUT_BLOCK_VOLUME;
        dev->pages = pages;
        dev->pgbase = 0;
        dev->pglen = PAGE_SIZE * max_pages;
        dev->mincount = 0;

        dprintk("%s: dev_id: %s\n", __func__, dev->dev_id.data);
        rc = nfs4_proc_getdeviceinfo(server, dev);
        dprintk("%s getdevice info returns %d\n", __func__, rc);
        if (rc) {
                rv = ERR_PTR(rc);
                goto out_free;
        }

        rv = nfs4_blk_decode_device(server, dev);
 out_free:
        for (i = 0; i < max_pages; i++)
                __free_page(pages[i]);
        kfree(pages);
        kfree(dev);
        return rv;
}

static int
bl_set_layoutdriver(struct nfs_server *server, const struct nfs_fh *fh)
{
        struct block_mount_id *b_mt_id = NULL;
        struct pnfs_devicelist *dlist = NULL;
        struct pnfs_block_dev *bdev;
        LIST_HEAD(block_disklist);
        int status, i;

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

        if (server->pnfs_blksize == 0) {
                dprintk("%s Server did not return blksize\n", __func__);
                return -EINVAL;
        }
        b_mt_id = kzalloc(sizeof(struct block_mount_id), GFP_NOFS);
        if (!b_mt_id) {
                status = -ENOMEM;
                goto out_error;
        }
        /* Initialize nfs4 block layout mount id */
        spin_lock_init(&b_mt_id->bm_lock);
        INIT_LIST_HEAD(&b_mt_id->bm_devlist);

        dlist = kmalloc(sizeof(struct pnfs_devicelist), GFP_NOFS);
        if (!dlist) {
                status = -ENOMEM;
                goto out_error;
        }
        dlist->eof = 0;
        while (!dlist->eof) {
                status = nfs4_proc_getdevicelist(server, fh, dlist);
                if (status)
                        goto out_error;
                dprintk("%s GETDEVICELIST numdevs=%i, eof=%i\n",
                        __func__, dlist->num_devs, dlist->eof);
                for (i = 0; i < dlist->num_devs; i++) {
                        bdev = nfs4_blk_get_deviceinfo(server, fh,
                                                       &dlist->dev_id[i]);
                        if (IS_ERR(bdev)) {
                                status = PTR_ERR(bdev);
                                goto out_error;
                        }
                        spin_lock(&b_mt_id->bm_lock);
                        list_add(&bdev->bm_node, &b_mt_id->bm_devlist);
                        spin_unlock(&b_mt_id->bm_lock);
                }
        }
        dprintk("%s SUCCESS\n", __func__);
        server->pnfs_ld_data = b_mt_id;

 out_return:
        kfree(dlist);
        return status;

 out_error:
        free_blk_mountid(b_mt_id);
        goto out_return;
}

static int
bl_clear_layoutdriver(struct nfs_server *server)
{
        struct block_mount_id *b_mt_id = server->pnfs_ld_data;

        dprintk("%s enter\n", __func__);
        free_blk_mountid(b_mt_id);
        dprintk("%s RETURNS\n", __func__);
        return 0;
}

static bool
is_aligned_req(struct nfs_page *req, unsigned int alignment)
{
        return IS_ALIGNED(req->wb_offset, alignment) &&
               IS_ALIGNED(req->wb_bytes, alignment);
}

static void
bl_pg_init_read(struct nfs_pageio_descriptor *pgio, struct nfs_page *req)
{
        if (pgio->pg_dreq != NULL &&
            !is_aligned_req(req, SECTOR_SIZE))
                nfs_pageio_reset_read_mds(pgio);
        else
                pnfs_generic_pg_init_read(pgio, req);
}

static bool
bl_pg_test_read(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
                struct nfs_page *req)
{
        if (pgio->pg_dreq != NULL &&
            !is_aligned_req(req, SECTOR_SIZE))
                return false;

        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 != NFS_I(inode)->npages) {
                rcu_read_lock();
                end = radix_tree_next_hole(&mapping->page_tree, 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)
{
        if (pgio->pg_dreq != NULL &&
            !is_aligned_req(req, PAGE_CACHE_SIZE)) {
                nfs_pageio_reset_write_mds(pgio);
        } else {
                u64 wb_size;
                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);
        }
}

static bool
bl_pg_test_write(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
                 struct nfs_page *req)
{
        if (pgio->pg_dreq != NULL &&
            !is_aligned_req(req, PAGE_CACHE_SIZE))
                return false;

        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,
};

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,
};

static struct pnfs_layoutdriver_type blocklayout_type = {
        .id                             = LAYOUT_BLOCK_VOLUME,
        .name                           = "LAYOUT_BLOCK_VOLUME",
        .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,
        .encode_layoutcommit            = bl_encode_layoutcommit,
        .cleanup_layoutcommit           = bl_cleanup_layoutcommit,
        .set_layoutdriver               = bl_set_layoutdriver,
        .clear_layoutdriver             = bl_clear_layoutdriver,
        .pg_read_ops                    = &bl_pg_read_ops,
        .pg_write_ops                   = &bl_pg_write_ops,
};

static const struct rpc_pipe_ops bl_upcall_ops = {
        .upcall         = rpc_pipe_generic_upcall,
        .downcall       = bl_pipe_downcall,
        .destroy_msg    = bl_pipe_destroy_msg,
};

static struct dentry *nfs4blocklayout_register_sb(struct super_block *sb,
                                            struct rpc_pipe *pipe)
{
        struct dentry *dir, *dentry;

        dir = rpc_d_lookup_sb(sb, NFS_PIPE_DIRNAME);
        if (dir == NULL)
                return ERR_PTR(-ENOENT);
        dentry = rpc_mkpipe_dentry(dir, "blocklayout", NULL, pipe);
        dput(dir);
        return dentry;
}

static void nfs4blocklayout_unregister_sb(struct super_block *sb,
                                          struct rpc_pipe *pipe)
{
        if (pipe->dentry)
                rpc_unlink(pipe->dentry);
}

static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event,
                           void *ptr)
{
        struct super_block *sb = ptr;
        struct net *net = sb->s_fs_info;
        struct nfs_net *nn = net_generic(net, nfs_net_id);
        struct dentry *dentry;
        int ret = 0;

        if (!try_module_get(THIS_MODULE))
                return 0;

        if (nn->bl_device_pipe == NULL) {
                module_put(THIS_MODULE);
                return 0;
        }

        switch (event) {
        case RPC_PIPEFS_MOUNT:
                dentry = nfs4blocklayout_register_sb(sb, nn->bl_device_pipe);
                if (IS_ERR(dentry)) {
                        ret = PTR_ERR(dentry);
                        break;
                }
                nn->bl_device_pipe->dentry = dentry;
                break;
        case RPC_PIPEFS_UMOUNT:
                if (nn->bl_device_pipe->dentry)
                        nfs4blocklayout_unregister_sb(sb, nn->bl_device_pipe);
                break;
        default:
                ret = -ENOTSUPP;
                break;
        }
        module_put(THIS_MODULE);
        return ret;
}

static struct notifier_block nfs4blocklayout_block = {
        .notifier_call = rpc_pipefs_event,
};

static struct dentry *nfs4blocklayout_register_net(struct net *net,
                                                   struct rpc_pipe *pipe)
{
        struct super_block *pipefs_sb;
        struct dentry *dentry;

        pipefs_sb = rpc_get_sb_net(net);
        if (!pipefs_sb)
                return NULL;
        dentry = nfs4blocklayout_register_sb(pipefs_sb, pipe);
        rpc_put_sb_net(net);
        return dentry;
}

static void nfs4blocklayout_unregister_net(struct net *net,
                                           struct rpc_pipe *pipe)
{
        struct super_block *pipefs_sb;

        pipefs_sb = rpc_get_sb_net(net);
        if (pipefs_sb) {
                nfs4blocklayout_unregister_sb(pipefs_sb, pipe);
                rpc_put_sb_net(net);
        }
}

static int nfs4blocklayout_net_init(struct net *net)
{
        struct nfs_net *nn = net_generic(net, nfs_net_id);
        struct dentry *dentry;

        init_waitqueue_head(&nn->bl_wq);
        nn->bl_device_pipe = rpc_mkpipe_data(&bl_upcall_ops, 0);
        if (IS_ERR(nn->bl_device_pipe))
                return PTR_ERR(nn->bl_device_pipe);
        dentry = nfs4blocklayout_register_net(net, nn->bl_device_pipe);
        if (IS_ERR(dentry)) {
                rpc_destroy_pipe_data(nn->bl_device_pipe);
                return PTR_ERR(dentry);
        }
        nn->bl_device_pipe->dentry = dentry;
        return 0;
}

static void nfs4blocklayout_net_exit(struct net *net)
{
        struct nfs_net *nn = net_generic(net, nfs_net_id);

        nfs4blocklayout_unregister_net(net, nn->bl_device_pipe);
        rpc_destroy_pipe_data(nn->bl_device_pipe);
        nn->bl_device_pipe = NULL;
}

static struct pernet_operations nfs4blocklayout_net_ops = {
        .init = nfs4blocklayout_net_init,
        .exit = nfs4blocklayout_net_exit,
};

static int __init nfs4blocklayout_init(void)
{
        int ret;

        dprintk("%s: NFSv4 Block Layout Driver Registering...\n", __func__);

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

        ret = rpc_pipefs_notifier_register(&nfs4blocklayout_block);
        if (ret)
                goto out_remove;
        ret = register_pernet_subsys(&nfs4blocklayout_net_ops);
        if (ret)
                goto out_notifier;
out:
        return ret;

out_notifier:
        rpc_pipefs_notifier_unregister(&nfs4blocklayout_block);
out_remove:
        pnfs_unregister_layoutdriver(&blocklayout_type);
        return ret;
}

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

        rpc_pipefs_notifier_unregister(&nfs4blocklayout_block);
        unregister_pernet_subsys(&nfs4blocklayout_net_ops);
        pnfs_unregister_layoutdriver(&blocklayout_type);
}

MODULE_ALIAS("nfs-layouttype4-3");

module_init(nfs4blocklayout_init);
module_exit(nfs4blocklayout_exit);