blocklayout.c

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/*
 *  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 <[email protected]>
 *  Fred Isaman <[email protected]>
 *
 * 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 "../internal.h"
#include "blocklayout.h"

#define NFSDBG_FACILITY NFSDBG_PNFS_LD

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Andy Adamson <[email protected]>");
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);