MIPS: Yosemite, Emma: Fix off-by-two in arcs_cmdline buffer size check

[linux-2.6/linux-mips.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 "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");

struct dentry *bl_device_pipe;
wait_queue_head_t bl_wq;

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;
        struct rpc_call_ops call_ops;
        void (*pnfs_callback) (void *data);
        void *data;
};

static inline struct parallel_io *alloc_parallel(void *data)
{
        struct parallel_io *rv;

        rv  = kmalloc(sizeof(*rv), GFP_NOFS);
        if (rv) {
                rv->data = data;
                kref_init(&rv->refcnt);
        }
        return rv;
}

static inline void get_parallel(struct parallel_io *p)
{
        kref_get(&p->refcnt);
}

static void destroy_parallel(struct kref *kref)
{
        struct parallel_io *p = container_of(kref, struct parallel_io, refcnt);

        dprintk("%s enter\n", __func__);
        p->pnfs_callback(p->data);
        kfree(p);
}

static inline void put_parallel(struct parallel_io *p)
{
        kref_put(&p->refcnt, destroy_parallel);
}

static struct bio *
bl_submit_bio(int rw, struct bio *bio)
{
        if (bio) {
                get_parallel(bio->bi_private);
                dprintk("%s submitting %s bio %u@%llu\n", __func__,
                        rw == READ ? "read" : "write",
                        bio->bi_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;

        bio = bio_alloc(GFP_NOIO, npg);
        if (!bio)
                return NULL;

        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 *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)
{
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, PAGE_CACHE_SIZE, 0) < PAGE_CACHE_SIZE) {
                bio = bl_submit_bio(rw, bio);
                goto retry;
        }
        return bio;
}

/* 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;
        struct nfs_read_data *rdata = (struct nfs_read_data *)par->data;

        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) {
                if (!rdata->pnfs_error)
                        rdata->pnfs_error = -EIO;
                pnfs_set_lo_fail(rdata->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)
{
        struct nfs_read_data *rdata = data;

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

/* We don't want normal .rpc_call_done callback used, so we replace it
 * with this stub.
 */
static void bl_rpc_do_nothing(struct rpc_task *task, void *calldata)
{
        return;
}

static enum pnfs_try_status
bl_read_pagelist(struct nfs_read_data *rdata)
{
        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 count = rdata->args.count;
        struct page **pages = rdata->args.pages;
        int pg_index = rdata->args.pgbase >> PAGE_CACHE_SHIFT;

        dprintk("%s enter nr_pages %u offset %lld count %Zd\n", __func__,
               rdata->npages, f_offset, count);

        par = alloc_parallel(rdata);
        if (!par)
                goto use_mds;
        par->call_ops = *rdata->mds_ops;
        par->call_ops.rpc_call_done = bl_rpc_do_nothing;
        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->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(rdata->lseg),
                                             isect, &cow_read);
                        if (!be) {
                                rdata->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);
                        }
                }
                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], 0, PAGE_CACHE_SIZE);
                        print_page(pages[i]);
                        SetPageUptodate(pages[i]);
                } else {
                        struct pnfs_block_extent *be_read;

                        be_read = (hole && cow_read) ? cow_read : be;
                        bio = bl_add_page_to_bio(bio, rdata->npages - i, READ,
                                                 isect, pages[i], be_read,
                                                 bl_end_io_read, par);
                        if (IS_ERR(bio)) {
                                rdata->pnfs_error = PTR_ERR(bio);
                                bio = NULL;
                                goto out;
                        }
                }
                isect += PAGE_CACHE_SECTORS;
                extent_length -= PAGE_CACHE_SECTORS;
        }
        if ((isect << SECTOR_SHIFT) >= rdata->inode->i_size) {
                rdata->res.eof = 1;
                rdata->res.count = rdata->inode->i_size - f_offset;
        } else {
                rdata->res.count = (isect << SECTOR_SHIFT) - f_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;

        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)
                        bl_mark_for_commit(be, isect, len); /* What if fails? */
                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;
        struct nfs_write_data *wdata = (struct nfs_write_data *)par->data;

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

/* This is basically copied from mpage_end_io_read */
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 *wdata = (struct nfs_write_data *)par->data;

        if (!uptodate) {
                if (!wdata->pnfs_error)
                        wdata->pnfs_error = -EIO;
                pnfs_set_lo_fail(wdata->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 (!wdata->pnfs_error) {
                /* Marks for LAYOUTCOMMIT */
                mark_extents_written(BLK_LSEG2EXT(wdata->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)
{
        struct nfs_write_data *wdata = data;

        wdata->task.tk_status = 0;
        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;
}

/* 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:
        bl_put_extent(cow_read);
        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;
}

static enum pnfs_try_status
bl_write_pagelist(struct nfs_write_data *wdata, int sync)
{
        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;
        loff_t offset = wdata->args.offset;
        size_t count = wdata->args.count;
        struct page **pages = wdata->args.pages;
        struct page *page;
        pgoff_t index;
        u64 temp;
        int npg_per_block =
            NFS_SERVER(wdata->inode)->pnfs_blksize >> PAGE_CACHE_SHIFT;

        dprintk("%s enter, %Zu@%lld\n", __func__, count, offset);
        /* 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)
                return PNFS_NOT_ATTEMPTED;
        par->call_ops = *wdata->mds_ops;
        par->call_ops.rpc_call_done = bl_rpc_do_nothing;
        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(wdata->lseg), isect, &cow_read);
        if (!be || !is_writable(be, isect)) {
                dprintk("%s no matching extents!\n", __func__);
                wdata->pnfs_error = -EINVAL;
                goto out;
        }

        /* First page inside INVALID extent */
        if (be->be_state == PNFS_BLOCK_INVALID_DATA) {
                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 =
                            find_or_create_page(wdata->inode->i_mapping, index,
                                                GFP_NOFS);
                        if (!page) {
                                dprintk("%s oom\n", __func__);
                                wdata->pnfs_error = -ENOMEM;
                                goto out;
                        }

                        /* PageDirty: Other will write this out
                         * PageWriteback: Other is writing this out
                         * PageUptodate: It was read before
                         * sector_initialized: already written out
                         */
                        if (PageDirty(page) || PageWriteback(page)) {
                                print_page(page);
                                unlock_page(page);
                                page_cache_release(page);
                                goto next_page;
                        }
                        if (!PageUptodate(page)) {
                                /* New page, readin or zero it */
                                init_page_for_write(page, cow_read);
                        }
                        set_page_writeback(page);
                        unlock_page(page);

                        ret = bl_mark_sectors_init(be->be_inval, isect,
                                                       PAGE_CACHE_SECTORS,
                                                       NULL);
                        if (unlikely(ret)) {
                                dprintk("%s bl_mark_sectors_init fail %d\n",
                                        __func__, ret);
                                end_page_writeback(page);
                                page_cache_release(page);
                                wdata->pnfs_error = ret;
                                goto out;
                        }
                        bio = bl_add_page_to_bio(bio, npg_zero, WRITE,
                                                 isect, page, be,
                                                 bl_end_io_write_zero, par);
                        if (IS_ERR(bio)) {
                                wdata->pnfs_error = PTR_ERR(bio);
                                bio = NULL;
                                goto out;
                        }
                        /* FIXME: This should be done in bi_end_io */
                        mark_extents_written(BLK_LSEG2EXT(wdata->lseg),
                                             page->index << PAGE_CACHE_SHIFT,
                                             PAGE_CACHE_SIZE);
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->npages; i++) {
                if (!extent_length) {
                        /* We've used up the previous extent */
                        bl_put_extent(be);
                        bio = bl_submit_bio(WRITE, bio);
                        /* Get the next one */
                        be = bl_find_get_extent(BLK_LSEG2EXT(wdata->lseg),
                                             isect, NULL);
                        if (!be || !is_writable(be, isect)) {
                                wdata->pnfs_error = -EINVAL;
                                goto out;
                        }
                        extent_length = be->be_length -
                            (isect - be->be_f_offset);
                }
                if (be->be_state == PNFS_BLOCK_INVALID_DATA) {
                        ret = bl_mark_sectors_init(be->be_inval, isect,
                                                       PAGE_CACHE_SECTORS,
                                                       NULL);
                        if (unlikely(ret)) {
                                dprintk("%s bl_mark_sectors_init fail %d\n",
                                        __func__, ret);
                                wdata->pnfs_error = ret;
                                goto out;
                        }
                }
                bio = bl_add_page_to_bio(bio, wdata->npages - i, WRITE,
                                         isect, pages[i], be,
                                         bl_end_io_write, par);
                if (IS_ERR(bio)) {
                        wdata->pnfs_error = PTR_ERR(bio);
                        bio = NULL;
                        goto out;
                }
                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 = (last_isect << SECTOR_SHIFT) - (offset);
        if (count < wdata->res.count) {
                wdata->res.count = count;
        }
out:
        bl_put_extent(be);
        bl_submit_bio(WRITE, bio);
        put_parallel(par);
        return PNFS_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;

        list_for_each_entry_safe(pos, temp, &marks->im_tree.mtt_stub, it_link) {
                list_del(&pos->it_link);
                kfree(pos);
        }
        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;
                spin_lock(&mid->bm_lock);
                while (!list_empty(&mid->bm_devlist)) {
                        dev = list_first_entry(&mid->bm_devlist,
                                               struct pnfs_block_dev,
                                               bm_node);
                        list_del(&dev->bm_node);
                        bl_free_block_dev(dev);
                }
                spin_unlock(&mid->bm_lock);
                kfree(mid);
        }
}

/* This is mostly copied from the filelayout's 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 = max_resp_sz >> PAGE_SHIFT;
        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 const struct nfs_pageio_ops bl_pg_read_ops = {
        .pg_init = pnfs_generic_pg_init_read,
        .pg_test = pnfs_generic_pg_test,
        .pg_doio = pnfs_generic_pg_readpages,
};

static const struct nfs_pageio_ops bl_pg_write_ops = {
        .pg_init = pnfs_generic_pg_init_write,
        .pg_test = pnfs_generic_pg_test,
        .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 int __init nfs4blocklayout_init(void)
{
        struct vfsmount *mnt;
        struct path path;
        int ret;

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

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

        init_waitqueue_head(&bl_wq);

        mnt = rpc_get_mount();
        if (IS_ERR(mnt)) {
                ret = PTR_ERR(mnt);
                goto out_remove;
        }

        ret = vfs_path_lookup(mnt->mnt_root,
                              mnt,
                              NFS_PIPE_DIRNAME, 0, &path);
        if (ret)
                goto out_putrpc;

        bl_device_pipe = rpc_mkpipe(path.dentry, "blocklayout", NULL,
                                    &bl_upcall_ops, 0);
        path_put(&path);
        if (IS_ERR(bl_device_pipe)) {
                ret = PTR_ERR(bl_device_pipe);
                goto out_putrpc;
        }
out:
        return ret;

out_putrpc:
        rpc_put_mount();
out_remove:
        pnfs_unregister_layoutdriver(&blocklayout_type);
        return ret;
}

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

        pnfs_unregister_layoutdriver(&blocklayout_type);
        rpc_unlink(bl_device_pipe);
        rpc_put_mount();
}

MODULE_ALIAS("nfs-layouttype4-3");

module_init(nfs4blocklayout_init);
module_exit(nfs4blocklayout_exit);