/*
 *  Module for the pnfs nfs4 file layout driver.
 *  Defines all I/O and Policy interface operations, plus code
 *  to register itself with the pNFS client.
 *
 *  Copyright (c) 2002
 *  The Regents of the University of Michigan
 *  All Rights Reserved
 *
 *  Dean Hildebrand <dhildebz@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 or warranty
 *  of any kind either express or implied, including without limitation
 *  the implied warranties of merchantability, fitness for a particular
 *  purpose, or noninfringement.  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 of 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/nfs_fs.h>
#include <linux/nfs_page.h>
#include <linux/module.h>

#include "internal.h"
#include "nfs4filelayout.h"

#define NFSDBG_FACILITY         NFSDBG_PNFS_LD

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Dean Hildebrand <dhildebz@umich.edu>");
MODULE_DESCRIPTION("The NFSv4 file layout driver");

#define FILELAYOUT_POLL_RETRY_MAX     (15*HZ)

static loff_t
filelayout_get_dense_offset(struct nfs4_filelayout_segment *flseg,
                            loff_t offset)
{
        u32 stripe_width = flseg->stripe_unit * flseg->dsaddr->stripe_count;
        u64 tmp;

        offset -= flseg->pattern_offset;
        tmp = offset;
        do_div(tmp, stripe_width);

        return tmp * flseg->stripe_unit + do_div(offset, flseg->stripe_unit);
}

/* This function is used by the layout driver to calculate the
 * offset of the file on the dserver based on whether the
 * layout type is STRIPE_DENSE or STRIPE_SPARSE
 */
static loff_t
filelayout_get_dserver_offset(struct pnfs_layout_segment *lseg, loff_t offset)
{
        struct nfs4_filelayout_segment *flseg = FILELAYOUT_LSEG(lseg);

        switch (flseg->stripe_type) {
        case STRIPE_SPARSE:
                return offset;

        case STRIPE_DENSE:
                return filelayout_get_dense_offset(flseg, offset);
        }

        BUG();
}

static int filelayout_async_handle_error(struct rpc_task *task,
                                         struct nfs4_state *state,
                                         struct nfs_client *clp,
                                         int *reset)
{
        if (task->tk_status >= 0)
                return 0;

        *reset = 0;

        switch (task->tk_status) {
        case -NFS4ERR_BADSESSION:
        case -NFS4ERR_BADSLOT:
        case -NFS4ERR_BAD_HIGH_SLOT:
        case -NFS4ERR_DEADSESSION:
        case -NFS4ERR_CONN_NOT_BOUND_TO_SESSION:
        case -NFS4ERR_SEQ_FALSE_RETRY:
        case -NFS4ERR_SEQ_MISORDERED:
                dprintk("%s ERROR %d, Reset session. Exchangeid "
                        "flags 0x%x\n", __func__, task->tk_status,
                        clp->cl_exchange_flags);
                nfs4_schedule_session_recovery(clp->cl_session);
                break;
        case -NFS4ERR_DELAY:
        case -NFS4ERR_GRACE:
        case -EKEYEXPIRED:
                rpc_delay(task, FILELAYOUT_POLL_RETRY_MAX);
                break;
        case -NFS4ERR_RETRY_UNCACHED_REP:
                break;
        default:
                dprintk("%s DS error. Retry through MDS %d\n", __func__,
                        task->tk_status);
                *reset = 1;
                break;
        }
        task->tk_status = 0;
        return -EAGAIN;
}

/* NFS_PROTO call done callback routines */

static int filelayout_read_done_cb(struct rpc_task *task,
                                struct nfs_read_data *data)
{
        int reset = 0;

        dprintk("%s DS read\n", __func__);

        if (filelayout_async_handle_error(task, data->args.context->state,
                                          data->ds_clp, &reset) == -EAGAIN) {
                dprintk("%s calling restart ds_clp %p ds_clp->cl_session %p\n",
                        __func__, data->ds_clp, data->ds_clp->cl_session);
                if (reset) {
                        pnfs_set_lo_fail(data->lseg);
                        nfs4_reset_read(task, data);
                }
                rpc_restart_call_prepare(task);
                return -EAGAIN;
        }

        return 0;
}

/*
 * We reference the rpc_cred of the first WRITE that triggers the need for
 * a LAYOUTCOMMIT, and use it to send the layoutcommit compound.
 * rfc5661 is not clear about which credential should be used.
 */
static void
filelayout_set_layoutcommit(struct nfs_write_data *wdata)
{
        if (FILELAYOUT_LSEG(wdata->lseg)->commit_through_mds ||
            wdata->res.verf->committed == NFS_FILE_SYNC)
                return;

        pnfs_set_layoutcommit(wdata);
        dprintk("%s ionde %lu pls_end_pos %lu\n", __func__, wdata->inode->i_ino,
                (unsigned long) NFS_I(wdata->inode)->layout->plh_lwb);
}

/*
 * Call ops for the async read/write cases
 * In the case of dense layouts, the offset needs to be reset to its
 * original value.
 */
static void filelayout_read_prepare(struct rpc_task *task, void *data)
{
        struct nfs_read_data *rdata = (struct nfs_read_data *)data;

        rdata->read_done_cb = filelayout_read_done_cb;

        if (nfs41_setup_sequence(rdata->ds_clp->cl_session,
                                &rdata->args.seq_args, &rdata->res.seq_res,
                                0, task))
                return;

        rpc_call_start(task);
}

static void filelayout_read_call_done(struct rpc_task *task, void *data)
{
        struct nfs_read_data *rdata = (struct nfs_read_data *)data;

        dprintk("--> %s task->tk_status %d\n", __func__, task->tk_status);

        /* Note this may cause RPC to be resent */
        rdata->mds_ops->rpc_call_done(task, data);
}

static void filelayout_read_release(void *data)
{
        struct nfs_read_data *rdata = (struct nfs_read_data *)data;

        rdata->mds_ops->rpc_release(data);
}

static int filelayout_write_done_cb(struct rpc_task *task,
                                struct nfs_write_data *data)
{
        int reset = 0;

        if (filelayout_async_handle_error(task, data->args.context->state,
                                          data->ds_clp, &reset) == -EAGAIN) {
                dprintk("%s calling restart ds_clp %p ds_clp->cl_session %p\n",
                        __func__, data->ds_clp, data->ds_clp->cl_session);
                if (reset) {
                        pnfs_set_lo_fail(data->lseg);
                        nfs4_reset_write(task, data);
                }
                rpc_restart_call_prepare(task);
                return -EAGAIN;
        }

        filelayout_set_layoutcommit(data);
        return 0;
}

/* Fake up some data that will cause nfs_commit_release to retry the writes. */
static void prepare_to_resend_writes(struct nfs_write_data *data)
{
        struct nfs_page *first = nfs_list_entry(data->pages.next);

        data->task.tk_status = 0;
        memcpy(data->verf.verifier, first->wb_verf.verifier,
               sizeof(first->wb_verf.verifier));
        data->verf.verifier[0]++; /* ensure verifier mismatch */
}

static int filelayout_commit_done_cb(struct rpc_task *task,
                                     struct nfs_write_data *data)
{
        int reset = 0;

        if (filelayout_async_handle_error(task, data->args.context->state,
                                          data->ds_clp, &reset) == -EAGAIN) {
                dprintk("%s calling restart ds_clp %p ds_clp->cl_session %p\n",
                        __func__, data->ds_clp, data->ds_clp->cl_session);
                if (reset) {
                        prepare_to_resend_writes(data);
                        pnfs_set_lo_fail(data->lseg);
                } else
                        rpc_restart_call_prepare(task);
                return -EAGAIN;
        }

        return 0;
}

static void filelayout_write_prepare(struct rpc_task *task, void *data)
{
        struct nfs_write_data *wdata = (struct nfs_write_data *)data;

        if (nfs41_setup_sequence(wdata->ds_clp->cl_session,
                                &wdata->args.seq_args, &wdata->res.seq_res,
                                0, task))
                return;

        rpc_call_start(task);
}

static void filelayout_write_call_done(struct rpc_task *task, void *data)
{
        struct nfs_write_data *wdata = (struct nfs_write_data *)data;

        /* Note this may cause RPC to be resent */
        wdata->mds_ops->rpc_call_done(task, data);
}

static void filelayout_write_release(void *data)
{
        struct nfs_write_data *wdata = (struct nfs_write_data *)data;

        wdata->mds_ops->rpc_release(data);
}

static void filelayout_commit_release(void *data)
{
        struct nfs_write_data *wdata = (struct nfs_write_data *)data;

        nfs_commit_release_pages(wdata);
        if (atomic_dec_and_test(&NFS_I(wdata->inode)->commits_outstanding))
                nfs_commit_clear_lock(NFS_I(wdata->inode));
        nfs_commitdata_release(wdata);
}

struct rpc_call_ops filelayout_read_call_ops = {
        .rpc_call_prepare = filelayout_read_prepare,
        .rpc_call_done = filelayout_read_call_done,
        .rpc_release = filelayout_read_release,
};

struct rpc_call_ops filelayout_write_call_ops = {
        .rpc_call_prepare = filelayout_write_prepare,
        .rpc_call_done = filelayout_write_call_done,
        .rpc_release = filelayout_write_release,
};

struct rpc_call_ops filelayout_commit_call_ops = {
        .rpc_call_prepare = filelayout_write_prepare,
        .rpc_call_done = filelayout_write_call_done,
        .rpc_release = filelayout_commit_release,
};

static enum pnfs_try_status
filelayout_read_pagelist(struct nfs_read_data *data)
{
        struct pnfs_layout_segment *lseg = data->lseg;
        struct nfs4_pnfs_ds *ds;
        loff_t offset = data->args.offset;
        u32 j, idx;
        struct nfs_fh *fh;
        int status;

        dprintk("--> %s ino %lu pgbase %u req %Zu@%llu\n",
                __func__, data->inode->i_ino,
                data->args.pgbase, (size_t)data->args.count, offset);

        if (test_bit(NFS_DEVICEID_INVALID, &FILELAYOUT_DEVID_NODE(lseg)->flags))
                return PNFS_NOT_ATTEMPTED;

        /* Retrieve the correct rpc_client for the byte range */
        j = nfs4_fl_calc_j_index(lseg, offset);
        idx = nfs4_fl_calc_ds_index(lseg, j);
        ds = nfs4_fl_prepare_ds(lseg, idx);
        if (!ds) {
                /* Either layout fh index faulty, or ds connect failed */
                set_bit(lo_fail_bit(IOMODE_RW), &lseg->pls_layout->plh_flags);
                set_bit(lo_fail_bit(IOMODE_READ), &lseg->pls_layout->plh_flags);
                return PNFS_NOT_ATTEMPTED;
        }
        dprintk("%s USE DS: %s\n", __func__, ds->ds_remotestr);

        /* No multipath support. Use first DS */
        data->ds_clp = ds->ds_clp;
        fh = nfs4_fl_select_ds_fh(lseg, j);
        if (fh)
                data->args.fh = fh;

        data->args.offset = filelayout_get_dserver_offset(lseg, offset);
        data->mds_offset = offset;

        /* Perform an asynchronous read to ds */
        status = nfs_initiate_read(data, ds->ds_clp->cl_rpcclient,
                                   &filelayout_read_call_ops);
        BUG_ON(status != 0);
        return PNFS_ATTEMPTED;
}

/* Perform async writes. */
static enum pnfs_try_status
filelayout_write_pagelist(struct nfs_write_data *data, int sync)
{
        struct pnfs_layout_segment *lseg = data->lseg;
        struct nfs4_pnfs_ds *ds;
        loff_t offset = data->args.offset;
        u32 j, idx;
        struct nfs_fh *fh;
        int status;

        if (test_bit(NFS_DEVICEID_INVALID, &FILELAYOUT_DEVID_NODE(lseg)->flags))
                return PNFS_NOT_ATTEMPTED;

        /* Retrieve the correct rpc_client for the byte range */
        j = nfs4_fl_calc_j_index(lseg, offset);
        idx = nfs4_fl_calc_ds_index(lseg, j);
        ds = nfs4_fl_prepare_ds(lseg, idx);
        if (!ds) {
                printk(KERN_ERR "%s: prepare_ds failed, use MDS\n", __func__);
                set_bit(lo_fail_bit(IOMODE_RW), &lseg->pls_layout->plh_flags);
                set_bit(lo_fail_bit(IOMODE_READ), &lseg->pls_layout->plh_flags);
                return PNFS_NOT_ATTEMPTED;
        }
        dprintk("%s ino %lu sync %d req %Zu@%llu DS: %s\n", __func__,
                data->inode->i_ino, sync, (size_t) data->args.count, offset,
                ds->ds_remotestr);

        data->write_done_cb = filelayout_write_done_cb;
        data->ds_clp = ds->ds_clp;
        fh = nfs4_fl_select_ds_fh(lseg, j);
        if (fh)
                data->args.fh = fh;
        /*
         * Get the file offset on the dserver. Set the write offset to
         * this offset and save the original offset.
         */
        data->args.offset = filelayout_get_dserver_offset(lseg, offset);

        /* Perform an asynchronous write */
        status = nfs_initiate_write(data, ds->ds_clp->cl_rpcclient,
                                    &filelayout_write_call_ops, sync);
        BUG_ON(status != 0);
        return PNFS_ATTEMPTED;
}

/*
 * filelayout_check_layout()
 *
 * Make sure layout segment parameters are sane WRT the device.
 * At this point no generic layer initialization of the lseg has occurred,
 * and nothing has been added to the layout_hdr cache.
 *
 */
static int
filelayout_check_layout(struct pnfs_layout_hdr *lo,
                        struct nfs4_filelayout_segment *fl,
                        struct nfs4_layoutget_res *lgr,
                        struct nfs4_deviceid *id,
                        gfp_t gfp_flags)
{
        struct nfs4_deviceid_node *d;
        struct nfs4_file_layout_dsaddr *dsaddr;
        int status = -EINVAL;
        struct nfs_server *nfss = NFS_SERVER(lo->plh_inode);

        dprintk("--> %s\n", __func__);

        /* FIXME: remove this check when layout segment support is added */
        if (lgr->range.offset != 0 ||
            lgr->range.length != NFS4_MAX_UINT64) {
                dprintk("%s Only whole file layouts supported. Use MDS i/o\n",
                        __func__);
                goto out;
        }

        if (fl->pattern_offset > lgr->range.offset) {
                dprintk("%s pattern_offset %lld too large\n",
                                __func__, fl->pattern_offset);
                goto out;
        }

        if (!fl->stripe_unit || fl->stripe_unit % PAGE_SIZE) {
                dprintk("%s Invalid stripe unit (%u)\n",
                        __func__, fl->stripe_unit);
                goto out;
        }

        /* find and reference the deviceid */
        d = nfs4_find_get_deviceid(NFS_SERVER(lo->plh_inode)->pnfs_curr_ld,
                                   NFS_SERVER(lo->plh_inode)->nfs_client, id);
        if (d == NULL) {
                dsaddr = get_device_info(lo->plh_inode, id, gfp_flags);
                if (dsaddr == NULL)
                        goto out;
        } else
                dsaddr = container_of(d, struct nfs4_file_layout_dsaddr, id_node);
        /* Found deviceid is being reaped */
        if (test_bit(NFS_DEVICEID_INVALID, &dsaddr->id_node.flags))
                        goto out_put;

        fl->dsaddr = dsaddr;

        if (fl->first_stripe_index >= dsaddr->stripe_count) {
                dprintk("%s Bad first_stripe_index %u\n",
                                __func__, fl->first_stripe_index);
                goto out_put;
        }

        if ((fl->stripe_type == STRIPE_SPARSE &&
            fl->num_fh > 1 && fl->num_fh != dsaddr->ds_num) ||
            (fl->stripe_type == STRIPE_DENSE &&
            fl->num_fh != dsaddr->stripe_count)) {
                dprintk("%s num_fh %u not valid for given packing\n",
                        __func__, fl->num_fh);
                goto out_put;
        }

        if (fl->stripe_unit % nfss->rsize || fl->stripe_unit % nfss->wsize) {
                dprintk("%s Stripe unit (%u) not aligned with rsize %u "
                        "wsize %u\n", __func__, fl->stripe_unit, nfss->rsize,
                        nfss->wsize);
        }

        status = 0;
out:
        dprintk("--> %s returns %d\n", __func__, status);
        return status;
out_put:
        nfs4_fl_put_deviceid(dsaddr);
        goto out;
}

static void filelayout_free_fh_array(struct nfs4_filelayout_segment *fl)
{
        int i;

        for (i = 0; i < fl->num_fh; i++) {
                if (!fl->fh_array[i])
                        break;
                kfree(fl->fh_array[i]);
        }
        kfree(fl->fh_array);
        fl->fh_array = NULL;
}

static void
_filelayout_free_lseg(struct nfs4_filelayout_segment *fl)
{
        filelayout_free_fh_array(fl);
        kfree(fl);
}

static int
filelayout_decode_layout(struct pnfs_layout_hdr *flo,
                         struct nfs4_filelayout_segment *fl,
                         struct nfs4_layoutget_res *lgr,
                         struct nfs4_deviceid *id,
                         gfp_t gfp_flags)
{
        struct xdr_stream stream;
        struct xdr_buf buf;
        struct page *scratch;
        __be32 *p;
        uint32_t nfl_util;
        int i;

        dprintk("%s: set_layout_map Begin\n", __func__);

        scratch = alloc_page(gfp_flags);
        if (!scratch)
                return -ENOMEM;

        xdr_init_decode_pages(&stream, &buf, lgr->layoutp->pages, lgr->layoutp->len);
        xdr_set_scratch_buffer(&stream, page_address(scratch), PAGE_SIZE);

        /* 20 = ufl_util (4), first_stripe_index (4), pattern_offset (8),
         * num_fh (4) */
        p = xdr_inline_decode(&stream, NFS4_DEVICEID4_SIZE + 20);
        if (unlikely(!p))
                goto out_err;

        memcpy(id, p, sizeof(*id));
        p += XDR_QUADLEN(NFS4_DEVICEID4_SIZE);
        nfs4_print_deviceid(id);

        nfl_util = be32_to_cpup(p++);
        if (nfl_util & NFL4_UFLG_COMMIT_THRU_MDS)
                fl->commit_through_mds = 1;
        if (nfl_util & NFL4_UFLG_DENSE)
                fl->stripe_type = STRIPE_DENSE;
        else
                fl->stripe_type = STRIPE_SPARSE;
        fl->stripe_unit = nfl_util & ~NFL4_UFLG_MASK;

        fl->first_stripe_index = be32_to_cpup(p++);
        p = xdr_decode_hyper(p, &fl->pattern_offset);
        fl->num_fh = be32_to_cpup(p++);

        dprintk("%s: nfl_util 0x%X num_fh %u fsi %u po %llu\n",
                __func__, nfl_util, fl->num_fh, fl->first_stripe_index,
                fl->pattern_offset);

        /* Note that a zero value for num_fh is legal for STRIPE_SPARSE.
         * Futher checking is done in filelayout_check_layout */
        if (fl->num_fh >
            max(NFS4_PNFS_MAX_STRIPE_CNT, NFS4_PNFS_MAX_MULTI_CNT))
                goto out_err;

        if (fl->num_fh > 0) {
                fl->fh_array = kzalloc(fl->num_fh * sizeof(struct nfs_fh *),
                                       gfp_flags);
                if (!fl->fh_array)
                        goto out_err;
        }

        for (i = 0; i < fl->num_fh; i++) {
                /* Do we want to use a mempool here? */
                fl->fh_array[i] = kmalloc(sizeof(struct nfs_fh), gfp_flags);
                if (!fl->fh_array[i])
                        goto out_err_free;

                p = xdr_inline_decode(&stream, 4);
                if (unlikely(!p))
                        goto out_err_free;
                fl->fh_array[i]->size = be32_to_cpup(p++);
                if (sizeof(struct nfs_fh) < fl->fh_array[i]->size) {
                        printk(KERN_ERR "Too big fh %d received %d\n",
                               i, fl->fh_array[i]->size);
                        goto out_err_free;
                }

                p = xdr_inline_decode(&stream, fl->fh_array[i]->size);
                if (unlikely(!p))
                        goto out_err_free;
                memcpy(fl->fh_array[i]->data, p, fl->fh_array[i]->size);
                dprintk("DEBUG: %s: fh len %d\n", __func__,
                        fl->fh_array[i]->size);
        }

        __free_page(scratch);
        return 0;

out_err_free:
        filelayout_free_fh_array(fl);
out_err:
        __free_page(scratch);
        return -EIO;
}

static void
filelayout_free_lseg(struct pnfs_layout_segment *lseg)
{
        struct nfs4_filelayout_segment *fl = FILELAYOUT_LSEG(lseg);

        dprintk("--> %s\n", __func__);
        nfs4_fl_put_deviceid(fl->dsaddr);
        kfree(fl->commit_buckets);
        _filelayout_free_lseg(fl);
}

static struct pnfs_layout_segment *
filelayout_alloc_lseg(struct pnfs_layout_hdr *layoutid,
                      struct nfs4_layoutget_res *lgr,
                      gfp_t gfp_flags)
{
        struct nfs4_filelayout_segment *fl;
        int rc;
        struct nfs4_deviceid id;

        dprintk("--> %s\n", __func__);
        fl = kzalloc(sizeof(*fl), gfp_flags);
        if (!fl)
                return NULL;

        rc = filelayout_decode_layout(layoutid, fl, lgr, &id, gfp_flags);
        if (rc != 0 || filelayout_check_layout(layoutid, fl, lgr, &id, gfp_flags)) {
                _filelayout_free_lseg(fl);
                return NULL;
        }

        /* This assumes there is only one IOMODE_RW lseg.  What
         * we really want to do is have a layout_hdr level
         * dictionary of <multipath_list4, fh> keys, each
         * associated with a struct list_head, populated by calls
         * to filelayout_write_pagelist().
         * */
        if ((!fl->commit_through_mds) && (lgr->range.iomode == IOMODE_RW)) {
                int i;
                int size = (fl->stripe_type == STRIPE_SPARSE) ?
                        fl->dsaddr->ds_num : fl->dsaddr->stripe_count;

                fl->commit_buckets = kcalloc(size, sizeof(struct list_head), gfp_flags);
                if (!fl->commit_buckets) {
                        filelayout_free_lseg(&fl->generic_hdr);
                        return NULL;
                }
                fl->number_of_buckets = size;
                for (i = 0; i < size; i++)
                        INIT_LIST_HEAD(&fl->commit_buckets[i]);
        }
        return &fl->generic_hdr;
}

/*
 * filelayout_pg_test(). Called by nfs_can_coalesce_requests()
 *
 * return true  : coalesce page
 * return false : don't coalesce page
 */
static bool
filelayout_pg_test(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
                   struct nfs_page *req)
{
        u64 p_stripe, r_stripe;
        u32 stripe_unit;

        if (!pnfs_generic_pg_test(pgio, prev, req) ||
            !nfs_generic_pg_test(pgio, prev, req))
                return false;

        p_stripe = (u64)prev->wb_index << PAGE_CACHE_SHIFT;
        r_stripe = (u64)req->wb_index << PAGE_CACHE_SHIFT;
        stripe_unit = FILELAYOUT_LSEG(pgio->pg_lseg)->stripe_unit;

        do_div(p_stripe, stripe_unit);
        do_div(r_stripe, stripe_unit);

        return (p_stripe == r_stripe);
}

void
filelayout_pg_init_read(struct nfs_pageio_descriptor *pgio,
                        struct nfs_page *req)
{
        BUG_ON(pgio->pg_lseg != NULL);

        pgio->pg_lseg = pnfs_update_layout(pgio->pg_inode,
                                           req->wb_context,
                                           0,
                                           NFS4_MAX_UINT64,
                                           IOMODE_READ,
                                           GFP_KERNEL);
        /* If no lseg, fall back to read through mds */
        if (pgio->pg_lseg == NULL)
                nfs_pageio_reset_read_mds(pgio);
}

void
filelayout_pg_init_write(struct nfs_pageio_descriptor *pgio,
                         struct nfs_page *req)
{
        BUG_ON(pgio->pg_lseg != NULL);

        pgio->pg_lseg = pnfs_update_layout(pgio->pg_inode,
                                           req->wb_context,
                                           0,
                                           NFS4_MAX_UINT64,
                                           IOMODE_RW,
                                           GFP_NOFS);
        /* If no lseg, fall back to write through mds */
        if (pgio->pg_lseg == NULL)
                nfs_pageio_reset_write_mds(pgio);
}

static const struct nfs_pageio_ops filelayout_pg_read_ops = {
        .pg_init = filelayout_pg_init_read,
        .pg_test = filelayout_pg_test,
        .pg_doio = pnfs_generic_pg_readpages,
};

static const struct nfs_pageio_ops filelayout_pg_write_ops = {
        .pg_init = filelayout_pg_init_write,
        .pg_test = filelayout_pg_test,
        .pg_doio = pnfs_generic_pg_writepages,
};

static bool filelayout_mark_pnfs_commit(struct pnfs_layout_segment *lseg)
{
        return !FILELAYOUT_LSEG(lseg)->commit_through_mds;
}

static u32 select_bucket_index(struct nfs4_filelayout_segment *fl, u32 j)
{
        if (fl->stripe_type == STRIPE_SPARSE)
                return nfs4_fl_calc_ds_index(&fl->generic_hdr, j);
        else
                return j;
}

struct list_head *filelayout_choose_commit_list(struct nfs_page *req)
{
        struct pnfs_layout_segment *lseg = req->wb_commit_lseg;
        struct nfs4_filelayout_segment *fl = FILELAYOUT_LSEG(lseg);
        u32 i, j;
        struct list_head *list;

        /* Note that we are calling nfs4_fl_calc_j_index on each page
         * that ends up being committed to a data server.  An attractive
         * alternative is to add a field to nfs_write_data and nfs_page
         * to store the value calculated in filelayout_write_pagelist
         * and just use that here.
         */
        j = nfs4_fl_calc_j_index(lseg,
                                 (loff_t)req->wb_index << PAGE_CACHE_SHIFT);
        i = select_bucket_index(fl, j);
        list = &fl->commit_buckets[i];
        if (list_empty(list)) {
                /* Non-empty buckets hold a reference on the lseg */
                get_lseg(lseg);
        }
        return list;
}

static u32 calc_ds_index_from_commit(struct pnfs_layout_segment *lseg, u32 i)
{
        struct nfs4_filelayout_segment *flseg = FILELAYOUT_LSEG(lseg);

        if (flseg->stripe_type == STRIPE_SPARSE)
                return i;
        else
                return nfs4_fl_calc_ds_index(lseg, i);
}

static struct nfs_fh *
select_ds_fh_from_commit(struct pnfs_layout_segment *lseg, u32 i)
{
        struct nfs4_filelayout_segment *flseg = FILELAYOUT_LSEG(lseg);

        if (flseg->stripe_type == STRIPE_SPARSE) {
                if (flseg->num_fh == 1)
                        i = 0;
                else if (flseg->num_fh == 0)
                        /* Use the MDS OPEN fh set in nfs_read_rpcsetup */
                        return NULL;
        }
        return flseg->fh_array[i];
}

static int filelayout_initiate_commit(struct nfs_write_data *data, int how)
{
        struct pnfs_layout_segment *lseg = data->lseg;
        struct nfs4_pnfs_ds *ds;
        u32 idx;
        struct nfs_fh *fh;

        idx = calc_ds_index_from_commit(lseg, data->ds_commit_index);
        ds = nfs4_fl_prepare_ds(lseg, idx);
        if (!ds) {
                printk(KERN_ERR "%s: prepare_ds failed, use MDS\n", __func__);
                set_bit(lo_fail_bit(IOMODE_RW), &lseg->pls_layout->plh_flags);
                set_bit(lo_fail_bit(IOMODE_READ), &lseg->pls_layout->plh_flags);
                prepare_to_resend_writes(data);
                data->mds_ops->rpc_release(data);
                return -EAGAIN;
        }
        dprintk("%s ino %lu, how %d\n", __func__, data->inode->i_ino, how);
        data->write_done_cb = filelayout_commit_done_cb;
        data->ds_clp = ds->ds_clp;
        fh = select_ds_fh_from_commit(lseg, data->ds_commit_index);
        if (fh)
                data->args.fh = fh;
        return nfs_initiate_commit(data, ds->ds_clp->cl_rpcclient,
                                   &filelayout_commit_call_ops, how);
}

/*
 * This is only useful while we are using whole file layouts.
 */
static struct pnfs_layout_segment *find_only_write_lseg(struct inode *inode)
{
        struct pnfs_layout_segment *lseg, *rv = NULL;

        spin_lock(&inode->i_lock);
        list_for_each_entry(lseg, &NFS_I(inode)->layout->plh_segs, pls_list)
                if (lseg->pls_range.iomode == IOMODE_RW)
                        rv = get_lseg(lseg);
        spin_unlock(&inode->i_lock);
        return rv;
}

static int alloc_ds_commits(struct inode *inode, struct list_head *list)
{
        struct pnfs_layout_segment *lseg;
        struct nfs4_filelayout_segment *fl;
        struct nfs_write_data *data;
        int i, j;

        /* Won't need this when non-whole file layout segments are supported
         * instead we will use a pnfs_layout_hdr structure */
        lseg = find_only_write_lseg(inode);
        if (!lseg)
                return 0;
        fl = FILELAYOUT_LSEG(lseg);
        for (i = 0; i < fl->number_of_buckets; i++) {
                if (list_empty(&fl->commit_buckets[i]))
                        continue;
                data = nfs_commitdata_alloc();
                if (!data)
                        goto out_bad;
                data->ds_commit_index = i;
                data->lseg = lseg;
                list_add(&data->pages, list);
        }
        put_lseg(lseg);
        return 0;

out_bad:
        for (j = i; j < fl->number_of_buckets; j++) {
                if (list_empty(&fl->commit_buckets[i]))
                        continue;
                nfs_retry_commit(&fl->commit_buckets[i], lseg);
                put_lseg(lseg);  /* associated with emptying bucket */
        }
        put_lseg(lseg);
        /* Caller will clean up entries put on list */
        return -ENOMEM;
}

/* This follows nfs_commit_list pretty closely */
static int
filelayout_commit_pagelist(struct inode *inode, struct list_head *mds_pages,
                           int how)
{
        struct nfs_write_data   *data, *tmp;
        LIST_HEAD(list);

        if (!list_empty(mds_pages)) {
                data = nfs_commitdata_alloc();
                if (!data)
                        goto out_bad;
                data->lseg = NULL;
                list_add(&data->pages, &list);
        }

        if (alloc_ds_commits(inode, &list))
                goto out_bad;

        list_for_each_entry_safe(data, tmp, &list, pages) {
                list_del_init(&data->pages);
                atomic_inc(&NFS_I(inode)->commits_outstanding);
                if (!data->lseg) {
                        nfs_init_commit(data, mds_pages, NULL);
                        nfs_initiate_commit(data, NFS_CLIENT(inode),
                                            data->mds_ops, how);
                } else {
                        nfs_init_commit(data, &FILELAYOUT_LSEG(data->lseg)->commit_buckets[data->ds_commit_index], data->lseg);
                        filelayout_initiate_commit(data, how);
                }
        }
        return 0;
 out_bad:
        list_for_each_entry_safe(data, tmp, &list, pages) {
                nfs_retry_commit(&data->pages, data->lseg);
                list_del_init(&data->pages);
                nfs_commit_free(data);
        }
        nfs_retry_commit(mds_pages, NULL);
        nfs_commit_clear_lock(NFS_I(inode));
        return -ENOMEM;
}

static void
filelayout_free_deveiceid_node(struct nfs4_deviceid_node *d)
{
        nfs4_fl_free_deviceid(container_of(d, struct nfs4_file_layout_dsaddr, id_node));
}

static struct pnfs_layoutdriver_type filelayout_type = {
        .id                     = LAYOUT_NFSV4_1_FILES,
        .name                   = "LAYOUT_NFSV4_1_FILES",
        .owner                  = THIS_MODULE,
        .alloc_lseg             = filelayout_alloc_lseg,
        .free_lseg              = filelayout_free_lseg,
        .pg_read_ops            = &filelayout_pg_read_ops,
        .pg_write_ops           = &filelayout_pg_write_ops,
        .mark_pnfs_commit       = filelayout_mark_pnfs_commit,
        .choose_commit_list     = filelayout_choose_commit_list,
        .commit_pagelist        = filelayout_commit_pagelist,
        .read_pagelist          = filelayout_read_pagelist,
        .write_pagelist         = filelayout_write_pagelist,
        .free_deviceid_node     = filelayout_free_deveiceid_node,
};

static int __init nfs4filelayout_init(void)
{
        printk(KERN_INFO "%s: NFSv4 File Layout Driver Registering...\n",
               __func__);
        return pnfs_register_layoutdriver(&filelayout_type);
}

static void __exit nfs4filelayout_exit(void)
{
        printk(KERN_INFO "%s: NFSv4 File Layout Driver Unregistering...\n",
               __func__);
        pnfs_unregister_layoutdriver(&filelayout_type);
}

MODULE_ALIAS("nfs-layouttype4-1");

module_init(nfs4filelayout_init);
module_exit(nfs4filelayout_exit);