Linux 3.8-rc7

[cris-mirror.git] / fs / nfs / nfs4filelayout.c

/*
 *  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 <linux/sunrpc/metrics.h>

#include "nfs4session.h"
#include "internal.h"
#include "delegation.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 stripe_no;
        u32 rem;

        offset -= flseg->pattern_offset;
        stripe_no = div_u64(offset, stripe_width);
        div_u64_rem(offset, flseg->stripe_unit, &rem);

        return stripe_no * flseg->stripe_unit + rem;
}

/* 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 void filelayout_reset_write(struct nfs_write_data *data)
{
        struct nfs_pgio_header *hdr = data->header;
        struct rpc_task *task = &data->task;

        if (!test_and_set_bit(NFS_IOHDR_REDO, &hdr->flags)) {
                dprintk("%s Reset task %5u for i/o through MDS "
                        "(req %s/%lld, %u bytes @ offset %llu)\n", __func__,
                        data->task.tk_pid,
                        hdr->inode->i_sb->s_id,
                        (long long)NFS_FILEID(hdr->inode),
                        data->args.count,
                        (unsigned long long)data->args.offset);

                task->tk_status = pnfs_write_done_resend_to_mds(hdr->inode,
                                                        &hdr->pages,
                                                        hdr->completion_ops);
        }
}

static void filelayout_reset_read(struct nfs_read_data *data)
{
        struct nfs_pgio_header *hdr = data->header;
        struct rpc_task *task = &data->task;

        if (!test_and_set_bit(NFS_IOHDR_REDO, &hdr->flags)) {
                dprintk("%s Reset task %5u for i/o through MDS "
                        "(req %s/%lld, %u bytes @ offset %llu)\n", __func__,
                        data->task.tk_pid,
                        hdr->inode->i_sb->s_id,
                        (long long)NFS_FILEID(hdr->inode),
                        data->args.count,
                        (unsigned long long)data->args.offset);

                task->tk_status = pnfs_read_done_resend_to_mds(hdr->inode,
                                                        &hdr->pages,
                                                        hdr->completion_ops);
        }
}

static void filelayout_fenceme(struct inode *inode, struct pnfs_layout_hdr *lo)
{
        if (!test_and_clear_bit(NFS_LAYOUT_RETURN, &lo->plh_flags))
                return;
        clear_bit(NFS_INO_LAYOUTCOMMIT, &NFS_I(inode)->flags);
        pnfs_return_layout(inode);
}

static int filelayout_async_handle_error(struct rpc_task *task,
                                         struct nfs4_state *state,
                                         struct nfs_client *clp,
                                         struct pnfs_layout_segment *lseg)
{
        struct pnfs_layout_hdr *lo = lseg->pls_layout;
        struct inode *inode = lo->plh_inode;
        struct nfs_server *mds_server = NFS_SERVER(inode);
        struct nfs4_deviceid_node *devid = FILELAYOUT_DEVID_NODE(lseg);
        struct nfs_client *mds_client = mds_server->nfs_client;
        struct nfs4_slot_table *tbl = &clp->cl_session->fc_slot_table;

        if (task->tk_status >= 0)
                return 0;

        switch (task->tk_status) {
        /* MDS state errors */
        case -NFS4ERR_DELEG_REVOKED:
        case -NFS4ERR_ADMIN_REVOKED:
        case -NFS4ERR_BAD_STATEID:
                if (state == NULL)
                        break;
                nfs_remove_bad_delegation(state->inode);
        case -NFS4ERR_OPENMODE:
                if (state == NULL)
                        break;
                nfs4_schedule_stateid_recovery(mds_server, state);
                goto wait_on_recovery;
        case -NFS4ERR_EXPIRED:
                if (state != NULL)
                        nfs4_schedule_stateid_recovery(mds_server, state);
                nfs4_schedule_lease_recovery(mds_client);
                goto wait_on_recovery;
        /* DS session errors */
        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, task->tk_status);
                break;
        case -NFS4ERR_DELAY:
        case -NFS4ERR_GRACE:
                rpc_delay(task, FILELAYOUT_POLL_RETRY_MAX);
                break;
        case -NFS4ERR_RETRY_UNCACHED_REP:
                break;
        /* Invalidate Layout errors */
        case -NFS4ERR_PNFS_NO_LAYOUT:
        case -ESTALE:           /* mapped NFS4ERR_STALE */
        case -EBADHANDLE:       /* mapped NFS4ERR_BADHANDLE */
        case -EISDIR:           /* mapped NFS4ERR_ISDIR */
        case -NFS4ERR_FHEXPIRED:
        case -NFS4ERR_WRONG_TYPE:
                dprintk("%s Invalid layout error %d\n", __func__,
                        task->tk_status);
                /*
                 * Destroy layout so new i/o will get a new layout.
                 * Layout will not be destroyed until all current lseg
                 * references are put. Mark layout as invalid to resend failed
                 * i/o and all i/o waiting on the slot table to the MDS until
                 * layout is destroyed and a new valid layout is obtained.
                 */
                pnfs_destroy_layout(NFS_I(inode));
                rpc_wake_up(&tbl->slot_tbl_waitq);
                goto reset;
        /* RPC connection errors */
        case -ECONNREFUSED:
        case -EHOSTDOWN:
        case -EHOSTUNREACH:
        case -ENETUNREACH:
        case -EIO:
        case -ETIMEDOUT:
        case -EPIPE:
                dprintk("%s DS connection error %d\n", __func__,
                        task->tk_status);
                nfs4_mark_deviceid_unavailable(devid);
                set_bit(NFS_LAYOUT_RETURN, &lo->plh_flags);
                rpc_wake_up(&tbl->slot_tbl_waitq);
                /* fall through */
        default:
reset:
                dprintk("%s Retry through MDS. Error %d\n", __func__,
                        task->tk_status);
                return -NFS4ERR_RESET_TO_MDS;
        }
out:
        task->tk_status = 0;
        return -EAGAIN;
wait_on_recovery:
        rpc_sleep_on(&mds_client->cl_rpcwaitq, task, NULL);
        if (test_bit(NFS4CLNT_MANAGER_RUNNING, &mds_client->cl_state) == 0)
                rpc_wake_up_queued_task(&mds_client->cl_rpcwaitq, task);
        goto out;
}

/* NFS_PROTO call done callback routines */

static int filelayout_read_done_cb(struct rpc_task *task,
                                struct nfs_read_data *data)
{
        struct nfs_pgio_header *hdr = data->header;
        int err;

        err = filelayout_async_handle_error(task, data->args.context->state,
                                            data->ds_clp, hdr->lseg);

        switch (err) {
        case -NFS4ERR_RESET_TO_MDS:
                filelayout_reset_read(data);
                return task->tk_status;
        case -EAGAIN:
                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)
{
        struct nfs_pgio_header *hdr = wdata->header;

        if (FILELAYOUT_LSEG(hdr->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__, hdr->inode->i_ino,
                (unsigned long) NFS_I(hdr->inode)->layout->plh_lwb);
}

bool
filelayout_test_devid_unavailable(struct nfs4_deviceid_node *node)
{
        return filelayout_test_devid_invalid(node) ||
                nfs4_test_deviceid_unavailable(node);
}

static bool
filelayout_reset_to_mds(struct pnfs_layout_segment *lseg)
{
        struct nfs4_deviceid_node *node = FILELAYOUT_DEVID_NODE(lseg);

        return filelayout_test_devid_unavailable(node);
}

/*
 * 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 = data;

        if (filelayout_reset_to_mds(rdata->header->lseg)) {
                dprintk("%s task %u reset io to MDS\n", __func__, task->tk_pid);
                filelayout_reset_read(rdata);
                rpc_exit(task, 0);
                return;
        }
        rdata->read_done_cb = filelayout_read_done_cb;

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

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

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

        if (test_bit(NFS_IOHDR_REDO, &rdata->header->flags) &&
            task->tk_status == 0)
                return;

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

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

        rpc_count_iostats(task, NFS_SERVER(rdata->header->inode)->client->cl_metrics);
}

static void filelayout_read_release(void *data)
{
        struct nfs_read_data *rdata = data;
        struct pnfs_layout_hdr *lo = rdata->header->lseg->pls_layout;

        filelayout_fenceme(lo->plh_inode, lo);
        nfs_put_client(rdata->ds_clp);
        rdata->header->mds_ops->rpc_release(data);
}

static int filelayout_write_done_cb(struct rpc_task *task,
                                struct nfs_write_data *data)
{
        struct nfs_pgio_header *hdr = data->header;
        int err;

        err = filelayout_async_handle_error(task, data->args.context->state,
                                            data->ds_clp, hdr->lseg);

        switch (err) {
        case -NFS4ERR_RESET_TO_MDS:
                filelayout_reset_write(data);
                return task->tk_status;
        case -EAGAIN:
                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_commit_data *data)
{
        struct nfs_page *first = nfs_list_entry(data->pages.next);

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

static int filelayout_commit_done_cb(struct rpc_task *task,
                                     struct nfs_commit_data *data)
{
        int err;

        err = filelayout_async_handle_error(task, NULL, data->ds_clp,
                                            data->lseg);

        switch (err) {
        case -NFS4ERR_RESET_TO_MDS:
                prepare_to_resend_writes(data);
                return -EAGAIN;
        case -EAGAIN:
                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 = data;

        if (filelayout_reset_to_mds(wdata->header->lseg)) {
                dprintk("%s task %u reset io to MDS\n", __func__, task->tk_pid);
                filelayout_reset_write(wdata);
                rpc_exit(task, 0);
                return;
        }
        nfs41_setup_sequence(wdata->ds_clp->cl_session,
                        &wdata->args.seq_args,
                        &wdata->res.seq_res,
                        task);
}

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

        if (test_bit(NFS_IOHDR_REDO, &wdata->header->flags) &&
            task->tk_status == 0)
                return;

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

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

        rpc_count_iostats(task, NFS_SERVER(wdata->header->inode)->client->cl_metrics);
}

static void filelayout_write_release(void *data)
{
        struct nfs_write_data *wdata = data;
        struct pnfs_layout_hdr *lo = wdata->header->lseg->pls_layout;

        filelayout_fenceme(lo->plh_inode, lo);
        nfs_put_client(wdata->ds_clp);
        wdata->header->mds_ops->rpc_release(data);
}

static void filelayout_commit_prepare(struct rpc_task *task, void *data)
{
        struct nfs_commit_data *wdata = data;

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

static void filelayout_write_commit_done(struct rpc_task *task, void *data)
{
        struct nfs_commit_data *wdata = data;

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

static void filelayout_commit_count_stats(struct rpc_task *task, void *data)
{
        struct nfs_commit_data *cdata = data;

        rpc_count_iostats(task, NFS_SERVER(cdata->inode)->client->cl_metrics);
}

static void filelayout_commit_release(void *calldata)
{
        struct nfs_commit_data *data = calldata;

        data->completion_ops->completion(data);
        pnfs_put_lseg(data->lseg);
        nfs_put_client(data->ds_clp);
        nfs_commitdata_release(data);
}

static const struct rpc_call_ops filelayout_read_call_ops = {
        .rpc_call_prepare = filelayout_read_prepare,
        .rpc_call_done = filelayout_read_call_done,
        .rpc_count_stats = filelayout_read_count_stats,
        .rpc_release = filelayout_read_release,
};

static const struct rpc_call_ops filelayout_write_call_ops = {
        .rpc_call_prepare = filelayout_write_prepare,
        .rpc_call_done = filelayout_write_call_done,
        .rpc_count_stats = filelayout_write_count_stats,
        .rpc_release = filelayout_write_release,
};

static const struct rpc_call_ops filelayout_commit_call_ops = {
        .rpc_call_prepare = filelayout_commit_prepare,
        .rpc_call_done = filelayout_write_commit_done,
        .rpc_count_stats = filelayout_commit_count_stats,
        .rpc_release = filelayout_commit_release,
};

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

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

        /* 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)
                return PNFS_NOT_ATTEMPTED;
        dprintk("%s USE DS: %s cl_count %d\n", __func__,
                ds->ds_remotestr, atomic_read(&ds->ds_clp->cl_count));

        /* No multipath support. Use first DS */
        atomic_inc(&ds->ds_clp->cl_count);
        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 */
        nfs_initiate_read(ds->ds_clp->cl_rpcclient, data,
                                  &filelayout_read_call_ops, RPC_TASK_SOFTCONN);
        return PNFS_ATTEMPTED;
}

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

        /* 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)
                return PNFS_NOT_ATTEMPTED;
        dprintk("%s ino %lu sync %d req %Zu@%llu DS: %s cl_count %d\n",
                __func__, hdr->inode->i_ino, sync, (size_t) data->args.count,
                offset, ds->ds_remotestr, atomic_read(&ds->ds_clp->cl_count));

        data->write_done_cb = filelayout_write_done_cb;
        atomic_inc(&ds->ds_clp->cl_count);
        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 */
        nfs_initiate_write(ds->ds_clp->cl_rpcclient, data,
                                    &filelayout_write_call_ops, sync,
                                    RPC_TASK_SOFTCONN);
        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 = filelayout_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 unavailable */
        if (filelayout_test_devid_unavailable(&dsaddr->id_node))
                        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 = kcalloc(fl->num_fh, sizeof(fl->fh_array[0]),
                                       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 "NFS: 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);
        /* This assumes a single RW lseg */
        if (lseg->pls_range.iomode == IOMODE_RW) {
                struct nfs4_filelayout *flo;

                flo = FILELAYOUT_FROM_HDR(lseg->pls_layout);
                flo->commit_info.nbuckets = 0;
                kfree(flo->commit_info.buckets);
                flo->commit_info.buckets = NULL;
        }
        _filelayout_free_lseg(fl);
}

static int
filelayout_alloc_commit_info(struct pnfs_layout_segment *lseg,
                             struct nfs_commit_info *cinfo,
                             gfp_t gfp_flags)
{
        struct nfs4_filelayout_segment *fl = FILELAYOUT_LSEG(lseg);
        struct pnfs_commit_bucket *buckets;
        int size;

        if (fl->commit_through_mds)
                return 0;
        if (cinfo->ds->nbuckets != 0) {
                /* 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().
                 * */
                return 0;
        }

        size = (fl->stripe_type == STRIPE_SPARSE) ?
                fl->dsaddr->ds_num : fl->dsaddr->stripe_count;

        buckets = kcalloc(size, sizeof(struct pnfs_commit_bucket),
                          gfp_flags);
        if (!buckets)
                return -ENOMEM;
        else {
                int i;

                spin_lock(cinfo->lock);
                if (cinfo->ds->nbuckets != 0)
                        kfree(buckets);
                else {
                        cinfo->ds->buckets = buckets;
                        cinfo->ds->nbuckets = size;
                        for (i = 0; i < size; i++) {
                                INIT_LIST_HEAD(&buckets[i].written);
                                INIT_LIST_HEAD(&buckets[i].committing);
                        }
                }
                spin_unlock(cinfo->lock);
                return 0;
        }
}

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;
        }
        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)req_offset(prev);
        r_stripe = (u64)req_offset(req);
        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);
}

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

        if (req->wb_offset != req->wb_pgbase) {
                /*
                 * Handling unaligned pages is difficult, because have to
                 * somehow split a req in two in certain cases in the
                 * pg.test code.  Avoid this by just not using pnfs
                 * in this case.
                 */
                nfs_pageio_reset_read_mds(pgio);
                return;
        }
        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);
}

static void
filelayout_pg_init_write(struct nfs_pageio_descriptor *pgio,
                         struct nfs_page *req)
{
        struct nfs_commit_info cinfo;
        int status;

        WARN_ON_ONCE(pgio->pg_lseg != NULL);

        if (req->wb_offset != req->wb_pgbase)
                goto out_mds;
        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)
                goto out_mds;
        nfs_init_cinfo(&cinfo, pgio->pg_inode, pgio->pg_dreq);
        status = filelayout_alloc_commit_info(pgio->pg_lseg, &cinfo, GFP_NOFS);
        if (status < 0) {
                pnfs_put_lseg(pgio->pg_lseg);
                pgio->pg_lseg = NULL;
                goto out_mds;
        }
        return;
out_mds:
        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 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;
}

/* The generic layer is about to remove the req from the commit list.
 * If this will make the bucket empty, it will need to put the lseg reference.
 */
static void
filelayout_clear_request_commit(struct nfs_page *req,
                                struct nfs_commit_info *cinfo)
{
        struct pnfs_layout_segment *freeme = NULL;

        spin_lock(cinfo->lock);
        if (!test_and_clear_bit(PG_COMMIT_TO_DS, &req->wb_flags))
                goto out;
        cinfo->ds->nwritten--;
        if (list_is_singular(&req->wb_list)) {
                struct pnfs_commit_bucket *bucket;

                bucket = list_first_entry(&req->wb_list,
                                          struct pnfs_commit_bucket,
                                          written);
                freeme = bucket->wlseg;
                bucket->wlseg = NULL;
        }
out:
        nfs_request_remove_commit_list(req, cinfo);
        spin_unlock(cinfo->lock);
        pnfs_put_lseg(freeme);
}

static struct list_head *
filelayout_choose_commit_list(struct nfs_page *req,
                              struct pnfs_layout_segment *lseg,
                              struct nfs_commit_info *cinfo)
{
        struct nfs4_filelayout_segment *fl = FILELAYOUT_LSEG(lseg);
        u32 i, j;
        struct list_head *list;
        struct pnfs_commit_bucket *buckets;

        if (fl->commit_through_mds)
                return &cinfo->mds->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, req_offset(req));
        i = select_bucket_index(fl, j);
        buckets = cinfo->ds->buckets;
        list = &buckets[i].written;
        if (list_empty(list)) {
                /* Non-empty buckets hold a reference on the lseg.  That ref
                 * is normally transferred to the COMMIT call and released
                 * there.  It could also be released if the last req is pulled
                 * off due to a rewrite, in which case it will be done in
                 * filelayout_clear_request_commit
                 */
                buckets[i].wlseg = pnfs_get_lseg(lseg);
        }
        set_bit(PG_COMMIT_TO_DS, &req->wb_flags);
        cinfo->ds->nwritten++;
        return list;
}

static void
filelayout_mark_request_commit(struct nfs_page *req,
                               struct pnfs_layout_segment *lseg,
                               struct nfs_commit_info *cinfo)
{
        struct list_head *list;

        list = filelayout_choose_commit_list(req, lseg, cinfo);
        nfs_request_add_commit_list(req, list, cinfo);
}

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_commit_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) {
                prepare_to_resend_writes(data);
                filelayout_commit_release(data);
                return -EAGAIN;
        }
        dprintk("%s ino %lu, how %d cl_count %d\n", __func__,
                data->inode->i_ino, how, atomic_read(&ds->ds_clp->cl_count));
        data->commit_done_cb = filelayout_commit_done_cb;
        atomic_inc(&ds->ds_clp->cl_count);
        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(ds->ds_clp->cl_rpcclient, data,
                                   &filelayout_commit_call_ops, how,
                                   RPC_TASK_SOFTCONN);
}

static int
transfer_commit_list(struct list_head *src, struct list_head *dst,
                     struct nfs_commit_info *cinfo, int max)
{
        struct nfs_page *req, *tmp;
        int ret = 0;

        list_for_each_entry_safe(req, tmp, src, wb_list) {
                if (!nfs_lock_request(req))
                        continue;
                kref_get(&req->wb_kref);
                if (cond_resched_lock(cinfo->lock))
                        list_safe_reset_next(req, tmp, wb_list);
                nfs_request_remove_commit_list(req, cinfo);
                clear_bit(PG_COMMIT_TO_DS, &req->wb_flags);
                nfs_list_add_request(req, dst);
                ret++;
                if ((ret == max) && !cinfo->dreq)
                        break;
        }
        return ret;
}

static int
filelayout_scan_ds_commit_list(struct pnfs_commit_bucket *bucket,
                               struct nfs_commit_info *cinfo,
                               int max)
{
        struct list_head *src = &bucket->written;
        struct list_head *dst = &bucket->committing;
        int ret;

        ret = transfer_commit_list(src, dst, cinfo, max);
        if (ret) {
                cinfo->ds->nwritten -= ret;
                cinfo->ds->ncommitting += ret;
                bucket->clseg = bucket->wlseg;
                if (list_empty(src))
                        bucket->wlseg = NULL;
                else
                        pnfs_get_lseg(bucket->clseg);
        }
        return ret;
}

/* Move reqs from written to committing lists, returning count of number moved.
 * Note called with cinfo->lock held.
 */
static int filelayout_scan_commit_lists(struct nfs_commit_info *cinfo,
                                        int max)
{
        int i, rv = 0, cnt;

        for (i = 0; i < cinfo->ds->nbuckets && max != 0; i++) {
                cnt = filelayout_scan_ds_commit_list(&cinfo->ds->buckets[i],
                                                     cinfo, max);
                max -= cnt;
                rv += cnt;
        }
        return rv;
}

/* Pull everything off the committing lists and dump into @dst */
static void filelayout_recover_commit_reqs(struct list_head *dst,
                                           struct nfs_commit_info *cinfo)
{
        struct pnfs_commit_bucket *b;
        int i;

        /* NOTE cinfo->lock is NOT held, relying on fact that this is
         * only called on single thread per dreq.
         * Can't take the lock because need to do pnfs_put_lseg
         */
        for (i = 0, b = cinfo->ds->buckets; i < cinfo->ds->nbuckets; i++, b++) {
                if (transfer_commit_list(&b->written, dst, cinfo, 0)) {
                        pnfs_put_lseg(b->wlseg);
                        b->wlseg = NULL;
                }
        }
        cinfo->ds->nwritten = 0;
}

static unsigned int
alloc_ds_commits(struct nfs_commit_info *cinfo, struct list_head *list)
{
        struct pnfs_ds_commit_info *fl_cinfo;
        struct pnfs_commit_bucket *bucket;
        struct nfs_commit_data *data;
        int i, j;
        unsigned int nreq = 0;

        fl_cinfo = cinfo->ds;
        bucket = fl_cinfo->buckets;
        for (i = 0; i < fl_cinfo->nbuckets; i++, bucket++) {
                if (list_empty(&bucket->committing))
                        continue;
                data = nfs_commitdata_alloc();
                if (!data)
                        break;
                data->ds_commit_index = i;
                data->lseg = bucket->clseg;
                bucket->clseg = NULL;
                list_add(&data->pages, list);
                nreq++;
        }

        /* Clean up on error */
        for (j = i; j < fl_cinfo->nbuckets; j++, bucket++) {
                if (list_empty(&bucket->committing))
                        continue;
                nfs_retry_commit(&bucket->committing, bucket->clseg, cinfo);
                pnfs_put_lseg(bucket->clseg);
                bucket->clseg = NULL;
        }
        /* Caller will clean up entries put on list */
        return nreq;
}

/* This follows nfs_commit_list pretty closely */
static int
filelayout_commit_pagelist(struct inode *inode, struct list_head *mds_pages,
                           int how, struct nfs_commit_info *cinfo)
{
        struct nfs_commit_data *data, *tmp;
        LIST_HEAD(list);
        unsigned int nreq = 0;

        if (!list_empty(mds_pages)) {
                data = nfs_commitdata_alloc();
                if (data != NULL) {
                        data->lseg = NULL;
                        list_add(&data->pages, &list);
                        nreq++;
                } else
                        nfs_retry_commit(mds_pages, NULL, cinfo);
        }

        nreq += alloc_ds_commits(cinfo, &list);

        if (nreq == 0) {
                cinfo->completion_ops->error_cleanup(NFS_I(inode));
                goto out;
        }

        atomic_add(nreq, &cinfo->mds->rpcs_out);

        list_for_each_entry_safe(data, tmp, &list, pages) {
                list_del_init(&data->pages);
                if (!data->lseg) {
                        nfs_init_commit(data, mds_pages, NULL, cinfo);
                        nfs_initiate_commit(NFS_CLIENT(inode), data,
                                            data->mds_ops, how, 0);
                } else {
                        struct pnfs_commit_bucket *buckets;

                        buckets = cinfo->ds->buckets;
                        nfs_init_commit(data, &buckets[data->ds_commit_index].committing, data->lseg, cinfo);
                        filelayout_initiate_commit(data, how);
                }
        }
out:
        cinfo->ds->ncommitting = 0;
        return PNFS_ATTEMPTED;
}

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_layout_hdr *
filelayout_alloc_layout_hdr(struct inode *inode, gfp_t gfp_flags)
{
        struct nfs4_filelayout *flo;

        flo = kzalloc(sizeof(*flo), gfp_flags);
        return &flo->generic_hdr;
}

static void
filelayout_free_layout_hdr(struct pnfs_layout_hdr *lo)
{
        kfree(FILELAYOUT_FROM_HDR(lo));
}

static struct pnfs_ds_commit_info *
filelayout_get_ds_info(struct inode *inode)
{
        struct pnfs_layout_hdr *layout = NFS_I(inode)->layout;

        if (layout == NULL)
                return NULL;
        else
                return &FILELAYOUT_FROM_HDR(layout)->commit_info;
}

static struct pnfs_layoutdriver_type filelayout_type = {
        .id                     = LAYOUT_NFSV4_1_FILES,
        .name                   = "LAYOUT_NFSV4_1_FILES",
        .owner                  = THIS_MODULE,
        .alloc_layout_hdr       = filelayout_alloc_layout_hdr,
        .free_layout_hdr        = filelayout_free_layout_hdr,
        .alloc_lseg             = filelayout_alloc_lseg,
        .free_lseg              = filelayout_free_lseg,
        .pg_read_ops            = &filelayout_pg_read_ops,
        .pg_write_ops           = &filelayout_pg_write_ops,
        .get_ds_info            = &filelayout_get_ds_info,
        .mark_request_commit    = filelayout_mark_request_commit,
        .clear_request_commit   = filelayout_clear_request_commit,
        .scan_commit_lists      = filelayout_scan_commit_lists,
        .recover_commit_reqs    = filelayout_recover_commit_reqs,
        .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);