nfs4filelayout.c

Go to the documentation of this file.

/*
 *  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 <[email protected]>
 *
 *  Permission is granted to use, copy, create derivative works, and
 *  redistribute this software and such derivative works for any purpose,
 *  so long as the name of the University of Michigan is not used in
 *  any advertising or publicity pertaining to the use or distribution
 *  of this software without specific, written prior authorization. If
 *  the above copyright notice or any other identification of the
 *  University of Michigan is included in any copy of any portion of
 *  this software, then the disclaimer below must also be included.
 *
 *  This software is provided as is, without representation 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 "internal.h"
#include "delegation.h"
#include "nfs4filelayout.h"

#define NFSDBG_FACILITY         NFSDBG_PNFS_LD

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Dean Hildebrand <[email protected]>");
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:
    case -EKEYEXPIRED:
        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;

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

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

    rpc_call_start(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;

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

    rpc_call_start(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;
    int status;

    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 */
    status = nfs_initiate_read(ds->ds_clp->cl_rpcclient, data,
                  &filelayout_read_call_ops, RPC_TASK_SOFTCONN);
    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 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;
    int status;

    /* 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 */
    status = nfs_initiate_write(ds->ds_clp->cl_rpcclient, data,
                    &filelayout_write_call_ops, sync,
                    RPC_TASK_SOFTCONN);
    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 = 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)
{
    BUG_ON(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;

    BUG_ON(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)) {
            BUG_ON(!list_empty(&b->written));
            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);