/*
 *  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/backing-dev.h>

#include <linux/sunrpc/metrics.h>

#include "../nfs4session.h"
#include "../internal.h"
#include "../delegation.h"
#include "filelayout.h"
#include "../nfs4trace.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 const struct pnfs_commit_ops filelayout_commit_ops;

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_pgio_header *hdr)
{
        struct rpc_task *task = &hdr->task;

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

                task->tk_status = pnfs_write_done_resend_to_mds(hdr);
        }
}

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

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

                task->tk_status = pnfs_read_done_resend_to_mds(hdr);
        }
}

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 nfs4_deviceid_node *devid = FILELAYOUT_DEVID_NODE(lseg);
        struct nfs4_slot_table *tbl = &clp->cl_session->fc_slot_table;

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

        switch (task->tk_status) {
        /* 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_ACCESS:
        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:
        case -EPROTO:
        case -ENODEV:
                dprintk("%s DS connection error %d\n", __func__,
                        task->tk_status);
                nfs4_mark_deviceid_unavailable(devid);
                pnfs_error_mark_layout_for_return(inode, lseg);
                pnfs_set_lo_fail(lseg);
                rpc_wake_up(&tbl->slot_tbl_waitq);
                fallthrough;
        default:
reset:
                dprintk("%s Retry through MDS. Error %d\n", __func__,
                        task->tk_status);
                return -NFS4ERR_RESET_TO_MDS;
        }
        task->tk_status = 0;
        return -EAGAIN;
}

/* NFS_PROTO call done callback routines */

static int filelayout_read_done_cb(struct rpc_task *task,
                                struct nfs_pgio_header *hdr)
{
        int err;

        trace_nfs4_pnfs_read(hdr, task->tk_status);
        err = filelayout_async_handle_error(task, hdr->args.context->state,
                                            hdr->ds_clp, hdr->lseg);

        switch (err) {
        case -NFS4ERR_RESET_TO_MDS:
                filelayout_reset_read(hdr);
                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_pgio_header *hdr)
{
        loff_t end_offs = 0;

        if (FILELAYOUT_LSEG(hdr->lseg)->commit_through_mds ||
            hdr->res.verf->committed == NFS_FILE_SYNC)
                return;
        if (hdr->res.verf->committed == NFS_DATA_SYNC)
                end_offs = hdr->mds_offset + (loff_t)hdr->res.count;

        /* Note: if the write is unstable, don't set end_offs until commit */
        pnfs_set_layoutcommit(hdr->inode, hdr->lseg, end_offs);
        dprintk("%s inode %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_pgio_header *hdr = data;

        if (unlikely(test_bit(NFS_CONTEXT_BAD, &hdr->args.context->flags))) {
                rpc_exit(task, -EIO);
                return;
        }
        if (filelayout_reset_to_mds(hdr->lseg)) {
                dprintk("%s task %u reset io to MDS\n", __func__, task->tk_pid);
                filelayout_reset_read(hdr);
                rpc_exit(task, 0);
                return;
        }
        hdr->pgio_done_cb = filelayout_read_done_cb;

        if (nfs4_setup_sequence(hdr->ds_clp,
                        &hdr->args.seq_args,
                        &hdr->res.seq_res,
                        task))
                return;
        if (nfs4_set_rw_stateid(&hdr->args.stateid, hdr->args.context,
                        hdr->args.lock_context, FMODE_READ) == -EIO)
                rpc_exit(task, -EIO); /* lost lock, terminate I/O */
}

static void filelayout_read_call_done(struct rpc_task *task, void *data)
{
        struct nfs_pgio_header *hdr = data;

        if (test_bit(NFS_IOHDR_REDO, &hdr->flags) &&
            task->tk_status == 0) {
                nfs41_sequence_done(task, &hdr->res.seq_res);
                return;
        }

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

static void filelayout_read_count_stats(struct rpc_task *task, void *data)
{
        struct nfs_pgio_header *hdr = data;

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

static int filelayout_write_done_cb(struct rpc_task *task,
                                struct nfs_pgio_header *hdr)
{
        int err;

        trace_nfs4_pnfs_write(hdr, task->tk_status);
        err = filelayout_async_handle_error(task, hdr->args.context->state,
                                            hdr->ds_clp, hdr->lseg);

        switch (err) {
        case -NFS4ERR_RESET_TO_MDS:
                filelayout_reset_write(hdr);
                return task->tk_status;
        case -EAGAIN:
                rpc_restart_call_prepare(task);
                return -EAGAIN;
        }

        filelayout_set_layoutcommit(hdr);

        /* zero out the fattr */
        hdr->fattr.valid = 0;
        if (task->tk_status >= 0)
                nfs_writeback_update_inode(hdr);

        return 0;
}

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

        trace_nfs4_pnfs_commit_ds(data, task->tk_status);
        err = filelayout_async_handle_error(task, NULL, data->ds_clp,
                                            data->lseg);

        switch (err) {
        case -NFS4ERR_RESET_TO_MDS:
                pnfs_generic_prepare_to_resend_writes(data);
                return -EAGAIN;
        case -EAGAIN:
                rpc_restart_call_prepare(task);
                return -EAGAIN;
        }

        pnfs_set_layoutcommit(data->inode, data->lseg, data->lwb);

        return 0;
}

static void filelayout_write_prepare(struct rpc_task *task, void *data)
{
        struct nfs_pgio_header *hdr = data;

        if (unlikely(test_bit(NFS_CONTEXT_BAD, &hdr->args.context->flags))) {
                rpc_exit(task, -EIO);
                return;
        }
        if (filelayout_reset_to_mds(hdr->lseg)) {
                dprintk("%s task %u reset io to MDS\n", __func__, task->tk_pid);
                filelayout_reset_write(hdr);
                rpc_exit(task, 0);
                return;
        }
        if (nfs4_setup_sequence(hdr->ds_clp,
                        &hdr->args.seq_args,
                        &hdr->res.seq_res,
                        task))
                return;
        if (nfs4_set_rw_stateid(&hdr->args.stateid, hdr->args.context,
                        hdr->args.lock_context, FMODE_WRITE) == -EIO)
                rpc_exit(task, -EIO); /* lost lock, terminate I/O */
}

static void filelayout_write_call_done(struct rpc_task *task, void *data)
{
        struct nfs_pgio_header *hdr = data;

        if (test_bit(NFS_IOHDR_REDO, &hdr->flags) &&
            task->tk_status == 0) {
                nfs41_sequence_done(task, &hdr->res.seq_res);
                return;
        }

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

static void filelayout_write_count_stats(struct rpc_task *task, void *data)
{
        struct nfs_pgio_header *hdr = data;

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

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

        nfs4_setup_sequence(wdata->ds_clp,
                        &wdata->args.seq_args,
                        &wdata->res.seq_res,
                        task);
}

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 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 = pnfs_generic_rw_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 = pnfs_generic_rw_release,
};

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

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

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

        ds_clnt = nfs4_find_or_create_ds_client(ds->ds_clp, hdr->inode);
        if (IS_ERR(ds_clnt))
                return PNFS_NOT_ATTEMPTED;

        dprintk("%s USE DS: %s cl_count %d\n", __func__,
                ds->ds_remotestr, refcount_read(&ds->ds_clp->cl_count));

        /* No multipath support. Use first DS */
        refcount_inc(&ds->ds_clp->cl_count);
        hdr->ds_clp = ds->ds_clp;
        hdr->ds_commit_idx = idx;
        fh = nfs4_fl_select_ds_fh(lseg, j);
        if (fh)
                hdr->args.fh = fh;

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

        /* Perform an asynchronous read to ds */
        nfs_initiate_pgio(ds_clnt, hdr, hdr->cred,
                          NFS_PROTO(hdr->inode), &filelayout_read_call_ops,
                          0, RPC_TASK_SOFTCONN, NULL);
        return PNFS_ATTEMPTED;
}

/* Perform async writes. */
static enum pnfs_try_status
filelayout_write_pagelist(struct nfs_pgio_header *hdr, int sync)
{
        struct pnfs_layout_segment *lseg = hdr->lseg;
        struct nfs4_pnfs_ds *ds;
        struct rpc_clnt *ds_clnt;
        loff_t offset = hdr->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;

        ds_clnt = nfs4_find_or_create_ds_client(ds->ds_clp, hdr->inode);
        if (IS_ERR(ds_clnt))
                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) hdr->args.count,
                offset, ds->ds_remotestr, refcount_read(&ds->ds_clp->cl_count));

        hdr->pgio_done_cb = filelayout_write_done_cb;
        refcount_inc(&ds->ds_clp->cl_count);
        hdr->ds_clp = ds->ds_clp;
        hdr->ds_commit_idx = idx;
        fh = nfs4_fl_select_ds_fh(lseg, j);
        if (fh)
                hdr->args.fh = fh;
        hdr->args.offset = filelayout_get_dserver_offset(lseg, offset);

        /* Perform an asynchronous write */
        nfs_initiate_pgio(ds_clnt, hdr, hdr->cred,
                          NFS_PROTO(hdr->inode), &filelayout_write_call_ops,
                          sync, RPC_TASK_SOFTCONN, NULL);
        return PNFS_ATTEMPTED;
}

static int
filelayout_check_deviceid(struct pnfs_layout_hdr *lo,
                          struct nfs4_filelayout_segment *fl,
                          gfp_t gfp_flags)
{
        struct nfs4_deviceid_node *d;
        struct nfs4_file_layout_dsaddr *dsaddr;
        int status = -EINVAL;

        /* Is the deviceid already set? If so, we're good. */
        if (fl->dsaddr != NULL)
                return 0;

        /* find and reference the deviceid */
        d = nfs4_find_get_deviceid(NFS_SERVER(lo->plh_inode), &fl->deviceid,
                        lo->plh_lc_cred, gfp_flags);
        if (d == NULL)
                goto out;

        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;

        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;
        }
        status = 0;

        /*
         * Atomic compare and xchange to ensure we don't scribble
         * over a non-NULL pointer.
         */
        if (cmpxchg(&fl->dsaddr, NULL, dsaddr) != NULL)
                goto out_put;
out:
        return status;
out_put:
        nfs4_fl_put_deviceid(dsaddr);
        goto out;
}

/*
 * 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,
                        gfp_t gfp_flags)
{
        int status = -EINVAL;

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

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

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

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

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

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

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

        scratch = folio_alloc(gfp_flags, 0);
        if (!scratch)
                return -ENOMEM;

        xdr_init_decode_pages(&stream, &buf, lgr->layoutp->pages, lgr->layoutp->len);
        xdr_set_scratch_folio(&stream, scratch);

        /* 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(&fl->deviceid, p, sizeof(fl->deviceid));
        p += XDR_QUADLEN(NFS4_DEVICEID4_SIZE);
        nfs4_print_deviceid(&fl->deviceid);

        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_objs(fl->fh_array[0], fl->num_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_obj(struct nfs_fh, gfp_flags);
                if (!fl->fh_array[i])
                        goto out_err;

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

                p = xdr_inline_decode(&stream, fl->fh_array[i]->size);
                if (unlikely(!p))
                        goto out_err;
                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);
        }

        folio_put(scratch);
        return 0;

out_err:
        folio_put(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__);
        if (fl->dsaddr != NULL)
                nfs4_fl_put_deviceid(fl->dsaddr);
        /* This assumes a single RW lseg */
        if (lseg->pls_range.iomode == IOMODE_RW) {
                struct nfs4_filelayout *flo;
                struct inode *inode;

                flo = FILELAYOUT_FROM_HDR(lseg->pls_layout);
                inode = flo->generic_hdr.plh_inode;
                spin_lock(&inode->i_lock);
                pnfs_generic_ds_cinfo_release_lseg(&flo->commit_info, lseg);
                spin_unlock(&inode->i_lock);
        }
        _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;

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

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

static bool
filelayout_lseg_is_striped(const struct nfs4_filelayout_segment *flseg)
{
        return flseg->num_fh > 1;
}

/*
 * filelayout_pg_test(). Called by nfs_can_coalesce_requests()
 *
 * Return 0 if @req cannot be coalesced into @pgio, otherwise return the number
 * of bytes (maximum @req->wb_bytes) that can be coalesced.
 */
static size_t
filelayout_pg_test(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
                   struct nfs_page *req)
{
        unsigned int size;
        u64 p_stripe, r_stripe;
        u32 stripe_offset;
        u64 segment_offset = pgio->pg_lseg->pls_range.offset;
        u32 stripe_unit = FILELAYOUT_LSEG(pgio->pg_lseg)->stripe_unit;

        /* calls nfs_generic_pg_test */
        size = pnfs_generic_pg_test(pgio, prev, req);
        if (!size)
                return 0;
        else if (!filelayout_lseg_is_striped(FILELAYOUT_LSEG(pgio->pg_lseg)))
                return size;

        /* see if req and prev are in the same stripe */
        if (prev) {
                p_stripe = (u64)req_offset(prev) - segment_offset;
                r_stripe = (u64)req_offset(req) - segment_offset;
                do_div(p_stripe, stripe_unit);
                do_div(r_stripe, stripe_unit);

                if (p_stripe != r_stripe)
                        return 0;
        }

        /* calculate remaining bytes in the current stripe */
        div_u64_rem((u64)req_offset(req) - segment_offset,
                        stripe_unit,
                        &stripe_offset);
        WARN_ON_ONCE(stripe_offset > stripe_unit);
        if (stripe_offset >= stripe_unit)
                return 0;
        return min(stripe_unit - (unsigned int)stripe_offset, size);
}

static struct pnfs_layout_segment *
fl_pnfs_update_layout(struct inode *ino,
                      struct nfs_open_context *ctx,
                      loff_t pos,
                      u64 count,
                      enum pnfs_iomode iomode,
                      bool strict_iomode,
                      gfp_t gfp_flags)
{
        struct pnfs_layout_segment *lseg = NULL;
        struct pnfs_layout_hdr *lo;
        struct nfs4_filelayout_segment *fl;
        int status;

        lseg = pnfs_update_layout(ino, ctx, pos, count, iomode, strict_iomode,
                                  gfp_flags);
        if (IS_ERR(lseg)) {
                /* Fall back to MDS on recoverable errors */
                if (!nfs_error_is_fatal_on_server(PTR_ERR(lseg)))
                        lseg = NULL;
                goto out;
        } else if (!lseg)
                goto out;

        lo = NFS_I(ino)->layout;
        fl = FILELAYOUT_LSEG(lseg);

        status = filelayout_check_deviceid(lo, fl, gfp_flags);
        if (status) {
                pnfs_error_mark_layout_for_return(ino, lseg);
                pnfs_set_lo_fail(lseg);
                pnfs_put_lseg(lseg);
                lseg = NULL;
        }
out:
        return lseg;
}

static void
filelayout_pg_init_read(struct nfs_pageio_descriptor *pgio,
                        struct nfs_page *req)
{
        pnfs_generic_pg_check_layout(pgio, req);
        if (!pgio->pg_lseg) {
                pgio->pg_lseg = fl_pnfs_update_layout(pgio->pg_inode,
                                                      nfs_req_openctx(req),
                                                      req_offset(req),
                                                      req->wb_bytes,
                                                      IOMODE_READ,
                                                      false,
                                                      nfs_io_gfp_mask());
                if (IS_ERR(pgio->pg_lseg)) {
                        pgio->pg_error = PTR_ERR(pgio->pg_lseg);
                        pgio->pg_lseg = NULL;
                        return;
                }
        }
        /* 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)
{
        pnfs_generic_pg_check_layout(pgio, req);
        if (!pgio->pg_lseg) {
                pgio->pg_lseg = fl_pnfs_update_layout(pgio->pg_inode,
                                                      nfs_req_openctx(req),
                                                      req_offset(req),
                                                      req->wb_bytes,
                                                      IOMODE_RW,
                                                      false,
                                                      nfs_io_gfp_mask());
                if (IS_ERR(pgio->pg_lseg)) {
                        pgio->pg_error = PTR_ERR(pgio->pg_lseg);
                        pgio->pg_lseg = NULL;
                        return;
                }
        }

        /* 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,
        .pg_cleanup = pnfs_generic_pg_cleanup,
};

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,
        .pg_cleanup = pnfs_generic_pg_cleanup,
};

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;
}

static void
filelayout_mark_request_commit(struct nfs_page *req,
                               struct pnfs_layout_segment *lseg,
                               struct nfs_commit_info *cinfo,
                               u32 ds_commit_idx)

{
        struct nfs4_filelayout_segment *fl = FILELAYOUT_LSEG(lseg);
        u32 i, j;

        if (fl->commit_through_mds) {
                nfs_request_add_commit_list(req, cinfo);
        } else {
                /* 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);
                pnfs_layout_mark_request_commit(req, lseg, cinfo, i);
        }
}

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;
        struct rpc_clnt *ds_clnt;
        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)
                goto out_err;

        ds_clnt = nfs4_find_or_create_ds_client(ds->ds_clp, data->inode);
        if (IS_ERR(ds_clnt))
                goto out_err;

        dprintk("%s ino %lu, how %d cl_count %d\n", __func__,
                data->inode->i_ino, how, refcount_read(&ds->ds_clp->cl_count));
        data->commit_done_cb = filelayout_commit_done_cb;
        refcount_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_clnt, data, NFS_PROTO(data->inode),
                                   &filelayout_commit_call_ops, how,
                                   RPC_TASK_SOFTCONN, NULL);
out_err:
        pnfs_generic_prepare_to_resend_writes(data);
        pnfs_generic_commit_release(data);
        return -EAGAIN;
}

static int
filelayout_commit_pagelist(struct inode *inode, struct list_head *mds_pages,
                           int how, struct nfs_commit_info *cinfo)
{
        return pnfs_generic_commit_pagelist(inode, mds_pages, how, cinfo,
                                            filelayout_initiate_commit);
}

static struct nfs4_deviceid_node *
filelayout_alloc_deviceid_node(struct nfs_server *server,
                struct pnfs_device *pdev, gfp_t gfp_flags)
{
        struct nfs4_file_layout_dsaddr *dsaddr;

        dsaddr = nfs4_fl_alloc_deviceid_node(server, pdev, gfp_flags);
        if (!dsaddr)
                return NULL;
        return &dsaddr->id_node;
}

static void
filelayout_free_deviceid_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_obj(*flo, gfp_flags);
        if (flo == NULL)
                return NULL;
        pnfs_init_ds_commit_info(&flo->commit_info);
        flo->commit_info.ops = &filelayout_commit_ops;
        return &flo->generic_hdr;
}

static void
filelayout_free_layout_hdr(struct pnfs_layout_hdr *lo)
{
        kfree_rcu(FILELAYOUT_FROM_HDR(lo), generic_hdr.plh_rcu);
}

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 void
filelayout_setup_ds_info(struct pnfs_ds_commit_info *fl_cinfo,
                struct pnfs_layout_segment *lseg)
{
        struct nfs4_filelayout_segment *fl = FILELAYOUT_LSEG(lseg);
        struct inode *inode = lseg->pls_layout->plh_inode;
        struct pnfs_commit_array *array, *new;
        unsigned int size = (fl->stripe_type == STRIPE_SPARSE) ?
                fl->dsaddr->ds_num : fl->dsaddr->stripe_count;

        new = pnfs_alloc_commit_array(size, nfs_io_gfp_mask());
        if (new) {
                spin_lock(&inode->i_lock);
                array = pnfs_add_commit_array(fl_cinfo, new, lseg);
                spin_unlock(&inode->i_lock);
                if (array != new)
                        pnfs_free_commit_array(new);
        }
}

static void
filelayout_release_ds_info(struct pnfs_ds_commit_info *fl_cinfo,
                struct inode *inode)
{
        spin_lock(&inode->i_lock);
        pnfs_generic_ds_cinfo_destroy(fl_cinfo);
        spin_unlock(&inode->i_lock);
}

static const struct pnfs_commit_ops filelayout_commit_ops = {
        .setup_ds_info          = filelayout_setup_ds_info,
        .release_ds_info        = filelayout_release_ds_info,
        .mark_request_commit    = filelayout_mark_request_commit,
        .clear_request_commit   = pnfs_generic_clear_request_commit,
        .scan_commit_lists      = pnfs_generic_scan_commit_lists,
        .recover_commit_reqs    = pnfs_generic_recover_commit_reqs,
        .commit_pagelist        = filelayout_commit_pagelist,
};

static struct pnfs_layoutdriver_type filelayout_type = {
        .id                     = LAYOUT_NFSV4_1_FILES,
        .name                   = "LAYOUT_NFSV4_1_FILES",
        .owner                  = THIS_MODULE,
        .flags                  = PNFS_LAYOUTGET_ON_OPEN,
        .max_layoutget_response = 4096, /* 1 page or so... */
        .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,
        .read_pagelist          = filelayout_read_pagelist,
        .write_pagelist         = filelayout_write_pagelist,
        .alloc_deviceid_node    = filelayout_alloc_deviceid_node,
        .free_deviceid_node     = filelayout_free_deviceid_node,
        .sync                   = pnfs_nfs_generic_sync,
};

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);