cfq-iosched: Rename few functions related to selecting workload

[linux-2.6/btrfs-unstable.git] / fs / nfs / nfs4filelayoutdev.c

/*
 *  Device operations for the pnfs nfs4 file layout driver.
 *
 *  Copyright (c) 2002
 *  The Regents of the University of Michigan
 *  All Rights Reserved
 *
 *  Dean Hildebrand <dhildebz@umich.edu>
 *  Garth Goodson   <Garth.Goodson@netapp.com>
 *
 *  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/vmalloc.h>
#include <linux/module.h>

#include "internal.h"
#include "nfs4session.h"
#include "nfs4filelayout.h"

#define NFSDBG_FACILITY         NFSDBG_PNFS_LD

static unsigned int dataserver_timeo = NFS4_DEF_DS_TIMEO;
static unsigned int dataserver_retrans = NFS4_DEF_DS_RETRANS;

/*
 * Data server cache
 *
 * Data servers can be mapped to different device ids.
 * nfs4_pnfs_ds reference counting
 *   - set to 1 on allocation
 *   - incremented when a device id maps a data server already in the cache.
 *   - decremented when deviceid is removed from the cache.
 */
static DEFINE_SPINLOCK(nfs4_ds_cache_lock);
static LIST_HEAD(nfs4_data_server_cache);

/* Debug routines */
void
print_ds(struct nfs4_pnfs_ds *ds)
{
        if (ds == NULL) {
                printk("%s NULL device\n", __func__);
                return;
        }
        printk("        ds %s\n"
                "        ref count %d\n"
                "        client %p\n"
                "        cl_exchange_flags %x\n",
                ds->ds_remotestr,
                atomic_read(&ds->ds_count), ds->ds_clp,
                ds->ds_clp ? ds->ds_clp->cl_exchange_flags : 0);
}

static bool
same_sockaddr(struct sockaddr *addr1, struct sockaddr *addr2)
{
        struct sockaddr_in *a, *b;
        struct sockaddr_in6 *a6, *b6;

        if (addr1->sa_family != addr2->sa_family)
                return false;

        switch (addr1->sa_family) {
        case AF_INET:
                a = (struct sockaddr_in *)addr1;
                b = (struct sockaddr_in *)addr2;

                if (a->sin_addr.s_addr == b->sin_addr.s_addr &&
                    a->sin_port == b->sin_port)
                        return true;
                break;

        case AF_INET6:
                a6 = (struct sockaddr_in6 *)addr1;
                b6 = (struct sockaddr_in6 *)addr2;

                /* LINKLOCAL addresses must have matching scope_id */
                if (ipv6_addr_scope(&a6->sin6_addr) ==
                    IPV6_ADDR_SCOPE_LINKLOCAL &&
                    a6->sin6_scope_id != b6->sin6_scope_id)
                        return false;

                if (ipv6_addr_equal(&a6->sin6_addr, &b6->sin6_addr) &&
                    a6->sin6_port == b6->sin6_port)
                        return true;
                break;

        default:
                dprintk("%s: unhandled address family: %u\n",
                        __func__, addr1->sa_family);
                return false;
        }

        return false;
}

static bool
_same_data_server_addrs_locked(const struct list_head *dsaddrs1,
                               const struct list_head *dsaddrs2)
{
        struct nfs4_pnfs_ds_addr *da1, *da2;

        /* step through both lists, comparing as we go */
        for (da1 = list_first_entry(dsaddrs1, typeof(*da1), da_node),
             da2 = list_first_entry(dsaddrs2, typeof(*da2), da_node);
             da1 != NULL && da2 != NULL;
             da1 = list_entry(da1->da_node.next, typeof(*da1), da_node),
             da2 = list_entry(da2->da_node.next, typeof(*da2), da_node)) {
                if (!same_sockaddr((struct sockaddr *)&da1->da_addr,
                                   (struct sockaddr *)&da2->da_addr))
                        return false;
        }
        if (da1 == NULL && da2 == NULL)
                return true;

        return false;
}

/*
 * Lookup DS by addresses.  nfs4_ds_cache_lock is held
 */
static struct nfs4_pnfs_ds *
_data_server_lookup_locked(const struct list_head *dsaddrs)
{
        struct nfs4_pnfs_ds *ds;

        list_for_each_entry(ds, &nfs4_data_server_cache, ds_node)
                if (_same_data_server_addrs_locked(&ds->ds_addrs, dsaddrs))
                        return ds;
        return NULL;
}

/*
 * Create an rpc connection to the nfs4_pnfs_ds data server
 * Currently only supports IPv4 and IPv6 addresses
 */
static int
nfs4_ds_connect(struct nfs_server *mds_srv, struct nfs4_pnfs_ds *ds)
{
        struct nfs_client *clp = ERR_PTR(-EIO);
        struct nfs4_pnfs_ds_addr *da;
        int status = 0;

        dprintk("--> %s DS %s au_flavor %d\n", __func__, ds->ds_remotestr,
                mds_srv->nfs_client->cl_rpcclient->cl_auth->au_flavor);

        list_for_each_entry(da, &ds->ds_addrs, da_node) {
                dprintk("%s: DS %s: trying address %s\n",
                        __func__, ds->ds_remotestr, da->da_remotestr);

                clp = nfs4_set_ds_client(mds_srv->nfs_client,
                                        (struct sockaddr *)&da->da_addr,
                                        da->da_addrlen, IPPROTO_TCP,
                                        dataserver_timeo, dataserver_retrans);
                if (!IS_ERR(clp))
                        break;
        }

        if (IS_ERR(clp)) {
                status = PTR_ERR(clp);
                goto out;
        }

        status = nfs4_init_ds_session(clp, mds_srv->nfs_client->cl_lease_time);
        if (status)
                goto out_put;

        ds->ds_clp = clp;
        dprintk("%s [new] addr: %s\n", __func__, ds->ds_remotestr);
out:
        return status;
out_put:
        nfs_put_client(clp);
        goto out;
}

static void
destroy_ds(struct nfs4_pnfs_ds *ds)
{
        struct nfs4_pnfs_ds_addr *da;

        dprintk("--> %s\n", __func__);
        ifdebug(FACILITY)
                print_ds(ds);

        if (ds->ds_clp)
                nfs_put_client(ds->ds_clp);

        while (!list_empty(&ds->ds_addrs)) {
                da = list_first_entry(&ds->ds_addrs,
                                      struct nfs4_pnfs_ds_addr,
                                      da_node);
                list_del_init(&da->da_node);
                kfree(da->da_remotestr);
                kfree(da);
        }

        kfree(ds->ds_remotestr);
        kfree(ds);
}

void
nfs4_fl_free_deviceid(struct nfs4_file_layout_dsaddr *dsaddr)
{
        struct nfs4_pnfs_ds *ds;
        int i;

        nfs4_print_deviceid(&dsaddr->id_node.deviceid);

        for (i = 0; i < dsaddr->ds_num; i++) {
                ds = dsaddr->ds_list[i];
                if (ds != NULL) {
                        if (atomic_dec_and_lock(&ds->ds_count,
                                                &nfs4_ds_cache_lock)) {
                                list_del_init(&ds->ds_node);
                                spin_unlock(&nfs4_ds_cache_lock);
                                destroy_ds(ds);
                        }
                }
        }
        kfree(dsaddr->stripe_indices);
        kfree(dsaddr);
}

/*
 * Create a string with a human readable address and port to avoid
 * complicated setup around many dprinks.
 */
static char *
nfs4_pnfs_remotestr(struct list_head *dsaddrs, gfp_t gfp_flags)
{
        struct nfs4_pnfs_ds_addr *da;
        char *remotestr;
        size_t len;
        char *p;

        len = 3;        /* '{', '}' and eol */
        list_for_each_entry(da, dsaddrs, da_node) {
                len += strlen(da->da_remotestr) + 1;    /* string plus comma */
        }

        remotestr = kzalloc(len, gfp_flags);
        if (!remotestr)
                return NULL;

        p = remotestr;
        *(p++) = '{';
        len--;
        list_for_each_entry(da, dsaddrs, da_node) {
                size_t ll = strlen(da->da_remotestr);

                if (ll > len)
                        goto out_err;

                memcpy(p, da->da_remotestr, ll);
                p += ll;
                len -= ll;

                if (len < 1)
                        goto out_err;
                (*p++) = ',';
                len--;
        }
        if (len < 2)
                goto out_err;
        *(p++) = '}';
        *p = '\0';
        return remotestr;
out_err:
        kfree(remotestr);
        return NULL;
}

static struct nfs4_pnfs_ds *
nfs4_pnfs_ds_add(struct list_head *dsaddrs, gfp_t gfp_flags)
{
        struct nfs4_pnfs_ds *tmp_ds, *ds = NULL;
        char *remotestr;

        if (list_empty(dsaddrs)) {
                dprintk("%s: no addresses defined\n", __func__);
                goto out;
        }

        ds = kzalloc(sizeof(*ds), gfp_flags);
        if (!ds)
                goto out;

        /* this is only used for debugging, so it's ok if its NULL */
        remotestr = nfs4_pnfs_remotestr(dsaddrs, gfp_flags);

        spin_lock(&nfs4_ds_cache_lock);
        tmp_ds = _data_server_lookup_locked(dsaddrs);
        if (tmp_ds == NULL) {
                INIT_LIST_HEAD(&ds->ds_addrs);
                list_splice_init(dsaddrs, &ds->ds_addrs);
                ds->ds_remotestr = remotestr;
                atomic_set(&ds->ds_count, 1);
                INIT_LIST_HEAD(&ds->ds_node);
                ds->ds_clp = NULL;
                list_add(&ds->ds_node, &nfs4_data_server_cache);
                dprintk("%s add new data server %s\n", __func__,
                        ds->ds_remotestr);
        } else {
                kfree(remotestr);
                kfree(ds);
                atomic_inc(&tmp_ds->ds_count);
                dprintk("%s data server %s found, inc'ed ds_count to %d\n",
                        __func__, tmp_ds->ds_remotestr,
                        atomic_read(&tmp_ds->ds_count));
                ds = tmp_ds;
        }
        spin_unlock(&nfs4_ds_cache_lock);
out:
        return ds;
}

/*
 * Currently only supports ipv4, ipv6 and one multi-path address.
 */
static struct nfs4_pnfs_ds_addr *
decode_ds_addr(struct net *net, struct xdr_stream *streamp, gfp_t gfp_flags)
{
        struct nfs4_pnfs_ds_addr *da = NULL;
        char *buf, *portstr;
        __be16 port;
        int nlen, rlen;
        int tmp[2];
        __be32 *p;
        char *netid, *match_netid;
        size_t len, match_netid_len;
        char *startsep = "";
        char *endsep = "";


        /* r_netid */
        p = xdr_inline_decode(streamp, 4);
        if (unlikely(!p))
                goto out_err;
        nlen = be32_to_cpup(p++);

        p = xdr_inline_decode(streamp, nlen);
        if (unlikely(!p))
                goto out_err;

        netid = kmalloc(nlen+1, gfp_flags);
        if (unlikely(!netid))
                goto out_err;

        netid[nlen] = '\0';
        memcpy(netid, p, nlen);

        /* r_addr: ip/ip6addr with port in dec octets - see RFC 5665 */
        p = xdr_inline_decode(streamp, 4);
        if (unlikely(!p))
                goto out_free_netid;
        rlen = be32_to_cpup(p);

        p = xdr_inline_decode(streamp, rlen);
        if (unlikely(!p))
                goto out_free_netid;

        /* port is ".ABC.DEF", 8 chars max */
        if (rlen > INET6_ADDRSTRLEN + IPV6_SCOPE_ID_LEN + 8) {
                dprintk("%s: Invalid address, length %d\n", __func__,
                        rlen);
                goto out_free_netid;
        }
        buf = kmalloc(rlen + 1, gfp_flags);
        if (!buf) {
                dprintk("%s: Not enough memory\n", __func__);
                goto out_free_netid;
        }
        buf[rlen] = '\0';
        memcpy(buf, p, rlen);

        /* replace port '.' with '-' */
        portstr = strrchr(buf, '.');
        if (!portstr) {
                dprintk("%s: Failed finding expected dot in port\n",
                        __func__);
                goto out_free_buf;
        }
        *portstr = '-';

        /* find '.' between address and port */
        portstr = strrchr(buf, '.');
        if (!portstr) {
                dprintk("%s: Failed finding expected dot between address and "
                        "port\n", __func__);
                goto out_free_buf;
        }
        *portstr = '\0';

        da = kzalloc(sizeof(*da), gfp_flags);
        if (unlikely(!da))
                goto out_free_buf;

        INIT_LIST_HEAD(&da->da_node);

        if (!rpc_pton(net, buf, portstr-buf, (struct sockaddr *)&da->da_addr,
                      sizeof(da->da_addr))) {
                dprintk("%s: error parsing address %s\n", __func__, buf);
                goto out_free_da;
        }

        portstr++;
        sscanf(portstr, "%d-%d", &tmp[0], &tmp[1]);
        port = htons((tmp[0] << 8) | (tmp[1]));

        switch (da->da_addr.ss_family) {
        case AF_INET:
                ((struct sockaddr_in *)&da->da_addr)->sin_port = port;
                da->da_addrlen = sizeof(struct sockaddr_in);
                match_netid = "tcp";
                match_netid_len = 3;
                break;

        case AF_INET6:
                ((struct sockaddr_in6 *)&da->da_addr)->sin6_port = port;
                da->da_addrlen = sizeof(struct sockaddr_in6);
                match_netid = "tcp6";
                match_netid_len = 4;
                startsep = "[";
                endsep = "]";
                break;

        default:
                dprintk("%s: unsupported address family: %u\n",
                        __func__, da->da_addr.ss_family);
                goto out_free_da;
        }

        if (nlen != match_netid_len || strncmp(netid, match_netid, nlen)) {
                dprintk("%s: ERROR: r_netid \"%s\" != \"%s\"\n",
                        __func__, netid, match_netid);
                goto out_free_da;
        }

        /* save human readable address */
        len = strlen(startsep) + strlen(buf) + strlen(endsep) + 7;
        da->da_remotestr = kzalloc(len, gfp_flags);

        /* NULL is ok, only used for dprintk */
        if (da->da_remotestr)
                snprintf(da->da_remotestr, len, "%s%s%s:%u", startsep,
                         buf, endsep, ntohs(port));

        dprintk("%s: Parsed DS addr %s\n", __func__, da->da_remotestr);
        kfree(buf);
        kfree(netid);
        return da;

out_free_da:
        kfree(da);
out_free_buf:
        dprintk("%s: Error parsing DS addr: %s\n", __func__, buf);
        kfree(buf);
out_free_netid:
        kfree(netid);
out_err:
        return NULL;
}

/* Decode opaque device data and return the result */
static struct nfs4_file_layout_dsaddr*
decode_device(struct inode *ino, struct pnfs_device *pdev, gfp_t gfp_flags)
{
        int i;
        u32 cnt, num;
        u8 *indexp;
        __be32 *p;
        u8 *stripe_indices;
        u8 max_stripe_index;
        struct nfs4_file_layout_dsaddr *dsaddr = NULL;
        struct xdr_stream stream;
        struct xdr_buf buf;
        struct page *scratch;
        struct list_head dsaddrs;
        struct nfs4_pnfs_ds_addr *da;

        /* set up xdr stream */
        scratch = alloc_page(gfp_flags);
        if (!scratch)
                goto out_err;

        xdr_init_decode_pages(&stream, &buf, pdev->pages, pdev->pglen);
        xdr_set_scratch_buffer(&stream, page_address(scratch), PAGE_SIZE);

        /* Get the stripe count (number of stripe index) */
        p = xdr_inline_decode(&stream, 4);
        if (unlikely(!p))
                goto out_err_free_scratch;

        cnt = be32_to_cpup(p);
        dprintk("%s stripe count  %d\n", __func__, cnt);
        if (cnt > NFS4_PNFS_MAX_STRIPE_CNT) {
                printk(KERN_WARNING "NFS: %s: stripe count %d greater than "
                       "supported maximum %d\n", __func__,
                        cnt, NFS4_PNFS_MAX_STRIPE_CNT);
                goto out_err_free_scratch;
        }

        /* read stripe indices */
        stripe_indices = kcalloc(cnt, sizeof(u8), gfp_flags);
        if (!stripe_indices)
                goto out_err_free_scratch;

        p = xdr_inline_decode(&stream, cnt << 2);
        if (unlikely(!p))
                goto out_err_free_stripe_indices;

        indexp = &stripe_indices[0];
        max_stripe_index = 0;
        for (i = 0; i < cnt; i++) {
                *indexp = be32_to_cpup(p++);
                max_stripe_index = max(max_stripe_index, *indexp);
                indexp++;
        }

        /* Check the multipath list count */
        p = xdr_inline_decode(&stream, 4);
        if (unlikely(!p))
                goto out_err_free_stripe_indices;

        num = be32_to_cpup(p);
        dprintk("%s ds_num %u\n", __func__, num);
        if (num > NFS4_PNFS_MAX_MULTI_CNT) {
                printk(KERN_WARNING "NFS: %s: multipath count %d greater than "
                        "supported maximum %d\n", __func__,
                        num, NFS4_PNFS_MAX_MULTI_CNT);
                goto out_err_free_stripe_indices;
        }

        /* validate stripe indices are all < num */
        if (max_stripe_index >= num) {
                printk(KERN_WARNING "NFS: %s: stripe index %u >= num ds %u\n",
                        __func__, max_stripe_index, num);
                goto out_err_free_stripe_indices;
        }

        dsaddr = kzalloc(sizeof(*dsaddr) +
                        (sizeof(struct nfs4_pnfs_ds *) * (num - 1)),
                        gfp_flags);
        if (!dsaddr)
                goto out_err_free_stripe_indices;

        dsaddr->stripe_count = cnt;
        dsaddr->stripe_indices = stripe_indices;
        stripe_indices = NULL;
        dsaddr->ds_num = num;
        nfs4_init_deviceid_node(&dsaddr->id_node,
                                NFS_SERVER(ino)->pnfs_curr_ld,
                                NFS_SERVER(ino)->nfs_client,
                                &pdev->dev_id);

        INIT_LIST_HEAD(&dsaddrs);

        for (i = 0; i < dsaddr->ds_num; i++) {
                int j;
                u32 mp_count;

                p = xdr_inline_decode(&stream, 4);
                if (unlikely(!p))
                        goto out_err_free_deviceid;

                mp_count = be32_to_cpup(p); /* multipath count */
                for (j = 0; j < mp_count; j++) {
                        da = decode_ds_addr(NFS_SERVER(ino)->nfs_client->cl_net,
                                            &stream, gfp_flags);
                        if (da)
                                list_add_tail(&da->da_node, &dsaddrs);
                }
                if (list_empty(&dsaddrs)) {
                        dprintk("%s: no suitable DS addresses found\n",
                                __func__);
                        goto out_err_free_deviceid;
                }

                dsaddr->ds_list[i] = nfs4_pnfs_ds_add(&dsaddrs, gfp_flags);
                if (!dsaddr->ds_list[i])
                        goto out_err_drain_dsaddrs;

                /* If DS was already in cache, free ds addrs */
                while (!list_empty(&dsaddrs)) {
                        da = list_first_entry(&dsaddrs,
                                              struct nfs4_pnfs_ds_addr,
                                              da_node);
                        list_del_init(&da->da_node);
                        kfree(da->da_remotestr);
                        kfree(da);
                }
        }

        __free_page(scratch);
        return dsaddr;

out_err_drain_dsaddrs:
        while (!list_empty(&dsaddrs)) {
                da = list_first_entry(&dsaddrs, struct nfs4_pnfs_ds_addr,
                                      da_node);
                list_del_init(&da->da_node);
                kfree(da->da_remotestr);
                kfree(da);
        }
out_err_free_deviceid:
        nfs4_fl_free_deviceid(dsaddr);
        /* stripe_indicies was part of dsaddr */
        goto out_err_free_scratch;
out_err_free_stripe_indices:
        kfree(stripe_indices);
out_err_free_scratch:
        __free_page(scratch);
out_err:
        dprintk("%s ERROR: returning NULL\n", __func__);
        return NULL;
}

/*
 * Decode the opaque device specified in 'dev' and add it to the cache of
 * available devices.
 */
static struct nfs4_file_layout_dsaddr *
decode_and_add_device(struct inode *inode, struct pnfs_device *dev, gfp_t gfp_flags)
{
        struct nfs4_deviceid_node *d;
        struct nfs4_file_layout_dsaddr *n, *new;

        new = decode_device(inode, dev, gfp_flags);
        if (!new) {
                printk(KERN_WARNING "NFS: %s: Could not decode or add device\n",
                        __func__);
                return NULL;
        }

        d = nfs4_insert_deviceid_node(&new->id_node);
        n = container_of(d, struct nfs4_file_layout_dsaddr, id_node);
        if (n != new) {
                nfs4_fl_free_deviceid(new);
                return n;
        }

        return new;
}

/*
 * Retrieve the information for dev_id, add it to the list
 * of available devices, and return it.
 */
struct nfs4_file_layout_dsaddr *
filelayout_get_device_info(struct inode *inode, struct nfs4_deviceid *dev_id, gfp_t gfp_flags)
{
        struct pnfs_device *pdev = NULL;
        u32 max_resp_sz;
        int max_pages;
        struct page **pages = NULL;
        struct nfs4_file_layout_dsaddr *dsaddr = NULL;
        int rc, i;
        struct nfs_server *server = NFS_SERVER(inode);

        /*
         * Use the session max response size as the basis for setting
         * GETDEVICEINFO's maxcount
         */
        max_resp_sz = server->nfs_client->cl_session->fc_attrs.max_resp_sz;
        max_pages = nfs_page_array_len(0, max_resp_sz);
        dprintk("%s inode %p max_resp_sz %u max_pages %d\n",
                __func__, inode, max_resp_sz, max_pages);

        pdev = kzalloc(sizeof(struct pnfs_device), gfp_flags);
        if (pdev == NULL)
                return NULL;

        pages = kzalloc(max_pages * sizeof(struct page *), gfp_flags);
        if (pages == NULL) {
                kfree(pdev);
                return NULL;
        }
        for (i = 0; i < max_pages; i++) {
                pages[i] = alloc_page(gfp_flags);
                if (!pages[i])
                        goto out_free;
        }

        memcpy(&pdev->dev_id, dev_id, sizeof(*dev_id));
        pdev->layout_type = LAYOUT_NFSV4_1_FILES;
        pdev->pages = pages;
        pdev->pgbase = 0;
        pdev->pglen = max_resp_sz;
        pdev->mincount = 0;

        rc = nfs4_proc_getdeviceinfo(server, pdev);
        dprintk("%s getdevice info returns %d\n", __func__, rc);
        if (rc)
                goto out_free;

        /*
         * Found new device, need to decode it and then add it to the
         * list of known devices for this mountpoint.
         */
        dsaddr = decode_and_add_device(inode, pdev, gfp_flags);
out_free:
        for (i = 0; i < max_pages; i++)
                __free_page(pages[i]);
        kfree(pages);
        kfree(pdev);
        dprintk("<-- %s dsaddr %p\n", __func__, dsaddr);
        return dsaddr;
}

void
nfs4_fl_put_deviceid(struct nfs4_file_layout_dsaddr *dsaddr)
{
        nfs4_put_deviceid_node(&dsaddr->id_node);
}

/*
 * Want res = (offset - layout->pattern_offset)/ layout->stripe_unit
 * Then: ((res + fsi) % dsaddr->stripe_count)
 */
u32
nfs4_fl_calc_j_index(struct pnfs_layout_segment *lseg, loff_t offset)
{
        struct nfs4_filelayout_segment *flseg = FILELAYOUT_LSEG(lseg);
        u64 tmp;

        tmp = offset - flseg->pattern_offset;
        do_div(tmp, flseg->stripe_unit);
        tmp += flseg->first_stripe_index;
        return do_div(tmp, flseg->dsaddr->stripe_count);
}

u32
nfs4_fl_calc_ds_index(struct pnfs_layout_segment *lseg, u32 j)
{
        return FILELAYOUT_LSEG(lseg)->dsaddr->stripe_indices[j];
}

struct nfs_fh *
nfs4_fl_select_ds_fh(struct pnfs_layout_segment *lseg, u32 j)
{
        struct nfs4_filelayout_segment *flseg = FILELAYOUT_LSEG(lseg);
        u32 i;

        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;
                else
                        i = nfs4_fl_calc_ds_index(lseg, j);
        } else
                i = j;
        return flseg->fh_array[i];
}

struct nfs4_pnfs_ds *
nfs4_fl_prepare_ds(struct pnfs_layout_segment *lseg, u32 ds_idx)
{
        struct nfs4_file_layout_dsaddr *dsaddr = FILELAYOUT_LSEG(lseg)->dsaddr;
        struct nfs4_pnfs_ds *ds = dsaddr->ds_list[ds_idx];
        struct nfs4_deviceid_node *devid = FILELAYOUT_DEVID_NODE(lseg);

        if (filelayout_test_devid_unavailable(devid))
                return NULL;

        if (ds == NULL) {
                printk(KERN_ERR "NFS: %s: No data server for offset index %d\n",
                        __func__, ds_idx);
                filelayout_mark_devid_invalid(devid);
                return NULL;
        }

        if (!ds->ds_clp) {
                struct nfs_server *s = NFS_SERVER(lseg->pls_layout->plh_inode);
                int err;

                err = nfs4_ds_connect(s, ds);
                if (err) {
                        nfs4_mark_deviceid_unavailable(devid);
                        return NULL;
                }
        }
        return ds;
}

module_param(dataserver_retrans, uint, 0644);
MODULE_PARM_DESC(dataserver_retrans, "The  number of times the NFSv4.1 client "
                        "retries a request before it attempts further "
                        " recovery  action.");
module_param(dataserver_timeo, uint, 0644);
MODULE_PARM_DESC(dataserver_timeo, "The time (in tenths of a second) the "
                        "NFSv4.1  client  waits for a response from a "
                        " data server before it retries an NFS request.");