/* AFS volume management
 *
 * Copyright (C) 2002, 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/sched.h>
#include "internal.h"

static const char *afs_voltypes[] = { "R/W", "R/O", "BAK" };

/*
 * lookup a volume by name
 * - this can be one of the following:
 *      "%[cell:]volume[.]"             R/W volume
 *      "#[cell:]volume[.]"             R/O or R/W volume (rwparent=0),
 *                                       or R/W (rwparent=1) volume
 *      "%[cell:]volume.readonly"       R/O volume
 *      "#[cell:]volume.readonly"       R/O volume
 *      "%[cell:]volume.backup"         Backup volume
 *      "#[cell:]volume.backup"         Backup volume
 *
 * The cell name is optional, and defaults to the current cell.
 *
 * See "The Rules of Mount Point Traversal" in Chapter 5 of the AFS SysAdmin
 * Guide
 * - Rule 1: Explicit type suffix forces access of that type or nothing
 *           (no suffix, then use Rule 2 & 3)
 * - Rule 2: If parent volume is R/O, then mount R/O volume by preference, R/W
 *           if not available
 * - Rule 3: If parent volume is R/W, then only mount R/W volume unless
 *           explicitly told otherwise
 */
struct afs_volume *afs_volume_lookup(struct afs_mount_params *params)
{
        struct afs_vlocation *vlocation = NULL;
        struct afs_volume *volume = NULL;
        struct afs_server *server = NULL;
        char srvtmask;
        int ret, loop;

        _enter("{%*.*s,%d}",
               params->volnamesz, params->volnamesz, params->volname, params->rwpath);

        /* lookup the volume location record */
        vlocation = afs_vlocation_lookup(params->cell, params->key,
                                         params->volname, params->volnamesz);
        if (IS_ERR(vlocation)) {
                ret = PTR_ERR(vlocation);
                vlocation = NULL;
                goto error;
        }

        /* make the final decision on the type we want */
        ret = -ENOMEDIUM;
        if (params->force && !(vlocation->vldb.vidmask & (1 << params->type)))
                goto error;

        srvtmask = 0;
        for (loop = 0; loop < vlocation->vldb.nservers; loop++)
                srvtmask |= vlocation->vldb.srvtmask[loop];

        if (params->force) {
                if (!(srvtmask & (1 << params->type)))
                        goto error;
        } else if (srvtmask & AFS_VOL_VTM_RO) {
                params->type = AFSVL_ROVOL;
        } else if (srvtmask & AFS_VOL_VTM_RW) {
                params->type = AFSVL_RWVOL;
        } else {
                goto error;
        }

        down_write(&params->cell->vl_sem);

        /* is the volume already active? */
        if (vlocation->vols[params->type]) {
                /* yes - re-use it */
                volume = vlocation->vols[params->type];
                afs_get_volume(volume);
                goto success;
        }

        /* create a new volume record */
        _debug("creating new volume record");

        ret = -ENOMEM;
        volume = kzalloc(sizeof(struct afs_volume), GFP_KERNEL);
        if (!volume)
                goto error_up;

        atomic_set(&volume->usage, 1);
        volume->type            = params->type;
        volume->type_force      = params->force;
        volume->cell            = params->cell;
        volume->vid             = vlocation->vldb.vid[params->type];

        init_rwsem(&volume->server_sem);

        /* look up all the applicable server records */
        for (loop = 0; loop < 8; loop++) {
                if (vlocation->vldb.srvtmask[loop] & (1 << volume->type)) {
                        server = afs_lookup_server(
                               volume->cell, &vlocation->vldb.servers[loop]);
                        if (IS_ERR(server)) {
                                ret = PTR_ERR(server);
                                goto error_discard;
                        }

                        volume->servers[volume->nservers] = server;
                        volume->nservers++;
                }
        }

        /* attach the cache and volume location */
#ifdef CONFIG_AFS_FSCACHE
        volume->cache = fscache_acquire_cookie(vlocation->cache,
                                               &afs_volume_cache_index_def,
                                               volume, true);
#endif
        afs_get_vlocation(vlocation);
        volume->vlocation = vlocation;

        vlocation->vols[volume->type] = volume;

success:
        _debug("kAFS selected %s volume %08x",
               afs_voltypes[volume->type], volume->vid);
        up_write(&params->cell->vl_sem);
        afs_put_vlocation(vlocation);
        _leave(" = %p", volume);
        return volume;

        /* clean up */
error_up:
        up_write(&params->cell->vl_sem);
error:
        afs_put_vlocation(vlocation);
        _leave(" = %d", ret);
        return ERR_PTR(ret);

error_discard:
        up_write(&params->cell->vl_sem);

        for (loop = volume->nservers - 1; loop >= 0; loop--)
                afs_put_server(volume->servers[loop]);

        kfree(volume);
        goto error;
}

/*
 * destroy a volume record
 */
void afs_put_volume(struct afs_volume *volume)
{
        struct afs_vlocation *vlocation;
        int loop;

        if (!volume)
                return;

        _enter("%p", volume);

        ASSERTCMP(atomic_read(&volume->usage), >, 0);

        vlocation = volume->vlocation;

        /* to prevent a race, the decrement and the dequeue must be effectively
         * atomic */
        down_write(&vlocation->cell->vl_sem);

        if (likely(!atomic_dec_and_test(&volume->usage))) {
                up_write(&vlocation->cell->vl_sem);
                _leave("");
                return;
        }

        vlocation->vols[volume->type] = NULL;

        up_write(&vlocation->cell->vl_sem);

        /* finish cleaning up the volume */
#ifdef CONFIG_AFS_FSCACHE
        fscache_relinquish_cookie(volume->cache, 0);
#endif
        afs_put_vlocation(vlocation);

        for (loop = volume->nservers - 1; loop >= 0; loop--)
                afs_put_server(volume->servers[loop]);

        kfree(volume);

        _leave(" [destroyed]");
}

/*
 * pick a server to use to try accessing this volume
 * - returns with an elevated usage count on the server chosen
 */
struct afs_server *afs_volume_pick_fileserver(struct afs_vnode *vnode)
{
        struct afs_volume *volume = vnode->volume;
        struct afs_server *server;
        int ret, state, loop;

        _enter("%s", volume->vlocation->vldb.name);

        /* stick with the server we're already using if we can */
        if (vnode->server && vnode->server->fs_state == 0) {
                afs_get_server(vnode->server);
                _leave(" = %p [current]", vnode->server);
                return vnode->server;
        }

        down_read(&volume->server_sem);

        /* handle the no-server case */
        if (volume->nservers == 0) {
                ret = volume->rjservers ? -ENOMEDIUM : -ESTALE;
                up_read(&volume->server_sem);
                _leave(" = %d [no servers]", ret);
                return ERR_PTR(ret);
        }

        /* basically, just search the list for the first live server and use
         * that */
        ret = 0;
        for (loop = 0; loop < volume->nservers; loop++) {
                server = volume->servers[loop];
                state = server->fs_state;

                _debug("consider %d [%d]", loop, state);

                switch (state) {
                        /* found an apparently healthy server */
                case 0:
                        afs_get_server(server);
                        up_read(&volume->server_sem);
                        _leave(" = %p (picked %08x)",
                               server, ntohl(server->addr.s_addr));
                        return server;

                case -ENETUNREACH:
                        if (ret == 0)
                                ret = state;
                        break;

                case -EHOSTUNREACH:
                        if (ret == 0 ||
                            ret == -ENETUNREACH)
                                ret = state;
                        break;

                case -ECONNREFUSED:
                        if (ret == 0 ||
                            ret == -ENETUNREACH ||
                            ret == -EHOSTUNREACH)
                                ret = state;
                        break;

                default:
                case -EREMOTEIO:
                        if (ret == 0 ||
                            ret == -ENETUNREACH ||
                            ret == -EHOSTUNREACH ||
                            ret == -ECONNREFUSED)
                                ret = state;
                        break;
                }
        }

        /* no available servers
         * - TODO: handle the no active servers case better
         */
        up_read(&volume->server_sem);
        _leave(" = %d", ret);
        return ERR_PTR(ret);
}

/*
 * release a server after use
 * - releases the ref on the server struct that was acquired by picking
 * - records result of using a particular server to access a volume
 * - return 0 to try again, 1 if okay or to issue error
 * - the caller must release the server struct if result was 0
 */
int afs_volume_release_fileserver(struct afs_vnode *vnode,
                                  struct afs_server *server,
                                  int result)
{
        struct afs_volume *volume = vnode->volume;
        unsigned loop;

        _enter("%s,%08x,%d",
               volume->vlocation->vldb.name, ntohl(server->addr.s_addr),
               result);

        switch (result) {
                /* success */
        case 0:
                server->fs_act_jif = jiffies;
                server->fs_state = 0;
                _leave("");
                return 1;

                /* the fileserver denied all knowledge of the volume */
        case -ENOMEDIUM:
                server->fs_act_jif = jiffies;
                down_write(&volume->server_sem);

                /* firstly, find where the server is in the active list (if it
                 * is) */
                for (loop = 0; loop < volume->nservers; loop++)
                        if (volume->servers[loop] == server)
                                goto present;

                /* no longer there - may have been discarded by another op */
                goto try_next_server_upw;

        present:
                volume->nservers--;
                memmove(&volume->servers[loop],
                        &volume->servers[loop + 1],
                        sizeof(volume->servers[loop]) *
                        (volume->nservers - loop));
                volume->servers[volume->nservers] = NULL;
                afs_put_server(server);
                volume->rjservers++;

                if (volume->nservers > 0)
                        /* another server might acknowledge its existence */
                        goto try_next_server_upw;

                /* handle the case where all the fileservers have rejected the
                 * volume
                 * - TODO: try asking the fileservers for volume information
                 * - TODO: contact the VL server again to see if the volume is
                 *         no longer registered
                 */
                up_write(&volume->server_sem);
                afs_put_server(server);
                _leave(" [completely rejected]");
                return 1;

                /* problem reaching the server */
        case -ENETUNREACH:
        case -EHOSTUNREACH:
        case -ECONNREFUSED:
        case -ETIME:
        case -ETIMEDOUT:
        case -EREMOTEIO:
                /* mark the server as dead
                 * TODO: vary dead timeout depending on error
                 */
                spin_lock(&server->fs_lock);
                if (!server->fs_state) {
                        server->fs_dead_jif = jiffies + HZ * 10;
                        server->fs_state = result;
                        printk("kAFS: SERVER DEAD state=%d\n", result);
                }
                spin_unlock(&server->fs_lock);
                goto try_next_server;

                /* miscellaneous error */
        default:
                server->fs_act_jif = jiffies;
        case -ENOMEM:
        case -ENONET:
                /* tell the caller to accept the result */
                afs_put_server(server);
                _leave(" [local failure]");
                return 1;
        }

        /* tell the caller to loop around and try the next server */
try_next_server_upw:
        up_write(&volume->server_sem);
try_next_server:
        afs_put_server(server);
        _leave(" [try next server]");
        return 0;
}