volume.c

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/* AFS volume management
 *
 * Copyright (C) 2002, 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([email protected])
 *
 * 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];

    ret = bdi_setup_and_register(&volume->bdi, "afs", BDI_CAP_MAP_COPY);
    if (ret)
        goto error_bdi;

    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);
#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:
    bdi_destroy(&volume->bdi);
error_bdi:
    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]);

    bdi_destroy(&volume->bdi);
    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;
}