cell.c

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/* AFS cell and server record management
 *
 * Copyright (C) 2002 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/module.h>
#include <linux/slab.h>
#include <linux/key.h>
#include <linux/ctype.h>
#include <linux/dns_resolver.h>
#include <linux/sched.h>
#include <keys/rxrpc-type.h>
#include "internal.h"

DECLARE_RWSEM(afs_proc_cells_sem);
LIST_HEAD(afs_proc_cells);

static LIST_HEAD(afs_cells);
static DEFINE_RWLOCK(afs_cells_lock);
static DECLARE_RWSEM(afs_cells_sem); /* add/remove serialisation */
static DECLARE_WAIT_QUEUE_HEAD(afs_cells_freeable_wq);
static struct afs_cell *afs_cell_root;

/*
 * allocate a cell record and fill in its name, VL server address list and
 * allocate an anonymous key
 */
static struct afs_cell *afs_cell_alloc(const char *name, unsigned namelen,
                       char *vllist)
{
    struct afs_cell *cell;
    struct key *key;
    char keyname[4 + AFS_MAXCELLNAME + 1], *cp, *dp, *next;
    char  *dvllist = NULL, *_vllist = NULL;
    char  delimiter = ':';
    int ret;

    _enter("%*.*s,%s", namelen, namelen, name ?: "", vllist);

    BUG_ON(!name); /* TODO: want to look up "this cell" in the cache */

    if (namelen > AFS_MAXCELLNAME) {
        _leave(" = -ENAMETOOLONG");
        return ERR_PTR(-ENAMETOOLONG);
    }

    /* allocate and initialise a cell record */
    cell = kzalloc(sizeof(struct afs_cell) + namelen + 1, GFP_KERNEL);
    if (!cell) {
        _leave(" = -ENOMEM");
        return ERR_PTR(-ENOMEM);
    }

    memcpy(cell->name, name, namelen);
    cell->name[namelen] = 0;

    atomic_set(&cell->usage, 1);
    INIT_LIST_HEAD(&cell->link);
    rwlock_init(&cell->servers_lock);
    INIT_LIST_HEAD(&cell->servers);
    init_rwsem(&cell->vl_sem);
    INIT_LIST_HEAD(&cell->vl_list);
    spin_lock_init(&cell->vl_lock);

    /* if the ip address is invalid, try dns query */
    if (!vllist || strlen(vllist) < 7) {
        ret = dns_query("afsdb", name, namelen, "ipv4", &dvllist, NULL);
        if (ret < 0) {
            if (ret == -ENODATA || ret == -EAGAIN || ret == -ENOKEY)
                /* translate these errors into something
                 * userspace might understand */
                ret = -EDESTADDRREQ;
            _leave(" = %d", ret);
            return ERR_PTR(ret);
        }
        _vllist = dvllist;

        /* change the delimiter for user-space reply */
        delimiter = ',';

    } else {
        _vllist = vllist;
    }

    /* fill in the VL server list from the rest of the string */
    do {
        unsigned a, b, c, d;

        next = strchr(_vllist, delimiter);
        if (next)
            *next++ = 0;

        if (sscanf(_vllist, "%u.%u.%u.%u", &a, &b, &c, &d) != 4)
            goto bad_address;

        if (a > 255 || b > 255 || c > 255 || d > 255)
            goto bad_address;

        cell->vl_addrs[cell->vl_naddrs++].s_addr =
            htonl((a << 24) | (b << 16) | (c << 8) | d);

    } while (cell->vl_naddrs < AFS_CELL_MAX_ADDRS && (_vllist = next));

    /* create a key to represent an anonymous user */
    memcpy(keyname, "afs@", 4);
    dp = keyname + 4;
    cp = cell->name;
    do {
        *dp++ = toupper(*cp);
    } while (*cp++);

    key = rxrpc_get_null_key(keyname);
    if (IS_ERR(key)) {
        _debug("no key");
        ret = PTR_ERR(key);
        goto error;
    }
    cell->anonymous_key = key;

    _debug("anon key %p{%x}",
           cell->anonymous_key, key_serial(cell->anonymous_key));

    _leave(" = %p", cell);
    return cell;

bad_address:
    printk(KERN_ERR "kAFS: bad VL server IP address\n");
    ret = -EINVAL;
error:
    key_put(cell->anonymous_key);
    kfree(dvllist);
    kfree(cell);
    _leave(" = %d", ret);
    return ERR_PTR(ret);
}

/*
 * afs_cell_crate() - create a cell record
 * @name:   is the name of the cell.
 * @namsesz:    is the strlen of the cell name.
 * @vllist: is a colon separated list of IP addresses in "a.b.c.d" format.
 * @retref: is T to return the cell reference when the cell exists.
 */
struct afs_cell *afs_cell_create(const char *name, unsigned namesz,
                 char *vllist, bool retref)
{
    struct afs_cell *cell;
    int ret;

    _enter("%*.*s,%s", namesz, namesz, name ?: "", vllist);

    down_write(&afs_cells_sem);
    read_lock(&afs_cells_lock);
    list_for_each_entry(cell, &afs_cells, link) {
        if (strncasecmp(cell->name, name, namesz) == 0)
            goto duplicate_name;
    }
    read_unlock(&afs_cells_lock);

    cell = afs_cell_alloc(name, namesz, vllist);
    if (IS_ERR(cell)) {
        _leave(" = %ld", PTR_ERR(cell));
        up_write(&afs_cells_sem);
        return cell;
    }

    /* add a proc directory for this cell */
    ret = afs_proc_cell_setup(cell);
    if (ret < 0)
        goto error;

#ifdef CONFIG_AFS_FSCACHE
    /* put it up for caching (this never returns an error) */
    cell->cache = fscache_acquire_cookie(afs_cache_netfs.primary_index,
                         &afs_cell_cache_index_def,
                         cell);
#endif

    /* add to the cell lists */
    write_lock(&afs_cells_lock);
    list_add_tail(&cell->link, &afs_cells);
    write_unlock(&afs_cells_lock);

    down_write(&afs_proc_cells_sem);
    list_add_tail(&cell->proc_link, &afs_proc_cells);
    up_write(&afs_proc_cells_sem);
    up_write(&afs_cells_sem);

    _leave(" = %p", cell);
    return cell;

error:
    up_write(&afs_cells_sem);
    key_put(cell->anonymous_key);
    kfree(cell);
    _leave(" = %d", ret);
    return ERR_PTR(ret);

duplicate_name:
    if (retref && !IS_ERR(cell))
        afs_get_cell(cell);

    read_unlock(&afs_cells_lock);
    up_write(&afs_cells_sem);

    if (retref) {
        _leave(" = %p", cell);
        return cell;
    }

    _leave(" = -EEXIST");
    return ERR_PTR(-EEXIST);
}

/*
 * set the root cell information
 * - can be called with a module parameter string
 * - can be called from a write to /proc/fs/afs/rootcell
 */
int afs_cell_init(char *rootcell)
{
    struct afs_cell *old_root, *new_root;
    char *cp;

    _enter("");

    if (!rootcell) {
        /* module is loaded with no parameters, or built statically.
         * - in the future we might initialize cell DB here.
         */
        _leave(" = 0 [no root]");
        return 0;
    }

    cp = strchr(rootcell, ':');
    if (!cp)
        _debug("kAFS: no VL server IP addresses specified");
    else
        *cp++ = 0;

    /* allocate a cell record for the root cell */
    new_root = afs_cell_create(rootcell, strlen(rootcell), cp, false);
    if (IS_ERR(new_root)) {
        _leave(" = %ld", PTR_ERR(new_root));
        return PTR_ERR(new_root);
    }

    /* install the new cell */
    write_lock(&afs_cells_lock);
    old_root = afs_cell_root;
    afs_cell_root = new_root;
    write_unlock(&afs_cells_lock);
    afs_put_cell(old_root);

    _leave(" = 0");
    return 0;
}

/*
 * lookup a cell record
 */
struct afs_cell *afs_cell_lookup(const char *name, unsigned namesz,
                 bool dns_cell)
{
    struct afs_cell *cell;

    _enter("\"%*.*s\",", namesz, namesz, name ?: "");

    down_read(&afs_cells_sem);
    read_lock(&afs_cells_lock);

    if (name) {
        /* if the cell was named, look for it in the cell record list */
        list_for_each_entry(cell, &afs_cells, link) {
            if (strncmp(cell->name, name, namesz) == 0) {
                afs_get_cell(cell);
                goto found;
            }
        }
        cell = ERR_PTR(-ENOENT);
        if (dns_cell)
            goto create_cell;
    found:
        ;
    } else {
        cell = afs_cell_root;
        if (!cell) {
            /* this should not happen unless user tries to mount
             * when root cell is not set. Return an impossibly
             * bizarre errno to alert the user. Things like
             * ENOENT might be "more appropriate" but they happen
             * for other reasons.
             */
            cell = ERR_PTR(-EDESTADDRREQ);
        } else {
            afs_get_cell(cell);
        }

    }

    read_unlock(&afs_cells_lock);
    up_read(&afs_cells_sem);
    _leave(" = %p", cell);
    return cell;

create_cell:
    read_unlock(&afs_cells_lock);
    up_read(&afs_cells_sem);

    cell = afs_cell_create(name, namesz, NULL, true);

    _leave(" = %p", cell);
    return cell;
}

#if 0
/*
 * try and get a cell record
 */
struct afs_cell *afs_get_cell_maybe(struct afs_cell *cell)
{
    write_lock(&afs_cells_lock);

    if (cell && !list_empty(&cell->link))
        afs_get_cell(cell);
    else
        cell = NULL;

    write_unlock(&afs_cells_lock);
    return cell;
}
#endif  /*  0  */

/*
 * destroy a cell record
 */
void afs_put_cell(struct afs_cell *cell)
{
    if (!cell)
        return;

    _enter("%p{%d,%s}", cell, atomic_read(&cell->usage), cell->name);

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

    /* to prevent a race, the decrement and the dequeue must be effectively
     * atomic */
    write_lock(&afs_cells_lock);

    if (likely(!atomic_dec_and_test(&cell->usage))) {
        write_unlock(&afs_cells_lock);
        _leave("");
        return;
    }

    ASSERT(list_empty(&cell->servers));
    ASSERT(list_empty(&cell->vl_list));

    write_unlock(&afs_cells_lock);

    wake_up(&afs_cells_freeable_wq);

    _leave(" [unused]");
}

/*
 * destroy a cell record
 * - must be called with the afs_cells_sem write-locked
 * - cell->link should have been broken by the caller
 */
static void afs_cell_destroy(struct afs_cell *cell)
{
    _enter("%p{%d,%s}", cell, atomic_read(&cell->usage), cell->name);

    ASSERTCMP(atomic_read(&cell->usage), >=, 0);
    ASSERT(list_empty(&cell->link));

    /* wait for everyone to stop using the cell */
    if (atomic_read(&cell->usage) > 0) {
        DECLARE_WAITQUEUE(myself, current);

        _debug("wait for cell %s", cell->name);
        set_current_state(TASK_UNINTERRUPTIBLE);
        add_wait_queue(&afs_cells_freeable_wq, &myself);

        while (atomic_read(&cell->usage) > 0) {
            schedule();
            set_current_state(TASK_UNINTERRUPTIBLE);
        }

        remove_wait_queue(&afs_cells_freeable_wq, &myself);
        set_current_state(TASK_RUNNING);
    }

    _debug("cell dead");
    ASSERTCMP(atomic_read(&cell->usage), ==, 0);
    ASSERT(list_empty(&cell->servers));
    ASSERT(list_empty(&cell->vl_list));

    afs_proc_cell_remove(cell);

    down_write(&afs_proc_cells_sem);
    list_del_init(&cell->proc_link);
    up_write(&afs_proc_cells_sem);

#ifdef CONFIG_AFS_FSCACHE
    fscache_relinquish_cookie(cell->cache, 0);
#endif
    key_put(cell->anonymous_key);
    kfree(cell);

    _leave(" [destroyed]");
}

/*
 * purge in-memory cell database on module unload or afs_init() failure
 * - the timeout daemon is stopped before calling this
 */
void afs_cell_purge(void)
{
    struct afs_cell *cell;

    _enter("");

    afs_put_cell(afs_cell_root);

    down_write(&afs_cells_sem);

    while (!list_empty(&afs_cells)) {
        cell = NULL;

        /* remove the next cell from the front of the list */
        write_lock(&afs_cells_lock);

        if (!list_empty(&afs_cells)) {
            cell = list_entry(afs_cells.next,
                      struct afs_cell, link);
            list_del_init(&cell->link);
        }

        write_unlock(&afs_cells_lock);

        if (cell) {
            _debug("PURGING CELL %s (%d)",
                   cell->name, atomic_read(&cell->usage));

            /* now the cell should be left with no references */
            afs_cell_destroy(cell);
        }
    }

    up_write(&afs_cells_sem);
    _leave("");
}