super.c

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/* AFS superblock handling
 *
 * Copyright (c) 2002, 2007 Red Hat, Inc. All rights reserved.
 *
 * This software may be freely redistributed under the terms of the
 * GNU General Public License.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * Authors: David Howells <[email protected]>
 *          David Woodhouse <[email protected]>
 *
 */

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

#define AFS_FS_MAGIC 0x6B414653 /* 'kAFS' */

static void afs_i_init_once(void *foo);
static struct dentry *afs_mount(struct file_system_type *fs_type,
              int flags, const char *dev_name, void *data);
static void afs_kill_super(struct super_block *sb);
static struct inode *afs_alloc_inode(struct super_block *sb);
static void afs_destroy_inode(struct inode *inode);
static int afs_statfs(struct dentry *dentry, struct kstatfs *buf);

struct file_system_type afs_fs_type = {
    .owner      = THIS_MODULE,
    .name       = "afs",
    .mount      = afs_mount,
    .kill_sb    = afs_kill_super,
    .fs_flags   = 0,
};

static const struct super_operations afs_super_ops = {
    .statfs     = afs_statfs,
    .alloc_inode    = afs_alloc_inode,
    .drop_inode = afs_drop_inode,
    .destroy_inode  = afs_destroy_inode,
    .evict_inode    = afs_evict_inode,
    .show_options   = generic_show_options,
};

static struct kmem_cache *afs_inode_cachep;
static atomic_t afs_count_active_inodes;

enum {
    afs_no_opt,
    afs_opt_cell,
    afs_opt_rwpath,
    afs_opt_vol,
    afs_opt_autocell,
};

static const match_table_t afs_options_list = {
    { afs_opt_cell,     "cell=%s"   },
    { afs_opt_rwpath,   "rwpath"    },
    { afs_opt_vol,      "vol=%s"    },
    { afs_opt_autocell, "autocell"  },
    { afs_no_opt,       NULL        },
};

/*
 * initialise the filesystem
 */
int __init afs_fs_init(void)
{
    int ret;

    _enter("");

    /* create ourselves an inode cache */
    atomic_set(&afs_count_active_inodes, 0);

    ret = -ENOMEM;
    afs_inode_cachep = kmem_cache_create("afs_inode_cache",
                         sizeof(struct afs_vnode),
                         0,
                         SLAB_HWCACHE_ALIGN,
                         afs_i_init_once);
    if (!afs_inode_cachep) {
        printk(KERN_NOTICE "kAFS: Failed to allocate inode cache\n");
        return ret;
    }

    /* now export our filesystem to lesser mortals */
    ret = register_filesystem(&afs_fs_type);
    if (ret < 0) {
        kmem_cache_destroy(afs_inode_cachep);
        _leave(" = %d", ret);
        return ret;
    }

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

/*
 * clean up the filesystem
 */
void __exit afs_fs_exit(void)
{
    _enter("");

    afs_mntpt_kill_timer();
    unregister_filesystem(&afs_fs_type);

    if (atomic_read(&afs_count_active_inodes) != 0) {
        printk("kAFS: %d active inode objects still present\n",
               atomic_read(&afs_count_active_inodes));
        BUG();
    }

    /*
     * Make sure all delayed rcu free inodes are flushed before we
     * destroy cache.
     */
    rcu_barrier();
    kmem_cache_destroy(afs_inode_cachep);
    _leave("");
}

/*
 * parse the mount options
 * - this function has been shamelessly adapted from the ext3 fs which
 *   shamelessly adapted it from the msdos fs
 */
static int afs_parse_options(struct afs_mount_params *params,
                 char *options, const char **devname)
{
    struct afs_cell *cell;
    substring_t args[MAX_OPT_ARGS];
    char *p;
    int token;

    _enter("%s", options);

    options[PAGE_SIZE - 1] = 0;

    while ((p = strsep(&options, ","))) {
        if (!*p)
            continue;

        token = match_token(p, afs_options_list, args);
        switch (token) {
        case afs_opt_cell:
            cell = afs_cell_lookup(args[0].from,
                           args[0].to - args[0].from,
                           false);
            if (IS_ERR(cell))
                return PTR_ERR(cell);
            afs_put_cell(params->cell);
            params->cell = cell;
            break;

        case afs_opt_rwpath:
            params->rwpath = 1;
            break;

        case afs_opt_vol:
            *devname = args[0].from;
            break;

        case afs_opt_autocell:
            params->autocell = 1;
            break;

        default:
            printk(KERN_ERR "kAFS:"
                   " Unknown or invalid mount option: '%s'\n", p);
            return -EINVAL;
        }
    }

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

/*
 * parse a device name to get cell name, volume name, volume type and R/W
 * selector
 * - this can be one of the following:
 *  "%[cell:]volume[.]"     R/W volume
 *  "#[cell:]volume[.]"     R/O or R/W volume (rwpath=0),
 *                   or R/W (rwpath=1) volume
 *  "%[cell:]volume.readonly"   R/O volume
 *  "#[cell:]volume.readonly"   R/O volume
 *  "%[cell:]volume.backup"     Backup volume
 *  "#[cell:]volume.backup"     Backup volume
 */
static int afs_parse_device_name(struct afs_mount_params *params,
                 const char *name)
{
    struct afs_cell *cell;
    const char *cellname, *suffix;
    int cellnamesz;

    _enter(",%s", name);

    if (!name) {
        printk(KERN_ERR "kAFS: no volume name specified\n");
        return -EINVAL;
    }

    if ((name[0] != '%' && name[0] != '#') || !name[1]) {
        printk(KERN_ERR "kAFS: unparsable volume name\n");
        return -EINVAL;
    }

    /* determine the type of volume we're looking for */
    params->type = AFSVL_ROVOL;
    params->force = false;
    if (params->rwpath || name[0] == '%') {
        params->type = AFSVL_RWVOL;
        params->force = true;
    }
    name++;

    /* split the cell name out if there is one */
    params->volname = strchr(name, ':');
    if (params->volname) {
        cellname = name;
        cellnamesz = params->volname - name;
        params->volname++;
    } else {
        params->volname = name;
        cellname = NULL;
        cellnamesz = 0;
    }

    /* the volume type is further affected by a possible suffix */
    suffix = strrchr(params->volname, '.');
    if (suffix) {
        if (strcmp(suffix, ".readonly") == 0) {
            params->type = AFSVL_ROVOL;
            params->force = true;
        } else if (strcmp(suffix, ".backup") == 0) {
            params->type = AFSVL_BACKVOL;
            params->force = true;
        } else if (suffix[1] == 0) {
        } else {
            suffix = NULL;
        }
    }

    params->volnamesz = suffix ?
        suffix - params->volname : strlen(params->volname);

    _debug("cell %*.*s [%p]",
           cellnamesz, cellnamesz, cellname ?: "", params->cell);

    /* lookup the cell record */
    if (cellname || !params->cell) {
        cell = afs_cell_lookup(cellname, cellnamesz, true);
        if (IS_ERR(cell)) {
            printk(KERN_ERR "kAFS: unable to lookup cell '%*.*s'\n",
                   cellnamesz, cellnamesz, cellname ?: "");
            return PTR_ERR(cell);
        }
        afs_put_cell(params->cell);
        params->cell = cell;
    }

    _debug("CELL:%s [%p] VOLUME:%*.*s SUFFIX:%s TYPE:%d%s",
           params->cell->name, params->cell,
           params->volnamesz, params->volnamesz, params->volname,
           suffix ?: "-", params->type, params->force ? " FORCE" : "");

    return 0;
}

/*
 * check a superblock to see if it's the one we're looking for
 */
static int afs_test_super(struct super_block *sb, void *data)
{
    struct afs_super_info *as1 = data;
    struct afs_super_info *as = sb->s_fs_info;

    return as->volume == as1->volume;
}

static int afs_set_super(struct super_block *sb, void *data)
{
    sb->s_fs_info = data;
    return set_anon_super(sb, NULL);
}

/*
 * fill in the superblock
 */
static int afs_fill_super(struct super_block *sb,
              struct afs_mount_params *params)
{
    struct afs_super_info *as = sb->s_fs_info;
    struct afs_fid fid;
    struct inode *inode = NULL;
    int ret;

    _enter("");

    /* fill in the superblock */
    sb->s_blocksize     = PAGE_CACHE_SIZE;
    sb->s_blocksize_bits    = PAGE_CACHE_SHIFT;
    sb->s_magic     = AFS_FS_MAGIC;
    sb->s_op        = &afs_super_ops;
    sb->s_bdi       = &as->volume->bdi;
    strlcpy(sb->s_id, as->volume->vlocation->vldb.name, sizeof(sb->s_id));

    /* allocate the root inode and dentry */
    fid.vid     = as->volume->vid;
    fid.vnode   = 1;
    fid.unique  = 1;
    inode = afs_iget(sb, params->key, &fid, NULL, NULL);
    if (IS_ERR(inode))
        return PTR_ERR(inode);

    if (params->autocell)
        set_bit(AFS_VNODE_AUTOCELL, &AFS_FS_I(inode)->flags);

    ret = -ENOMEM;
    sb->s_root = d_make_root(inode);
    if (!sb->s_root)
        goto error;

    sb->s_d_op = &afs_fs_dentry_operations;

    _leave(" = 0");
    return 0;

error:
    _leave(" = %d", ret);
    return ret;
}

/*
 * get an AFS superblock
 */
static struct dentry *afs_mount(struct file_system_type *fs_type,
              int flags, const char *dev_name, void *options)
{
    struct afs_mount_params params;
    struct super_block *sb;
    struct afs_volume *vol;
    struct key *key;
    char *new_opts = kstrdup(options, GFP_KERNEL);
    struct afs_super_info *as;
    int ret;

    _enter(",,%s,%p", dev_name, options);

    memset(&params, 0, sizeof(params));

    /* parse the options and device name */
    if (options) {
        ret = afs_parse_options(&params, options, &dev_name);
        if (ret < 0)
            goto error;
    }

    ret = afs_parse_device_name(&params, dev_name);
    if (ret < 0)
        goto error;

    /* try and do the mount securely */
    key = afs_request_key(params.cell);
    if (IS_ERR(key)) {
        _leave(" = %ld [key]", PTR_ERR(key));
        ret = PTR_ERR(key);
        goto error;
    }
    params.key = key;

    /* parse the device name */
    vol = afs_volume_lookup(&params);
    if (IS_ERR(vol)) {
        ret = PTR_ERR(vol);
        goto error;
    }

    /* allocate a superblock info record */
    as = kzalloc(sizeof(struct afs_super_info), GFP_KERNEL);
    if (!as) {
        ret = -ENOMEM;
        afs_put_volume(vol);
        goto error;
    }
    as->volume = vol;

    /* allocate a deviceless superblock */
    sb = sget(fs_type, afs_test_super, afs_set_super, flags, as);
    if (IS_ERR(sb)) {
        ret = PTR_ERR(sb);
        afs_put_volume(vol);
        kfree(as);
        goto error;
    }

    if (!sb->s_root) {
        /* initial superblock/root creation */
        _debug("create");
        ret = afs_fill_super(sb, &params);
        if (ret < 0) {
            deactivate_locked_super(sb);
            goto error;
        }
        save_mount_options(sb, new_opts);
        sb->s_flags |= MS_ACTIVE;
    } else {
        _debug("reuse");
        ASSERTCMP(sb->s_flags, &, MS_ACTIVE);
        afs_put_volume(vol);
        kfree(as);
    }

    afs_put_cell(params.cell);
    kfree(new_opts);
    _leave(" = 0 [%p]", sb);
    return dget(sb->s_root);

error:
    afs_put_cell(params.cell);
    key_put(params.key);
    kfree(new_opts);
    _leave(" = %d", ret);
    return ERR_PTR(ret);
}

static void afs_kill_super(struct super_block *sb)
{
    struct afs_super_info *as = sb->s_fs_info;
    kill_anon_super(sb);
    afs_put_volume(as->volume);
    kfree(as);
}

/*
 * initialise an inode cache slab element prior to any use
 */
static void afs_i_init_once(void *_vnode)
{
    struct afs_vnode *vnode = _vnode;

    memset(vnode, 0, sizeof(*vnode));
    inode_init_once(&vnode->vfs_inode);
    init_waitqueue_head(&vnode->update_waitq);
    mutex_init(&vnode->permits_lock);
    mutex_init(&vnode->validate_lock);
    spin_lock_init(&vnode->writeback_lock);
    spin_lock_init(&vnode->lock);
    INIT_LIST_HEAD(&vnode->writebacks);
    INIT_LIST_HEAD(&vnode->pending_locks);
    INIT_LIST_HEAD(&vnode->granted_locks);
    INIT_DELAYED_WORK(&vnode->lock_work, afs_lock_work);
    INIT_WORK(&vnode->cb_broken_work, afs_broken_callback_work);
}

/*
 * allocate an AFS inode struct from our slab cache
 */
static struct inode *afs_alloc_inode(struct super_block *sb)
{
    struct afs_vnode *vnode;

    vnode = kmem_cache_alloc(afs_inode_cachep, GFP_KERNEL);
    if (!vnode)
        return NULL;

    atomic_inc(&afs_count_active_inodes);

    memset(&vnode->fid, 0, sizeof(vnode->fid));
    memset(&vnode->status, 0, sizeof(vnode->status));

    vnode->volume       = NULL;
    vnode->update_cnt   = 0;
    vnode->flags        = 1 << AFS_VNODE_UNSET;
    vnode->cb_promised  = false;

    _leave(" = %p", &vnode->vfs_inode);
    return &vnode->vfs_inode;
}

static void afs_i_callback(struct rcu_head *head)
{
    struct inode *inode = container_of(head, struct inode, i_rcu);
    struct afs_vnode *vnode = AFS_FS_I(inode);
    kmem_cache_free(afs_inode_cachep, vnode);
}

/*
 * destroy an AFS inode struct
 */
static void afs_destroy_inode(struct inode *inode)
{
    struct afs_vnode *vnode = AFS_FS_I(inode);

    _enter("%p{%x:%u}", inode, vnode->fid.vid, vnode->fid.vnode);

    _debug("DESTROY INODE %p", inode);

    ASSERTCMP(vnode->server, ==, NULL);

    call_rcu(&inode->i_rcu, afs_i_callback);
    atomic_dec(&afs_count_active_inodes);
}

/*
 * return information about an AFS volume
 */
static int afs_statfs(struct dentry *dentry, struct kstatfs *buf)
{
    struct afs_volume_status vs;
    struct afs_vnode *vnode = AFS_FS_I(dentry->d_inode);
    struct key *key;
    int ret;

    key = afs_request_key(vnode->volume->cell);
    if (IS_ERR(key))
        return PTR_ERR(key);

    ret = afs_vnode_get_volume_status(vnode, key, &vs);
    key_put(key);
    if (ret < 0) {
        _leave(" = %d", ret);
        return ret;
    }

    buf->f_type = dentry->d_sb->s_magic;
    buf->f_bsize    = AFS_BLOCK_SIZE;
    buf->f_namelen  = AFSNAMEMAX - 1;

    if (vs.max_quota == 0)
        buf->f_blocks = vs.part_max_blocks;
    else
        buf->f_blocks = vs.max_quota;
    buf->f_bavail = buf->f_bfree = buf->f_blocks - vs.blocks_in_use;
    return 0;
}