/* Bind and unbind a cache from the filesystem backing it
 *
 * Copyright (C) 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 Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/completion.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/namei.h>
#include <linux/mount.h>
#include <linux/statfs.h>
#include <linux/ctype.h>
#include "internal.h"

static int cachefiles_daemon_add_cache(struct cachefiles_cache *caches);

/*
 * bind a directory as a cache
 */
int cachefiles_daemon_bind(struct cachefiles_cache *cache, char *args)
{
        _enter("{%u,%u,%u,%u,%u,%u},%s",
               cache->frun_percent,
               cache->fcull_percent,
               cache->fstop_percent,
               cache->brun_percent,
               cache->bcull_percent,
               cache->bstop_percent,
               args);

        /* start by checking things over */
        ASSERT(cache->fstop_percent >= 0 &&
               cache->fstop_percent < cache->fcull_percent &&
               cache->fcull_percent < cache->frun_percent &&
               cache->frun_percent  < 100);

        ASSERT(cache->bstop_percent >= 0 &&
               cache->bstop_percent < cache->bcull_percent &&
               cache->bcull_percent < cache->brun_percent &&
               cache->brun_percent  < 100);

        if (*args) {
                kerror("'bind' command doesn't take an argument");
                return -EINVAL;
        }

        if (!cache->rootdirname) {
                kerror("No cache directory specified");
                return -EINVAL;
        }

        /* don't permit already bound caches to be re-bound */
        if (test_bit(CACHEFILES_READY, &cache->flags)) {
                kerror("Cache already bound");
                return -EBUSY;
        }

        /* make sure we have copies of the tag and dirname strings */
        if (!cache->tag) {
                /* the tag string is released by the fops->release()
                 * function, so we don't release it on error here */
                cache->tag = kstrdup("CacheFiles", GFP_KERNEL);
                if (!cache->tag)
                        return -ENOMEM;
        }

        /* add the cache */
        return cachefiles_daemon_add_cache(cache);
}

/*
 * add a cache
 */
static int cachefiles_daemon_add_cache(struct cachefiles_cache *cache)
{
        struct cachefiles_object *fsdef;
        struct path path;
        struct kstatfs stats;
        struct dentry *graveyard, *cachedir, *root;
        const struct cred *saved_cred;
        int ret;

        _enter("");

        /* we want to work under the module's security ID */
        ret = cachefiles_get_security_ID(cache);
        if (ret < 0)
                return ret;

        cachefiles_begin_secure(cache, &saved_cred);

        /* allocate the root index object */
        ret = -ENOMEM;

        fsdef = kmem_cache_alloc(cachefiles_object_jar, GFP_KERNEL);
        if (!fsdef)
                goto error_root_object;

        ASSERTCMP(fsdef->backer, ==, NULL);

        atomic_set(&fsdef->usage, 1);
        fsdef->type = FSCACHE_COOKIE_TYPE_INDEX;

        _debug("- fsdef %p", fsdef);

        /* look up the directory at the root of the cache */
        ret = kern_path(cache->rootdirname, LOOKUP_DIRECTORY, &path);
        if (ret < 0)
                goto error_open_root;

        cache->mnt = path.mnt;
        root = path.dentry;

        /* check parameters */
        ret = -EOPNOTSUPP;
        if (!root->d_inode ||
            !root->d_inode->i_op ||
            !root->d_inode->i_op->lookup ||
            !root->d_inode->i_op->mkdir ||
            !root->d_inode->i_op->setxattr ||
            !root->d_inode->i_op->getxattr ||
            !root->d_sb ||
            !root->d_sb->s_op ||
            !root->d_sb->s_op->statfs ||
            !root->d_sb->s_op->sync_fs)
                goto error_unsupported;

        ret = -EROFS;
        if (root->d_sb->s_flags & MS_RDONLY)
                goto error_unsupported;

        /* determine the security of the on-disk cache as this governs
         * security ID of files we create */
        ret = cachefiles_determine_cache_security(cache, root, &saved_cred);
        if (ret < 0)
                goto error_unsupported;

        /* get the cache size and blocksize */
        ret = vfs_statfs(&path, &stats);
        if (ret < 0)
                goto error_unsupported;

        ret = -ERANGE;
        if (stats.f_bsize <= 0)
                goto error_unsupported;

        ret = -EOPNOTSUPP;
        if (stats.f_bsize > PAGE_SIZE)
                goto error_unsupported;

        cache->bsize = stats.f_bsize;
        cache->bshift = 0;
        if (stats.f_bsize < PAGE_SIZE)
                cache->bshift = PAGE_SHIFT - ilog2(stats.f_bsize);

        _debug("blksize %u (shift %u)",
               cache->bsize, cache->bshift);

        _debug("size %llu, avail %llu",
               (unsigned long long) stats.f_blocks,
               (unsigned long long) stats.f_bavail);

        /* set up caching limits */
        do_div(stats.f_files, 100);
        cache->fstop = stats.f_files * cache->fstop_percent;
        cache->fcull = stats.f_files * cache->fcull_percent;
        cache->frun  = stats.f_files * cache->frun_percent;

        _debug("limits {%llu,%llu,%llu} files",
               (unsigned long long) cache->frun,
               (unsigned long long) cache->fcull,
               (unsigned long long) cache->fstop);

        stats.f_blocks >>= cache->bshift;
        do_div(stats.f_blocks, 100);
        cache->bstop = stats.f_blocks * cache->bstop_percent;
        cache->bcull = stats.f_blocks * cache->bcull_percent;
        cache->brun  = stats.f_blocks * cache->brun_percent;

        _debug("limits {%llu,%llu,%llu} blocks",
               (unsigned long long) cache->brun,
               (unsigned long long) cache->bcull,
               (unsigned long long) cache->bstop);

        /* get the cache directory and check its type */
        cachedir = cachefiles_get_directory(cache, root, "cache");
        if (IS_ERR(cachedir)) {
                ret = PTR_ERR(cachedir);
                goto error_unsupported;
        }

        fsdef->dentry = cachedir;
        fsdef->fscache.cookie = NULL;

        ret = cachefiles_check_object_type(fsdef);
        if (ret < 0)
                goto error_unsupported;

        /* get the graveyard directory */
        graveyard = cachefiles_get_directory(cache, root, "graveyard");
        if (IS_ERR(graveyard)) {
                ret = PTR_ERR(graveyard);
                goto error_unsupported;
        }

        cache->graveyard = graveyard;

        /* publish the cache */
        fscache_init_cache(&cache->cache,
                           &cachefiles_cache_ops,
                           "%s",
                           fsdef->dentry->d_sb->s_id);

        fscache_object_init(&fsdef->fscache, NULL, &cache->cache);

        ret = fscache_add_cache(&cache->cache, &fsdef->fscache, cache->tag);
        if (ret < 0)
                goto error_add_cache;

        /* done */
        set_bit(CACHEFILES_READY, &cache->flags);
        dput(root);

        printk(KERN_INFO "CacheFiles:"
               " File cache on %s registered\n",
               cache->cache.identifier);

        /* check how much space the cache has */
        cachefiles_has_space(cache, 0, 0);
        cachefiles_end_secure(cache, saved_cred);
        return 0;

error_add_cache:
        dput(cache->graveyard);
        cache->graveyard = NULL;
error_unsupported:
        mntput(cache->mnt);
        cache->mnt = NULL;
        dput(fsdef->dentry);
        fsdef->dentry = NULL;
        dput(root);
error_open_root:
        kmem_cache_free(cachefiles_object_jar, fsdef);
error_root_object:
        cachefiles_end_secure(cache, saved_cred);
        kerror("Failed to register: %d", ret);
        return ret;
}

/*
 * unbind a cache on fd release
 */
void cachefiles_daemon_unbind(struct cachefiles_cache *cache)
{
        _enter("");

        if (test_bit(CACHEFILES_READY, &cache->flags)) {
                printk(KERN_INFO "CacheFiles:"
                       " File cache on %s unregistering\n",
                       cache->cache.identifier);

                fscache_withdraw_cache(&cache->cache);
        }

        dput(cache->graveyard);
        mntput(cache->mnt);

        kfree(cache->rootdirname);
        kfree(cache->secctx);
        kfree(cache->tag);

        _leave("");
}