/* FS-Cache interface to CacheFiles
 *
 * 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/slab.h>
#include <linux/mount.h>
#include <linux/buffer_head.h>
#include "internal.h"

#define list_to_page(head) (list_entry((head)->prev, struct page, lru))

struct cachefiles_lookup_data {
        struct cachefiles_xattr *auxdata;       /* auxiliary data */
        char                    *key;           /* key path */
};

static int cachefiles_attr_changed(struct fscache_object *_object);

/*
 * allocate an object record for a cookie lookup and prepare the lookup data
 */
static struct fscache_object *cachefiles_alloc_object(
        struct fscache_cache *_cache,
        struct fscache_cookie *cookie)
{
        struct cachefiles_lookup_data *lookup_data;
        struct cachefiles_object *object;
        struct cachefiles_cache *cache;
        struct cachefiles_xattr *auxdata;
        unsigned keylen, auxlen;
        void *buffer;
        char *key;

        cache = container_of(_cache, struct cachefiles_cache, cache);

        _enter("{%s},%p,", cache->cache.identifier, cookie);

        lookup_data = kmalloc(sizeof(*lookup_data), GFP_KERNEL);
        if (!lookup_data)
                goto nomem_lookup_data;

        /* create a new object record and a temporary leaf image */
        object = kmem_cache_alloc(cachefiles_object_jar, GFP_KERNEL);
        if (!object)
                goto nomem_object;

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

        BUG_ON(test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));
        atomic_set(&object->usage, 1);

        fscache_object_init(&object->fscache, cookie, &cache->cache);

        object->type = cookie->def->type;

        /* get hold of the raw key
         * - stick the length on the front and leave space on the back for the
         *   encoder
         */
        buffer = kmalloc((2 + 512) + 3, GFP_KERNEL);
        if (!buffer)
                goto nomem_buffer;

        keylen = cookie->def->get_key(cookie->netfs_data, buffer + 2, 512);
        ASSERTCMP(keylen, <, 512);

        *(uint16_t *)buffer = keylen;
        ((char *)buffer)[keylen + 2] = 0;
        ((char *)buffer)[keylen + 3] = 0;
        ((char *)buffer)[keylen + 4] = 0;

        /* turn the raw key into something that can work with as a filename */
        key = cachefiles_cook_key(buffer, keylen + 2, object->type);
        if (!key)
                goto nomem_key;

        /* get hold of the auxiliary data and prepend the object type */
        auxdata = buffer;
        auxlen = 0;
        if (cookie->def->get_aux) {
                auxlen = cookie->def->get_aux(cookie->netfs_data,
                                              auxdata->data, 511);
                ASSERTCMP(auxlen, <, 511);
        }

        auxdata->len = auxlen + 1;
        auxdata->type = cookie->def->type;

        lookup_data->auxdata = auxdata;
        lookup_data->key = key;
        object->lookup_data = lookup_data;

        _leave(" = %p [%p]", &object->fscache, lookup_data);
        return &object->fscache;

nomem_key:
        kfree(buffer);
nomem_buffer:
        BUG_ON(test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));
        kmem_cache_free(cachefiles_object_jar, object);
        fscache_object_destroyed(&cache->cache);
nomem_object:
        kfree(lookup_data);
nomem_lookup_data:
        _leave(" = -ENOMEM");
        return ERR_PTR(-ENOMEM);
}

/*
 * attempt to look up the nominated node in this cache
 * - return -ETIMEDOUT to be scheduled again
 */
static int cachefiles_lookup_object(struct fscache_object *_object)
{
        struct cachefiles_lookup_data *lookup_data;
        struct cachefiles_object *parent, *object;
        struct cachefiles_cache *cache;
        const struct cred *saved_cred;
        int ret;

        _enter("{OBJ%x}", _object->debug_id);

        cache = container_of(_object->cache, struct cachefiles_cache, cache);
        parent = container_of(_object->parent,
                              struct cachefiles_object, fscache);
        object = container_of(_object, struct cachefiles_object, fscache);
        lookup_data = object->lookup_data;

        ASSERTCMP(lookup_data, !=, NULL);

        /* look up the key, creating any missing bits */
        cachefiles_begin_secure(cache, &saved_cred);
        ret = cachefiles_walk_to_object(parent, object,
                                        lookup_data->key,
                                        lookup_data->auxdata);
        cachefiles_end_secure(cache, saved_cred);

        /* polish off by setting the attributes of non-index files */
        if (ret == 0 &&
            object->fscache.cookie->def->type != FSCACHE_COOKIE_TYPE_INDEX)
                cachefiles_attr_changed(&object->fscache);

        if (ret < 0 && ret != -ETIMEDOUT) {
                if (ret != -ENOBUFS)
                        printk(KERN_WARNING
                               "CacheFiles: Lookup failed error %d\n", ret);
                fscache_object_lookup_error(&object->fscache);
        }

        _leave(" [%d]", ret);
        return ret;
}

/*
 * indication of lookup completion
 */
static void cachefiles_lookup_complete(struct fscache_object *_object)
{
        struct cachefiles_object *object;

        object = container_of(_object, struct cachefiles_object, fscache);

        _enter("{OBJ%x,%p}", object->fscache.debug_id, object->lookup_data);

        if (object->lookup_data) {
                kfree(object->lookup_data->key);
                kfree(object->lookup_data->auxdata);
                kfree(object->lookup_data);
                object->lookup_data = NULL;
        }
}

/*
 * increment the usage count on an inode object (may fail if unmounting)
 */
static
struct fscache_object *cachefiles_grab_object(struct fscache_object *_object)
{
        struct cachefiles_object *object =
                container_of(_object, struct cachefiles_object, fscache);

        _enter("{OBJ%x,%d}", _object->debug_id, atomic_read(&object->usage));

#ifdef CACHEFILES_DEBUG_SLAB
        ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
#endif

        atomic_inc(&object->usage);
        return &object->fscache;
}

/*
 * update the auxilliary data for an object object on disk
 */
static void cachefiles_update_object(struct fscache_object *_object)
{
        struct cachefiles_object *object;
        struct cachefiles_xattr *auxdata;
        struct cachefiles_cache *cache;
        struct fscache_cookie *cookie;
        const struct cred *saved_cred;
        unsigned auxlen;

        _enter("{OBJ%x}", _object->debug_id);

        object = container_of(_object, struct cachefiles_object, fscache);
        cache = container_of(object->fscache.cache, struct cachefiles_cache,
                             cache);
        cookie = object->fscache.cookie;

        if (!cookie->def->get_aux) {
                _leave(" [no aux]");
                return;
        }

        auxdata = kmalloc(2 + 512 + 3, GFP_KERNEL);
        if (!auxdata) {
                _leave(" [nomem]");
                return;
        }

        auxlen = cookie->def->get_aux(cookie->netfs_data, auxdata->data, 511);
        ASSERTCMP(auxlen, <, 511);

        auxdata->len = auxlen + 1;
        auxdata->type = cookie->def->type;

        cachefiles_begin_secure(cache, &saved_cred);
        cachefiles_update_object_xattr(object, auxdata);
        cachefiles_end_secure(cache, saved_cred);
        kfree(auxdata);
        _leave("");
}

/*
 * discard the resources pinned by an object and effect retirement if
 * requested
 */
static void cachefiles_drop_object(struct fscache_object *_object)
{
        struct cachefiles_object *object;
        struct cachefiles_cache *cache;
        const struct cred *saved_cred;

        ASSERT(_object);

        object = container_of(_object, struct cachefiles_object, fscache);

        _enter("{OBJ%x,%d}",
               object->fscache.debug_id, atomic_read(&object->usage));

        cache = container_of(object->fscache.cache,
                             struct cachefiles_cache, cache);

#ifdef CACHEFILES_DEBUG_SLAB
        ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
#endif

        /* delete retired objects */
        if (object->fscache.state == FSCACHE_OBJECT_RECYCLING &&
            _object != cache->cache.fsdef
            ) {
                _debug("- retire object OBJ%x", object->fscache.debug_id);
                cachefiles_begin_secure(cache, &saved_cred);
                cachefiles_delete_object(cache, object);
                cachefiles_end_secure(cache, saved_cred);
        }

        /* close the filesystem stuff attached to the object */
        if (object->backer != object->dentry)
                dput(object->backer);
        object->backer = NULL;

        /* note that the object is now inactive */
        if (test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags)) {
                write_lock(&cache->active_lock);
                if (!test_and_clear_bit(CACHEFILES_OBJECT_ACTIVE,
                                        &object->flags))
                        BUG();
                rb_erase(&object->active_node, &cache->active_nodes);
                wake_up_bit(&object->flags, CACHEFILES_OBJECT_ACTIVE);
                write_unlock(&cache->active_lock);
        }

        dput(object->dentry);
        object->dentry = NULL;

        _leave("");
}

/*
 * dispose of a reference to an object
 */
static void cachefiles_put_object(struct fscache_object *_object)
{
        struct cachefiles_object *object;
        struct fscache_cache *cache;

        ASSERT(_object);

        object = container_of(_object, struct cachefiles_object, fscache);

        _enter("{OBJ%x,%d}",
               object->fscache.debug_id, atomic_read(&object->usage));

#ifdef CACHEFILES_DEBUG_SLAB
        ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
#endif

        ASSERTIFCMP(object->fscache.parent,
                    object->fscache.parent->n_children, >, 0);

        if (atomic_dec_and_test(&object->usage)) {
                _debug("- kill object OBJ%x", object->fscache.debug_id);

                ASSERT(!test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));
                ASSERTCMP(object->fscache.parent, ==, NULL);
                ASSERTCMP(object->backer, ==, NULL);
                ASSERTCMP(object->dentry, ==, NULL);
                ASSERTCMP(object->fscache.n_ops, ==, 0);
                ASSERTCMP(object->fscache.n_children, ==, 0);

                if (object->lookup_data) {
                        kfree(object->lookup_data->key);
                        kfree(object->lookup_data->auxdata);
                        kfree(object->lookup_data);
                        object->lookup_data = NULL;
                }

                cache = object->fscache.cache;
                fscache_object_destroy(&object->fscache);
                kmem_cache_free(cachefiles_object_jar, object);
                fscache_object_destroyed(cache);
        }

        _leave("");
}

/*
 * sync a cache
 */
static void cachefiles_sync_cache(struct fscache_cache *_cache)
{
        struct cachefiles_cache *cache;
        const struct cred *saved_cred;
        int ret;

        _enter("%p", _cache);

        cache = container_of(_cache, struct cachefiles_cache, cache);

        /* make sure all pages pinned by operations on behalf of the netfs are
         * written to disc */
        cachefiles_begin_secure(cache, &saved_cred);
        down_read(&cache->mnt->mnt_sb->s_umount);
        ret = sync_filesystem(cache->mnt->mnt_sb);
        up_read(&cache->mnt->mnt_sb->s_umount);
        cachefiles_end_secure(cache, saved_cred);

        if (ret == -EIO)
                cachefiles_io_error(cache,
                                    "Attempt to sync backing fs superblock"
                                    " returned error %d",
                                    ret);
}

/*
 * notification the attributes on an object have changed
 * - called with reads/writes excluded by FS-Cache
 */
static int cachefiles_attr_changed(struct fscache_object *_object)
{
        struct cachefiles_object *object;
        struct cachefiles_cache *cache;
        const struct cred *saved_cred;
        struct iattr newattrs;
        uint64_t ni_size;
        loff_t oi_size;
        int ret;

        _object->cookie->def->get_attr(_object->cookie->netfs_data, &ni_size);

        _enter("{OBJ%x},[%llu]",
               _object->debug_id, (unsigned long long) ni_size);

        object = container_of(_object, struct cachefiles_object, fscache);
        cache = container_of(object->fscache.cache,
                             struct cachefiles_cache, cache);

        if (ni_size == object->i_size)
                return 0;

        if (!object->backer)
                return -ENOBUFS;

        ASSERT(S_ISREG(object->backer->d_inode->i_mode));

        fscache_set_store_limit(&object->fscache, ni_size);

        oi_size = i_size_read(object->backer->d_inode);
        if (oi_size == ni_size)
                return 0;

        cachefiles_begin_secure(cache, &saved_cred);
        mutex_lock(&object->backer->d_inode->i_mutex);

        /* if there's an extension to a partial page at the end of the backing
         * file, we need to discard the partial page so that we pick up new
         * data after it */
        if (oi_size & ~PAGE_MASK && ni_size > oi_size) {
                _debug("discard tail %llx", oi_size);
                newattrs.ia_valid = ATTR_SIZE;
                newattrs.ia_size = oi_size & PAGE_MASK;
                ret = notify_change(object->backer, &newattrs);
                if (ret < 0)
                        goto truncate_failed;
        }

        newattrs.ia_valid = ATTR_SIZE;
        newattrs.ia_size = ni_size;
        ret = notify_change(object->backer, &newattrs);

truncate_failed:
        mutex_unlock(&object->backer->d_inode->i_mutex);
        cachefiles_end_secure(cache, saved_cred);

        if (ret == -EIO) {
                fscache_set_store_limit(&object->fscache, 0);
                cachefiles_io_error_obj(object, "Size set failed");
                ret = -ENOBUFS;
        }

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

/*
 * dissociate a cache from all the pages it was backing
 */
static void cachefiles_dissociate_pages(struct fscache_cache *cache)
{
        _enter("");
}

const struct fscache_cache_ops cachefiles_cache_ops = {
        .name                   = "cachefiles",
        .alloc_object           = cachefiles_alloc_object,
        .lookup_object          = cachefiles_lookup_object,
        .lookup_complete        = cachefiles_lookup_complete,
        .grab_object            = cachefiles_grab_object,
        .update_object          = cachefiles_update_object,
        .drop_object            = cachefiles_drop_object,
        .put_object             = cachefiles_put_object,
        .sync_cache             = cachefiles_sync_cache,
        .attr_changed           = cachefiles_attr_changed,
        .read_or_alloc_page     = cachefiles_read_or_alloc_page,
        .read_or_alloc_pages    = cachefiles_read_or_alloc_pages,
        .allocate_page          = cachefiles_allocate_page,
        .allocate_pages         = cachefiles_allocate_pages,
        .write_page             = cachefiles_write_page,
        .uncache_page           = cachefiles_uncache_page,
        .dissociate_pages       = cachefiles_dissociate_pages,
};