/* 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 "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
  ", 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 auxiliary 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,
  };