/* 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->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
  ",
  	       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
  ",
  		       cache->cache.identifier);
  
  		fscache_withdraw_cache(&cache->cache);
  	}
  
  	dput(cache->graveyard);
  	mntput(cache->mnt);
  
  	kfree(cache->rootdirname);
  	kfree(cache->secctx);
  	kfree(cache->tag);
  
  	_leave("");
  }