/* CacheFiles extended attribute management
   *
   * 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/sched.h>
  #include <linux/file.h>
  #include <linux/fs.h>
  #include <linux/fsnotify.h>
  #include <linux/quotaops.h>
  #include <linux/xattr.h>
  #include <linux/slab.h>
  #include "internal.h"
  
  static const char cachefiles_xattr_cache[] =
  	XATTR_USER_PREFIX "CacheFiles.cache";
  
  /*
   * check the type label on an object
   * - done using xattrs
   */
  int cachefiles_check_object_type(struct cachefiles_object *object)
  {
  	struct dentry *dentry = object->dentry;
  	char type[3], xtype[3];
  	int ret;
  
  	ASSERT(dentry);
  	ASSERT(dentry->d_inode);
  
  	if (!object->fscache.cookie)
  		strcpy(type, "C3");
  	else
  		snprintf(type, 3, "%02x", object->fscache.cookie->def->type);
  
  	_enter("%p{%s}", object, type);
  
  	/* attempt to install a type label directly */
  	ret = vfs_setxattr(dentry, cachefiles_xattr_cache, type, 2,
  			   XATTR_CREATE);
  	if (ret == 0) {
  		_debug("SET"); /* we succeeded */
  		goto error;
  	}
  
  	if (ret != -EEXIST) {
  		kerror("Can't set xattr on %*.*s [%lu] (err %d)",
  		       dentry->d_name.len, dentry->d_name.len,
  		       dentry->d_name.name, dentry->d_inode->i_ino,
  		       -ret);
  		goto error;
  	}
  
  	/* read the current type label */
  	ret = vfs_getxattr(dentry, cachefiles_xattr_cache, xtype, 3);
  	if (ret < 0) {
  		if (ret == -ERANGE)
  			goto bad_type_length;
  
  		kerror("Can't read xattr on %*.*s [%lu] (err %d)",
  		       dentry->d_name.len, dentry->d_name.len,
  		       dentry->d_name.name, dentry->d_inode->i_ino,
  		       -ret);
  		goto error;
  	}
  
  	/* check the type is what we're expecting */
  	if (ret != 2)
  		goto bad_type_length;
  
  	if (xtype[0] != type[0] || xtype[1] != type[1])
  		goto bad_type;
  
  	ret = 0;
  
  error:
  	_leave(" = %d", ret);
  	return ret;
  
  bad_type_length:
  	kerror("Cache object %lu type xattr length incorrect",
  	       dentry->d_inode->i_ino);
  	ret = -EIO;
  	goto error;
  
  bad_type:
  	xtype[2] = 0;
  	kerror("Cache object %*.*s [%lu] type %s not %s",
  	       dentry->d_name.len, dentry->d_name.len,
  	       dentry->d_name.name, dentry->d_inode->i_ino,
  	       xtype, type);
  	ret = -EIO;
  	goto error;
  }
  
  /*
   * set the state xattr on a cache file
   */
  int cachefiles_set_object_xattr(struct cachefiles_object *object,
  				struct cachefiles_xattr *auxdata)
  {
  	struct dentry *dentry = object->dentry;
  	int ret;
  
  	ASSERT(dentry);
  
  	_enter("%p,#%d", object, auxdata->len);
  
  	/* attempt to install the cache metadata directly */
  	_debug("SET #%u", auxdata->len);
  
  	ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
  			   &auxdata->type, auxdata->len,
  			   XATTR_CREATE);
  	if (ret < 0 && ret != -ENOMEM)
  		cachefiles_io_error_obj(
  			object,
  			"Failed to set xattr with error %d", ret);
  
  	_leave(" = %d", ret);
  	return ret;
  }
  
  /*
   * update the state xattr on a cache file
   */
  int cachefiles_update_object_xattr(struct cachefiles_object *object,
  				   struct cachefiles_xattr *auxdata)
  {
  	struct dentry *dentry = object->dentry;
  	int ret;
  
  	ASSERT(dentry);
  
  	_enter("%p,#%d", object, auxdata->len);
  
  	/* attempt to install the cache metadata directly */
  	_debug("SET #%u", auxdata->len);
  
  	ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
  			   &auxdata->type, auxdata->len,
  			   XATTR_REPLACE);
  	if (ret < 0 && ret != -ENOMEM)
  		cachefiles_io_error_obj(
  			object,
  			"Failed to update xattr with error %d", ret);
  
  	_leave(" = %d", ret);
  	return ret;
  }
  
  /*
   * check the consistency between the backing cache and the FS-Cache cookie
   */
  int cachefiles_check_auxdata(struct cachefiles_object *object)
  {
  	struct cachefiles_xattr *auxbuf;
  	enum fscache_checkaux validity;
  	struct dentry *dentry = object->dentry;
  	ssize_t xlen;
  	int ret;
  
  	ASSERT(dentry);
  	ASSERT(dentry->d_inode);
  	ASSERT(object->fscache.cookie->def->check_aux);
  
  	auxbuf = kmalloc(sizeof(struct cachefiles_xattr) + 512, GFP_KERNEL);
  	if (!auxbuf)
  		return -ENOMEM;
  
  	xlen = vfs_getxattr(dentry, cachefiles_xattr_cache,
  			    &auxbuf->type, 512 + 1);
  	ret = -ESTALE;
  	if (xlen < 1 ||
  	    auxbuf->type != object->fscache.cookie->def->type)
  		goto error;
  
  	xlen--;
  	validity = fscache_check_aux(&object->fscache, &auxbuf->data, xlen);
  	if (validity != FSCACHE_CHECKAUX_OKAY)
  		goto error;
  
  	ret = 0;
  error:
  	kfree(auxbuf);
  	return ret;
  }
  
  /*
   * check the state xattr on a cache file
   * - return -ESTALE if the object should be deleted
   */
  int cachefiles_check_object_xattr(struct cachefiles_object *object,
  				  struct cachefiles_xattr *auxdata)
  {
  	struct cachefiles_xattr *auxbuf;
  	struct dentry *dentry = object->dentry;
  	int ret;
  
  	_enter("%p,#%d", object, auxdata->len);
  
  	ASSERT(dentry);
  	ASSERT(dentry->d_inode);
  
  	auxbuf = kmalloc(sizeof(struct cachefiles_xattr) + 512, cachefiles_gfp);
  	if (!auxbuf) {
  		_leave(" = -ENOMEM");
  		return -ENOMEM;
  	}
  
  	/* read the current type label */
  	ret = vfs_getxattr(dentry, cachefiles_xattr_cache,
  			   &auxbuf->type, 512 + 1);
  	if (ret < 0) {
  		if (ret == -ENODATA)
  			goto stale; /* no attribute - power went off
  				     * mid-cull? */
  
  		if (ret == -ERANGE)
  			goto bad_type_length;
  
  		cachefiles_io_error_obj(object,
  					"Can't read xattr on %lu (err %d)",
  					dentry->d_inode->i_ino, -ret);
  		goto error;
  	}
  
  	/* check the on-disk object */
  	if (ret < 1)
  		goto bad_type_length;
  
  	if (auxbuf->type != auxdata->type)
  		goto stale;
  
  	auxbuf->len = ret;
  
  	/* consult the netfs */
  	if (object->fscache.cookie->def->check_aux) {
  		enum fscache_checkaux result;
  		unsigned int dlen;
  
  		dlen = auxbuf->len - 1;
  
  		_debug("checkaux %s #%u",
  		       object->fscache.cookie->def->name, dlen);
  
  		result = fscache_check_aux(&object->fscache,
  					   &auxbuf->data, dlen);
  
  		switch (result) {
  			/* entry okay as is */
  		case FSCACHE_CHECKAUX_OKAY:
  			goto okay;
  
  			/* entry requires update */
  		case FSCACHE_CHECKAUX_NEEDS_UPDATE:
  			break;
  
  			/* entry requires deletion */
  		case FSCACHE_CHECKAUX_OBSOLETE:
  			goto stale;
  
  		default:
  			BUG();
  		}
  
  		/* update the current label */
  		ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
  				   &auxdata->type, auxdata->len,
  				   XATTR_REPLACE);
  		if (ret < 0) {
  			cachefiles_io_error_obj(object,
  						"Can't update xattr on %lu"
  						" (error %d)",
  						dentry->d_inode->i_ino, -ret);
  			goto error;
  		}
  	}
  
  okay:
  	ret = 0;
  
  error:
  	kfree(auxbuf);
  	_leave(" = %d", ret);
  	return ret;
  
  bad_type_length:
  	kerror("Cache object %lu xattr length incorrect",
  	       dentry->d_inode->i_ino);
  	ret = -EIO;
  	goto error;
  
  stale:
  	ret = -ESTALE;
  	goto error;
  }
  
  /*
   * remove the object's xattr to mark it stale
   */
  int cachefiles_remove_object_xattr(struct cachefiles_cache *cache,
  				   struct dentry *dentry)
  {
  	int ret;
  
  	ret = vfs_removexattr(dentry, cachefiles_xattr_cache);
  	if (ret < 0) {
  		if (ret == -ENOENT || ret == -ENODATA)
  			ret = 0;
  		else if (ret != -ENOMEM)
  			cachefiles_io_error(cache,
  					    "Can't remove xattr from %lu"
  					    " (error %d)",
  					    dentry->d_inode->i_ino, -ret);
  	}
  
  	_leave(" = %d", ret);
  	return ret;
  }