// SPDX-License-Identifier: GPL-2.0-or-later

  /* Daemon interface
   *
   * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.com)

   */
  
  #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/poll.h>
  #include <linux/mount.h>
  #include <linux/statfs.h>
  #include <linux/ctype.h>

  #include <linux/string.h>

  #include <linux/fs_struct.h>
  #include "internal.h"
  
  static int cachefiles_daemon_open(struct inode *, struct file *);
  static int cachefiles_daemon_release(struct inode *, struct file *);
  static ssize_t cachefiles_daemon_read(struct file *, char __user *, size_t,
  				      loff_t *);
  static ssize_t cachefiles_daemon_write(struct file *, const char __user *,
  				       size_t, loff_t *);

  static __poll_t cachefiles_daemon_poll(struct file *,

  					   struct poll_table_struct *);
  static int cachefiles_daemon_frun(struct cachefiles_cache *, char *);
  static int cachefiles_daemon_fcull(struct cachefiles_cache *, char *);
  static int cachefiles_daemon_fstop(struct cachefiles_cache *, char *);
  static int cachefiles_daemon_brun(struct cachefiles_cache *, char *);
  static int cachefiles_daemon_bcull(struct cachefiles_cache *, char *);
  static int cachefiles_daemon_bstop(struct cachefiles_cache *, char *);
  static int cachefiles_daemon_cull(struct cachefiles_cache *, char *);
  static int cachefiles_daemon_debug(struct cachefiles_cache *, char *);
  static int cachefiles_daemon_dir(struct cachefiles_cache *, char *);
  static int cachefiles_daemon_inuse(struct cachefiles_cache *, char *);
  static int cachefiles_daemon_secctx(struct cachefiles_cache *, char *);
  static int cachefiles_daemon_tag(struct cachefiles_cache *, char *);
  
  static unsigned long cachefiles_open;
  
  const struct file_operations cachefiles_daemon_fops = {
  	.owner		= THIS_MODULE,
  	.open		= cachefiles_daemon_open,
  	.release	= cachefiles_daemon_release,
  	.read		= cachefiles_daemon_read,
  	.write		= cachefiles_daemon_write,
  	.poll		= cachefiles_daemon_poll,

  	.llseek		= noop_llseek,

  };
  
  struct cachefiles_daemon_cmd {
  	char name[8];
  	int (*handler)(struct cachefiles_cache *cache, char *args);
  };
  
  static const struct cachefiles_daemon_cmd cachefiles_daemon_cmds[] = {
  	{ "bind",	cachefiles_daemon_bind		},
  	{ "brun",	cachefiles_daemon_brun		},
  	{ "bcull",	cachefiles_daemon_bcull		},
  	{ "bstop",	cachefiles_daemon_bstop		},
  	{ "cull",	cachefiles_daemon_cull		},
  	{ "debug",	cachefiles_daemon_debug		},
  	{ "dir",	cachefiles_daemon_dir		},
  	{ "frun",	cachefiles_daemon_frun		},
  	{ "fcull",	cachefiles_daemon_fcull		},
  	{ "fstop",	cachefiles_daemon_fstop		},
  	{ "inuse",	cachefiles_daemon_inuse		},
  	{ "secctx",	cachefiles_daemon_secctx	},
  	{ "tag",	cachefiles_daemon_tag		},
  	{ "",		NULL				}
  };
  
  
  /*
   * do various checks
   */
  static int cachefiles_daemon_open(struct inode *inode, struct file *file)
  {
  	struct cachefiles_cache *cache;
  
  	_enter("");
  
  	/* only the superuser may do this */
  	if (!capable(CAP_SYS_ADMIN))
  		return -EPERM;
  
  	/* the cachefiles device may only be open once at a time */
  	if (xchg(&cachefiles_open, 1) == 1)
  		return -EBUSY;
  
  	/* allocate a cache record */
  	cache = kzalloc(sizeof(struct cachefiles_cache), GFP_KERNEL);
  	if (!cache) {
  		cachefiles_open = 0;
  		return -ENOMEM;
  	}
  
  	mutex_init(&cache->daemon_mutex);
  	cache->active_nodes = RB_ROOT;
  	rwlock_init(&cache->active_lock);
  	init_waitqueue_head(&cache->daemon_pollwq);
  
  	/* set default caching limits
  	 * - limit at 1% free space and/or free files
  	 * - cull below 5% free space and/or free files
  	 * - cease culling above 7% free space and/or free files
  	 */
  	cache->frun_percent = 7;
  	cache->fcull_percent = 5;
  	cache->fstop_percent = 1;
  	cache->brun_percent = 7;
  	cache->bcull_percent = 5;
  	cache->bstop_percent = 1;
  
  	file->private_data = cache;
  	cache->cachefilesd = file;
  	return 0;
  }
  
  /*
   * release a cache
   */
  static int cachefiles_daemon_release(struct inode *inode, struct file *file)
  {
  	struct cachefiles_cache *cache = file->private_data;
  
  	_enter("");
  
  	ASSERT(cache);
  
  	set_bit(CACHEFILES_DEAD, &cache->flags);
  
  	cachefiles_daemon_unbind(cache);
  
  	ASSERT(!cache->active_nodes.rb_node);
  
  	/* clean up the control file interface */
  	cache->cachefilesd = NULL;
  	file->private_data = NULL;
  	cachefiles_open = 0;
  
  	kfree(cache);
  
  	_leave("");
  	return 0;
  }
  
  /*
   * read the cache state
   */
  static ssize_t cachefiles_daemon_read(struct file *file, char __user *_buffer,
  				      size_t buflen, loff_t *pos)
  {
  	struct cachefiles_cache *cache = file->private_data;

  	unsigned long long b_released;
  	unsigned f_released;

  	char buffer[256];
  	int n;
  
  	//_enter(",,%zu,", buflen);
  
  	if (!test_bit(CACHEFILES_READY, &cache->flags))
  		return 0;
  
  	/* check how much space the cache has */
  	cachefiles_has_space(cache, 0, 0);
  
  	/* summarise */

  	f_released = atomic_xchg(&cache->f_released, 0);
  	b_released = atomic_long_xchg(&cache->b_released, 0);

  	clear_bit(CACHEFILES_STATE_CHANGED, &cache->flags);
  
  	n = snprintf(buffer, sizeof(buffer),
  		     "cull=%c"
  		     " frun=%llx"
  		     " fcull=%llx"
  		     " fstop=%llx"
  		     " brun=%llx"
  		     " bcull=%llx"

  		     " bstop=%llx"
  		     " freleased=%x"
  		     " breleased=%llx",

  		     test_bit(CACHEFILES_CULLING, &cache->flags) ? '1' : '0',
  		     (unsigned long long) cache->frun,
  		     (unsigned long long) cache->fcull,
  		     (unsigned long long) cache->fstop,
  		     (unsigned long long) cache->brun,
  		     (unsigned long long) cache->bcull,

  		     (unsigned long long) cache->bstop,
  		     f_released,
  		     b_released);

  
  	if (n > buflen)
  		return -EMSGSIZE;
  
  	if (copy_to_user(_buffer, buffer, n) != 0)
  		return -EFAULT;
  
  	return n;
  }
  
  /*
   * command the cache
   */
  static ssize_t cachefiles_daemon_write(struct file *file,
  				       const char __user *_data,
  				       size_t datalen,
  				       loff_t *pos)
  {
  	const struct cachefiles_daemon_cmd *cmd;
  	struct cachefiles_cache *cache = file->private_data;
  	ssize_t ret;
  	char *data, *args, *cp;
  
  	//_enter(",,%zu,", datalen);
  
  	ASSERT(cache);
  
  	if (test_bit(CACHEFILES_DEAD, &cache->flags))
  		return -EIO;
  
  	if (datalen < 0 || datalen > PAGE_SIZE - 1)
  		return -EOPNOTSUPP;
  
  	/* drag the command string into the kernel so we can parse it */

  	data = memdup_user_nul(_data, datalen);
  	if (IS_ERR(data))
  		return PTR_ERR(data);

  
  	ret = -EINVAL;
  	if (memchr(data, '\0', datalen))
  		goto error;
  
  	/* strip any newline */
  	cp = memchr(data, '
  ', datalen);
  	if (cp) {
  		if (cp == data)
  			goto error;
  
  		*cp = '\0';
  	}
  
  	/* parse the command */
  	ret = -EOPNOTSUPP;
  
  	for (args = data; *args; args++)
  		if (isspace(*args))
  			break;
  	if (*args) {
  		if (args == data)
  			goto error;
  		*args = '\0';

  		args = skip_spaces(++args);

  	}
  
  	/* run the appropriate command handler */
  	for (cmd = cachefiles_daemon_cmds; cmd->name[0]; cmd++)
  		if (strcmp(cmd->name, data) == 0)
  			goto found_command;
  
  error:
  	kfree(data);
  	//_leave(" = %zd", ret);
  	return ret;
  
  found_command:
  	mutex_lock(&cache->daemon_mutex);
  
  	ret = -EIO;
  	if (!test_bit(CACHEFILES_DEAD, &cache->flags))
  		ret = cmd->handler(cache, args);
  
  	mutex_unlock(&cache->daemon_mutex);
  
  	if (ret == 0)
  		ret = datalen;
  	goto error;
  }
  
  /*
   * poll for culling state

   * - use EPOLLOUT to indicate culling state

   */

  static __poll_t cachefiles_daemon_poll(struct file *file,

  					   struct poll_table_struct *poll)
  {
  	struct cachefiles_cache *cache = file->private_data;

  	__poll_t mask;

  
  	poll_wait(file, &cache->daemon_pollwq, poll);
  	mask = 0;
  
  	if (test_bit(CACHEFILES_STATE_CHANGED, &cache->flags))

  		mask |= EPOLLIN;

  
  	if (test_bit(CACHEFILES_CULLING, &cache->flags))

  		mask |= EPOLLOUT;

  
  	return mask;
  }
  
  /*
   * give a range error for cache space constraints
   * - can be tail-called
   */
  static int cachefiles_daemon_range_error(struct cachefiles_cache *cache,
  					 char *args)
  {

  	pr_err("Free space limits must be in range 0%%<=stop<cull<run<100%%
  ");

  
  	return -EINVAL;
  }
  
  /*
   * set the percentage of files at which to stop culling
   * - command: "frun <N>%"
   */
  static int cachefiles_daemon_frun(struct cachefiles_cache *cache, char *args)
  {
  	unsigned long frun;
  
  	_enter(",%s", args);
  
  	if (!*args)
  		return -EINVAL;
  
  	frun = simple_strtoul(args, &args, 10);
  	if (args[0] != '%' || args[1] != '\0')
  		return -EINVAL;
  
  	if (frun <= cache->fcull_percent || frun >= 100)
  		return cachefiles_daemon_range_error(cache, args);
  
  	cache->frun_percent = frun;
  	return 0;
  }
  
  /*
   * set the percentage of files at which to start culling
   * - command: "fcull <N>%"
   */
  static int cachefiles_daemon_fcull(struct cachefiles_cache *cache, char *args)
  {
  	unsigned long fcull;
  
  	_enter(",%s", args);
  
  	if (!*args)
  		return -EINVAL;
  
  	fcull = simple_strtoul(args, &args, 10);
  	if (args[0] != '%' || args[1] != '\0')
  		return -EINVAL;
  
  	if (fcull <= cache->fstop_percent || fcull >= cache->frun_percent)
  		return cachefiles_daemon_range_error(cache, args);
  
  	cache->fcull_percent = fcull;
  	return 0;
  }
  
  /*
   * set the percentage of files at which to stop allocating
   * - command: "fstop <N>%"
   */
  static int cachefiles_daemon_fstop(struct cachefiles_cache *cache, char *args)
  {
  	unsigned long fstop;
  
  	_enter(",%s", args);
  
  	if (!*args)
  		return -EINVAL;
  
  	fstop = simple_strtoul(args, &args, 10);
  	if (args[0] != '%' || args[1] != '\0')
  		return -EINVAL;
  
  	if (fstop < 0 || fstop >= cache->fcull_percent)
  		return cachefiles_daemon_range_error(cache, args);
  
  	cache->fstop_percent = fstop;
  	return 0;
  }
  
  /*
   * set the percentage of blocks at which to stop culling
   * - command: "brun <N>%"
   */
  static int cachefiles_daemon_brun(struct cachefiles_cache *cache, char *args)
  {
  	unsigned long brun;
  
  	_enter(",%s", args);
  
  	if (!*args)
  		return -EINVAL;
  
  	brun = simple_strtoul(args, &args, 10);
  	if (args[0] != '%' || args[1] != '\0')
  		return -EINVAL;
  
  	if (brun <= cache->bcull_percent || brun >= 100)
  		return cachefiles_daemon_range_error(cache, args);
  
  	cache->brun_percent = brun;
  	return 0;
  }
  
  /*
   * set the percentage of blocks at which to start culling
   * - command: "bcull <N>%"
   */
  static int cachefiles_daemon_bcull(struct cachefiles_cache *cache, char *args)
  {
  	unsigned long bcull;
  
  	_enter(",%s", args);
  
  	if (!*args)
  		return -EINVAL;
  
  	bcull = simple_strtoul(args, &args, 10);
  	if (args[0] != '%' || args[1] != '\0')
  		return -EINVAL;
  
  	if (bcull <= cache->bstop_percent || bcull >= cache->brun_percent)
  		return cachefiles_daemon_range_error(cache, args);
  
  	cache->bcull_percent = bcull;
  	return 0;
  }
  
  /*
   * set the percentage of blocks at which to stop allocating
   * - command: "bstop <N>%"
   */
  static int cachefiles_daemon_bstop(struct cachefiles_cache *cache, char *args)
  {
  	unsigned long bstop;
  
  	_enter(",%s", args);
  
  	if (!*args)
  		return -EINVAL;
  
  	bstop = simple_strtoul(args, &args, 10);
  	if (args[0] != '%' || args[1] != '\0')
  		return -EINVAL;
  
  	if (bstop < 0 || bstop >= cache->bcull_percent)
  		return cachefiles_daemon_range_error(cache, args);
  
  	cache->bstop_percent = bstop;
  	return 0;
  }
  
  /*
   * set the cache directory
   * - command: "dir <name>"
   */
  static int cachefiles_daemon_dir(struct cachefiles_cache *cache, char *args)
  {
  	char *dir;
  
  	_enter(",%s", args);
  
  	if (!*args) {

  		pr_err("Empty directory specified
  ");

  		return -EINVAL;
  	}
  
  	if (cache->rootdirname) {

  		pr_err("Second cache directory specified
  ");

  		return -EEXIST;
  	}
  
  	dir = kstrdup(args, GFP_KERNEL);
  	if (!dir)
  		return -ENOMEM;
  
  	cache->rootdirname = dir;
  	return 0;
  }
  
  /*
   * set the cache security context
   * - command: "secctx <ctx>"
   */
  static int cachefiles_daemon_secctx(struct cachefiles_cache *cache, char *args)
  {
  	char *secctx;
  
  	_enter(",%s", args);
  
  	if (!*args) {

  		pr_err("Empty security context specified
  ");

  		return -EINVAL;
  	}
  
  	if (cache->secctx) {

  		pr_err("Second security context specified
  ");

  		return -EINVAL;
  	}
  
  	secctx = kstrdup(args, GFP_KERNEL);
  	if (!secctx)
  		return -ENOMEM;
  
  	cache->secctx = secctx;
  	return 0;
  }
  
  /*
   * set the cache tag
   * - command: "tag <name>"
   */
  static int cachefiles_daemon_tag(struct cachefiles_cache *cache, char *args)
  {
  	char *tag;
  
  	_enter(",%s", args);
  
  	if (!*args) {

  		pr_err("Empty tag specified
  ");

  		return -EINVAL;
  	}
  
  	if (cache->tag)
  		return -EEXIST;
  
  	tag = kstrdup(args, GFP_KERNEL);
  	if (!tag)
  		return -ENOMEM;
  
  	cache->tag = tag;
  	return 0;
  }
  
  /*
   * request a node in the cache be culled from the current working directory
   * - command: "cull <name>"
   */
  static int cachefiles_daemon_cull(struct cachefiles_cache *cache, char *args)
  {

  	struct path path;

  	const struct cred *saved_cred;
  	int ret;
  
  	_enter(",%s", args);
  
  	if (strchr(args, '/'))
  		goto inval;
  
  	if (!test_bit(CACHEFILES_READY, &cache->flags)) {

  		pr_err("cull applied to unready cache
  ");

  		return -EIO;
  	}
  
  	if (test_bit(CACHEFILES_DEAD, &cache->flags)) {

  		pr_err("cull applied to dead cache
  ");

  		return -EIO;
  	}
  
  	/* extract the directory dentry from the cwd */

  	get_fs_pwd(current->fs, &path);

  	if (!d_can_lookup(path.dentry))

  		goto notdir;
  
  	cachefiles_begin_secure(cache, &saved_cred);

  	ret = cachefiles_cull(cache, path.dentry, args);

  	cachefiles_end_secure(cache, saved_cred);

  	path_put(&path);

  	_leave(" = %d", ret);
  	return ret;
  
  notdir:

  	path_put(&path);

  	pr_err("cull command requires dirfd to be a directory
  ");

  	return -ENOTDIR;
  
  inval:

  	pr_err("cull command requires dirfd and filename
  ");

  	return -EINVAL;
  }
  
  /*
   * set debugging mode
   * - command: "debug <mask>"
   */
  static int cachefiles_daemon_debug(struct cachefiles_cache *cache, char *args)
  {
  	unsigned long mask;
  
  	_enter(",%s", args);
  
  	mask = simple_strtoul(args, &args, 0);
  	if (args[0] != '\0')
  		goto inval;
  
  	cachefiles_debug = mask;
  	_leave(" = 0");
  	return 0;
  
  inval:

  	pr_err("debug command requires mask
  ");

  	return -EINVAL;
  }
  
  /*
   * find out whether an object in the current working directory is in use or not
   * - command: "inuse <name>"
   */
  static int cachefiles_daemon_inuse(struct cachefiles_cache *cache, char *args)
  {

  	struct path path;

  	const struct cred *saved_cred;
  	int ret;
  
  	//_enter(",%s", args);
  
  	if (strchr(args, '/'))
  		goto inval;
  
  	if (!test_bit(CACHEFILES_READY, &cache->flags)) {

  		pr_err("inuse applied to unready cache
  ");

  		return -EIO;
  	}
  
  	if (test_bit(CACHEFILES_DEAD, &cache->flags)) {

  		pr_err("inuse applied to dead cache
  ");

  		return -EIO;
  	}
  
  	/* extract the directory dentry from the cwd */

  	get_fs_pwd(current->fs, &path);

  	if (!d_can_lookup(path.dentry))

  		goto notdir;
  
  	cachefiles_begin_secure(cache, &saved_cred);

  	ret = cachefiles_check_in_use(cache, path.dentry, args);

  	cachefiles_end_secure(cache, saved_cred);

  	path_put(&path);

  	//_leave(" = %d", ret);
  	return ret;
  
  notdir:

  	path_put(&path);

  	pr_err("inuse command requires dirfd to be a directory
  ");

  	return -ENOTDIR;
  
  inval:

  	pr_err("inuse command requires dirfd and filename
  ");

  	return -EINVAL;
  }
  
  /*
   * see if we have space for a number of pages and/or a number of files in the
   * cache
   */
  int cachefiles_has_space(struct cachefiles_cache *cache,
  			 unsigned fnr, unsigned bnr)
  {
  	struct kstatfs stats;

  	struct path path = {
  		.mnt	= cache->mnt,
  		.dentry	= cache->mnt->mnt_root,
  	};

  	int ret;
  
  	//_enter("{%llu,%llu,%llu,%llu,%llu,%llu},%u,%u",
  	//       (unsigned long long) cache->frun,
  	//       (unsigned long long) cache->fcull,
  	//       (unsigned long long) cache->fstop,
  	//       (unsigned long long) cache->brun,
  	//       (unsigned long long) cache->bcull,
  	//       (unsigned long long) cache->bstop,
  	//       fnr, bnr);
  
  	/* find out how many pages of blockdev are available */
  	memset(&stats, 0, sizeof(stats));

  	ret = vfs_statfs(&path, &stats);

  	if (ret < 0) {
  		if (ret == -EIO)
  			cachefiles_io_error(cache, "statfs failed");
  		_leave(" = %d", ret);
  		return ret;
  	}
  
  	stats.f_bavail >>= cache->bshift;
  
  	//_debug("avail %llu,%llu",
  	//       (unsigned long long) stats.f_ffree,
  	//       (unsigned long long) stats.f_bavail);
  
  	/* see if there is sufficient space */
  	if (stats.f_ffree > fnr)
  		stats.f_ffree -= fnr;
  	else
  		stats.f_ffree = 0;
  
  	if (stats.f_bavail > bnr)
  		stats.f_bavail -= bnr;
  	else
  		stats.f_bavail = 0;
  
  	ret = -ENOBUFS;
  	if (stats.f_ffree < cache->fstop ||
  	    stats.f_bavail < cache->bstop)
  		goto begin_cull;
  
  	ret = 0;
  	if (stats.f_ffree < cache->fcull ||
  	    stats.f_bavail < cache->bcull)
  		goto begin_cull;
  
  	if (test_bit(CACHEFILES_CULLING, &cache->flags) &&
  	    stats.f_ffree >= cache->frun &&
  	    stats.f_bavail >= cache->brun &&
  	    test_and_clear_bit(CACHEFILES_CULLING, &cache->flags)
  	    ) {
  		_debug("cease culling");
  		cachefiles_state_changed(cache);
  	}
  
  	//_leave(" = 0");
  	return 0;
  
  begin_cull:
  	if (!test_and_set_bit(CACHEFILES_CULLING, &cache->flags)) {
  		_debug("### CULL CACHE ###");
  		cachefiles_state_changed(cache);
  	}
  
  	_leave(" = %d", ret);
  	return ret;
  }