/* Daemon interface
 *
 * 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/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 unsigned int 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;
        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 */
        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",
                     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
                     );

        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 = kmalloc(datalen + 1, GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        ret = -EFAULT;
        if (copy_from_user(data, _data, datalen) != 0)
                goto error;

        data[datalen] = '\0';

        ret = -EINVAL;
        if (memchr(data, '\0', datalen))
                goto error;

        /* strip any newline */
        cp = memchr(data, '\n', 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 POLLOUT to indicate culling state
 */
static unsigned int cachefiles_daemon_poll(struct file *file,
                                           struct poll_table_struct *poll)
{
        struct cachefiles_cache *cache = file->private_data;
        unsigned int mask;

        poll_wait(file, &cache->daemon_pollwq, poll);
        mask = 0;

        if (test_bit(CACHEFILES_STATE_CHANGED, &cache->flags))
                mask |= POLLIN;

        if (test_bit(CACHEFILES_CULLING, &cache->flags))
                mask |= POLLOUT;

        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%%\n");

        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\n");
                return -EINVAL;
        }

        if (cache->rootdirname) {
                pr_err("Second cache directory specified\n");
                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\n");
                return -EINVAL;
        }

        if (cache->secctx) {
                pr_err("Second security context specified\n");
                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\n");
                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\n");
                return -EIO;
        }

        if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
                pr_err("cull applied to dead cache\n");
                return -EIO;
        }

        /* extract the directory dentry from the cwd */
        get_fs_pwd(current->fs, &path);

        if (!S_ISDIR(path.dentry->d_inode->i_mode))
                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\n");
        return -ENOTDIR;

inval:
        pr_err("cull command requires dirfd and filename\n");
        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\n");
        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\n");
                return -EIO;
        }

        if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
                pr_err("inuse applied to dead cache\n");
                return -EIO;
        }

        /* extract the directory dentry from the cwd */
        get_fs_pwd(current->fs, &path);

        if (!S_ISDIR(path.dentry->d_inode->i_mode))
                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\n");
        return -ENOTDIR;

inval:
        pr_err("inuse command requires dirfd and filename\n");
        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;
}