daemon.c

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/* Daemon interface
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([email protected])
 *
 * 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)
{
    kerror("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) {
        kerror("Empty directory specified");
        return -EINVAL;
    }

    if (cache->rootdirname) {
        kerror("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) {
        kerror("Empty security context specified");
        return -EINVAL;
    }

    if (cache->secctx) {
        kerror("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) {
        kerror("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)) {
        kerror("cull applied to unready cache");
        return -EIO;
    }

    if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
        kerror("cull applied to dead cache");
        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);
    kerror("cull command requires dirfd to be a directory");
    return -ENOTDIR;

inval:
    kerror("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:
    kerror("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)) {
        kerror("inuse applied to unready cache");
        return -EIO;
    }

    if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
        kerror("inuse applied to dead cache");
        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);
    kerror("inuse command requires dirfd to be a directory");
    return -ENOTDIR;

inval:
    kerror("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;
}