invalidate_path.c

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/*
  FUSE: Filesystem in Userspace
  Copyright (C) 2016 Nikolaus Rath <Nikolaus@rath.org>
            (C) 2017 EditShare LLC <slawek.rudnicki@editshare.com>

  This program can be distributed under the terms of the GNU GPL.
  See the file COPYING.
 */

#define FUSE_USE_VERSION 31

#include <fuse.h>
#include <fuse_lowlevel.h>  /* for fuse_cmdline_opts */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <assert.h>
#include <stddef.h>
#include <unistd.h>
#include <pthread.h>

/* We can't actually tell the kernel that there is no
   timeout, so we just send a big value */
#define NO_TIMEOUT 500000

#define MAX_STR_LEN 128
#define TIME_FILE_NAME "current_time"
#define TIME_FILE_INO 2
#define GROW_FILE_NAME "growing"
#define GROW_FILE_INO 3

static char time_file_contents[MAX_STR_LEN];
static size_t grow_file_size;

/* Command line parsing */
struct options {
        int no_notify;
        int update_interval;
};
static struct options options = {
                .no_notify = 0,
                .update_interval = 1,
};

#define OPTION(t, p) { t, offsetof(struct options, p), 1 }
static const struct fuse_opt option_spec[] = {
                OPTION("--no-notify", no_notify),
                OPTION("--update-interval=%d", update_interval),
                FUSE_OPT_END
};

static void *xmp_init(struct fuse_conn_info *conn, struct fuse_config *cfg)
{
        (void) conn;
        cfg->entry_timeout = NO_TIMEOUT;
        cfg->attr_timeout = NO_TIMEOUT;
        cfg->negative_timeout = 0;

        return NULL;
}

static int xmp_getattr(const char *path,
                struct stat *stbuf, struct fuse_file_info* fi) {
        (void) fi;
        if (strcmp(path, "/") == 0) {
                stbuf->st_ino = 1;
                stbuf->st_mode = S_IFDIR | 0755;
                stbuf->st_nlink = 1;
        } else if (strcmp(path, "/" TIME_FILE_NAME) == 0) {
                stbuf->st_ino = TIME_FILE_INO;
                stbuf->st_mode = S_IFREG | 0444;
                stbuf->st_nlink = 1;
                stbuf->st_size = strlen(time_file_contents);
        } else if (strcmp(path, "/" GROW_FILE_NAME) == 0) {
                stbuf->st_ino = GROW_FILE_INO;
                stbuf->st_mode = S_IFREG | 0444;
                stbuf->st_nlink = 1;
                stbuf->st_size = grow_file_size;
        } else {
                return -ENOENT;
        }

        return 0;
}

static int xmp_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
                off_t offset, struct fuse_file_info *fi,
                enum fuse_readdir_flags flags) {
        (void) fi;
        (void) offset;
        (void) flags;
        if (strcmp(path, "/") != 0) {
                return -ENOTDIR;
        } else {
                (void) filler;
                (void) buf;
                struct stat file_stat;
                xmp_getattr("/" TIME_FILE_NAME, &file_stat, NULL);
                filler(buf, TIME_FILE_NAME, &file_stat, 0, 0);
                xmp_getattr("/" GROW_FILE_NAME, &file_stat, NULL);
                filler(buf, GROW_FILE_NAME, &file_stat, 0, 0);
                return 0;
        }
}

static int xmp_open(const char *path, struct fuse_file_info *fi) {
        (void) path;
        /* Make cache persistent even if file is closed,
       this makes it easier to see the effects */
        fi->keep_cache = 1;
        return 0;
}

static int xmp_read(const char *path, char *buf, size_t size, off_t offset,
                struct fuse_file_info *fi) {
        (void) fi;
        (void) offset;
        if (strcmp(path, "/" TIME_FILE_NAME) == 0) {
                int file_length = strlen(time_file_contents);
                int to_copy = offset + size <= file_length
                                ? size
                                                : file_length - offset;
                memcpy(buf, time_file_contents, to_copy);
                return to_copy;
        } else {
                assert(strcmp(path, "/" GROW_FILE_NAME) == 0);
                int to_copy = offset + size <= grow_file_size
                                ? size
                                                : grow_file_size - offset;
                memset(buf, 'x', to_copy);
                return to_copy;
        }
}

static struct fuse_operations xmp_oper = {
                .init     = xmp_init,
                .getattr  = xmp_getattr,
                .readdir  = xmp_readdir,
                .open     = xmp_open,
                .read     = xmp_read,
};

static void update_fs(void) {
        static int count = 0;
        struct tm *now;
        time_t t;
        t = time(NULL);
        now = localtime(&t);
        assert(now != NULL);

        int time_file_size = strftime(time_file_contents, MAX_STR_LEN,
                        "The current time is %H:%M:%S\n", now);
        assert(time_file_size != 0);

        grow_file_size = count++;
}

static int invalidate(struct fuse *fuse, const char *path) {
        int status = fuse_invalidate_path(fuse, path);
        if (status == -ENOENT) {
                return 0;
        } else {
                return status;
        }
}

static void* update_fs_loop(void *data) {
        struct fuse *fuse = (struct fuse*) data;

        while (1) {
                update_fs();
                if (!options.no_notify) {
                        assert(invalidate(fuse, "/" TIME_FILE_NAME) == 0);
                        assert(invalidate(fuse, "/" GROW_FILE_NAME) == 0);
                }
                sleep(options.update_interval);
        }
        return NULL;
}

static void show_help(const char *progname)
{
        printf("usage: %s [options] <mountpoint>\n\n", progname);
        printf("File-system specific options:\n"
                        "    --update-interval=<secs>  Update-rate of file system contents\n"
                        "    --no-notify            Disable kernel notifications\n"
                        "\n");
}

int main(int argc, char *argv[]) {
        struct fuse_args args = FUSE_ARGS_INIT(argc, argv);
        struct fuse *fuse;
        struct fuse_cmdline_opts opts;
        int res;

        /* Initialize the files */
        update_fs();

        if (fuse_opt_parse(&args, &options, option_spec, NULL) == -1)
                return 1;

        if (fuse_parse_cmdline(&args, &opts) != 0)
                return 1;

        if (opts.show_version) {
                printf("FUSE library version %s\n", fuse_pkgversion());
                fuse_lowlevel_version();
                res = 0;
                goto out1;
        } else if (opts.show_help) {
                show_help(argv[0]);
                fuse_cmdline_help();
                fuse_lib_help(&args);
                res = 0;
                goto out1;
        } else if (!opts.mountpoint) {
                fprintf(stderr, "error: no mountpoint specified\n");
                res = 1;
                goto out1;
        }

        fuse = fuse_new(&args, &xmp_oper, sizeof(xmp_oper), NULL);
        if (fuse == NULL) {
                res = 1;
                goto out1;
        }

        if (fuse_mount(fuse,opts.mountpoint) != 0) {
                res = 1;
                goto out2;
        }

        if (fuse_daemonize(opts.foreground) != 0) {
                res = 1;
                goto out3;
        }

        pthread_t updater;     /* Start thread to update file contents */
        int ret = pthread_create(&updater, NULL, update_fs_loop, (void *) fuse);
        if (ret != 0) {
                fprintf(stderr, "pthread_create failed with %s\n", strerror(ret));
                return 1;
        };

        struct fuse_session *se = fuse_get_session(fuse);
        if (fuse_set_signal_handlers(se) != 0) {
                res = 1;
                goto out3;
        }

        if (opts.singlethread)
                res = fuse_loop(fuse);
        else
                res = fuse_loop_mt(fuse, opts.clone_fd);
        if (res)
                res = 1;

        fuse_remove_signal_handlers(se);
out3:
        fuse_unmount(fuse);
out2:
        fuse_destroy(fuse);
out1:
        free(opts.mountpoint);
        fuse_opt_free_args(&args);
        return res;
}