/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/

/***
  This file is part of systemd.

  Copyright 2010 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/

#include <errno.h>
#include <inttypes.h>
#include <fcntl.h>
#include <linux/limits.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/select.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <getopt.h>
#include <sys/inotify.h>

#include <systemd/sd-daemon.h>

#include "missing.h"
#include "util.h"
#include "set.h"
#include "ioprio.h"
#include "readahead-common.h"
#include "virt.h"

static off_t arg_file_size_max = READAHEAD_FILE_SIZE_MAX;

static ReadaheadShared *shared = NULL;

static int unpack_file(FILE *pack) {
        char fn[PATH_MAX];
        int r = 0, fd = -1;
        bool any = false;
        struct stat st;

        assert(pack);

        if (!fgets(fn, sizeof(fn), pack))
                return 0;

        char_array_0(fn);
        truncate_nl(fn);

        if ((fd = open(fn, O_RDONLY|O_CLOEXEC|O_NOATIME|O_NOCTTY|O_NOFOLLOW)) < 0) {

                if (errno != ENOENT && errno != EPERM && errno != EACCES)
                        log_warning("open(%s) failed: %m", fn);

        } else if (file_verify(fd, fn, arg_file_size_max, &st) <= 0) {
                close_nointr_nofail(fd);
                fd = -1;
        }

        for (;;) {
                uint32_t b, c;

                if (fread(&b, sizeof(b), 1, pack) != 1 ||
                    fread(&c, sizeof(c), 1, pack) != 1) {
                        log_error("Premature end of pack file.");
                        r = -EIO;
                        goto finish;
                }

                if (b == 0 && c == 0)
                        break;

                if (c <= b) {
                        log_error("Invalid pack file.");
                        r = -EIO;
                        goto finish;
                }

                log_debug("%s: page %u to %u", fn, b, c);

                any = true;

                if (fd >= 0)
                        if (posix_fadvise(fd, b * page_size(), (c - b) * page_size(), POSIX_FADV_WILLNEED) < 0) {
                                log_warning("posix_fadvise() failed: %m");
                                goto finish;
                        }
        }

        if (!any && fd >= 0) {
                /* if no range is encoded in the pack file this is
                 * intended to mean that the whole file shall be
                 * read */

                if (posix_fadvise(fd, 0, st.st_size, POSIX_FADV_WILLNEED) < 0) {
                        log_warning("posix_fadvise() failed: %m");
                        goto finish;
                }
        }

finish:
        if (fd >= 0)
                close_nointr_nofail(fd);

        return r;
}

static int replay(const char *root) {
        FILE *pack = NULL;
        char line[LINE_MAX];
        int r = 0;
        char *pack_fn = NULL;
        int c;
        bool on_ssd, ready = false;
        int prio;
        int inotify_fd = -1;

        assert(root);

        write_one_line_file("/proc/self/oom_score_adj", "1000");
        block_bump_request_nr(root);

        if (asprintf(&pack_fn, "%s/.readahead", root) < 0) {
                log_error("Out of memory");
                r = -ENOMEM;
                goto finish;
        }

        if ((!(pack = fopen(pack_fn, "re")))) {
                if (errno == ENOENT)
                        log_debug("No pack file found.");
                else {
                        log_error("Failed to open pack file: %m");
                        r = -errno;
                }

                goto finish;
        }

        posix_fadvise(fileno(pack), 0, 0, POSIX_FADV_WILLNEED);

        if ((inotify_fd = open_inotify()) < 0) {
                r = inotify_fd;
                goto finish;
        }

        if (!(fgets(line, sizeof(line), pack))) {
                log_error("Premature end of pack file.");
                r = -EIO;
                goto finish;
        }

        char_array_0(line);

        if (!streq(line, CANONICAL_HOST "\n")) {
                log_debug("Pack file host type mismatch.");
                goto finish;
        }

        if ((c = getc(pack)) == EOF) {
                log_debug("Premature end of pack file.");
                r = -EIO;
                goto finish;
        }

        /* We do not retest SSD here, so that we can start replaying
         * before udev is up.*/
        on_ssd = c == 'S';
        log_debug("On SSD: %s", yes_no(on_ssd));

        if (on_ssd)
                prio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0);
        else
                /* We are not using RT here, since we'd starve IO that
                we didn't record (which is for example blkid, since
                its disk accesses go directly to the block device and
                are thus not visible in fallocate) to death. However,
                we do ask for an IO prio that is slightly higher than
                the default (which is BE. 4) */
                prio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, 2);

        if (ioprio_set(IOPRIO_WHO_PROCESS, getpid(), prio) < 0)
                log_warning("Failed to set IDLE IO priority class: %m");

        sd_notify(0, "STATUS=Replaying readahead data");

        log_debug("Replaying...");

        if (access("/run/systemd/readahead/noreplay", F_OK) >= 0) {
                log_debug("Got termination request");
                goto done;
        }

        while (!feof(pack) && !ferror(pack)) {
                uint8_t inotify_buffer[sizeof(struct inotify_event) + FILENAME_MAX];
                int k;
                ssize_t n;

                if ((n = read(inotify_fd, &inotify_buffer, sizeof(inotify_buffer))) < 0) {
                        if (errno != EINTR && errno != EAGAIN) {
                                log_error("Failed to read inotify event: %m");
                                r = -errno;
                                goto finish;
                        }
                } else {
                        struct inotify_event *e = (struct inotify_event*) inotify_buffer;

                        while (n > 0) {
                                size_t step;

                                if ((e->mask & IN_CREATE) && streq(e->name, "noreplay")) {
                                        log_debug("Got termination request");
                                        goto done;
                                }

                                step = sizeof(struct inotify_event) + e->len;
                                assert(step <= (size_t) n);

                                e = (struct inotify_event*) ((uint8_t*) e + step);
                                n -= step;
                        }
                }

                if ((k = unpack_file(pack)) < 0) {
                        r = k;
                        goto finish;
                }

                if (!ready) {
                        /* We delay the ready notification until we
                         * queued at least one read */
                        sd_notify(0, "READY=1");
                        ready = true;
                }
        }

done:
        if (!ready)
                sd_notify(0, "READY=1");

        if (ferror(pack)) {
                log_error("Failed to read pack file.");
                r = -EIO;
                goto finish;
        }

        log_debug("Done.");

finish:
        if (pack)
                fclose(pack);

        if (inotify_fd >= 0)
                close_nointr_nofail(inotify_fd);

        free(pack_fn);

        return r;
}


static int help(void) {

        printf("%s [OPTIONS...] [DIRECTORY]\n\n"
               "Replay collected read-ahead data on early boot.\n\n"
               "  -h --help                 Show this help\n"
               "     --max-file-size=BYTES  Maximum size of files to read ahead\n",
               program_invocation_short_name);

        return 0;
}

static int parse_argv(int argc, char *argv[]) {

        enum {
                ARG_FILE_SIZE_MAX
        };

        static const struct option options[] = {
                { "help",          no_argument,       NULL, 'h'                },
                { "file-size-max", required_argument, NULL, ARG_FILE_SIZE_MAX  },
                { NULL,            0,                 NULL, 0                  }
        };

        int c;

        assert(argc >= 0);
        assert(argv);

        while ((c = getopt_long(argc, argv, "h", options, NULL)) >= 0) {

                switch (c) {

                case 'h':
                        help();
                        return 0;

                case ARG_FILE_SIZE_MAX: {
                        unsigned long long ull;

                        if (safe_atollu(optarg, &ull) < 0 || ull <= 0) {
                                log_error("Failed to parse maximum file size %s.", optarg);
                                return -EINVAL;
                        }

                        arg_file_size_max = (off_t) ull;
                        break;
                }

                case '?':
                        return -EINVAL;

                default:
                        log_error("Unknown option code %c", c);
                        return -EINVAL;
                }
        }

        if (optind != argc &&
            optind != argc-1) {
                help();
                return -EINVAL;
        }

        return 1;
}

int main(int argc, char*argv[]) {
        int r;
        const char *root;

        log_set_target(LOG_TARGET_AUTO);
        log_parse_environment();
        log_open();

        umask(0022);

        r = parse_argv(argc, argv);
        if (r <= 0)
                return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;

        root = optind < argc ? argv[optind] : "/";

        if (!enough_ram()) {
                log_info("Disabling readahead replay due to low memory.");
                return 0;
        }

        shared = shared_get();
        if (!shared)
                return 1;

        shared->replay = getpid();
        __sync_synchronize();

        if (replay(root) < 0)
                return 1;

        return 0;
}