path: root/src/readahead/readahead-common.c

/*-*- 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 <stdlib.h>
#include <string.h>
#include <sys/sysinfo.h>
#include <sys/inotify.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <unistd.h>
#include <libudev.h>

#include "log.h"
#include "readahead-common.h"
#include "util.h"

int file_verify(int fd, const char *fn, off_t file_size_max, struct stat *st) {
        assert(fd >= 0);
        assert(fn);
        assert(st);

        if (fstat(fd, st) < 0) {
                log_warning("fstat(%s) failed: %m", fn);
                return -errno;
        }

        if (!S_ISREG(st->st_mode)) {
                log_debug("Not preloading special file %s", fn);
                return 0;
        }

        if (st->st_size <= 0 || st->st_size > file_size_max) {
                log_debug("Not preloading file %s with size out of bounds %llu", fn, (unsigned long long) st->st_size);
                return 0;
        }

        return 1;
}

int fs_on_ssd(const char *p) {
        struct stat st;
        struct udev *udev = NULL;
        struct udev_device *udev_device = NULL, *look_at = NULL;
        bool b = false;
        const char *devtype, *rotational, *model, *id;

        assert(p);

        if (stat(p, &st) < 0)
                return -errno;

        if (major(st.st_dev) == 0)
                return false;

        udev = udev_new();
        if (!udev)
                return -ENOMEM;

        udev_device = udev_device_new_from_devnum(udev, 'b', st.st_dev);
        if (!udev_device)
                goto finish;

        devtype = udev_device_get_property_value(udev_device, "DEVTYPE");
        if (devtype && streq(devtype, "partition"))
                look_at = udev_device_get_parent(udev_device);
        else
                look_at = udev_device;

        if (!look_at)
                goto finish;

        /* First, try high-level property */
        id = udev_device_get_property_value(look_at, "ID_SSD");
        if (id) {
                b = streq(id, "1");
                goto finish;
        }

        /* Second, try kernel attribute */
        rotational = udev_device_get_sysattr_value(look_at, "queue/rotational");
        if (rotational)
                if ((b = streq(rotational, "0")))
                        goto finish;

        /* Finally, fallback to heuristics */
        look_at = udev_device_get_parent(look_at);
        if (!look_at)
                goto finish;

        model = udev_device_get_sysattr_value(look_at, "model");
        if (model)
                b = !!strstr(model, "SSD");

finish:
        if (udev_device)
                udev_device_unref(udev_device);

        if (udev)
                udev_unref(udev);

        return b;
}

int fs_on_read_only(const char *p) {
        struct stat st;
        struct udev *udev = NULL;
        struct udev_device *udev_device = NULL;
        bool b = false;
        const char *read_only;

        assert(p);

        if (stat(p, &st) < 0)
                return -errno;

        if (major(st.st_dev) == 0)
                return false;

        if (!(udev = udev_new()))
                return -ENOMEM;

        if (!(udev_device = udev_device_new_from_devnum(udev, 'b', st.st_dev)))
                goto finish;

        if ((read_only = udev_device_get_sysattr_value(udev_device, "ro")))
                if ((b = streq(read_only, "1")))
                        goto finish;

finish:
        if (udev_device)
                udev_device_unref(udev_device);

        if (udev)
                udev_unref(udev);

        return b;
}

bool enough_ram(void) {
        struct sysinfo si;

        assert_se(sysinfo(&si) >= 0);

        /* Enable readahead only with at least 128MB memory */
        return si.totalram > 127 * 1024*1024 / si.mem_unit;
}

int open_inotify(void) {
        int fd;

        if ((fd = inotify_init1(IN_CLOEXEC|IN_NONBLOCK)) < 0) {
                log_error("Failed to create inotify handle: %m");
                return -errno;
        }

        mkdir("/run/systemd", 0755);
        mkdir("/run/systemd/readahead", 0755);

        if (inotify_add_watch(fd, "/run/systemd/readahead", IN_CREATE) < 0) {
                log_error("Failed to watch /run/systemd/readahead: %m");
                close_nointr_nofail(fd);
                return -errno;
        }

        return fd;
}

ReadaheadShared *shared_get(void) {
        int fd;
        ReadaheadShared *m = NULL;

        mkdir("/run/systemd", 0755);
        mkdir("/run/systemd/readahead", 0755);

        if ((fd = open("/run/systemd/readahead/shared", O_CREAT|O_RDWR|O_CLOEXEC, 0644)) < 0) {
                log_error("Failed to create shared memory segment: %m");
                goto finish;
        }

        if (ftruncate(fd, sizeof(ReadaheadShared)) < 0) {
                log_error("Failed to truncate shared memory segment: %m");
                goto finish;
        }

        if ((m = mmap(NULL, sizeof(ReadaheadShared), PROT_WRITE|PROT_READ, MAP_SHARED, fd, 0)) == MAP_FAILED) {
                log_error("Failed to mmap shared memory segment: %m");
                m = NULL;
                goto finish;
        }

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

        return m;
}

/* We use 20K instead of the more human digestable 16K here. Why?
   Simply so that it is more unlikely that users end up picking this
   value too so that we can recognize better whether the user changed
   the value while we had it temporarily bumped. */
#define BUMP_REQUEST_NR (20*1024)

int block_bump_request_nr(const char *p) {
        struct stat st;
        uint64_t u;
        char *ap = NULL, *line = NULL;
        int r;
        dev_t d;

        assert(p);

        if (stat(p, &st) < 0)
                return -errno;

        if (major(st.st_dev) == 0)
                return 0;

        d = st.st_dev;
        block_get_whole_disk(d, &d);

        if (asprintf(&ap, "/sys/dev/block/%u:%u/queue/nr_requests", major(d), minor(d)) < 0) {
                r= -ENOMEM;
                goto finish;
        }

        r = read_one_line_file(ap, &line);
        if (r < 0) {
                if (r == -ENOENT)
                        r = 0;
                goto finish;
        }

        r = safe_atou64(line, &u);
        if (r >= 0 && u >= BUMP_REQUEST_NR) {
                r = 0;
                goto finish;
        }

        free(line);
        line = NULL;

        if (asprintf(&line, "%lu", (unsigned long) BUMP_REQUEST_NR) < 0) {
                r = -ENOMEM;
                goto finish;
        }

        r = write_one_line_file(ap, line);
        if (r < 0)
                goto finish;

        log_info("Bumped block_nr parameter of %u:%u to %lu. This is a temporary hack and should be removed one day.", major(d), minor(d), (unsigned long) BUMP_REQUEST_NR);
        r = 1;

finish:
        free(ap);
        free(line);

        return r;
}

int block_get_readahead(const char *p, uint64_t *bytes) {
        struct stat st;
        char *ap = NULL, *line = NULL;
        int r;
        dev_t d;
        uint64_t u;

        assert(p);
        assert(bytes);

        if (stat(p, &st) < 0)
                return -errno;

        if (major(st.st_dev) == 0)
                return 0;

        d = st.st_dev;
        block_get_whole_disk(d, &d);

        if (asprintf(&ap, "/sys/dev/block/%u:%u/bdi/read_ahead_kb", major(d), minor(d)) < 0) {
                r = -ENOMEM;
                goto finish;
        }

        r = read_one_line_file(ap, &line);
        if (r < 0)
                goto finish;

        r = safe_atou64(line, &u);
        if (r < 0)
                goto finish;

        *bytes = u * 1024ULL;

finish:
        free(ap);
        free(line);

        return r;
}

int block_set_readahead(const char *p, uint64_t bytes) {
        struct stat st;
        char *ap = NULL, *line = NULL;
        int r;
        dev_t d;

        assert(p);
        assert(bytes);

        if (stat(p, &st) < 0)
                return -errno;

        if (major(st.st_dev) == 0)
                return 0;

        d = st.st_dev;
        block_get_whole_disk(d, &d);

        if (asprintf(&ap, "/sys/dev/block/%u:%u/bdi/read_ahead_kb", major(d), minor(d)) < 0) {
                r = -ENOMEM;
                goto finish;
        }

        if (asprintf(&line, "%llu", (unsigned long long) bytes / 1024ULL) < 0) {
                r = -ENOMEM;
                goto finish;
        }

        r = write_one_line_file(ap, line);
        if (r < 0)
                goto finish;

finish:
        free(ap);
        free(line);

        return r;
}