src/lib/file-dotlock.c

	file-dotlock.c revision ac67a027f8db99d0b65c656fe1e4f26261ae750f
89a126810703c666309310d0f3189e9834d70b5bTimo Sirainen/* Copyright (C) 2003 Timo Sirainen */
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen#include "lib.h"
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen#include "str.h"
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen#include "hex-binary.h"
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen#include "hostpid.h"
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen#include "randgen.h"
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen#include "write-full.h"
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen#include "file-dotlock.h"
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen#include <stdio.h>
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen#include <stdlib.h>
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen#include <signal.h>
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen#include <time.h>
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen#include <sys/stat.h>
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen#define DEFAULT_LOCK_SUFFIX ".lock"
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen/* 0.1 .. 0.2msec */
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen#define LOCK_RANDOM_USLEEP_TIME (100000 + (unsigned int)rand() % 100000)
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainenstruct lock_info {
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    const char *path, *lock_path, *temp_path;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    unsigned int stale_timeout;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    unsigned int immediate_stale_timeout;
ebfbf5d78dcf95e8b176429f4b5b0694eb4e17d5Timo Sirainen    int fd;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen
ebfbf5d78dcf95e8b176429f4b5b0694eb4e17d5Timo Sirainen    dev_t dev;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    ino_t ino;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    off_t size;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    time_t ctime, mtime;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    off_t last_size;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    time_t last_ctime, last_mtime;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    time_t last_change;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    pid_t pid;
88187ee880b4829443e0d55ea7d145d9d5880217Timo Sirainen    time_t last_pid_check;
1777c974563740daac427d3ef738903d8f6ad7d0Timo Sirainen};
1777c974563740daac427d3ef738903d8f6ad7d0Timo Sirainen
1777c974563740daac427d3ef738903d8f6ad7d0Timo Sirainenstatic pid_t read_local_pid(const char *lock_path)
ebfbf5d78dcf95e8b176429f4b5b0694eb4e17d5Timo Sirainen{
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    char buf[512], *host;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    int fd;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    ssize_t ret;
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen
ebfbf5d78dcf95e8b176429f4b5b0694eb4e17d5Timo Sirainen    fd = open(lock_path, O_RDONLY);
ebfbf5d78dcf95e8b176429f4b5b0694eb4e17d5Timo Sirainen    if (fd == -1)
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen        return -1; /* ignore the actual error */
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    /* read line */
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    ret = read(fd, buf, sizeof(buf)-1);
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    (void)close(fd);
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    if (ret <= 0)
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen        return -1;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen    /* fix the string */
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    if (buf[ret-1] == '\n')
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen        ret--;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    buf[ret] = '\0';
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    /* it should contain pid:host */
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    host = strchr(buf, ':');
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    if (host == NULL)
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen        return -1;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    *host++ = '\0';
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    /* host must be ours */
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    if (strcmp(host, my_hostname) != 0)
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen        return -1;
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen    if (!is_numeric(buf, '\0'))
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen        return -1;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    return (pid_t)strtoul(buf, NULL, 0);
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen}
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainenstatic int check_lock(time_t now, struct lock_info *lock_info)
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen{
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen    struct stat st;
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    if (lstat(lock_info->lock_path, &st) < 0) {
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen        if (errno != ENOENT) {
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen            i_error("lstat(%s) failed: %m", lock_info->lock_path);
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen            return -1;
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen        }
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen        return 1;
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen    }
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    if (lock_info->immediate_stale_timeout != 0 &&
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen        now > st.st_mtime + (time_t)lock_info->immediate_stale_timeout &&
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen        now > st.st_ctime + (time_t)lock_info->immediate_stale_timeout) {
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen        /* old lock file */
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen        if (unlink(lock_info->lock_path) < 0 && errno != ENOENT) {
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen            i_error("unlink(%s) failed: %m", lock_info->lock_path);
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen            return -1;
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen        }
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen        return 1;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    }
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen    if (lock_info->stale_timeout == 0) {
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen        /* no change checking */
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen        return 0;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    }
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    if (lock_info->ino != st.st_ino ||
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen        !CMP_DEV_T(lock_info->dev, st.st_dev) ||
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen        lock_info->ctime != st.st_ctime ||
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen        lock_info->mtime != st.st_mtime ||
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen        lock_info->size != st.st_size) {
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen        /* either our first check or someone else got the lock file.
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen           check if it contains a pid whose existence we can verify */
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen        lock_info->dev = st.st_dev;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen        lock_info->ino = st.st_ino;
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen        lock_info->ctime = st.st_ctime;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen        lock_info->mtime = st.st_mtime;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen        lock_info->size = st.st_size;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen        lock_info->pid = read_local_pid(lock_info->lock_path);
43d32cbe60fdaef2699d99f1ca259053e9350411Timo Sirainen
43d32cbe60fdaef2699d99f1ca259053e9350411Timo Sirainen        lock_info->last_change = now;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    }
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    if (lock_info->pid != -1) {
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen        /* we've local PID. Check if it exists. */
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen        if (lock_info->last_pid_check == now)
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen            return 0;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen        if (kill(lock_info->pid, 0) == 0 || errno != ESRCH)
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen            return 0;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen        /* doesn't exist - go ahead and delete */
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen        if (unlink(lock_info->lock_path) < 0 && errno != ENOENT) {
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen            i_error("unlink(%s) failed: %m", lock_info->lock_path);
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen            return -1;
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen        }
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen        return 1;
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen    }
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen    if (lock_info->last_change != now) {
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen        if (stat(lock_info->path, &st) < 0) {
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen            if (errno == ENOENT) {
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen                /* file doesn't exist. treat it as if
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen                   it hasn't changed */
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen            } else {
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen                i_error("stat(%s) failed: %m", lock_info->path);
916221f976af0ed8b397f06f4f381c0ac0be3b86Timo Sirainen                return -1;
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen            }
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen        } else if (lock_info->last_size != st.st_size ||
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen               lock_info->last_ctime != st.st_ctime ||
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen               lock_info->last_mtime != st.st_mtime) {
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen            lock_info->last_change = now;
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen            lock_info->last_size = st.st_size;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen            lock_info->last_ctime = st.st_ctime;
916221f976af0ed8b397f06f4f381c0ac0be3b86Timo Sirainen            lock_info->last_mtime = st.st_mtime;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen        }
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen    }
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen    if (now > lock_info->last_change + (time_t)lock_info->stale_timeout) {
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen        /* no changes for a while, assume stale lock */
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen        if (unlink(lock_info->lock_path) < 0 && errno != ENOENT) {
916221f976af0ed8b397f06f4f381c0ac0be3b86Timo Sirainen            i_error("unlink(%s) failed: %m", lock_info->lock_path);
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen            return -1;
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen        }
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen        return 1;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    }
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    return 0;
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen}
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainenstatic int create_temp_file(const char *prefix, const char **path_r)
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen{
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    string_t *path;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    size_t len;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    struct stat st;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    char randbuf[8];
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    int fd;
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen    path = t_str_new(256);
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen    str_append(path, prefix);
e62f6437a4ff01d692a5a61369fe4168d69191edTimo Sirainen    len = str_len(path);
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen
1b0cfbf3cc77a670b92fff5c30f7b1eb17a63ab1Timo Sirainen    for (;;) {
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen        do {
74ab5ea66c0c4b388f1c774ae6a47ab94f1b4f18Timo Sirainen            random_fill(randbuf, sizeof(randbuf));
            str_truncate(path, len);
            str_append(path,
                   binary_to_hex(randbuf, sizeof(randbuf)));
            *path_r = str_c(path);
        } while (stat(*path_r, &st) == 0);

        if (errno != ENOENT) {
            i_error("stat(%s) failed: %m", *path_r);
            return -1;
        }

        fd = open(*path_r, O_RDWR | O_EXCL | O_CREAT, 0666);
        if (fd != -1)
            return fd;

        if (errno != EEXIST) {
            i_error("open(%s) failed: %m", *path_r);
            return -1;
        }
    }
}

static int try_create_lock(struct lock_info *lock_info, const char *temp_prefix)
{
    const char *str, *p;

    if (lock_info->temp_path == NULL) {
        /* we'll need our temp file first. */
        if (temp_prefix == NULL) {
            temp_prefix = t_strconcat(".temp.", my_hostname, ".",
                          my_pid, ".", NULL);
        }

        p = *temp_prefix == '/' ? NULL :
            strrchr(lock_info->lock_path, '/');
        if (p != NULL) {
            str = t_strdup_until(lock_info->lock_path, p+1);
            temp_prefix = t_strconcat(str, temp_prefix, NULL);
        }

        lock_info->fd = create_temp_file(temp_prefix, &str);
        if (lock_info->fd == -1)
            return -1;

                lock_info->temp_path = str;
    }

    if (link(lock_info->temp_path, lock_info->lock_path) < 0) {
        if (errno == EEXIST)
            return 0;

        i_error("link(%s, %s) failed: %m",
            lock_info->temp_path, lock_info->lock_path);
        return -1;
    }

    if (unlink(lock_info->temp_path) < 0 && errno != ENOENT) {
        i_error("unlink(%s) failed: %m", lock_info->temp_path);
        /* non-fatal, continue */
    }
    lock_info->temp_path = NULL;

    return 1;
}

static int
dotlock_create(const char *path, const char *temp_prefix,
           const char *lock_suffix, int checkonly, int *fd,
           unsigned int timeout, unsigned int stale_timeout,
           unsigned int immediate_stale_timeout,
           int (*callback)(unsigned int secs_left, int stale,
                   void *context),
           void *context)
{
    const char *lock_path;
        struct lock_info lock_info;
    unsigned int stale_notify_threshold;
    unsigned int change_secs, wait_left;
    time_t now, max_wait_time, last_notify;
    int do_wait, ret;

    now = time(NULL);

    lock_path = t_strconcat(path, lock_suffix, NULL);
    stale_notify_threshold = stale_timeout / 2;
    max_wait_time = now + timeout;

    memset(&lock_info, 0, sizeof(lock_info));
    lock_info.path = path;
    lock_info.lock_path = lock_path;
    lock_info.stale_timeout = stale_timeout;
    lock_info.immediate_stale_timeout = immediate_stale_timeout;
    lock_info.last_change = now;
    lock_info.fd = -1;

    last_notify = 0; do_wait = FALSE;

    do {
        if (do_wait) {
            usleep(LOCK_RANDOM_USLEEP_TIME);
            do_wait = FALSE;
        }

        ret = check_lock(now, &lock_info);
        if (ret < 0)
            break;

        if (ret == 1) {
            if (checkonly)
                break;

            ret = try_create_lock(&lock_info, temp_prefix);
            if (ret != 0)
                break;
        }

        do_wait = TRUE;
        if (last_notify != now && callback != NULL) {
            last_notify = now;
            change_secs = now - lock_info.last_change;
            wait_left = max_wait_time - now;

            t_push();
            if (change_secs >= stale_notify_threshold &&
                change_secs <= wait_left) {
                if (!callback(stale_timeout - change_secs,
                          TRUE, context)) {
                    /* we don't want to override */
                    lock_info.last_change = now;
                }
            } else {
                (void)callback(wait_left, FALSE, context);
            }
            t_pop();
        }

        now = time(NULL);
    } while (now < max_wait_time);

    if (ret <= 0 && lock_info.fd != -1) {
        int old_errno = errno;

        (void)close(lock_info.fd);
        lock_info.fd = -1;
        errno = old_errno;
    }
    *fd = lock_info.fd;

    if (ret == 0)
        errno = EAGAIN;
    return ret;
}

int file_lock_dotlock(const char *path, const char *temp_prefix, int checkonly,
              unsigned int timeout, unsigned int stale_timeout,
              unsigned int immediate_stale_timeout,
              int (*callback)(unsigned int secs_left, int stale,
                      void *context),
              void *context, struct dotlock *dotlock_r)
{
    const char *lock_path, *str;
    struct stat st;
    int fd, ret;

    lock_path = t_strconcat(path, DEFAULT_LOCK_SUFFIX, NULL);

    ret = dotlock_create(path, temp_prefix, DEFAULT_LOCK_SUFFIX,
                 checkonly, &fd, timeout, stale_timeout,
                 immediate_stale_timeout, callback, context);
    if (ret <= 0 || checkonly)
        return ret;

    /* write our pid and host, if possible */
    str = t_strdup_printf("%s:%s", my_pid, my_hostname);
    if (write_full(fd, str, strlen(str)) < 0) {
        /* failed, leave it empty then */
        if (ftruncate(fd, 0) < 0) {
            i_error("ftruncate(%s) failed: %m", lock_path);
            (void)close(fd);
            return -1;
        }
    }

    /* save the inode info after writing */
    if (fstat(fd, &st) < 0) {
        i_error("fstat(%s) failed: %m", lock_path);
        (void)close(fd);
        return -1;
    }

    if (close(fd) < 0) {
        i_error("fstat(%s) failed: %m", lock_path);
        return -1;
    }

    dotlock_r->dev = st.st_dev;
    dotlock_r->ino = st.st_ino;
    dotlock_r->mtime = st.st_mtime;
    return 1;
}

static int dotlock_delete(const char *path, const char *lock_suffix,
              const struct dotlock *dotlock, int check_mtime)
{
    const char *lock_path;
        struct stat st;

    lock_path = t_strconcat(path, lock_suffix, NULL);

    if (lstat(lock_path, &st) < 0) {
        if (errno == ENOENT) {
            i_warning("Our dotlock file %s was deleted", lock_path);
            return 0;
        }

        i_error("lstat(%s) failed: %m", lock_path);
        return -1;
    }

    if (dotlock->ino != st.st_ino ||
        !CMP_DEV_T(dotlock->dev, st.st_dev)) {
        i_warning("Our dotlock file %s was overridden", lock_path);
        errno = EEXIST;
        return 0;
    }

    if (dotlock->mtime != st.st_mtime && check_mtime) {
        i_warning("Our dotlock file %s was modified (%s vs %s), "
              "assuming it wasn't overridden", lock_path,
              dec2str(dotlock->mtime), dec2str(st.st_mtime));
    }

    if (unlink(lock_path) < 0) {
        if (errno == ENOENT) {
            i_warning("Our dotlock file %s was deleted", lock_path);
            return 0;
        }

        i_error("unlink(%s) failed: %m", lock_path);
        return -1;
    }

    return 1;
}

int file_unlock_dotlock(const char *path, const struct dotlock *dotlock)
{
    return dotlock_delete(path, DEFAULT_LOCK_SUFFIX, dotlock, TRUE);
}

int file_dotlock_open(const char *path,
              const char *temp_prefix, const char *lock_suffix,
              unsigned int timeout, unsigned int stale_timeout,
              unsigned int immediate_stale_timeout,
              int (*callback)(unsigned int secs_left, int stale,
                      void *context),
              void *context)
{
    int ret, fd;

    if (lock_suffix == NULL)
        lock_suffix = DEFAULT_LOCK_SUFFIX;

    ret = dotlock_create(path, temp_prefix, lock_suffix, FALSE, &fd,
                 timeout, stale_timeout, immediate_stale_timeout,
                 callback, context);
    if (ret <= 0)
        return -1;
    return fd;
}

int file_dotlock_replace(const char *path, const char *lock_suffix,
             int fd, int verify_owner)
{
    struct stat st, st2;
    const char *lock_path;
    int old_errno;

    if (lock_suffix == NULL)
        lock_suffix = DEFAULT_LOCK_SUFFIX;

    lock_path = t_strconcat(path, lock_suffix, NULL);
    if (verify_owner) {
        if (fstat(fd, &st) < 0) {
            old_errno = errno;
            i_error("fstat(%s) failed: %m", lock_path);
            (void)close(fd);
            errno = old_errno;
            return -1;
        }
    }
    if (close(fd) < 0) {
        i_error("close(%s) failed: %m", lock_path);
        return -1;
    }

    if (verify_owner) {
        if (lstat(lock_path, &st2) < 0) {
            i_error("lstat(%s) failed: %m", lock_path);
            return -1;
        }

        if (st.st_ino != st2.st_ino ||
            !CMP_DEV_T(st.st_dev, st2.st_dev)) {
            i_warning("Our dotlock file %s was overridden",
                  lock_path);
            errno = EEXIST;
            return 0;
        }
    }

    if (rename(lock_path, path) < 0) {
        i_error("rename(%s, %s) failed: %m", lock_path, path);
        return -1;
    }
    return 1;
}

int file_dotlock_delete(const char *path, const char *lock_suffix, int fd)
{
    struct dotlock dotlock;
    struct stat st;
    int old_errno;

    if (lock_suffix == NULL)
        lock_suffix = DEFAULT_LOCK_SUFFIX;

    if (fstat(fd, &st) < 0) {
        old_errno = errno;
        i_error("fstat(%s) failed: %m",
            t_strconcat(path, lock_suffix, NULL));
        (void)close(fd);
        errno = old_errno;
        return -1;
    }

    if (close(fd) < 0) {
        i_error("close(%s) failed: %m",
            t_strconcat(path, lock_suffix, NULL));
        return -1;
    }

    dotlock.dev = st.st_dev;
    dotlock.ino = st.st_ino;
    dotlock.mtime = st.st_mtime;

    return dotlock_delete(path, lock_suffix, &dotlock, FALSE);
}