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/*
* inotify-glue.c
*
* Copyright (C) 2004 Novell, Inc.
*
*/
/*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <time.h>
#include <unistd.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <sys/poll.h>
#include <sys/types.h>
#include "inotify.h"
#include "inotify-syscalls.h"
#define PROCFS_PREFIX "/proc/sys/fs/inotify"
#define PROCFS_MAX_USER_DEVICES PROCFS_PREFIX "/max_user_instances"
#define PROCFS_MAX_USER_WATCHES PROCFS_PREFIX "/max_user_watches"
#define PROCFS_MAX_QUEUED_EVENTS PROCFS_PREFIX "/max_queued_events"
/* Inotify sysfs knobs, initialized to their pre-sysfs defaults */
static int max_user_instances = 8;
static int max_user_watches = 8192;
static int max_queued_events = 256;
/* Paranoid code to read an integer from a sysfs (well, any) file. */
static void
read_int (const char *filename, int *var)
{
int fd, n;
char buffer[32];
char *buffer_endptr = NULL;
fd = open (filename, O_RDONLY);
if (fd == -1)
return;
if (read (fd, buffer, 31) > 0) {
n = (int) strtol (buffer, &buffer_endptr, 10);
if (*buffer != '\0' && *buffer_endptr == '\0')
*var = n;
}
close (fd);
}
int
inotify_glue_init (void)
{
static int fd = 0;
if (fd)
return fd;
fd = inotify_init ();
if (fd < 0) {
int err = errno;
perror ("inotify_init");
if (err == ENOSYS)
fprintf(stderr, "Inotify not supported! You need a "
"2.6.13 kernel or later with CONFIG_INOTIFY "
"enabled.");
}
read_int (PROCFS_MAX_USER_DEVICES, &max_user_instances);
read_int (PROCFS_MAX_USER_WATCHES, &max_user_watches);
read_int (PROCFS_MAX_QUEUED_EVENTS, &max_queued_events);
return fd;
}
int
inotify_glue_watch (int fd, const char *filename, __u32 mask)
{
int wd;
wd = inotify_add_watch (fd, filename, mask);
if (wd < 0) {
int err = errno;
perror ("inotify_add_watch");
if (err == ENOSPC)
fprintf(stderr, "Maximum watch limit hit. "
"Try adjusting " PROCFS_MAX_USER_WATCHES ".\n");
}
return wd;
}
int
inotify_glue_ignore (int fd, __u32 wd)
{
int ret;
ret = inotify_rm_watch (fd, wd);
if (ret < 0)
perror ("inotify_rm_watch");
return ret;
}
#define MAX_PENDING_COUNT 5
#define PENDING_PAUSE_NANOSECONDS 2000000
#define PENDING_THRESHOLD(qsize) ((unsigned int) (qsize) >> 1)
#define PENDING_MARGINAL_COST(p) ((unsigned int) (1 << (p)))
void
inotify_snarf_events (int fd, int timeout_ms, int *nr, void **buffer_out)
{
struct pollfd pollfd = { fd, POLLIN | POLLPRI, 0 };
unsigned int prev_pending = 0, pending_count = 0;
static struct inotify_event *buffer = NULL;
static size_t buffer_size;
int ret;
/* Allocate our buffer the first time we try to read events. */
if (buffer == NULL) {
/* guess the avg len */
buffer_size = sizeof (struct inotify_event) + 16;
buffer_size *= max_queued_events;
buffer = malloc (buffer_size);
if (!buffer) {
perror ("malloc");
*buffer_out = NULL;
return;
}
}
/* Set nr to 0, so it will be sure to contain something
valid if the poll times out. */
*nr = 0;
/* Wait for the file descriptor to be ready to read. */
ret = poll (&pollfd, 1, timeout_ms);
if (ret == -1 || ret == 0)
return;
/* Reading events in groups significantly helps performance.
* If there are some events (but not too many!) ready, wait a
* bit more to see if more events come in. */
while (pending_count < MAX_PENDING_COUNT) {
struct timespec ts = {0, PENDING_PAUSE_NANOSECONDS};
unsigned int pending;
if (ioctl (fd, FIONREAD, &pending) == -1)
break;
/* Don't wait if the number of pending events is too close
* to the maximum queue size. */
pending /= sizeof (struct inotify_event) + 16;
if (pending > PENDING_THRESHOLD (max_queued_events))
break;
/* With each successive iteration, the minimum rate for
* further sleep doubles. */
if (pending-prev_pending < PENDING_MARGINAL_COST(pending_count))
break;
prev_pending = pending;
++pending_count;
nanosleep (&ts, NULL);
}
*nr = read (fd, buffer, buffer_size);
*buffer_out = buffer;
}
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