util/filemonitor-inotify.c - qemu - Git at Google

 /*
  * QEMU file monitor Linux inotify impl
  *
  * Copyright (c) 2018 Red Hat, Inc.
  *
  * This library 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.
  *
  * This library 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 this library; if not, see <http://www.gnu.org/licenses/>.
  *
  */

 #include "qemu/osdep.h"
 #include "qemu/filemonitor.h"
 #include "qemu/main-loop.h"
 #include "qemu/error-report.h"
 #include "qapi/error.h"
 #include "trace.h"

 #include <sys/inotify.h>

 struct QFileMonitor {
     int fd;
     QemuMutex lock; /* protects dirs & idmap */
     GHashTable *dirs; /* dirname => QFileMonitorDir */
     GHashTable *idmap; /* inotify ID => dirname */
 };


 typedef struct {
     int64_t id; /* watch ID */
     char *filename; /* optional filter */
     QFileMonitorHandler cb;
     void *opaque;
 } QFileMonitorWatch;


 typedef struct {
     char *path;
     int inotify_id; /* inotify ID */
     int next_file_id; /* file ID counter */
     GArray *watches; /* QFileMonitorWatch elements */
 } QFileMonitorDir;


 static void qemu_file_monitor_watch(void *arg)
 {
     QFileMonitor *mon = arg;
     char buf[4096]
         __attribute__ ((aligned(__alignof__(struct inotify_event))));
     int used = 0;
     int len;

     qemu_mutex_lock(&mon->lock);

     if (mon->fd == -1) {
         qemu_mutex_unlock(&mon->lock);
         return;
     }

     len = read(mon->fd, buf, sizeof(buf));

     if (len < 0) {
         if (errno != EAGAIN) {
             error_report("Failure monitoring inotify FD '%s',"
                          "disabling events", strerror(errno));
             goto cleanup;
         }

         /* no more events right now */
         goto cleanup;
     }

     /* Loop over all events in the buffer */
     while (used < len) {
         const char *name;
         QFileMonitorDir *dir;
         uint32_t iev;
         int qev;
         gsize i;
         struct inotify_event *ev = (struct inotify_event *)(buf + used);

         /*
          * We trust the kenel to provide valid buffer with complete event
          * records.
          */
         assert(len - used >= sizeof(struct inotify_event));
         assert(len - used - sizeof(struct inotify_event) >= ev->len);

         name = ev->len ? ev->name : "";
         dir = g_hash_table_lookup(mon->idmap, GINT_TO_POINTER(ev->wd));
         iev = ev->mask &
             (IN_CREATE | IN_MODIFY | IN_DELETE | IN_IGNORED |
              IN_MOVED_TO | IN_MOVED_FROM | IN_ATTRIB);

         used += sizeof(struct inotify_event) + ev->len;

         if (!dir) {
             continue;
         }

         /*
          * During a rename operation, the old name gets
          * IN_MOVED_FROM and the new name gets IN_MOVED_TO.
          * To simplify life for callers, we turn these into
          * DELETED and CREATED events
          */
         switch (iev) {
         case IN_CREATE:
         case IN_MOVED_TO:
             qev = QFILE_MONITOR_EVENT_CREATED;
             break;
         case IN_MODIFY:
             qev = QFILE_MONITOR_EVENT_MODIFIED;
             break;
         case IN_DELETE:
         case IN_MOVED_FROM:
             qev = QFILE_MONITOR_EVENT_DELETED;
             break;
         case IN_ATTRIB:
             qev = QFILE_MONITOR_EVENT_ATTRIBUTES;
             break;
         case IN_IGNORED:
             qev = QFILE_MONITOR_EVENT_IGNORED;
             break;
         default:
             g_assert_not_reached();
         }

         trace_qemu_file_monitor_event(mon, dir->path, name, ev->mask,
                                       dir->inotify_id);
         for (i = 0; i < dir->watches->len; i++) {
             QFileMonitorWatch *watch = &g_array_index(dir->watches,
                                                       QFileMonitorWatch,
                                                       i);

             if (watch->filename == NULL ||
                 (name && g_str_equal(watch->filename, name))) {
                 trace_qemu_file_monitor_dispatch(mon, dir->path, name,
                                                  qev, watch->cb,
                                                  watch->opaque, watch->id);
                 watch->cb(watch->id, qev, name, watch->opaque);
             }
         }
     }

  cleanup:
     qemu_mutex_unlock(&mon->lock);
 }


 static void
 qemu_file_monitor_dir_free(void *data)
 {
     QFileMonitorDir *dir = data;
     gsize i;

     for (i = 0; i < dir->watches->len; i++) {
         QFileMonitorWatch *watch = &g_array_index(dir->watches,
                                                   QFileMonitorWatch, i);
         g_free(watch->filename);
     }
     g_array_unref(dir->watches);
     g_free(dir->path);
     g_free(dir);
 }


 QFileMonitor *
 qemu_file_monitor_new(Error **errp)
 {
     int fd;
     QFileMonitor *mon;

     fd = inotify_init1(IN_NONBLOCK);
     if (fd < 0) {
         error_setg_errno(errp, errno,
                          "Unable to initialize inotify");
         return NULL;
     }

     mon = g_new0(QFileMonitor, 1);
     qemu_mutex_init(&mon->lock);
     mon->fd = fd;

     mon->dirs = g_hash_table_new_full(g_str_hash, g_str_equal, NULL,
                                       qemu_file_monitor_dir_free);
     mon->idmap = g_hash_table_new(g_direct_hash, g_direct_equal);

     trace_qemu_file_monitor_new(mon, mon->fd);

     return mon;
 }

 static gboolean
 qemu_file_monitor_free_idle(void *opaque)
 {
     QFileMonitor *mon = opaque;

     if (!mon) {
         return G_SOURCE_REMOVE;
     }

     qemu_mutex_lock(&mon->lock);

     g_hash_table_unref(mon->idmap);
     g_hash_table_unref(mon->dirs);

     qemu_mutex_unlock(&mon->lock);

     qemu_mutex_destroy(&mon->lock);
     g_free(mon);

     return G_SOURCE_REMOVE;
 }

 void
 qemu_file_monitor_free(QFileMonitor *mon)
 {
     if (!mon) {
         return;
     }

     qemu_mutex_lock(&mon->lock);
     if (mon->fd != -1) {
         qemu_set_fd_handler(mon->fd, NULL, NULL, NULL);
         close(mon->fd);
         mon->fd = -1;
     }
     qemu_mutex_unlock(&mon->lock);

     /*
      * Can't free it yet, because another thread
      * may be running event loop, so the inotify
      * callback might be pending. Using an idle
      * source ensures we'll only free after the
      * pending callback is done
      */
     g_idle_add((GSourceFunc)qemu_file_monitor_free_idle, mon);
 }

 int64_t
 qemu_file_monitor_add_watch(QFileMonitor *mon,
                             const char *dirpath,
                             const char *filename,
                             QFileMonitorHandler cb,
                             void *opaque,
                             Error **errp)
 {
     QFileMonitorDir *dir;
     QFileMonitorWatch watch;
     int64_t ret = -1;

     qemu_mutex_lock(&mon->lock);
     dir = g_hash_table_lookup(mon->dirs, dirpath);
     if (!dir) {
         int rv = inotify_add_watch(mon->fd, dirpath,
                                    IN_CREATE | IN_DELETE | IN_MODIFY |
                                    IN_MOVED_TO | IN_MOVED_FROM | IN_ATTRIB);

         if (rv < 0) {
             error_setg_errno(errp, errno, "Unable to watch '%s'", dirpath);
             goto cleanup;
         }

         trace_qemu_file_monitor_enable_watch(mon, dirpath, rv);

         dir = g_new0(QFileMonitorDir, 1);
         dir->path = g_strdup(dirpath);
         dir->inotify_id = rv;
         dir->watches = g_array_new(FALSE, TRUE, sizeof(QFileMonitorWatch));

         g_hash_table_insert(mon->dirs, dir->path, dir);
         g_hash_table_insert(mon->idmap, GINT_TO_POINTER(rv), dir);

         if (g_hash_table_size(mon->dirs) == 1) {
             qemu_set_fd_handler(mon->fd, qemu_file_monitor_watch, NULL, mon);
         }
     }

     watch.id = (((int64_t)dir->inotify_id) << 32) | dir->next_file_id++;
     watch.filename = g_strdup(filename);
     watch.cb = cb;
     watch.opaque = opaque;

     g_array_append_val(dir->watches, watch);

     trace_qemu_file_monitor_add_watch(mon, dirpath,
                                       filename ? filename : "<none>",
                                       cb, opaque, watch.id);

     ret = watch.id;

  cleanup:
     qemu_mutex_unlock(&mon->lock);
     return ret;
 }


 void qemu_file_monitor_remove_watch(QFileMonitor *mon,
                                     const char *dirpath,
                                     int64_t id)
 {
     QFileMonitorDir *dir;
     gsize i;

     qemu_mutex_lock(&mon->lock);

     trace_qemu_file_monitor_remove_watch(mon, dirpath, id);

     dir = g_hash_table_lookup(mon->dirs, dirpath);
     if (!dir) {
         goto cleanup;
     }

     for (i = 0; i < dir->watches->len; i++) {
         QFileMonitorWatch *watch = &g_array_index(dir->watches,
                                                   QFileMonitorWatch, i);
         if (watch->id == id) {
             g_free(watch->filename);
             g_array_remove_index(dir->watches, i);
             break;
         }
     }

     if (dir->watches->len == 0) {
         inotify_rm_watch(mon->fd, dir->inotify_id);
         trace_qemu_file_monitor_disable_watch(mon, dir->path, dir->inotify_id);

         g_hash_table_remove(mon->idmap, GINT_TO_POINTER(dir->inotify_id));
         g_hash_table_remove(mon->dirs, dir->path);

         if (g_hash_table_size(mon->dirs) == 0) {
             qemu_set_fd_handler(mon->fd, NULL, NULL, NULL);
         }
     }

  cleanup:
     qemu_mutex_unlock(&mon->lock);
 }
	/*
	* QEMU file monitor Linux inotify impl
	*
	* Copyright (c) 2018 Red Hat, Inc.
	*
	* This library 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.
	*
	* This library 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 this library; if not, see <http://www.gnu.org/licenses/>.
	*
	*/

	#include "qemu/osdep.h"
	#include "qemu/filemonitor.h"
	#include "qemu/main-loop.h"
	#include "qemu/error-report.h"
	#include "qapi/error.h"
	#include "trace.h"

	#include <sys/inotify.h>

	struct QFileMonitor {
	int fd;
	QemuMutex lock; /* protects dirs & idmap */
	GHashTable dirs; / dirname => QFileMonitorDir */
	GHashTable idmap; / inotify ID => dirname */
	};


	typedef struct {
	int64_t id; /* watch ID */
	char filename; / optional filter */
	QFileMonitorHandler cb;
	void *opaque;
	} QFileMonitorWatch;


	typedef struct {
	char *path;
	int inotify_id; /* inotify ID */
	int next_file_id; /* file ID counter */
	GArray watches; / QFileMonitorWatch elements */
	} QFileMonitorDir;


	static void qemu_file_monitor_watch(void *arg)
	{
	QFileMonitor *mon = arg;
	char buf[4096]
	__attribute__ ((aligned(__alignof__(struct inotify_event))));
	int used = 0;
	int len;

	qemu_mutex_lock(&mon->lock);

	if (mon->fd == -1) {
	qemu_mutex_unlock(&mon->lock);
	return;
	}

	len = read(mon->fd, buf, sizeof(buf));

	if (len < 0) {
	if (errno != EAGAIN) {
	error_report("Failure monitoring inotify FD '%s',"
	"disabling events", strerror(errno));
	goto cleanup;
	}

	/* no more events right now */
	goto cleanup;
	}

	/* Loop over all events in the buffer */
	while (used < len) {
	const char *name;
	QFileMonitorDir *dir;
	uint32_t iev;
	int qev;
	gsize i;
	struct inotify_event ev = (struct inotify_event )(buf + used);

	/*
	* We trust the kenel to provide valid buffer with complete event
	* records.
	*/
	assert(len - used >= sizeof(struct inotify_event));
	assert(len - used - sizeof(struct inotify_event) >= ev->len);

	name = ev->len ? ev->name : "";
	dir = g_hash_table_lookup(mon->idmap, GINT_TO_POINTER(ev->wd));
	iev = ev->mask &
	(IN_CREATE \| IN_MODIFY \| IN_DELETE \| IN_IGNORED \|
	IN_MOVED_TO \| IN_MOVED_FROM \| IN_ATTRIB);

	used += sizeof(struct inotify_event) + ev->len;

	if (!dir) {
	continue;
	}

	/*
	* During a rename operation, the old name gets
	* IN_MOVED_FROM and the new name gets IN_MOVED_TO.
	* To simplify life for callers, we turn these into
	* DELETED and CREATED events
	*/
	switch (iev) {
	case IN_CREATE:
	case IN_MOVED_TO:
	qev = QFILE_MONITOR_EVENT_CREATED;
	break;
	case IN_MODIFY:
	qev = QFILE_MONITOR_EVENT_MODIFIED;
	break;
	case IN_DELETE:
	case IN_MOVED_FROM:
	qev = QFILE_MONITOR_EVENT_DELETED;
	break;
	case IN_ATTRIB:
	qev = QFILE_MONITOR_EVENT_ATTRIBUTES;
	break;
	case IN_IGNORED:
	qev = QFILE_MONITOR_EVENT_IGNORED;
	break;
	default:
	g_assert_not_reached();
	}

	trace_qemu_file_monitor_event(mon, dir->path, name, ev->mask,
	dir->inotify_id);
	for (i = 0; i < dir->watches->len; i++) {
	QFileMonitorWatch *watch = &g_array_index(dir->watches,
	QFileMonitorWatch,
	i);

	if (watch->filename == NULL \|\|
	(name && g_str_equal(watch->filename, name))) {
	trace_qemu_file_monitor_dispatch(mon, dir->path, name,
	qev, watch->cb,
	watch->opaque, watch->id);
	watch->cb(watch->id, qev, name, watch->opaque);
	}
	}
	}

	cleanup:
	qemu_mutex_unlock(&mon->lock);
	}


	static void
	qemu_file_monitor_dir_free(void *data)
	{
	QFileMonitorDir *dir = data;
	gsize i;

	for (i = 0; i < dir->watches->len; i++) {
	QFileMonitorWatch *watch = &g_array_index(dir->watches,
	QFileMonitorWatch, i);
	g_free(watch->filename);
	}
	g_array_unref(dir->watches);
	g_free(dir->path);
	g_free(dir);
	}


	QFileMonitor *
	qemu_file_monitor_new(Error **errp)
	{
	int fd;
	QFileMonitor *mon;

	fd = inotify_init1(IN_NONBLOCK);
	if (fd < 0) {
	error_setg_errno(errp, errno,
	"Unable to initialize inotify");
	return NULL;
	}

	mon = g_new0(QFileMonitor, 1);
	qemu_mutex_init(&mon->lock);
	mon->fd = fd;

	mon->dirs = g_hash_table_new_full(g_str_hash, g_str_equal, NULL,
	qemu_file_monitor_dir_free);
	mon->idmap = g_hash_table_new(g_direct_hash, g_direct_equal);

	trace_qemu_file_monitor_new(mon, mon->fd);

	return mon;
	}

	static gboolean
	qemu_file_monitor_free_idle(void *opaque)
	{
	QFileMonitor *mon = opaque;

	if (!mon) {
	return G_SOURCE_REMOVE;
	}

	qemu_mutex_lock(&mon->lock);

	g_hash_table_unref(mon->idmap);
	g_hash_table_unref(mon->dirs);

	qemu_mutex_unlock(&mon->lock);

	qemu_mutex_destroy(&mon->lock);
	g_free(mon);

	return G_SOURCE_REMOVE;
	}

	void
	qemu_file_monitor_free(QFileMonitor *mon)
	{
	if (!mon) {
	return;
	}

	qemu_mutex_lock(&mon->lock);
	if (mon->fd != -1) {
	qemu_set_fd_handler(mon->fd, NULL, NULL, NULL);
	close(mon->fd);
	mon->fd = -1;
	}
	qemu_mutex_unlock(&mon->lock);

	/*
	* Can't free it yet, because another thread
	* may be running event loop, so the inotify
	* callback might be pending. Using an idle
	* source ensures we'll only free after the
	* pending callback is done
	*/
	g_idle_add((GSourceFunc)qemu_file_monitor_free_idle, mon);
	}

	int64_t
	qemu_file_monitor_add_watch(QFileMonitor *mon,
	const char *dirpath,
	const char *filename,
	QFileMonitorHandler cb,
	void *opaque,
	Error **errp)
	{
	QFileMonitorDir *dir;
	QFileMonitorWatch watch;
	int64_t ret = -1;

	qemu_mutex_lock(&mon->lock);
	dir = g_hash_table_lookup(mon->dirs, dirpath);
	if (!dir) {
	int rv = inotify_add_watch(mon->fd, dirpath,
	IN_CREATE \| IN_DELETE \| IN_MODIFY \|
	IN_MOVED_TO \| IN_MOVED_FROM \| IN_ATTRIB);

	if (rv < 0) {
	error_setg_errno(errp, errno, "Unable to watch '%s'", dirpath);
	goto cleanup;
	}

	trace_qemu_file_monitor_enable_watch(mon, dirpath, rv);

	dir = g_new0(QFileMonitorDir, 1);
	dir->path = g_strdup(dirpath);
	dir->inotify_id = rv;
	dir->watches = g_array_new(FALSE, TRUE, sizeof(QFileMonitorWatch));

	g_hash_table_insert(mon->dirs, dir->path, dir);
	g_hash_table_insert(mon->idmap, GINT_TO_POINTER(rv), dir);

	if (g_hash_table_size(mon->dirs) == 1) {
	qemu_set_fd_handler(mon->fd, qemu_file_monitor_watch, NULL, mon);
	}
	}

	watch.id = (((int64_t)dir->inotify_id) << 32) \| dir->next_file_id++;
	watch.filename = g_strdup(filename);
	watch.cb = cb;
	watch.opaque = opaque;

	g_array_append_val(dir->watches, watch);

	trace_qemu_file_monitor_add_watch(mon, dirpath,
	filename ? filename : "<none>",
	cb, opaque, watch.id);

	ret = watch.id;

	cleanup:
	qemu_mutex_unlock(&mon->lock);
	return ret;
	}


	void qemu_file_monitor_remove_watch(QFileMonitor *mon,
	const char *dirpath,
	int64_t id)
	{
	QFileMonitorDir *dir;
	gsize i;

	qemu_mutex_lock(&mon->lock);

	trace_qemu_file_monitor_remove_watch(mon, dirpath, id);

	dir = g_hash_table_lookup(mon->dirs, dirpath);
	if (!dir) {
	goto cleanup;
	}

	for (i = 0; i < dir->watches->len; i++) {
	QFileMonitorWatch *watch = &g_array_index(dir->watches,
	QFileMonitorWatch, i);
	if (watch->id == id) {
	g_free(watch->filename);
	g_array_remove_index(dir->watches, i);
	break;
	}
	}

	if (dir->watches->len == 0) {
	inotify_rm_watch(mon->fd, dir->inotify_id);
	trace_qemu_file_monitor_disable_watch(mon, dir->path, dir->inotify_id);

	g_hash_table_remove(mon->idmap, GINT_TO_POINTER(dir->inotify_id));
	g_hash_table_remove(mon->dirs, dir->path);

	if (g_hash_table_size(mon->dirs) == 0) {
	qemu_set_fd_handler(mon->fd, NULL, NULL, NULL);
	}
	}

	cleanup:
	qemu_mutex_unlock(&mon->lock);
	}