The inotify userspace API for reading events is quite horrible, so it is useful to wrap it in a more friendly API to avoid duplicating code across many users in QEMU. Wrapping it also allows introduction of a platform portability layer, so that we can add impls for non-Linux based equivalents in future.
Signed-off-by: Daniel P. Berrangé <berra...@redhat.com> --- include/qemu/filemonitor.h | 117 ++++++++++++++ util/filemonitor.c | 315 +++++++++++++++++++++++++++++++++++++ MAINTAINERS | 6 + util/Makefile.objs | 1 + util/trace-events | 9 ++ 5 files changed, 448 insertions(+) create mode 100644 include/qemu/filemonitor.h create mode 100644 util/filemonitor.c diff --git a/include/qemu/filemonitor.h b/include/qemu/filemonitor.h new file mode 100644 index 0000000000..1326272f0a --- /dev/null +++ b/include/qemu/filemonitor.h @@ -0,0 +1,117 @@ +/* + * QEMU file monitor helper + * + * 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 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/>. + * + */ + +#ifndef QEMU_FILE_MONITOR_H +#define QEMU_FILE_MONITOR_H + +#include "qemu-common.h" + + +typedef struct QFileMonitor QFileMonitor; + +typedef enum { + /* File has been created in a dir */ + QFILE_MONITOR_EVENT_CREATED, + /* File has been modified in a dir */ + QFILE_MONITOR_EVENT_MODIFIED, + /* File has been deleted in a dir */ + QFILE_MONITOR_EVENT_DELETED, + /* Dir is no longer being monitored (due to deletion) */ + QFILE_MONITOR_EVENT_IGNORED, +} QFileMonitorEvent; + + +/** + * QFileMonitorHandler: + * @id: id from qemu_file_monitor_add_watch() + * @event: the file change that occurred + * @filename: the name of the file affected + * @opaque: opaque data provided to qemu_file_monitor_add_watch() + * + * Invoked whenever a file changes. If @event is + * QFILE_MONITOR_EVENT_IGNORED, @filename will be + * empty. + * + */ +typedef void (*QFileMonitorHandler)(int id, + QFileMonitorEvent event, + const char *filename, + void *opaque); + +/** + * qemu_file_monitor_get_instance: + * @errp: pointer to a NULL-initialized error object + * + * Acquire a handle to the shared file monitoring object. + * + * This object does locking internally to enable it to be + * safe to use from multiple threads + * + * If the platform does not support file monitoring, an + * error will be reported. Likewise if file monitoring + * is supported, but cannot be initialized + * + * Currently this is implemented on Linux platforms with + * the inotify subsystem. + * + * Returns: the shared monitoring object, or NULL on error + */ +QFileMonitor *qemu_file_monitor_get_instance(Error **errp); + +/** + * qemu_file_monitor_add_watch: + * @mon: the file monitor context + * @dirpath: the directory whose contents to watch + * @filename: optional filename to filter on + * @cb: the function to invoke when @dirpath has changes + * @opaque: data to pass to @cb + * @errp: pointer to a NULL-initialized error object + * + * Register to receive notifications of changes + * in the directory @dirpath. All files in the + * directory will be monitored. If the caller is + * only interested in one specific file, @filename + * can be used to filter events. + * + * Returns: a positive integer watch ID, or -1 on error + */ +int qemu_file_monitor_add_watch(QFileMonitor *mon, + const char *dirpath, + const char *filename, + QFileMonitorHandler cb, + void *opaque, + Error **errp); + +/** + * qemu_file_monitor_remove_watch: + * @mon: the file monitor context + * @dirpath: the directory whose contents to unwatch + * @id: id of the watch to remove + * + * Removes the file monitoring watch @id, associated + * with the directory @dirpath. This must never be + * called from a QFileMonitorHandler callback, or a + * deadlock will result. + */ +void qemu_file_monitor_remove_watch(QFileMonitor *mon, + const char *dirpath, + int id); + +#endif /* QEMU_FILE_MONITOR_H */ diff --git a/util/filemonitor.c b/util/filemonitor.c new file mode 100644 index 0000000000..67d7aedbe0 --- /dev/null +++ b/util/filemonitor.c @@ -0,0 +1,315 @@ +/* + * QEMU file_monitor helper + * + * 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 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" + +struct QFileMonitor { + QemuMutex lock; + int fd; + + GHashTable *dirs; /* dirname => QFileMonitorDir */ + GHashTable *idmap; /* inotify ID => dirname */ +}; + + +typedef struct { + int id; /* watch ID */ + char *filename; /* optional filter */ + QFileMonitorHandler cb; + void *opaque; +} QFileMonitorWatch; + + +typedef struct { + char *path; + int id; /* inotify ID */ + int nextid; /* watch ID counter */ + gsize nwatches; + QFileMonitorWatch *watches; +} QFileMonitorDir; + + +#ifdef CONFIG_INOTIFY1 +#include <sys/inotify.h> + +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 = read(mon->fd, buf, sizeof(buf)); + + qemu_mutex_lock(&mon->lock); + + if (len < 0) { + if (errno != EAGAIN) { + error_report("Failure monitoring inotify FD, disabling events"); + goto cleanup; + } + + /* no more events right now */ + goto cleanup; + } + + /* Loop over all events in the buffer */ + while (used < len) { + struct inotify_event *ev = + (struct inotify_event *)(buf + used); + const char *name = ev->len ? ev->name : ""; + QFileMonitorDir *dir = g_hash_table_lookup(mon->idmap, + GINT_TO_POINTER(ev->wd)); + uint32_t iev = ev->mask & + (IN_CREATE | IN_MODIFY | IN_DELETE | IN_IGNORED | + IN_MOVED_TO | IN_MOVED_FROM); + int qev; + gsize i; + + 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_IGNORED: + qev = QFILE_MONITOR_EVENT_IGNORED; + break; + default: + g_assert_not_reached(); + } + + trace_qemu_file_monitor_event(mon, dir->path, name, ev->mask, dir->id); + for (i = 0; i < dir->nwatches; i++) { + QFileMonitorWatch *watch = &dir->watches[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; + + g_free(dir->watches); + g_free(dir); +} + +#endif + +static QFileMonitor * +qemu_file_monitor_new(Error **errp) +{ +#ifdef CONFIG_INOTIFY1 + 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; +#else + error_setg(errp, "File monitoring not available on this platform"); + return NULL; +#endif +} + + +QFileMonitor *qemu_file_monitor_get_instance(Error **errp) +{ + static QFileMonitor *global; + + if (!global) { + global = qemu_file_monitor_new(errp); + } + + return global; +} + + +#ifdef CONFIG_INOTIFY1 +int +qemu_file_monitor_add_watch(QFileMonitor *mon, + const char *dirpath, + const char *filename, + QFileMonitorHandler cb, + void *opaque, + Error **errp) +{ + QFileMonitorDir *dir; + int 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); + + 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->id = rv; + + 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); + } + } + + dir->watches = g_renew(QFileMonitorWatch, dir->watches, dir->nwatches + 1); + + dir->watches[dir->nwatches].id = ++dir->nextid; + dir->watches[dir->nwatches].filename = filename ? g_strdup(filename) : NULL; + dir->watches[dir->nwatches].cb = cb; + dir->watches[dir->nwatches].opaque = opaque; + dir->nwatches++; + + trace_qemu_file_monitor_add_watch(mon, dirpath, + filename ? filename : "<none>", + cb, opaque, + dir->watches[dir->nwatches - 1].id); + + ret = 0; + + cleanup: + qemu_mutex_unlock(&mon->lock); + return ret; +} + + +void qemu_file_monitor_remove_watch(QFileMonitor *mon, + const char *dirpath, + int 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->nwatches; i++) { + if (dir->watches[i].id == id) { + if (i < (dir->nwatches - 1)) { + memmove(dir->watches + i, + dir->watches + i + 1, + sizeof(QFileMonitorWatch) * + (dir->nwatches - (i + 1))); + dir->watches = g_renew(QFileMonitorWatch, dir->watches, + dir->nwatches - 1); + dir->nwatches--; + } + break; + } + } + + if (dir->nwatches == 0) { + inotify_rm_watch(mon->fd, dir->id); + trace_qemu_file_monitor_disable_watch(mon, dir->path, dir->id); + + g_hash_table_remove(mon->idmap, GINT_TO_POINTER(dir->id)); + g_hash_table_remove(mon->dirs, dir->path); + } + + cleanup: + qemu_mutex_lock(&mon->lock); +} + +#else +int +qemu_file_monitor_add_watch(QFileMonitor *mon, + const char *dirpath, + const char *filename, + QFileMonitorHandler cb, + void *opaque, + Error **errp) +{ + error_setg(errp, "File monitoring not available on this platform"); + return -1; +} + +void qemu_file_monitor_remove_watch(QFileMonitor *mon, + const char *dirpath, + int id) +{ +} +#endif + diff --git a/MAINTAINERS b/MAINTAINERS index 40672c4eba..29bbcf8c25 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -1866,6 +1866,12 @@ F: include/qemu/sockets.h F: util/qemu-sockets.c F: qapi/sockets.json +File monitor +M: Daniel P. Berrange <berra...@redhat.com> +S: Odd fixes +F: util/filemonitor.c +F: include/qemu/filemonitor.h + Throttling infrastructure M: Alberto Garcia <be...@igalia.com> S: Supported diff --git a/util/Makefile.objs b/util/Makefile.objs index 0820923c18..4d7675d6e7 100644 --- a/util/Makefile.objs +++ b/util/Makefile.objs @@ -50,5 +50,6 @@ util-obj-y += range.o util-obj-y += stats64.o util-obj-y += systemd.o util-obj-y += iova-tree.o +util-obj-y += filemonitor.o util-obj-$(CONFIG_LINUX) += vfio-helpers.o util-obj-$(CONFIG_OPENGL) += drm.o diff --git a/util/trace-events b/util/trace-events index 79569b7fdf..ff19b253e2 100644 --- a/util/trace-events +++ b/util/trace-events @@ -21,6 +21,15 @@ buffer_move_empty(const char *buf, size_t len, const char *from) "%s: %zd bytes buffer_move(const char *buf, size_t len, const char *from) "%s: %zd bytes from %s" buffer_free(const char *buf, size_t len) "%s: capacity %zd" +# util/filemonitor.c +qemu_file_monitor_add_watch(void *mon, const char *dirpath, const char *filename, void *cb, void *opaque, int id) "File monitor %p add watch dir='%s' file='%s' cb=%p opaque=%p id=%u" +qemu_file_monitor_remove_watch(void *mon, const char *dirpath, int id) "File monitor %p remove watch dir='%s' id=%u" +qemu_file_monitor_new(void *mon, int fd) "File monitor %p created fd=%d" +qemu_file_monitor_enable_watch(void *mon, const char *dirpath, int id) "File monitor %p enable watch dir='%s' id=%u" +qemu_file_monitor_disable_watch(void *mon, const char *dirpath, int id) "Fle monitor %p disable watch dir='%s' id=%u" +qemu_file_monitor_event(void *mon, const char *dirpath, const char *filename, int mask, unsigned int id) "File monitor %p event dir='%s' file='%s' mask=0x%x id=%u" +qemu_file_monitor_dispatch(void *mon, const char *dirpath, const char *filename, int ev, void *cb, void *opaque, unsigned int id) "File monitor %p dispatch dir='%s' file='%s' ev=%d cb=%p opaque=%p id=%u" + # util/qemu-coroutine.c qemu_aio_coroutine_enter(void *ctx, void *from, void *to, void *opaque) "ctx %p from %p to %p opaque %p" qemu_coroutine_yield(void *from, void *to) "from %p to %p" -- 2.17.2
