From: Eric DeCosta <edecosta@xxxxxxxxxxxxx> Implement a filesystem change listener for Linux based on the inotify API: https://man7.org/linux/man-pages/man7/inotify.7.html inotify requires registering a watch on every directory in the worktree and special handling of moves/renames. Signed-off-by: Eric DeCosta <edecosta@xxxxxxxxxxxxx> --- compat/fsmonitor/fsm-listen-linux.c | 676 ++++++++++++++++++++++++++++ 1 file changed, 676 insertions(+) create mode 100644 compat/fsmonitor/fsm-listen-linux.c diff --git a/compat/fsmonitor/fsm-listen-linux.c b/compat/fsmonitor/fsm-listen-linux.c new file mode 100644 index 00000000000..e8548e4e009 --- /dev/null +++ b/compat/fsmonitor/fsm-listen-linux.c @@ -0,0 +1,676 @@ +#include "cache.h" +#include "fsmonitor.h" +#include "fsm-listen.h" +#include "fsmonitor--daemon.h" +#include <dirent.h> +#include <fcntl.h> +#include <sys/inotify.h> +#include <sys/stat.h> + +/* + * Safe value to bitwise OR with rest of mask for + * kernels that do not support IN_MASK_CREATE + */ +#ifndef IN_MASK_CREATE +#define IN_MASK_CREATE 0x00000000 +#endif + +enum shutdown_reason { + SHUTDOWN_CONTINUE = 0, + SHUTDOWN_STOP, + SHUTDOWN_ERROR, + SHUTDOWN_FORCE +}; + +struct watch_entry { + struct hashmap_entry ent; + int wd; + uint32_t cookie; + const char *dir; +}; + +struct rename_entry { + struct hashmap_entry ent; + time_t whence; + uint32_t cookie; + const char *dir; +}; + +struct fsm_listen_data { + int fd_inotify; + enum shutdown_reason shutdown; + struct hashmap watches; + struct hashmap renames; + struct hashmap revwatches; +}; + +static int watch_entry_cmp(const void *cmp_data, + const struct hashmap_entry *eptr, + const struct hashmap_entry *entry_or_key, + const void *keydata) +{ + const struct watch_entry *e1, *e2; + + e1 = container_of(eptr, const struct watch_entry, ent); + e2 = container_of(eptr, const struct watch_entry, ent); + return e1->wd != e2->wd; +} + +static int revwatches_entry_cmp(const void *cmp_data, + const struct hashmap_entry *eptr, + const struct hashmap_entry *entry_or_key, + const void *keydata) +{ + const struct watch_entry *e1, *e2; + + e1 = container_of(eptr, const struct watch_entry, ent); + e2 = container_of(eptr, const struct watch_entry, ent); + return strcmp(e1->dir, e2->dir); +} + +static int rename_entry_cmp(const void *cmp_data, + const struct hashmap_entry *eptr, + const struct hashmap_entry *entry_or_key, + const void *keydata) +{ + const struct rename_entry *e1, *e2; + + e1 = container_of(eptr, const struct rename_entry, ent); + e2 = container_of(eptr, const struct rename_entry, ent); + return e1->cookie != e2->cookie; +} + +/* + * Register an inotify watch, add watch descriptor to path mapping + * and the reverse mapping. + */ +static int add_watch(const char *path, struct fsm_listen_data *data) +{ + const char *interned = strintern(path); + struct watch_entry *w1, *w2; + + /* add the inotify watch, don't allow watches to be modified */ + int wd = inotify_add_watch(data->fd_inotify, interned, + (IN_ALL_EVENTS | IN_ONLYDIR | IN_MASK_CREATE) + ^ IN_ACCESS ^ IN_CLOSE ^ IN_OPEN); + if (wd < 0) + return error_errno("inotify_add_watch('%s') failed", interned); + + /* add watch descriptor -> directory mapping */ + CALLOC_ARRAY(w1, 1); + w1->wd = wd; + w1->dir = interned; + hashmap_entry_init(&w1->ent, memhash(&w1->wd, sizeof(int))); + hashmap_add(&data->watches, &w1->ent); + + /* add directory -> watch descriptor mapping */ + CALLOC_ARRAY(w2, 1); + w2->wd = wd; + w2->dir = interned; + hashmap_entry_init(&w2->ent, memhash(w2->dir, strlen(w2->dir))); + hashmap_add(&data->revwatches, &w2->ent); + + return 0; +} + +/* + * Remove the inotify watch, the watch descriptor to path mapping + * and the reverse mapping. + */ +static void remove_watch(struct watch_entry *w, + struct fsm_listen_data *data) +{ + struct watch_entry k1, k2, *w1, *w2; + + /* remove watch, ignore error if kernel already did it */ + if (inotify_rm_watch(data->fd_inotify, w->wd) && errno != EINVAL) + error_errno("inotify_rm_watch() failed"); + + hashmap_entry_init(&k1.ent, memhash(&w->wd, sizeof(int))); + w1 = hashmap_remove_entry(&data->watches, &k1, ent, NULL); + if (!w1) + BUG("Double remove of watch for '%s'", w->dir); + + if (w1->cookie) + BUG("Removing watch for '%s' which has a pending rename", w1->dir); + + hashmap_entry_init(&k2.ent, memhash(w->dir, strlen(w->dir))); + w2 = hashmap_remove_entry(&data->revwatches, &k2, ent, NULL); + if (!w2) + BUG("Double remove of reverse watch for '%s'", w->dir); + + /* w1->dir and w2->dir are interned strings, we don't own them */ + free(w1); + free(w2); +} + +/* + * Check for stale directory renames. + * + * https://man7.org/linux/man-pages/man7/inotify.7.html + * + * Allow for some small timeout to account for the fact that insertion of the + * IN_MOVED_FROM+IN_MOVED_TO event pair is not atomic, and the possibility that + * there may not be any IN_MOVED_TO event. + * + * If the IN_MOVED_TO event is not received within the timeout then events have + * been missed and the monitor is in an inconsistent state with respect to the + * filesystem. + */ +static int check_stale_dir_renames(struct hashmap *renames, time_t max_age) +{ + struct rename_entry *re; + struct hashmap_iter iter; + + hashmap_for_each_entry(renames, &iter, re, ent) { + if (re->whence <= max_age) + return -1; + } + return 0; +} + +/* + * Track pending renames. + * + * Tracking is done via a event cookie to watch descriptor mapping. + * + * A rename is not complete until matching a IN_MOVED_TO event is received + * for a corresponding IN_MOVED_FROM event. + */ +static void add_dir_rename(uint32_t cookie, const char *path, + struct fsm_listen_data *data) +{ + struct watch_entry k, *w; + struct rename_entry *re; + + /* lookup the watch descriptor for the given path */ + hashmap_entry_init(&k.ent, memhash(path, strlen(path))); + w = hashmap_get_entry(&data->revwatches, &k, ent, NULL); + if (!w) /* should never happen */ + BUG("No watch for '%s'", path); + w->cookie = cookie; + + /* add the pending rename to match against later */ + CALLOC_ARRAY(re, 1); + re->dir = w->dir; + re->cookie = w->cookie; + re->whence = time(NULL); + hashmap_entry_init(&re->ent, memhash(&re->cookie, sizeof(uint32_t))); + hashmap_add(&data->renames, &re->ent); +} + +/* + * Handle directory renames + * + * Once a IN_MOVED_TO event is received, lookup the rename tracking information + * via the event cookie and use this information to update the watch. + */ +static void rename_dir(uint32_t cookie, const char *path, + struct fsm_listen_data *data) +{ + struct rename_entry rek, *re; + struct watch_entry k, *w; + + /* lookup a pending rename to match */ + rek.cookie = cookie; + hashmap_entry_init(&rek.ent, memhash(&rek.cookie, sizeof(uint32_t))); + re = hashmap_get_entry(&data->renames, &rek, ent, NULL); + if (re) { + k.dir = re->dir; + hashmap_entry_init(&k.ent, memhash(k.dir, strlen(k.dir))); + w = hashmap_get_entry(&data->revwatches, &k, ent, NULL); + if (w) { + w->cookie = 0; /* rename handled */ + remove_watch(w, data); + add_watch(path, data); + } else { + BUG("No matching watch"); + } + } else { + BUG("No matching cookie"); + } +} + +/* + * Recursively add watches to every directory under path + */ +static int register_inotify(const char *path, + struct fsmonitor_daemon_state *state, + struct fsmonitor_batch *batch) +{ + DIR *dir; + const char *rel; + struct strbuf current = STRBUF_INIT; + struct dirent *de; + struct stat fs; + int ret = -1; + + dir = opendir(path); + if (!dir) + return error_errno("opendir('%s') failed", path); + + while ((de = readdir_skip_dot_and_dotdot(dir)) != NULL) { + strbuf_reset(¤t); + strbuf_addf(¤t, "%s/%s", path, de->d_name); + if (lstat(current.buf, &fs)) { + error_errno("lstat('%s') failed", current.buf); + goto failed; + } + + /* recurse into directory */ + if (S_ISDIR(fs.st_mode)) { + if (add_watch(current.buf, state->listen_data)) + goto failed; + if (register_inotify(current.buf, state, batch)) + goto failed; + } else if (batch) { + rel = current.buf + state->path_worktree_watch.len + 1; + trace_printf_key(&trace_fsmonitor, "explicitly adding '%s'", rel); + fsmonitor_batch__add_path(batch, rel); + } + } + ret = 0; + +failed: + strbuf_release(¤t); + if (closedir(dir) < 0) + return error_errno("closedir('%s') failed", path); + return ret; +} + +static int em_rename_dir_from(u_int32_t mask) +{ + return ((mask & IN_ISDIR) && (mask & IN_MOVED_FROM)); +} + +static int em_rename_dir_to(u_int32_t mask) +{ + return ((mask & IN_ISDIR) && (mask & IN_MOVED_TO)); +} + +static int em_remove_watch(u_int32_t mask) +{ + return (mask & IN_DELETE_SELF); +} + +static int em_dir_renamed(u_int32_t mask) +{ + return ((mask & IN_ISDIR) && (mask & IN_MOVE)); +} + +static int em_dir_created(u_int32_t mask) +{ + return ((mask & IN_ISDIR) && (mask & IN_CREATE)); +} + +static int em_dir_deleted(uint32_t mask) +{ + return ((mask & IN_ISDIR) && (mask & IN_DELETE)); +} + +static int em_force_shutdown(u_int32_t mask) +{ + return (mask & IN_UNMOUNT) || (mask & IN_Q_OVERFLOW); +} + +static int em_ignore(u_int32_t mask) +{ + return (mask & IN_IGNORED) || (mask & IN_MOVE_SELF); +} + +static void log_mask_set(const char *path, u_int32_t mask) +{ + struct strbuf msg = STRBUF_INIT; + + if (mask & IN_ACCESS) + strbuf_addstr(&msg, "IN_ACCESS|"); + if (mask & IN_MODIFY) + strbuf_addstr(&msg, "IN_MODIFY|"); + if (mask & IN_ATTRIB) + strbuf_addstr(&msg, "IN_ATTRIB|"); + if (mask & IN_CLOSE_WRITE) + strbuf_addstr(&msg, "IN_CLOSE_WRITE|"); + if (mask & IN_CLOSE_NOWRITE) + strbuf_addstr(&msg, "IN_CLOSE_NOWRITE|"); + if (mask & IN_OPEN) + strbuf_addstr(&msg, "IN_OPEN|"); + if (mask & IN_MOVED_FROM) + strbuf_addstr(&msg, "IN_MOVED_FROM|"); + if (mask & IN_MOVED_TO) + strbuf_addstr(&msg, "IN_MOVED_TO|"); + if (mask & IN_CREATE) + strbuf_addstr(&msg, "IN_CREATE|"); + if (mask & IN_DELETE) + strbuf_addstr(&msg, "IN_DELETE|"); + if (mask & IN_DELETE_SELF) + strbuf_addstr(&msg, "IN_DELETE_SELF|"); + if (mask & IN_MOVE_SELF) + strbuf_addstr(&msg, "IN_MOVE_SELF|"); + if (mask & IN_UNMOUNT) + strbuf_addstr(&msg, "IN_UNMOUNT|"); + if (mask & IN_Q_OVERFLOW) + strbuf_addstr(&msg, "IN_Q_OVERFLOW|"); + if (mask & IN_IGNORED) + strbuf_addstr(&msg, "IN_IGNORED|"); + if (mask & IN_ISDIR) + strbuf_addstr(&msg, "IN_ISDIR|"); + + trace_printf_key(&trace_fsmonitor, "inotify_event: '%s', mask=%#8.8x %s", + path, mask, msg.buf); + + strbuf_release(&msg); +} + +int fsm_listen__ctor(struct fsmonitor_daemon_state *state) +{ + int fd; + int ret = 0; + struct fsm_listen_data *data; + + CALLOC_ARRAY(data, 1); + state->listen_data = data; + state->listen_error_code = -1; + data->shutdown = SHUTDOWN_ERROR; + + fd = inotify_init1(O_NONBLOCK); + if (fd < 0) + return error_errno("inotify_init1() failed"); + + data->fd_inotify = fd; + + hashmap_init(&data->watches, watch_entry_cmp, NULL, 0); + hashmap_init(&data->renames, rename_entry_cmp, NULL, 0); + hashmap_init(&data->revwatches, revwatches_entry_cmp, NULL, 0); + + if (add_watch(state->path_worktree_watch.buf, data)) + ret = -1; + else if (register_inotify(state->path_worktree_watch.buf, state, NULL)) + ret = -1; + else if (state->nr_paths_watching > 1) { + if (add_watch(state->path_gitdir_watch.buf, data)) + ret = -1; + else if (register_inotify(state->path_gitdir_watch.buf, state, NULL)) + ret = -1; + } + + if (!ret) { + state->listen_error_code = 0; + data->shutdown = SHUTDOWN_CONTINUE; + } + + return ret; +} + +void fsm_listen__dtor(struct fsmonitor_daemon_state *state) +{ + struct fsm_listen_data *data; + struct hashmap_iter iter; + struct watch_entry *w; + int fd; + + if (!state || !state->listen_data) + return; + + data = state->listen_data; + fd = data->fd_inotify; + + hashmap_for_each_entry(&data->watches, &iter, w, ent) { + w->cookie = 0; /* ignore any pending renames */ + remove_watch(w, data); + } + hashmap_clear(&data->watches); + + hashmap_clear(&data->revwatches); /* remove_watch freed the entries */ + + hashmap_clear_and_free(&data->renames, struct rename_entry, ent); + + FREE_AND_NULL(state->listen_data); + + if (fd && (close(fd) < 0)) + error_errno(_("closing inotify file descriptor failed")); +} + +void fsm_listen__stop_async(struct fsmonitor_daemon_state *state) +{ + if (!state->listen_data->shutdown) + state->listen_data->shutdown = SHUTDOWN_STOP; +} + +/* + * Process a single inotify event and queue for publication. + */ +static int process_event(const char *path, + const struct inotify_event *event, + struct fsmonitor_batch *batch, + struct string_list *cookie_list, + struct fsmonitor_daemon_state *state) +{ + const char *rel; + const char *last_sep; + + switch (fsmonitor_classify_path_absolute(state, path)) { + case IS_INSIDE_DOT_GIT_WITH_COOKIE_PREFIX: + case IS_INSIDE_GITDIR_WITH_COOKIE_PREFIX: + /* Use just the filename of the cookie file. */ + last_sep = find_last_dir_sep(path); + string_list_append(cookie_list, + last_sep ? last_sep + 1 : path); + break; + case IS_INSIDE_DOT_GIT: + case IS_INSIDE_GITDIR: + break; + case IS_DOT_GIT: + case IS_GITDIR: + /* + * If .git directory is deleted or renamed away, + * we have to quit. + */ + if (em_dir_deleted(event->mask)) { + trace_printf_key(&trace_fsmonitor, + "event: gitdir removed"); + state->listen_data->shutdown = SHUTDOWN_FORCE; + goto done; + } + + if (em_dir_renamed(event->mask)) { + trace_printf_key(&trace_fsmonitor, + "event: gitdir renamed"); + state->listen_data->shutdown = SHUTDOWN_FORCE; + goto done; + } + break; + case IS_WORKDIR_PATH: + /* normal events in the working directory */ + if (trace_pass_fl(&trace_fsmonitor)) + log_mask_set(path, event->mask); + + rel = path + state->path_worktree_watch.len + 1; + fsmonitor_batch__add_path(batch, rel); + + if (em_dir_deleted(event->mask)) + break; + + /* received IN_MOVE_FROM, add tracking for expected IN_MOVE_TO */ + if (em_rename_dir_from(event->mask)) + add_dir_rename(event->cookie, path, state->listen_data); + + /* received IN_MOVE_TO, update watch to reflect new path */ + if (em_rename_dir_to(event->mask)) { + rename_dir(event->cookie, path, state->listen_data); + if (register_inotify(path, state, batch)) { + state->listen_data->shutdown = SHUTDOWN_ERROR; + goto done; + } + } + + if (em_dir_created(event->mask)) { + if (add_watch(path, state->listen_data)) { + state->listen_data->shutdown = SHUTDOWN_ERROR; + goto done; + } + if (register_inotify(path, state, batch)) { + state->listen_data->shutdown = SHUTDOWN_ERROR; + goto done; + } + } + break; + case IS_OUTSIDE_CONE: + default: + trace_printf_key(&trace_fsmonitor, + "ignoring '%s'", path); + break; + } + return 0; +done: + return -1; +} + +/* + * Read the inotify event stream and pre-process events before further + * processing and eventual publishing. + */ +static void handle_events(struct fsmonitor_daemon_state *state) +{ + /* See https://man7.org/linux/man-pages/man7/inotify.7.html */ + char buf[4096] + __attribute__ ((aligned(__alignof__(struct inotify_event)))); + + struct hashmap watches = state->listen_data->watches; + struct fsmonitor_batch *batch = NULL; + struct string_list cookie_list = STRING_LIST_INIT_DUP; + struct watch_entry k, *w; + struct strbuf path; + const struct inotify_event *event; + int fd = state->listen_data->fd_inotify; + ssize_t len; + char *ptr, *p; + + strbuf_init(&path, PATH_MAX); + + for(;;) { + len = read(fd, buf, sizeof(buf)); + if (len == -1 && errno != EAGAIN) { + error_errno(_("reading inotify message stream failed")); + state->listen_data->shutdown = SHUTDOWN_ERROR; + goto done; + } + + /* nothing to read */ + if (len <= 0) + goto done; + + /* Loop over all events in the buffer. */ + for (ptr = buf; ptr < buf + len; + ptr += sizeof(struct inotify_event) + event->len) { + + event = (const struct inotify_event *) ptr; + + if (em_ignore(event->mask)) + continue; + + /* File system was unmounted or event queue overflowed */ + if (em_force_shutdown(event->mask)) { + if (trace_pass_fl(&trace_fsmonitor)) + log_mask_set("Forcing shutdown", event->mask); + state->listen_data->shutdown = SHUTDOWN_FORCE; + goto done; + } + + hashmap_entry_init(&k.ent, memhash(&event->wd, sizeof(int))); + k.wd = event->wd; + + w = hashmap_get_entry(&watches, &k, ent, NULL); + if (!w) /* should never happen */ + BUG("No watch for '%s'", event->name); + + /* directory watch was removed */ + if (em_remove_watch(event->mask)) { + remove_watch(w, state->listen_data); + continue; + } + + strbuf_reset(&path); + strbuf_add(&path, w->dir, strlen(w->dir)); + strbuf_addch(&path, '/'); + strbuf_addstr(&path, event->name); + + p = fsmonitor__resolve_alias(path.buf, &state->alias); + if (!p) + p = strbuf_detach(&path, NULL); + + if (!batch) + batch = fsmonitor_batch__new(); + + if (process_event(p, event, batch, &cookie_list, state)) { + free(p); + goto done; + } + free(p); + } + strbuf_reset(&path); + fsmonitor_publish(state, batch, &cookie_list); + string_list_clear(&cookie_list, 0); + batch = NULL; + } +done: + strbuf_release(&path); + fsmonitor_batch__free_list(batch); + string_list_clear(&cookie_list, 0); +} + +/* + * Non-blocking read of the inotify events stream. The inotify fd is polled + * frequently to help minimize the number of queue overflows. + */ +void fsm_listen__loop(struct fsmonitor_daemon_state *state) +{ + int poll_num; + const int interval = 1000; + time_t checked = time(NULL); + struct pollfd fds[1]; + fds[0].fd = state->listen_data->fd_inotify; + fds[0].events = POLLIN; + + for(;;) { + switch (state->listen_data->shutdown) { + case SHUTDOWN_CONTINUE: + poll_num = poll(fds, 1, 1); + if (poll_num == -1) { + if (errno == EINTR) + continue; + error_errno(_("polling inotify message stream failed")); + state->listen_data->shutdown = SHUTDOWN_ERROR; + continue; + } + + if ((time(NULL) - checked) >= interval) { + checked = time(NULL); + if (check_stale_dir_renames(&state->listen_data->renames, + checked - interval)) { + trace_printf_key(&trace_fsmonitor, + "Missed IN_MOVED_TO events, forcing shutdown"); + state->listen_data->shutdown = SHUTDOWN_FORCE; + continue; + } + } + + if (poll_num > 0 && (fds[0].revents & POLLIN)) + handle_events(state); + + continue; + case SHUTDOWN_ERROR: + state->listen_error_code = -1; + ipc_server_stop_async(state->ipc_server_data); + break; + case SHUTDOWN_FORCE: + state->listen_error_code = 0; + ipc_server_stop_async(state->ipc_server_data); + break; + case SHUTDOWN_STOP: + default: + state->listen_error_code = 0; + break; + } + return; + } +} -- gitgitgadget
