Builtin FSMonitor Part 2

index 916cbea254f..c2d11acbc1e 100644
@@ -2,20 +2,585 @@
 #include "config.h"
 #include "fsmonitor.h"
 #include "fsm-listen.h"
+#include "fsmonitor--daemon.h"
+
+/*
+ * The documentation of ReadDirectoryChangesW() states that the maximum
+ * buffer size is 64K when the monitored directory is remote.
+ *
+ * Larger buffers may be used when the monitored directory is local and
+ * will help us receive events faster from the kernel and avoid dropped
+ * events.
+ *
+ * So we try to use a very large buffer and silently fallback to 64K if
+ * we get an error.
+ */
+#define MAX_RDCW_BUF_FALLBACK (65536)
+#define MAX_RDCW_BUF          (65536 * 8)
+
+struct one_watch
+{
+	char buffer[MAX_RDCW_BUF];
+	DWORD buf_len;
+	DWORD count;
+
+	struct strbuf path;
+	HANDLE hDir;
+	HANDLE hEvent;
+	OVERLAPPED overlapped;
+
+	/*
+	 * Is there an active ReadDirectoryChangesW() call pending.  If so, we
+	 * need to later call GetOverlappedResult() and possibly CancelIoEx().
+	 */
+	BOOL is_active;
+};
+
+struct fsmonitor_daemon_backend_data
+{
+	struct one_watch *watch_worktree;
+	struct one_watch *watch_gitdir;
+
+	HANDLE hEventShutdown;
+
+	HANDLE hListener[3]; /* we don't own these handles */
+#define LISTENER_SHUTDOWN 0
+#define LISTENER_HAVE_DATA_WORKTREE 1
+#define LISTENER_HAVE_DATA_GITDIR 2
+	int nr_listener_handles;
+};
+
+/*
+ * Convert the WCHAR path from the notification into UTF8 and
+ * then normalize it.
+ */
+static int normalize_path_in_utf8(FILE_NOTIFY_INFORMATION *info,
+				  struct strbuf *normalized_path)
+{
+	int reserve;
+	int len = 0;
+
+	strbuf_reset(normalized_path);
+	if (!info->FileNameLength)
+		goto normalize;
+
+	/*
+	 * Pre-reserve enough space in the UTF8 buffer for
+	 * each Unicode WCHAR character to be mapped into a
+	 * sequence of 2 UTF8 characters.  That should let us
+	 * avoid ERROR_INSUFFICIENT_BUFFER 99.9+% of the time.
+	 */
+	reserve = info->FileNameLength + 1;
+	strbuf_grow(normalized_path, reserve);
+
+	for (;;) {
+		len = WideCharToMultiByte(CP_UTF8, 0, info->FileName,
+					  info->FileNameLength / sizeof(WCHAR),
+					  normalized_path->buf,
+					  strbuf_avail(normalized_path) - 1,
+					  NULL, NULL);
+		if (len > 0)
+			goto normalize;
+		if (GetLastError() != ERROR_INSUFFICIENT_BUFFER) {
+			error("[GLE %ld] could not convert path to UTF-8: '%.*ls'",
+			      GetLastError(),
+			      (int)(info->FileNameLength / sizeof(WCHAR)),
+			      info->FileName);
+			return -1;
+		}
+
+		strbuf_grow(normalized_path,
+			    strbuf_avail(normalized_path) + reserve);
+	}
+
+normalize:
+	strbuf_setlen(normalized_path, len);
+	return strbuf_normalize_path(normalized_path);
+}
 
 void fsm_listen__stop_async(struct fsmonitor_daemon_state *state)
 {
+	SetEvent(state->backend_data->hListener[LISTENER_SHUTDOWN]);
+}
+
+static struct one_watch *create_watch(struct fsmonitor_daemon_state *state,
+				      const char *path)
+{
+	struct one_watch *watch = NULL;
+	DWORD desired_access = FILE_LIST_DIRECTORY;
+	DWORD share_mode =
+		FILE_SHARE_WRITE | FILE_SHARE_READ | FILE_SHARE_DELETE;
+	HANDLE hDir;
+	wchar_t wpath[MAX_PATH];
+
+	if (xutftowcs_path(wpath, path) < 0) {
+		error(_("could not convert to wide characters: '%s'"), path);
+		return NULL;
+	}
+
+	hDir = CreateFileW(wpath,
+			   desired_access, share_mode, NULL, OPEN_EXISTING,
+			   FILE_FLAG_BACKUP_SEMANTICS | FILE_FLAG_OVERLAPPED,
+			   NULL);
+	if (hDir == INVALID_HANDLE_VALUE) {
+		error(_("[GLE %ld] could not watch '%s'"),
+		      GetLastError(), path);
+		return NULL;
+	}
+
+	CALLOC_ARRAY(watch, 1);
+
+	watch->buf_len = sizeof(watch->buffer); /* assume full MAX_RDCW_BUF */
+
+	strbuf_init(&watch->path, 0);
+	strbuf_addstr(&watch->path, path);
+
+	watch->hDir = hDir;
+	watch->hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
+
+	return watch;
+}
+
+static void destroy_watch(struct one_watch *watch)
+{
+	if (!watch)
+		return;
+
+	strbuf_release(&watch->path);
+	if (watch->hDir != INVALID_HANDLE_VALUE)
+		CloseHandle(watch->hDir);
+	if (watch->hEvent != INVALID_HANDLE_VALUE)
+		CloseHandle(watch->hEvent);
+
+	free(watch);
+}
+
+static int start_rdcw_watch(struct fsmonitor_daemon_backend_data *data,
+			    struct one_watch *watch)
+{
+	DWORD dwNotifyFilter =
+		FILE_NOTIFY_CHANGE_FILE_NAME |
+		FILE_NOTIFY_CHANGE_DIR_NAME |
+		FILE_NOTIFY_CHANGE_ATTRIBUTES |
+		FILE_NOTIFY_CHANGE_SIZE |
+		FILE_NOTIFY_CHANGE_LAST_WRITE |
+		FILE_NOTIFY_CHANGE_CREATION;
+
+	ResetEvent(watch->hEvent);
+
+	memset(&watch->overlapped, 0, sizeof(watch->overlapped));
+	watch->overlapped.hEvent = watch->hEvent;
+
+	/*
+	 * Queue an async call using Overlapped IO.  This returns immediately.
+	 * Our event handle will be signalled when the real result is available.
+	 *
+	 * The return value here just means that we successfully queued it.
+	 * We won't know if the Read...() actually produces data until later.
+	 */
+	watch->is_active = ReadDirectoryChangesW(
+		watch->hDir, watch->buffer, watch->buf_len, TRUE,
+		dwNotifyFilter, &watch->count, &watch->overlapped, NULL);
+
+	if (watch->is_active)
+		return 0;
+
+	error("ReadDirectoryChangedW failed on '%s' [GLE %ld]",
+	      watch->path.buf, GetLastError());
+	return -1;
+}
+
+static int recv_rdcw_watch(struct one_watch *watch)
+{
+	DWORD gle;
+
+	watch->is_active = FALSE;
+
+	/*
+	 * The overlapped result is ready.  If the Read...() was successful
+	 * we finally receive the actual result into our buffer.
+	 */
+	if (GetOverlappedResult(watch->hDir, &watch->overlapped, &watch->count,
+				TRUE))
+		return 0;
+
+	gle = GetLastError();
+	if (gle == ERROR_INVALID_PARAMETER &&
+	    /*
+	     * The kernel throws an invalid parameter error when our
+	     * buffer is too big and we are pointed at a remote
+	     * directory (and possibly for other reasons).  Quietly
+	     * set it down and try again.
+	     *
+	     * See note about MAX_RDCW_BUF at the top.
+	     */
+	    watch->buf_len > MAX_RDCW_BUF_FALLBACK) {
+		watch->buf_len = MAX_RDCW_BUF_FALLBACK;
+		return -2;
+	}
+
+	/*
+	 * NEEDSWORK: If an external <gitdir> is deleted, the above
+	 * returns an error.  I'm not sure that there's anything that
+	 * we can do here other than failing -- the <worktree>/.git
+	 * link file would be broken anyway.  We might try to check
+	 * for that and return a better error message, but I'm not
+	 * sure it is worth it.
+	 */
+
+	error("GetOverlappedResult failed on '%s' [GLE %ld]",
+	      watch->path.buf, gle);
+	return -1;
+}
+
+static void cancel_rdcw_watch(struct one_watch *watch)
+{
+	DWORD count;
+
+	if (!watch || !watch->is_active)
+		return;
+
+	/*
+	 * The calls to ReadDirectoryChangesW() and GetOverlappedResult()
+	 * form a "pair" (my term) where we queue an IO and promise to
+	 * hang around and wait for the kernel to give us the result.
+	 *
+	 * If for some reason after we queue the IO, we have to quit
+	 * or otherwise not stick around for the second half, we must
+	 * tell the kernel to abort the IO.  This prevents the kernel
+	 * from writing to our buffer and/or signalling our event
+	 * after we free them.
+	 *
+	 * (Ask me how much fun it was to track that one down).
+	 */
+	CancelIoEx(watch->hDir, &watch->overlapped);
+	GetOverlappedResult(watch->hDir, &watch->overlapped, &count, TRUE);
+	watch->is_active = FALSE;
+}
+
+/*
+ * Process filesystem events that happen anywhere (recursively) under the
+ * <worktree> root directory.  For a normal working directory, this includes
+ * both version controlled files and the contents of the .git/ directory.
+ *
+ * If <worktree>/.git is a file, then we only see events for the file
+ * itself.
+ */
+static int process_worktree_events(struct fsmonitor_daemon_state *state)
+{
+	struct fsmonitor_daemon_backend_data *data = state->backend_data;
+	struct one_watch *watch = data->watch_worktree;
+	struct strbuf path = STRBUF_INIT;
+	struct string_list cookie_list = STRING_LIST_INIT_DUP;
+	struct fsmonitor_batch *batch = NULL;
+	const char *p = watch->buffer;
+
+	/*
+	 * If the kernel gets more events than will fit in the kernel
+	 * buffer associated with our RDCW handle, it drops them and
+	 * returns a count of zero.
+	 *
+	 * Yes, the call returns WITHOUT error and with length zero.
+	 * This is the documented behavior.  (My testing has confirmed
+	 * that it also sets the last error to ERROR_NOTIFY_ENUM_DIR,
+	 * but we do not rely on that since the function did not
+	 * return an error and it is not documented.)
+	 *
+	 * (The "overflow" case is not ambiguous with the "no data" case
+	 * because we did an INFINITE wait.)
+	 *
+	 * This means we have a gap in coverage.  Tell the daemon layer
+	 * to resync.
+	 */
+	if (!watch->count) {
+		trace2_data_string("fsmonitor", NULL, "fsm-listen/kernel",
+				   "overflow");
+		fsmonitor_force_resync(state);
+		return LISTENER_HAVE_DATA_WORKTREE;
+	}
+
+	/*
+	 * On Windows, `info` contains an "array" of paths that are
+	 * relative to the root of whichever directory handle received
+	 * the event.
+	 */
+	for (;;) {
+		FILE_NOTIFY_INFORMATION *info = (void *)p;
+		const char *slash;
+		enum fsmonitor_path_type t;
+
+		strbuf_reset(&path);
+		if (normalize_path_in_utf8(info, &path) == -1)
+			goto skip_this_path;
+
+		t = fsmonitor_classify_path_workdir_relative(path.buf);
+
+		switch (t) {
+		case IS_INSIDE_DOT_GIT_WITH_COOKIE_PREFIX:
+			/* special case cookie files within .git */
+
+			/* Use just the filename of the cookie file. */
+			slash = find_last_dir_sep(path.buf);
+			string_list_append(&cookie_list,
+					   slash ? slash + 1 : path.buf);
+			break;
+
+		case IS_INSIDE_DOT_GIT:
+			/* ignore everything inside of "<worktree>/.git/" */
+			break;
+
+		case IS_DOT_GIT:
+			/* "<worktree>/.git" was deleted (or renamed away) */
+			if ((info->Action == FILE_ACTION_REMOVED) ||
+			    (info->Action == FILE_ACTION_RENAMED_OLD_NAME)) {
+				trace2_data_string("fsmonitor", NULL,
+						   "fsm-listen/dotgit",
+						   "removed");
+				goto force_shutdown;
+			}
+			break;
+
+		case IS_WORKDIR_PATH:
+			/* queue normal pathname */
+			if (!batch)
+				batch = fsmonitor_batch__new();
+			fsmonitor_batch__add_path(batch, path.buf);
+			break;
+
+		case IS_GITDIR:
+		case IS_INSIDE_GITDIR:
+		case IS_INSIDE_GITDIR_WITH_COOKIE_PREFIX:
+		default:
+			BUG("unexpected path classification '%d' for '%s'",
+			    t, path.buf);
+		}
+
+skip_this_path:
+		if (!info->NextEntryOffset)
+			break;
+		p += info->NextEntryOffset;
+	}
+
+	fsmonitor_publish(state, batch, &cookie_list);
+	batch = NULL;
+	string_list_clear(&cookie_list, 0);
+	strbuf_release(&path);
+	return LISTENER_HAVE_DATA_WORKTREE;
+
+force_shutdown:
+	fsmonitor_batch__free_list(batch);
+	string_list_clear(&cookie_list, 0);
+	strbuf_release(&path);
+	return LISTENER_SHUTDOWN;
+}
+
+/*
+ * Process filesystem events that happened anywhere (recursively) under the
+ * external <gitdir> (such as non-primary worktrees or submodules).
+ * We only care about cookie files that our client threads created here.
+ *
+ * Note that we DO NOT get filesystem events on the external <gitdir>
+ * itself (it is not inside something that we are watching).  In particular,
+ * we do not get an event if the external <gitdir> is deleted.
+ */
+static int process_gitdir_events(struct fsmonitor_daemon_state *state)
+{
+	struct fsmonitor_daemon_backend_data *data = state->backend_data;
+	struct one_watch *watch = data->watch_gitdir;
+	struct strbuf path = STRBUF_INIT;
+	struct string_list cookie_list = STRING_LIST_INIT_DUP;
+	const char *p = watch->buffer;
+
+	if (!watch->count) {
+		trace2_data_string("fsmonitor", NULL, "fsm-listen/kernel",
+				   "overflow");
+		fsmonitor_force_resync(state);
+		return LISTENER_HAVE_DATA_GITDIR;
+	}
+
+	for (;;) {
+		FILE_NOTIFY_INFORMATION *info = (void *)p;
+		const char *slash;
+		enum fsmonitor_path_type t;
+
+		strbuf_reset(&path);
+		if (normalize_path_in_utf8(info, &path) == -1)
+			goto skip_this_path;
+
+		t = fsmonitor_classify_path_gitdir_relative(path.buf);
+
+		switch (t) {
+		case IS_INSIDE_GITDIR_WITH_COOKIE_PREFIX:
+			/* special case cookie files within gitdir */
+
+			/* Use just the filename of the cookie file. */
+			slash = find_last_dir_sep(path.buf);
+			string_list_append(&cookie_list,
+					   slash ? slash + 1 : path.buf);
+			break;
+
+		case IS_INSIDE_GITDIR:
+			goto skip_this_path;
+
+		default:
+			BUG("unexpected path classification '%d' for '%s'",
+			    t, path.buf);
+		}
+
+skip_this_path:
+		if (!info->NextEntryOffset)
+			break;
+		p += info->NextEntryOffset;
+	}
+
+	fsmonitor_publish(state, NULL, &cookie_list);
+	string_list_clear(&cookie_list, 0);
+	strbuf_release(&path);
+	return LISTENER_HAVE_DATA_GITDIR;
 }
 
 void fsm_listen__loop(struct fsmonitor_daemon_state *state)
 {
+	struct fsmonitor_daemon_backend_data *data = state->backend_data;
+	DWORD dwWait;
+	int result;
+
+	state->error_code = 0;
+
+	if (start_rdcw_watch(data, data->watch_worktree) == -1)
+		goto force_error_stop;
+
+	if (data->watch_gitdir &&
+	    start_rdcw_watch(data, data->watch_gitdir) == -1)
+		goto force_error_stop;
+
+	for (;;) {
+		dwWait = WaitForMultipleObjects(data->nr_listener_handles,
+						data->hListener,
+						FALSE, INFINITE);
+
+		if (dwWait == WAIT_OBJECT_0 + LISTENER_HAVE_DATA_WORKTREE) {
+			result = recv_rdcw_watch(data->watch_worktree);
+			if (result == -1) {
+				/* hard error */
+				goto force_error_stop;
+			}
+			if (result == -2) {
+				/* retryable error */
+				if (start_rdcw_watch(data, data->watch_worktree) == -1)
+					goto force_error_stop;
+				continue;
+			}
+
+			/* have data */
+			if (process_worktree_events(state) == LISTENER_SHUTDOWN)
+				goto force_shutdown;
+			if (start_rdcw_watch(data, data->watch_worktree) == -1)
+				goto force_error_stop;
+			continue;
+		}
+
+		if (dwWait == WAIT_OBJECT_0 + LISTENER_HAVE_DATA_GITDIR) {
+			result = recv_rdcw_watch(data->watch_gitdir);
+			if (result == -1) {
+				/* hard error */
+				goto force_error_stop;
+			}
+			if (result == -2) {
+				/* retryable error */
+				if (start_rdcw_watch(data, data->watch_gitdir) == -1)
+					goto force_error_stop;
+				continue;
+			}
+
+			/* have data */
+			if (process_gitdir_events(state) == LISTENER_SHUTDOWN)
+				goto force_shutdown;
+			if (start_rdcw_watch(data, data->watch_gitdir) == -1)
+				goto force_error_stop;
+			continue;
+		}
+
+		if (dwWait == WAIT_OBJECT_0 + LISTENER_SHUTDOWN)
+			goto clean_shutdown;
+
+		error(_("could not read directory changes [GLE %ld]"),
+		      GetLastError());
+		goto force_error_stop;
+	}
+
+force_error_stop:
+	state->error_code = -1;
+
+force_shutdown:
+	/*
+	 * Tell the IPC thead pool to stop (which completes the await
+	 * in the main thread (which will also signal this thread (if
+	 * we are still alive))).
+	 */
+	ipc_server_stop_async(state->ipc_server_data);
+
+clean_shutdown:
+	cancel_rdcw_watch(data->watch_worktree);
+	cancel_rdcw_watch(data->watch_gitdir);
 }
 
 int fsm_listen__ctor(struct fsmonitor_daemon_state *state)
 {
+	struct fsmonitor_daemon_backend_data *data;
+
+	CALLOC_ARRAY(data, 1);
+
+	data->hEventShutdown = CreateEvent(NULL, TRUE, FALSE, NULL);
+
+	data->watch_worktree = create_watch(state,
+					    state->path_worktree_watch.buf);
+	if (!data->watch_worktree)
+		goto failed;
+
+	if (state->nr_paths_watching > 1) {
+		data->watch_gitdir = create_watch(state,
+						  state->path_gitdir_watch.buf);
+		if (!data->watch_gitdir)
+			goto failed;
+	}
+
+	data->hListener[LISTENER_SHUTDOWN] = data->hEventShutdown;
+	data->nr_listener_handles++;
+
+	data->hListener[LISTENER_HAVE_DATA_WORKTREE] =
+		data->watch_worktree->hEvent;
+	data->nr_listener_handles++;
+
+	if (data->watch_gitdir) {
+		data->hListener[LISTENER_HAVE_DATA_GITDIR] =
+			data->watch_gitdir->hEvent;
+		data->nr_listener_handles++;
+	}
+
+	state->backend_data = data;
+	return 0;
+
+failed:
+	CloseHandle(data->hEventShutdown);
+	destroy_watch(data->watch_worktree);
+	destroy_watch(data->watch_gitdir);
+
 	return -1;
 }
 
 void fsm_listen__dtor(struct fsmonitor_daemon_state *state)
 {
+	struct fsmonitor_daemon_backend_data *data;
+
+	if (!state || !state->backend_data)
+		return;
+
+	data = state->backend_data;
+
+	CloseHandle(data->hEventShutdown);
+	destroy_watch(data->watch_worktree);
+	destroy_watch(data->watch_gitdir);
+
+	FREE_AND_NULL(state->backend_data);
 }

index c84e3344ab9..f424253d3eb 100644
@@ -1,3 +1,99 @@
+#if defined(__GNUC__)
+/*
+ * It is possible to #include CoreFoundation/CoreFoundation.h when compiling
+ * with clang, but not with GCC as of time of writing.
+ *
+ * See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93082 for details.
+ */
+typedef unsigned int FSEventStreamCreateFlags;
+#define kFSEventStreamEventFlagNone               0x00000000
+#define kFSEventStreamEventFlagMustScanSubDirs    0x00000001
+#define kFSEventStreamEventFlagUserDropped        0x00000002
+#define kFSEventStreamEventFlagKernelDropped      0x00000004
+#define kFSEventStreamEventFlagEventIdsWrapped    0x00000008
+#define kFSEventStreamEventFlagHistoryDone        0x00000010
+#define kFSEventStreamEventFlagRootChanged        0x00000020
+#define kFSEventStreamEventFlagMount              0x00000040
+#define kFSEventStreamEventFlagUnmount            0x00000080
+#define kFSEventStreamEventFlagItemCreated        0x00000100
+#define kFSEventStreamEventFlagItemRemoved        0x00000200
+#define kFSEventStreamEventFlagItemInodeMetaMod   0x00000400
+#define kFSEventStreamEventFlagItemRenamed        0x00000800
+#define kFSEventStreamEventFlagItemModified       0x00001000
+#define kFSEventStreamEventFlagItemFinderInfoMod  0x00002000
+#define kFSEventStreamEventFlagItemChangeOwner    0x00004000
+#define kFSEventStreamEventFlagItemXattrMod       0x00008000
+#define kFSEventStreamEventFlagItemIsFile         0x00010000
+#define kFSEventStreamEventFlagItemIsDir          0x00020000
+#define kFSEventStreamEventFlagItemIsSymlink      0x00040000
+#define kFSEventStreamEventFlagOwnEvent           0x00080000
+#define kFSEventStreamEventFlagItemIsHardlink     0x00100000
+#define kFSEventStreamEventFlagItemIsLastHardlink 0x00200000
+#define kFSEventStreamEventFlagItemCloned         0x00400000
+
+typedef struct __FSEventStream *FSEventStreamRef;
+typedef const FSEventStreamRef ConstFSEventStreamRef;
+
+typedef unsigned int CFStringEncoding;
+#define kCFStringEncodingUTF8 0x08000100
+
+typedef const struct __CFString *CFStringRef;
+typedef const struct __CFArray *CFArrayRef;
+typedef const struct __CFRunLoop *CFRunLoopRef;
+
+struct FSEventStreamContext {
+    long long version;
+    void *cb_data, *retain, *release, *copy_description;
+};
+
+typedef struct FSEventStreamContext FSEventStreamContext;
+typedef unsigned int FSEventStreamEventFlags;
+#define kFSEventStreamCreateFlagNoDefer 0x02
+#define kFSEventStreamCreateFlagWatchRoot 0x04
+#define kFSEventStreamCreateFlagFileEvents 0x10
+
+typedef unsigned long long FSEventStreamEventId;
+#define kFSEventStreamEventIdSinceNow 0xFFFFFFFFFFFFFFFFULL
+
+typedef void (*FSEventStreamCallback)(ConstFSEventStreamRef streamRef,
+				      void *context,
+				      __SIZE_TYPE__ num_of_events,
+				      void *event_paths,
+				      const FSEventStreamEventFlags event_flags[],
+				      const FSEventStreamEventId event_ids[]);
+typedef double CFTimeInterval;
+FSEventStreamRef FSEventStreamCreate(void *allocator,
+				     FSEventStreamCallback callback,
+				     FSEventStreamContext *context,
+				     CFArrayRef paths_to_watch,
+				     FSEventStreamEventId since_when,
+				     CFTimeInterval latency,
+				     FSEventStreamCreateFlags flags);
+CFStringRef CFStringCreateWithCString(void *allocator, const char *string,
+				      CFStringEncoding encoding);
+CFArrayRef CFArrayCreate(void *allocator, const void **items, long long count,
+			 void *callbacks);
+void CFRunLoopRun(void);
+void CFRunLoopStop(CFRunLoopRef run_loop);
+CFRunLoopRef CFRunLoopGetCurrent(void);
+extern CFStringRef kCFRunLoopDefaultMode;
+void FSEventStreamScheduleWithRunLoop(FSEventStreamRef stream,
+				      CFRunLoopRef run_loop,
+				      CFStringRef run_loop_mode);
+unsigned char FSEventStreamStart(FSEventStreamRef stream);
+void FSEventStreamStop(FSEventStreamRef stream);
+void FSEventStreamInvalidate(FSEventStreamRef stream);
+void FSEventStreamRelease(FSEventStreamRef stream);
+#else
+/*
+ * Let Apple's headers declare `isalnum()` first, before
+ * Git's headers override it via a constant
+ */
+#include <string.h>
+#include <CoreFoundation/CoreFoundation.h>
+#include <CoreServices/CoreServices.h>
+#endif
+
 #include "cache.h"
 #include "fsmonitor.h"
 #include "fsm-listen.h"

index f424253d3eb..2aefdc14d89 100644
@@ -1,4 +1,4 @@
-#if defined(__GNUC__)
+#ifndef __clang__
 /*
  * It is possible to #include CoreFoundation/CoreFoundation.h when compiling
  * with clang, but not with GCC as of time of writing.

@@ -97,20 +97,400 @@ void FSEventStreamRelease(FSEventStreamRef stream);
 #include "cache.h"
 #include "fsmonitor.h"
 #include "fsm-listen.h"
+#include "fsmonitor--daemon.h"
+
+struct fsmonitor_daemon_backend_data
+{
+	CFStringRef cfsr_worktree_path;
+	CFStringRef cfsr_gitdir_path;
+
+	CFArrayRef cfar_paths_to_watch;
+	int nr_paths_watching;
+
+	FSEventStreamRef stream;
+
+	CFRunLoopRef rl;
+
+	enum shutdown_style {
+		SHUTDOWN_EVENT = 0,
+		FORCE_SHUTDOWN,
+		FORCE_ERROR_STOP,
+	} shutdown_style;
+
+	unsigned int stream_scheduled:1;
+	unsigned int stream_started:1;
+};
+
+static void log_flags_set(const char *path, const FSEventStreamEventFlags flag)
+{
+	struct strbuf msg = STRBUF_INIT;
+
+	if (flag & kFSEventStreamEventFlagMustScanSubDirs)
+		strbuf_addstr(&msg, "MustScanSubDirs|");
+	if (flag & kFSEventStreamEventFlagUserDropped)
+		strbuf_addstr(&msg, "UserDropped|");
+	if (flag & kFSEventStreamEventFlagKernelDropped)
+		strbuf_addstr(&msg, "KernelDropped|");
+	if (flag & kFSEventStreamEventFlagEventIdsWrapped)
+		strbuf_addstr(&msg, "EventIdsWrapped|");
+	if (flag & kFSEventStreamEventFlagHistoryDone)
+		strbuf_addstr(&msg, "HistoryDone|");
+	if (flag & kFSEventStreamEventFlagRootChanged)
+		strbuf_addstr(&msg, "RootChanged|");
+	if (flag & kFSEventStreamEventFlagMount)
+		strbuf_addstr(&msg, "Mount|");
+	if (flag & kFSEventStreamEventFlagUnmount)
+		strbuf_addstr(&msg, "Unmount|");
+	if (flag & kFSEventStreamEventFlagItemChangeOwner)
+		strbuf_addstr(&msg, "ItemChangeOwner|");
+	if (flag & kFSEventStreamEventFlagItemCreated)
+		strbuf_addstr(&msg, "ItemCreated|");
+	if (flag & kFSEventStreamEventFlagItemFinderInfoMod)
+		strbuf_addstr(&msg, "ItemFinderInfoMod|");
+	if (flag & kFSEventStreamEventFlagItemInodeMetaMod)
+		strbuf_addstr(&msg, "ItemInodeMetaMod|");
+	if (flag & kFSEventStreamEventFlagItemIsDir)
+		strbuf_addstr(&msg, "ItemIsDir|");
+	if (flag & kFSEventStreamEventFlagItemIsFile)
+		strbuf_addstr(&msg, "ItemIsFile|");
+	if (flag & kFSEventStreamEventFlagItemIsHardlink)
+		strbuf_addstr(&msg, "ItemIsHardlink|");
+	if (flag & kFSEventStreamEventFlagItemIsLastHardlink)
+		strbuf_addstr(&msg, "ItemIsLastHardlink|");
+	if (flag & kFSEventStreamEventFlagItemIsSymlink)
+		strbuf_addstr(&msg, "ItemIsSymlink|");
+	if (flag & kFSEventStreamEventFlagItemModified)
+		strbuf_addstr(&msg, "ItemModified|");
+	if (flag & kFSEventStreamEventFlagItemRemoved)
+		strbuf_addstr(&msg, "ItemRemoved|");
+	if (flag & kFSEventStreamEventFlagItemRenamed)
+		strbuf_addstr(&msg, "ItemRenamed|");
+	if (flag & kFSEventStreamEventFlagItemXattrMod)
+		strbuf_addstr(&msg, "ItemXattrMod|");
+	if (flag & kFSEventStreamEventFlagOwnEvent)
+		strbuf_addstr(&msg, "OwnEvent|");
+	if (flag & kFSEventStreamEventFlagItemCloned)
+		strbuf_addstr(&msg, "ItemCloned|");
+
+	trace_printf_key(&trace_fsmonitor, "fsevent: '%s', flags=%u %s",
+			 path, flag, msg.buf);
+
+	strbuf_release(&msg);
+}
+
+static int ef_is_root_delete(const FSEventStreamEventFlags ef)
+{
+	return (ef & kFSEventStreamEventFlagItemIsDir &&
+		ef & kFSEventStreamEventFlagItemRemoved);
+}
+
+static int ef_is_root_renamed(const FSEventStreamEventFlags ef)
+{
+	return (ef & kFSEventStreamEventFlagItemIsDir &&
+		ef & kFSEventStreamEventFlagItemRenamed);
+}
+
+static int ef_is_dropped(const FSEventStreamEventFlags ef)
+{
+	return (ef & kFSEventStreamEventFlagMustScanSubDirs ||
+		ef & kFSEventStreamEventFlagKernelDropped ||
+		ef & kFSEventStreamEventFlagUserDropped);
+}
+
+static void fsevent_callback(ConstFSEventStreamRef streamRef,
+			     void *ctx,
+			     size_t num_of_events,
+			     void *event_paths,
+			     const FSEventStreamEventFlags event_flags[],
+			     const FSEventStreamEventId event_ids[])
+{
+	struct fsmonitor_daemon_state *state = ctx;
+	struct fsmonitor_daemon_backend_data *data = state->backend_data;
+	char **paths = (char **)event_paths;
+	struct fsmonitor_batch *batch = NULL;
+	struct string_list cookie_list = STRING_LIST_INIT_DUP;
+	const char *path_k;
+	const char *slash;
+	int k;
+	struct strbuf tmp = STRBUF_INIT;
+
+	/*
+	 * Build a list of all filesystem changes into a private/local
+	 * list and without holding any locks.
+	 */
+	for (k = 0; k < num_of_events; k++) {
+		/*
+		 * On Mac, we receive an array of absolute paths.
+		 */
+		path_k = paths[k];
+
+		/*
+		 * If you want to debug FSEvents, log them to GIT_TRACE_FSMONITOR.
+		 * Please don't log them to Trace2.
+		 *
+		 * trace_printf_key(&trace_fsmonitor, "Path: '%s'", path_k);
+		 */
+
+		/*
+		 * If event[k] is marked as dropped, we assume that we have
+		 * lost sync with the filesystem and should flush our cached
+		 * data.  We need to:
+		 *
+		 * [1] Abort/wake any client threads waiting for a cookie and
+		 *     flush the cached state data (the current token), and
+		 *     create a new token.
+		 *
+		 * [2] Discard the batch that we were locally building (since
+		 *     they are conceptually relative to the just flushed
+		 *     token).
+		 */
+		if (ef_is_dropped(event_flags[k])) {
+			if (trace_pass_fl(&trace_fsmonitor))
+				log_flags_set(path_k, event_flags[k]);
+
+			fsmonitor_force_resync(state);
+			fsmonitor_batch__free_list(batch);
+			string_list_clear(&cookie_list, 0);
+
+			/*
+			 * We assume that any events that we received
+			 * in this callback after this dropped event
+			 * may still be valid, so we continue rather
+			 * than break.  (And just in case there is a
+			 * delete of ".git" hiding in there.)
+			 */
+			continue;
+		}
+
+		switch (fsmonitor_classify_path_absolute(state, path_k)) {
+
+		case IS_INSIDE_DOT_GIT_WITH_COOKIE_PREFIX:
+		case IS_INSIDE_GITDIR_WITH_COOKIE_PREFIX:
+			/* special case cookie files within .git or gitdir */
+
+			/* Use just the filename of the cookie file. */
+			slash = find_last_dir_sep(path_k);
+			string_list_append(&cookie_list,
+					   slash ? slash + 1 : path_k);
+			break;
+
+		case IS_INSIDE_DOT_GIT:
+		case IS_INSIDE_GITDIR:
+			/* ignore all other paths inside of .git or gitdir */
+			break;
+
+		case IS_DOT_GIT:
+		case IS_GITDIR:
+			/*
+			 * If .git directory is deleted or renamed away,
+			 * we have to quit.
+			 */
+			if (ef_is_root_delete(event_flags[k])) {
+				trace_printf_key(&trace_fsmonitor,
+						 "event: gitdir removed");
+				goto force_shutdown;
+			}
+			if (ef_is_root_renamed(event_flags[k])) {
+				trace_printf_key(&trace_fsmonitor,
+						 "event: gitdir renamed");
+				goto force_shutdown;
+			}
+			break;
+
+		case IS_WORKDIR_PATH:
+			/* try to queue normal pathnames */
+
+			if (trace_pass_fl(&trace_fsmonitor))
+				log_flags_set(path_k, event_flags[k]);
+
+			/*
+			 * Because of the implicit "binning" (the
+			 * kernel calls us at a given frequency) and
+			 * de-duping (the kernel is free to combine
+			 * multiple events for a given pathname), an
+			 * individual fsevent could be marked as both
+			 * a file and directory.  Add it to the queue
+			 * with both spellings so that the client will
+			 * know how much to invalidate/refresh.
+			 */
+
+			if (event_flags[k] & kFSEventStreamEventFlagItemIsFile) {
+				const char *rel = path_k +
+					state->path_worktree_watch.len + 1;
+
+				if (!batch)
+					batch = fsmonitor_batch__new();
+				fsmonitor_batch__add_path(batch, rel);
+			}
+
+			if (event_flags[k] & kFSEventStreamEventFlagItemIsDir) {
+				const char *rel = path_k +
+					state->path_worktree_watch.len + 1;
+
+				strbuf_reset(&tmp);
+				strbuf_addstr(&tmp, rel);
+				strbuf_addch(&tmp, '/');
+
+				if (!batch)
+					batch = fsmonitor_batch__new();
+				fsmonitor_batch__add_path(batch, tmp.buf);
+			}
+
+			break;
+
+		case IS_OUTSIDE_CONE:
+		default:
+			trace_printf_key(&trace_fsmonitor,
+					 "ignoring '%s'", path_k);
+			break;
+		}
+	}
+
+	fsmonitor_publish(state, batch, &cookie_list);
+	string_list_clear(&cookie_list, 0);
+	strbuf_release(&tmp);
+	return;
+
+force_shutdown:
+	fsmonitor_batch__free_list(batch);
+	string_list_clear(&cookie_list, 0);
+
+	data->shutdown_style = FORCE_SHUTDOWN;
+	CFRunLoopStop(data->rl);
+	strbuf_release(&tmp);
+	return;
+}
+
+/*
+ * NEEDSWORK: Investigate the proper value for the `latency` argument
+ * in the call to `FSEventStreamCreate()`.  I'm not sure that this
+ * needs to be a config setting or just something that we tune after
+ * some testing.
+ *
+ * With a latency of 0.1, I was seeing lots of dropped events during
+ * the "touch 100000" files test within t/perf/p7519, but with a
+ * latency of 0.001 I did not see any dropped events.  So the
+ * "correct" value may be somewhere in between.
+ *
+ * https://developer.apple.com/documentation/coreservices/1443980-fseventstreamcreate
+ */
 
 int fsm_listen__ctor(struct fsmonitor_daemon_state *state)
 {
+	FSEventStreamCreateFlags flags = kFSEventStreamCreateFlagNoDefer |
+		kFSEventStreamCreateFlagWatchRoot |
+		kFSEventStreamCreateFlagFileEvents;
+	FSEventStreamContext ctx = {
+		0,
+		state,
+		NULL,
+		NULL,
+		NULL
+	};
+	struct fsmonitor_daemon_backend_data *data;
+	const void *dir_array[2];
+
+	CALLOC_ARRAY(data, 1);
+	state->backend_data = data;
+
+	data->cfsr_worktree_path = CFStringCreateWithCString(
+		NULL, state->path_worktree_watch.buf, kCFStringEncodingUTF8);
+	dir_array[data->nr_paths_watching++] = data->cfsr_worktree_path;
+
+	if (state->nr_paths_watching > 1) {
+		data->cfsr_gitdir_path = CFStringCreateWithCString(
+			NULL, state->path_gitdir_watch.buf,
+			kCFStringEncodingUTF8);
+		dir_array[data->nr_paths_watching++] = data->cfsr_gitdir_path;
+	}
+
+	data->cfar_paths_to_watch = CFArrayCreate(NULL, dir_array,
+						  data->nr_paths_watching,
+						  NULL);
+	data->stream = FSEventStreamCreate(NULL, fsevent_callback, &ctx,
+					   data->cfar_paths_to_watch,
+					   kFSEventStreamEventIdSinceNow,
+					   0.001, flags);
+	if (data->stream == NULL)
+		goto failed;
+
+	/*
+	 * `data->rl` needs to be set inside the listener thread.
+	 */
+
+	return 0;
+
+failed:
+	error("Unable to create FSEventStream.");
+
+	FREE_AND_NULL(state->backend_data);
 	return -1;
 }
 
 void fsm_listen__dtor(struct fsmonitor_daemon_state *state)
 {
+	struct fsmonitor_daemon_backend_data *data;
+
+	if (!state || !state->backend_data)
+		return;
+
+	data = state->backend_data;
+
+	if (data->stream) {
+		if (data->stream_started)
+			FSEventStreamStop(data->stream);
+		if (data->stream_scheduled)
+			FSEventStreamInvalidate(data->stream);
+		FSEventStreamRelease(data->stream);
+	}
+
+	FREE_AND_NULL(state->backend_data);
 }
 
 void fsm_listen__stop_async(struct fsmonitor_daemon_state *state)
 {
+	struct fsmonitor_daemon_backend_data *data;
+
+	data = state->backend_data;
+	data->shutdown_style = SHUTDOWN_EVENT;
+
+	CFRunLoopStop(data->rl);
 }
 
 void fsm_listen__loop(struct fsmonitor_daemon_state *state)
 {
+	struct fsmonitor_daemon_backend_data *data;
+
+	data = state->backend_data;
+
+	data->rl = CFRunLoopGetCurrent();
+
+	FSEventStreamScheduleWithRunLoop(data->stream, data->rl, kCFRunLoopDefaultMode);
+	data->stream_scheduled = 1;
+
+	if (!FSEventStreamStart(data->stream)) {
+		error("Failed to start the FSEventStream");
+		goto force_error_stop_without_loop;
+	}
+	data->stream_started = 1;
+
+	CFRunLoopRun();
+
+	switch (data->shutdown_style) {
+	case FORCE_ERROR_STOP:
+		state->error_code = -1;
+		/* fall thru */
+	case FORCE_SHUTDOWN:
+		ipc_server_stop_async(state->ipc_server_data);
+		/* fall thru */
+	case SHUTDOWN_EVENT:
+	default:
+		break;
+	}
+	return;
+
+force_error_stop_without_loop:
+	state->error_code = -1;
+	ipc_server_stop_async(state->ipc_server_data);
+	return;
 }

index 34603f23053..4c88171e06c 100644
@@ -7,6 +7,7 @@
 #include "fsmonitor--daemon.h"
 #include "simple-ipc.h"
 #include "khash.h"
+#include "pkt-line.h"
 
 static const char * const builtin_fsmonitor__daemon_usage[] = {
 	N_("git fsmonitor--daemon start [<options>]"),

@@ -351,6 +352,311 @@ void fsmonitor_force_resync(struct fsmonitor_daemon_state *state)
 	pthread_mutex_unlock(&state->main_lock);
 }
 
+/*
+ * Format an opaque token string to send to the client.
+ */
+static void with_lock__format_response_token(
+	struct strbuf *response_token,
+	const struct strbuf *response_token_id,
+	const struct fsmonitor_batch *batch)
+{
+	/* assert current thread holding state->main_lock */
+
+	strbuf_reset(response_token);
+	strbuf_addf(response_token, "builtin:%s:%"PRIu64,
+		    response_token_id->buf, batch->batch_seq_nr);
+}
+
+/*
+ * Parse an opaque token from the client.
+ * Returns -1 on error.
+ */
+static int fsmonitor_parse_client_token(const char *buf_token,
+					struct strbuf *requested_token_id,
+					uint64_t *seq_nr)
+{
+	const char *p;
+	char *p_end;
+
+	strbuf_reset(requested_token_id);
+	*seq_nr = 0;
+
+	if (!skip_prefix(buf_token, "builtin:", &p))
+		return -1;
+
+	while (*p && *p != ':')
+		strbuf_addch(requested_token_id, *p++);
+	if (!*p++)
+		return -1;
+
+	*seq_nr = (uint64_t)strtoumax(p, &p_end, 10);
+	if (*p_end)
+		return -1;
+
+	return 0;
+}
+
+KHASH_INIT(str, const char *, int, 0, kh_str_hash_func, kh_str_hash_equal)
+
+static int do_handle_client(struct fsmonitor_daemon_state *state,
+			    const char *command,
+			    ipc_server_reply_cb *reply,
+			    struct ipc_server_reply_data *reply_data)
+{
+	struct fsmonitor_token_data *token_data = NULL;
+	struct strbuf response_token = STRBUF_INIT;
+	struct strbuf requested_token_id = STRBUF_INIT;
+	struct strbuf payload = STRBUF_INIT;
+	uint64_t requested_oldest_seq_nr = 0;
+	uint64_t total_response_len = 0;
+	const char *p;
+	const struct fsmonitor_batch *batch_head;
+	const struct fsmonitor_batch *batch;
+	intmax_t count = 0, duplicates = 0;
+	kh_str_t *shown;
+	int hash_ret;
+	int do_trivial = 0;
+	int do_flush = 0;
+
+	/*
+	 * We expect `command` to be of the form:
+	 *
+	 * <command> := quit NUL
+	 *            | flush NUL
+	 *            | <V1-time-since-epoch-ns> NUL
+	 *            | <V2-opaque-fsmonitor-token> NUL
+	 */
+
+	if (!strcmp(command, "quit")) {
+		/*
+		 * A client has requested over the socket/pipe that the
+		 * daemon shutdown.
+		 *
+		 * Tell the IPC thread pool to shutdown (which completes
+		 * the await in the main thread (which can stop the
+		 * fsmonitor listener thread)).
+		 *
+		 * There is no reply to the client.
+		 */
+		return SIMPLE_IPC_QUIT;
+
+	} else if (!strcmp(command, "flush")) {
+		/*
+		 * Flush all of our cached data and generate a new token
+		 * just like if we lost sync with the filesystem.
+		 *
+		 * Then send a trivial response using the new token.
+		 */
+		do_flush = 1;
+		do_trivial = 1;
+
+	} else if (!skip_prefix(command, "builtin:", &p)) {
+		/* assume V1 timestamp or garbage */
+
+		char *p_end;
+
+		strtoumax(command, &p_end, 10);
+		trace_printf_key(&trace_fsmonitor,
+				 ((*p_end) ?
+				  "fsmonitor: invalid command line '%s'" :
+				  "fsmonitor: unsupported V1 protocol '%s'"),
+				 command);
+		do_trivial = 1;
+
+	} else {
+		/* We have "builtin:*" */
+		if (fsmonitor_parse_client_token(command, &requested_token_id,
+						 &requested_oldest_seq_nr)) {
+			trace_printf_key(&trace_fsmonitor,
+					 "fsmonitor: invalid V2 protocol token '%s'",
+					 command);
+			do_trivial = 1;
+
+		} else {
+			/*
+			 * We have a V2 valid token:
+			 *     "builtin:<token_id>:<seq_nr>"
+			 */
+		}
+	}
+
+	pthread_mutex_lock(&state->main_lock);
+
+	if (!state->current_token_data)
+		BUG("fsmonitor state does not have a current token");
+
+	if (do_flush)
+		with_lock__do_force_resync(state);
+
+	/*
+	 * We mark the current head of the batch list as "pinned" so
+	 * that the listener thread will treat this item as read-only
+	 * (and prevent any more paths from being added to it) from
+	 * now on.
+	 */
+	token_data = state->current_token_data;
+	batch_head = token_data->batch_head;
+	((struct fsmonitor_batch *)batch_head)->pinned_time = time(NULL);
+
+	/*
+	 * FSMonitor Protocol V2 requires that we send a response header
+	 * with a "new current token" and then all of the paths that changed
+	 * since the "requested token".  We send the seq_nr of the just-pinned
+	 * head batch so that future requests from a client will be relative
+	 * to it.
+	 */
+	with_lock__format_response_token(&response_token,
+					 &token_data->token_id, batch_head);
+
+	reply(reply_data, response_token.buf, response_token.len + 1);
+	total_response_len += response_token.len + 1;
+
+	trace2_data_string("fsmonitor", the_repository, "response/token",
+			   response_token.buf);
+	trace_printf_key(&trace_fsmonitor, "response token: %s",
+			 response_token.buf);
+
+	if (!do_trivial) {
+		if (strcmp(requested_token_id.buf, token_data->token_id.buf)) {
+			/*
+			 * The client last spoke to a different daemon
+			 * instance -OR- the daemon had to resync with
+			 * the filesystem (and lost events), so reject.
+			 */
+			trace2_data_string("fsmonitor", the_repository,
+					   "response/token", "different");
+			do_trivial = 1;
+
+		} else if (requested_oldest_seq_nr <
+			   token_data->batch_tail->batch_seq_nr) {
+			/*
+			 * The client wants older events than we have for
+			 * this token_id.  This means that the end of our
+			 * batch list was truncated and we cannot give the
+			 * client a complete snapshot relative to their
+			 * request.
+			 */
+			trace_printf_key(&trace_fsmonitor,
+					 "client requested truncated data");
+			do_trivial = 1;
+		}
+	}
+
+	if (do_trivial) {
+		pthread_mutex_unlock(&state->main_lock);
+
+		reply(reply_data, "/", 2);
+
+		trace2_data_intmax("fsmonitor", the_repository,
+				   "response/trivial", 1);
+
+		strbuf_release(&response_token);
+		strbuf_release(&requested_token_id);
+		return 0;
+	}
+
+	/*
+	 * We're going to hold onto a pointer to the current
+	 * token-data while we walk the list of batches of files.
+	 * During this time, we will NOT be under the lock.
+	 * So we ref-count it.
+	 *
+	 * This allows the listener thread to continue prepending
+	 * new batches of items to the token-data (which we'll ignore).
+	 *
+	 * AND it allows the listener thread to do a token-reset
+	 * (and install a new `current_token_data`).
+	 */
+	token_data->client_ref_count++;
+
+	pthread_mutex_unlock(&state->main_lock);
+
+	/*
+	 * The client request is relative to the token that they sent,
+	 * so walk the batch list backwards from the current head back
+	 * to the batch (sequence number) they named.
+	 *
+	 * We use khash to de-dup the list of pathnames.
+	 *
+	 * NEEDSWORK: each batch contains a list of interned strings,
+	 * so we only need to do pointer comparisons here to build the
+	 * hash table.  Currently, we're still comparing the string
+	 * values.
+	 */
+	shown = kh_init_str();
+	for (batch = batch_head;
+	     batch && batch->batch_seq_nr > requested_oldest_seq_nr;
+	     batch = batch->next) {
+		size_t k;
+
+		for (k = 0; k < batch->nr; k++) {
+			const char *s = batch->interned_paths[k];
+			size_t s_len;
+
+			if (kh_get_str(shown, s) != kh_end(shown))
+				duplicates++;
+			else {
+				kh_put_str(shown, s, &hash_ret);
+
+				trace_printf_key(&trace_fsmonitor,
+						 "send[%"PRIuMAX"]: %s",
+						 count, s);
+
+				/* Each path gets written with a trailing NUL */
+				s_len = strlen(s) + 1;
+
+				if (payload.len + s_len >=
+				    LARGE_PACKET_DATA_MAX) {
+					reply(reply_data, payload.buf,
+					      payload.len);
+					total_response_len += payload.len;
+					strbuf_reset(&payload);
+				}
+
+				strbuf_add(&payload, s, s_len);
+				count++;
+			}
+		}
+	}
+
+	if (payload.len) {
+		reply(reply_data, payload.buf, payload.len);
+		total_response_len += payload.len;
+	}
+
+	kh_release_str(shown);
+
+	pthread_mutex_lock(&state->main_lock);
+
+	if (token_data->client_ref_count > 0)
+		token_data->client_ref_count--;
+
+	if (token_data->client_ref_count == 0) {
+		if (token_data != state->current_token_data) {
+			/*
+			 * The listener thread did a token-reset while we were
+			 * walking the batch list.  Therefore, this token is
+			 * stale and can be discarded completely.  If we are
+			 * the last reader thread using this token, we own
+			 * that work.
+			 */
+			fsmonitor_free_token_data(token_data);
+		}
+	}
+
+	pthread_mutex_unlock(&state->main_lock);
+
+	trace2_data_intmax("fsmonitor", the_repository, "response/length", total_response_len);
+	trace2_data_intmax("fsmonitor", the_repository, "response/count/files", count);
+	trace2_data_intmax("fsmonitor", the_repository, "response/count/duplicates", duplicates);
+
+	strbuf_release(&response_token);
+	strbuf_release(&requested_token_id);
+	strbuf_release(&payload);
+
+	return 0;
+}
+
 static ipc_server_application_cb handle_client;
 
 static int handle_client(void *data,

@@ -358,7 +664,7 @@ static int handle_client(void *data,
 			 ipc_server_reply_cb *reply,
 			 struct ipc_server_reply_data *reply_data)
 {
-	/* struct fsmonitor_daemon_state *state = data; */
+	struct fsmonitor_daemon_state *state = data;
 	int result;
 
 	/*

@@ -369,10 +675,12 @@ static int handle_client(void *data,
 	if (command_len != strlen(command))
 		BUG("FSMonitor assumes text messages");
 
+	trace_printf_key(&trace_fsmonitor, "requested token: %s", command);
+
 	trace2_region_enter("fsmonitor", "handle_client", the_repository);
 	trace2_data_string("fsmonitor", the_repository, "request", command);
 
-	result = 0; /* TODO Do something here. */
+	result = do_handle_client(state, command, reply, reply_data);
 
 	trace2_region_leave("fsmonitor", "handle_client", the_repository);
 

index 71444906ddf..9112a51e84b 100644
@@ -12,6 +12,7 @@
 #include "refs.h"
 #include "parse-options.h"
 #include "prompt.h"
+#include "fsmonitor-ipc.h"
 
 struct category_description {
 	uint32_t category;

@@ -695,6 +696,9 @@ void get_version_info(struct strbuf *buf, int show_build_options)
 		strbuf_addf(buf, "sizeof-size_t: %d\n", (int)sizeof(size_t));
 		strbuf_addf(buf, "shell-path: %s\n", SHELL_PATH);
 		/* NEEDSWORK: also save and output GIT-BUILD_OPTIONS? */
+
+		if (fsmonitor_ipc__is_supported())
+			strbuf_addstr(buf, "feature: fsmonitor--daemon\n");
 	}
 }
 

121 lines not on this page · raw message

index 338a57b104d..a4c5647b2f1 100644
@@ -31,6 +31,7 @@ static struct test_cmd cmds[] = {
 	{ "dump-untracked-cache", cmd__dump_untracked_cache },
 	{ "example-decorate", cmd__example_decorate },
 	{ "fast-rebase", cmd__fast_rebase },
+	{ "fsmonitor-client", cmd__fsmonitor_client },
 	{ "genrandom", cmd__genrandom },
 	{ "genzeros", cmd__genzeros },
 	{ "getcwd", cmd__getcwd },

index 48cee1f4a2d..fa4c936310c 100644
@@ -22,6 +22,7 @@ int cmd__dump_untracked_cache(int argc, const char **argv);
 int cmd__dump_reftable(int argc, const char **argv);
 int cmd__example_decorate(int argc, const char **argv);
 int cmd__fast_rebase(int argc, const char **argv);
+int cmd__fsmonitor_client(int argc, const char **argv);
 int cmd__genrandom(int argc, const char **argv);
 int cmd__genzeros(int argc, const char **argv);
 int cmd__getcwd(int argc, const char **argv);

index 524b55ca496..dc28890a183 100644
@@ -134,6 +134,21 @@ int cmd__chmtime(int argc, const char **argv)
 		}
 
 		if (utb.modtime != sb.st_mtime && utime(argv[i], &utb) < 0) {
+#ifdef GIT_WINDOWS_NATIVE
+			if (S_ISDIR(sb.st_mode)) {
+				/*
+				 * NEEDSWORK: The Windows version of `utime()`
+				 * (aka `mingw_utime()`) does not correctly
+				 * handle directory arguments, since it uses
+				 * `_wopen()`.  Ignore it for now since this
+				 * is just a test.
+				 */
+				fprintf(stderr,
+					("Failed to modify time on directory %s. "
+					 "Skipping\n"), argv[i]);
+				continue;
+			}
+#endif
 			fprintf(stderr, "Failed to modify time on %s: %s\n",
 			        argv[i], strerror(errno));
 			return 1;

index 4c88171e06c..962b24569e1 100644
@@ -299,6 +299,75 @@ static void fsmonitor_batch__combine(struct fsmonitor_batch *batch_dest,
 			batch_src->interned_paths[k];
 }
 
+/*
+ * To keep the batch list from growing unbounded in response to filesystem
+ * activity, we try to truncate old batches from the end of the list as
+ * they become irrelevant.
+ *
+ * We assume that the .git/index will be updated with the most recent token
+ * any time the index is updated.  And future commands will only ask for
+ * recent changes *since* that new token.  So as tokens advance into the
+ * future, older batch items will never be requested/needed.  So we can
+ * truncate them without loss of functionality.
+ *
+ * However, multiple commands may be talking to the daemon concurrently
+ * or perform a slow command, so a little "token skew" is possible.
+ * Therefore, we want this to be a little bit lazy and have a generous
+ * delay.
+ *
+ * The current reader thread walked backwards in time from `token->batch_head`
+ * back to `batch_marker` somewhere in the middle of the batch list.
+ *
+ * Let's walk backwards in time from that marker an arbitrary delay
+ * and truncate the list there.  Note that these timestamps are completely
+ * artificial (based on when we pinned the batch item) and not on any
+ * filesystem activity.
+ *
+ * Return the obsolete portion of the list after we have removed it from
+ * the official list so that the caller can free it after leaving the lock.
+ */
+#define MY_TIME_DELAY_SECONDS (5 * 60) /* seconds */
+
+static struct fsmonitor_batch *with_lock__truncate_old_batches(
+	struct fsmonitor_daemon_state *state,
+	const struct fsmonitor_batch *batch_marker)
+{
+	/* assert current thread holding state->main_lock */
+
+	const struct fsmonitor_batch *batch;
+	struct fsmonitor_batch *remainder;
+
+	if (!batch_marker)
+		return NULL;
+
+	trace_printf_key(&trace_fsmonitor, "Truncate: mark (%"PRIu64",%"PRIu64")",
+			 batch_marker->batch_seq_nr,
+			 (uint64_t)batch_marker->pinned_time);
+
+	for (batch = batch_marker; batch; batch = batch->next) {
+		time_t t;
+
+		if (!batch->pinned_time) /* an overflow batch */
+			continue;
+
+		t = batch->pinned_time + MY_TIME_DELAY_SECONDS;
+		if (t > batch_marker->pinned_time) /* too close to marker */
+			continue;
+
+		goto truncate_past_here;
+	}
+
+	return NULL;
+
+truncate_past_here:
+	state->current_token_data->batch_tail = (struct fsmonitor_batch *)batch;
+
+	remainder = ((struct fsmonitor_batch *)batch)->next;
+	((struct fsmonitor_batch *)batch)->next = NULL;
+
+	return remainder;
+}
+
 static void fsmonitor_free_token_data(struct fsmonitor_token_data *token)
 {
 	if (!token)

@@ -412,6 +481,7 @@ static int do_handle_client(struct fsmonitor_daemon_state *state,
 	const char *p;
 	const struct fsmonitor_batch *batch_head;
 	const struct fsmonitor_batch *batch;
+	struct fsmonitor_batch *remainder = NULL;
 	intmax_t count = 0, duplicates = 0;
 	kh_str_t *shown;
 	int hash_ret;

@@ -641,11 +711,29 @@ static int do_handle_client(struct fsmonitor_daemon_state *state,
 			 * that work.
 			 */
 			fsmonitor_free_token_data(token_data);
+		} else if (batch) {
+			/*
+			 * We are holding the lock and are the only
+			 * reader of the ref-counted portion of the
+			 * list, so we get the honor of seeing if the
+			 * list can be truncated to save memory.
+			 *
+			 * The main loop did not walk to the end of the
+			 * list, so this batch is the first item in the
+			 * batch-list that is older than the requested
+			 * end-point sequence number.  See if the tail
+			 * end of the list is obsolete.
+			 */
+			remainder = with_lock__truncate_old_batches(state,
+								    batch);
 		}
 	}
 
 	pthread_mutex_unlock(&state->main_lock);
 
+	if (remainder)
+		fsmonitor_batch__free_list(remainder);
+
 	trace2_data_intmax("fsmonitor", the_repository, "response/length", total_response_len);
 	trace2_data_intmax("fsmonitor", the_repository, "response/count/files", count);
 	trace2_data_intmax("fsmonitor", the_repository, "response/count/duplicates", duplicates);

index 962b24569e1..6011fe42ee0 100644
@@ -94,6 +94,149 @@ static int do_as_client__status(void)
 	}
 }
 
+enum fsmonitor_cookie_item_result {
+	FCIR_ERROR = -1, /* could not create cookie file ? */
+	FCIR_INIT = 0,
+	FCIR_SEEN,
+	FCIR_ABORT,
+};
+
+struct fsmonitor_cookie_item {
+	struct hashmap_entry entry;
+	const char *name;
+	enum fsmonitor_cookie_item_result result;
+};
+
+static int cookies_cmp(const void *data, const struct hashmap_entry *he1,
+		     const struct hashmap_entry *he2, const void *keydata)
+{
+	const struct fsmonitor_cookie_item *a =
+		container_of(he1, const struct fsmonitor_cookie_item, entry);
+	const struct fsmonitor_cookie_item *b =
+		container_of(he2, const struct fsmonitor_cookie_item, entry);
+
+	return strcmp(a->name, keydata ? keydata : b->name);
+}
+
+static enum fsmonitor_cookie_item_result with_lock__wait_for_cookie(
+	struct fsmonitor_daemon_state *state)
+{
+	/* assert current thread holding state->main_lock */
+
+	int fd;
+	struct fsmonitor_cookie_item *cookie;
+	struct strbuf cookie_pathname = STRBUF_INIT;
+	struct strbuf cookie_filename = STRBUF_INIT;
+	enum fsmonitor_cookie_item_result result;
+	int my_cookie_seq;
+
+	CALLOC_ARRAY(cookie, 1);
+
+	my_cookie_seq = state->cookie_seq++;
+
+	strbuf_addf(&cookie_filename, "%i-%i", getpid(), my_cookie_seq);
+
+	strbuf_addbuf(&cookie_pathname, &state->path_cookie_prefix);
+	strbuf_addbuf(&cookie_pathname, &cookie_filename);
+
+	cookie->name = strbuf_detach(&cookie_filename, NULL);
+	cookie->result = FCIR_INIT;
+	hashmap_entry_init(&cookie->entry, strhash(cookie->name));
+
+	hashmap_add(&state->cookies, &cookie->entry);
+
+	trace_printf_key(&trace_fsmonitor, "cookie-wait: '%s' '%s'",
+			 cookie->name, cookie_pathname.buf);
+
+	/*
+	 * Create the cookie file on disk and then wait for a notification
+	 * that the listener thread has seen it.
+	 */
+	fd = open(cookie_pathname.buf, O_WRONLY | O_CREAT | O_EXCL, 0600);
+	if (fd >= 0) {
+		close(fd);
+		unlink(cookie_pathname.buf);
+
+		/*
+		 * NEEDSWORK: This is an infinite wait (well, unless another
+		 * thread sends us an abort).  I'd like to change this to
+		 * use `pthread_cond_timedwait()` and return an error/timeout
+		 * and let the caller do the trivial response thing.
+		 */
+		while (cookie->result == FCIR_INIT)
+			pthread_cond_wait(&state->cookies_cond,
+					  &state->main_lock);
+	} else {
+		error_errno(_("could not create fsmonitor cookie '%s'"),
+			    cookie->name);
+
+		cookie->result = FCIR_ERROR;
+	}
+
+	hashmap_remove(&state->cookies, &cookie->entry, NULL);
+
+	result = cookie->result;
+
+	free((char*)cookie->name);
+	free(cookie);
+	strbuf_release(&cookie_pathname);
+
+	return result;
+}
+
+/*
+ * Mark these cookies as _SEEN and wake up the corresponding client threads.
+ */
+static void with_lock__mark_cookies_seen(struct fsmonitor_daemon_state *state,
+					 const struct string_list *cookie_names)
+{
+	/* assert current thread holding state->main_lock */
+
+	int k;
+	int nr_seen = 0;
+
+	for (k = 0; k < cookie_names->nr; k++) {
+		struct fsmonitor_cookie_item key;
+		struct fsmonitor_cookie_item *cookie;
+
+		key.name = cookie_names->items[k].string;
+		hashmap_entry_init(&key.entry, strhash(key.name));
+
+		cookie = hashmap_get_entry(&state->cookies, &key, entry, NULL);
+		if (cookie) {
+			trace_printf_key(&trace_fsmonitor, "cookie-seen: '%s'",
+					 cookie->name);
+			cookie->result = FCIR_SEEN;
+			nr_seen++;
+		}
+	}
+
+	if (nr_seen)
+		pthread_cond_broadcast(&state->cookies_cond);
+}
+
+/*
+ * Set _ABORT on all pending cookies and wake up all client threads.
+ */
+static void with_lock__abort_all_cookies(struct fsmonitor_daemon_state *state)
+{
+	/* assert current thread holding state->main_lock */
+
+	struct hashmap_iter iter;
+	struct fsmonitor_cookie_item *cookie;
+	int nr_aborted = 0;
+
+	hashmap_for_each_entry(&state->cookies, &iter, cookie, entry) {
+		trace_printf_key(&trace_fsmonitor, "cookie-abort: '%s'",
+				 cookie->name);
+		cookie->result = FCIR_ABORT;
+		nr_aborted++;
+	}
+
+	if (nr_aborted)
+		pthread_cond_broadcast(&state->cookies_cond);
+}
+
 /*
  * Requests to and from a FSMonitor Protocol V2 provider use an opaque
  * "token" as a virtual timestamp.  Clients can request a summary of all

@@ -391,6 +534,9 @@ static void fsmonitor_free_token_data(struct fsmonitor_token_data *token)
  *     We should create a new token and start fresh (as if we just
  *     booted up).
  *
+ * [2] Some of those lost events may have been for cookie files.  We
+ *     should assume the worst and abort them rather letting them starve.
+ *
  * If there are no concurrent threads readering the current token data
  * series, we can free it now.  Otherwise, let the last reader free
  * it.

@@ -412,6 +558,8 @@ static void with_lock__do_force_resync(struct fsmonitor_daemon_state *state)
 	state->current_token_data = new_one;
 
 	fsmonitor_free_token_data(free_me);
+
+	with_lock__abort_all_cookies(state);
 }
 
 void fsmonitor_force_resync(struct fsmonitor_daemon_state *state)

@@ -487,6 +635,8 @@ static int do_handle_client(struct fsmonitor_daemon_state *state,
 	int hash_ret;
 	int do_trivial = 0;
 	int do_flush = 0;
+	int do_cookie = 0;
+	enum fsmonitor_cookie_item_result cookie_result;
 
 	/*
 	 * We expect `command` to be of the form:

@@ -547,6 +697,7 @@ static int do_handle_client(struct fsmonitor_daemon_state *state,
 			 * We have a V2 valid token:
 			 *     "builtin:<token_id>:<seq_nr>"
 			 */
+			do_cookie = 1;
 		}
 	}
 

@@ -555,6 +706,30 @@ static int do_handle_client(struct fsmonitor_daemon_state *state,
 	if (!state->current_token_data)
 		BUG("fsmonitor state does not have a current token");
 
+	/*
+	 * Write a cookie file inside the directory being watched in
+	 * an effort to flush out existing filesystem events that we
+	 * actually care about.  Suspend this client thread until we
+	 * see the filesystem events for this cookie file.
+	 *
+	 * Creating the cookie lets us guarantee that our FS listener
+	 * thread has drained the kernel queue and we are caught up
+	 * with the kernel.
+	 *
+	 * If we cannot create the cookie (or otherwise guarantee that
+	 * we are caught up), we send a trivial response.  We have to
+	 * assume that there might be some very, very recent activity
+	 * on the FS still in flight.
+	 */
+	if (do_cookie) {
+		cookie_result = with_lock__wait_for_cookie(state);
+		if (cookie_result != FCIR_SEEN) {
+			error(_("fsmonitor: cookie_result '%d' != SEEN"),
+			      cookie_result);
+			do_trivial = 1;
+		}
+	}
+
 	if (do_flush)
 		with_lock__do_force_resync(state);
 

@@ -775,7 +950,9 @@ static int handle_client(void *data,
 	return result;
 }
 
-#define FSMONITOR_COOKIE_PREFIX ".fsmonitor-daemon-"
+#define FSMONITOR_DIR           "fsmonitor--daemon"
+#define FSMONITOR_COOKIE_DIR    "cookies"
+#define FSMONITOR_COOKIE_PREFIX (FSMONITOR_DIR "/" FSMONITOR_COOKIE_DIR "/")
 
 enum fsmonitor_path_type fsmonitor_classify_path_workdir_relative(
 	const char *rel)

@@ -928,6 +1105,9 @@ void fsmonitor_publish(struct fsmonitor_daemon_state *state,
 		}
 	}
 
+	if (cookie_names->nr)
+		with_lock__mark_cookies_seen(state, cookie_names);
+
 	pthread_mutex_unlock(&state->main_lock);
 }
 

@@ -1019,7 +1199,9 @@ static int fsmonitor_run_daemon(void)
 
 	memset(&state, 0, sizeof(state));
 
+	hashmap_init(&state.cookies, cookies_cmp, NULL, 0);
 	pthread_mutex_init(&state.main_lock, NULL);
+	pthread_cond_init(&state.cookies_cond, NULL);
 	state.error_code = 0;
 	state.current_token_data = fsmonitor_new_token_data();
 

@@ -1044,6 +1226,44 @@ static int fsmonitor_run_daemon(void)
 		state.nr_paths_watching = 2;
 	}
 
+	/*
+	 * We will write filesystem syncing cookie files into
+	 * <gitdir>/<fsmonitor-dir>/<cookie-dir>/<pid>-<seq>.
+	 *
+	 * The extra layers of subdirectories here keep us from
+	 * changing the mtime on ".git/" or ".git/foo/" when we create
+	 * or delete cookie files.
+	 *
+	 * There have been problems with some IDEs that do a
+	 * non-recursive watch of the ".git/" directory and run a
+	 * series of commands any time something happens.
+	 *
+	 * For example, if we place our cookie files directly in
+	 * ".git/" or ".git/foo/" then a `git status` (or similar
+	 * command) from the IDE will cause a cookie file to be
+	 * created in one of those dirs.  This causes the mtime of
+	 * those dirs to change.  This triggers the IDE's watch
+	 * notification.  This triggers the IDE to run those commands
+	 * again.  And the process repeats and the machine never goes
+	 * idle.
+	 *
+	 * Adding the extra layers of subdirectories prevents the
+	 * mtime of ".git/" and ".git/foo" from changing when a
+	 * cookie file is created.
+	 */
+	strbuf_init(&state.path_cookie_prefix, 0);
+	strbuf_addbuf(&state.path_cookie_prefix, &state.path_gitdir_watch);
+
+	strbuf_addch(&state.path_cookie_prefix, '/');
+	strbuf_addstr(&state.path_cookie_prefix, FSMONITOR_DIR);
+	mkdir(state.path_cookie_prefix.buf, 0777);
+
+	strbuf_addch(&state.path_cookie_prefix, '/');
+	strbuf_addstr(&state.path_cookie_prefix, FSMONITOR_COOKIE_DIR);
+	mkdir(state.path_cookie_prefix.buf, 0777);
+
+	strbuf_addch(&state.path_cookie_prefix, '/');
+
 	/*
 	 * Confirm that we can create platform-specific resources for the
 	 * filesystem listener before we bother starting all the threads.

@@ -1056,6 +1276,7 @@ static int fsmonitor_run_daemon(void)
 	err = fsmonitor_run_daemon_1(&state);
 
 done:
+	pthread_cond_destroy(&state.cookies_cond);
 	pthread_mutex_destroy(&state.main_lock);
 	fsm_listen__dtor(&state);
 

@@ -1063,6 +1284,11 @@ done:
 
 	strbuf_release(&state.path_worktree_watch);
 	strbuf_release(&state.path_gitdir_watch);
+	strbuf_release(&state.path_cookie_prefix);
+
+	/*
+	 * NEEDSWORK: Consider "rm -rf <gitdir>/<fsmonitor-dir>"
+	 */
 
 	return err;
 }

index 20a815d80f8..c16ef095688 100644
@@ -45,6 +45,11 @@ struct fsmonitor_daemon_state {
 
 	struct fsmonitor_token_data *current_token_data;
 
+	struct strbuf path_cookie_prefix;
+	pthread_cond_t cookies_cond;
+	int cookie_seq;
+	struct hashmap cookies;
+
 	int error_code;
 	struct fsmonitor_daemon_backend_data *backend_data;
 

index 4287aad6bbb..8e3499d0667 100644
@@ -219,6 +219,45 @@ static void fsmonitor_refresh_callback(struct index_state *istate, char *name)
 	untracked_cache_invalidate_path(istate, name, 0);
 }
 
+/*
+ * The number of pathnames that we need to receive from FSMonitor
+ * before we force the index to be updated.
+ *
+ * Note that any pathname within the set of received paths MAY cause
+ * cache-entry or istate flag bits to be updated and thus cause the
+ * index to be updated on disk.
+ *
+ * However, the response may contain many paths (such as ignored
+ * paths) that will not update any flag bits.  And thus not force the
+ * index to be updated.  (This is fine and normal.)  It also means
+ * that the token will not be updated in the FSMonitor index
+ * extension.  So the next Git command will find the same token in the
+ * index, make the same token-relative request, and receive the same
+ * response (plus any newly changed paths).  If this response is large
+ * (and continues to grow), performance could be impacted.
+ *
+ * For example, if the user runs a build and it writes 100K object
+ * files but doesn't modify any source files, the index would not need
+ * to be updated.  The FSMonitor response (after the build and
+ * relative to a pre-build token) might be 5MB.  Each subsequent Git
+ * command will receive that same 100K/5MB response until something
+ * causes the index to be updated.  And `refresh_fsmonitor()` will
+ * have to iterate over those 100K paths each time.
+ *
+ * Performance could be improved if we optionally force update the
+ * index after a very large response and get an updated token into
+ * the FSMonitor index extension.  This should allow subsequent
+ * commands to get smaller and more current responses.
+ *
+ * The value chosen here does not need to be precise.  The index
+ * will be updated automatically the first time the user touches
+ * a tracked file and causes a command like `git status` to
+ * update an mtime to be updated and/or set a flag bit.
+ *
+ * NEEDSWORK: Does this need to be a config value?
+ */
+static int fsmonitor_force_update_threshold = 100;
+
 void refresh_fsmonitor(struct index_state *istate)
 {
 	struct strbuf query_result = STRBUF_INIT;

@@ -362,25 +401,39 @@ apply_results:
 	 *     information and that we should consider everything
 	 *     invalid.  We call this a trivial response.
 	 */
+	trace2_region_enter("fsmonitor", "apply_results", istate->repo);
+
 	if (query_success && !is_trivial) {
 		/*
 		 * Mark all pathnames returned by the monitor as dirty.
 		 *
 		 * This updates both the cache-entries and the untracked-cache.
 		 */
+		int count = 0;
+
 		buf = query_result.buf;
 		for (i = bol; i < query_result.len; i++) {
 			if (buf[i] != '\0')
 				continue;
 			fsmonitor_refresh_callback(istate, buf + bol);
 			bol = i + 1;
+			count++;
 		}
-		if (bol < query_result.len)
+		if (bol < query_result.len) {
 			fsmonitor_refresh_callback(istate, buf + bol);
+			count++;
+		}
 
 		/* Now mark the untracked cache for fsmonitor usage */
 		if (istate->untracked)
 			istate->untracked->use_fsmonitor = 1;
+
+		if (count > fsmonitor_force_update_threshold)
+			istate->cache_changed |= FSMONITOR_CHANGED;
+
+		trace2_data_intmax("fsmonitor", istate->repo, "apply_count",
+				   count);
+
 	} else {
 		/*
 		 * We failed to get a response or received a trivial response,

@@ -409,6 +462,8 @@ apply_results:
 		if (istate->untracked)
 			istate->untracked->use_fsmonitor = 0;
 	}
+	trace2_region_leave("fsmonitor", "apply_results", istate->repo);
+
 	strbuf_release(&query_result);
 
 	/* Now that we've updated istate, save the last_update_token */

index fed24ea1fb6..f94a89d30c8 100644
@@ -1227,18 +1227,18 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
 	if (fsmonitor > 0) {
 		enum fsmonitor_mode fsm_mode = fsm_settings__get_mode(r);
 		if (fsm_mode == FSMONITOR_MODE_DISABLED) {
-			warning(_("core.fsmonitor is unset; "
-				"set it if you really want to "
-				"enable fsmonitor"));
+			advise(_("core.fsmonitor is unset; "
+				 "set it if you really want to "
+				 "enable fsmonitor"));
 		}
 		add_fsmonitor(&the_index);
 		report(_("fsmonitor enabled"));
 	} else if (!fsmonitor) {
 		enum fsmonitor_mode fsm_mode = fsm_settings__get_mode(r);
 		if (fsm_mode > FSMONITOR_MODE_DISABLED)
-			warning(_("core.fsmonitor is set; "
-				"remove it if you really want to "
-				"disable fsmonitor"));
+			advise(_("core.fsmonitor is set; "
+				 "remove it if you really want to "
+				 "disable fsmonitor"));
 		remove_fsmonitor(&the_index);
 		report(_("fsmonitor disabled"));
 	}