1 files changed, 278 insertions, 0 deletions
diff --git a/compat/fsmonitor/fsm-health-win32.c b/compat/fsmonitor/fsm-health-win32.c
new file mode 100644
index 0000000..2ea08c1
--- /dev/null
+++ b/compat/fsmonitor/fsm-health-win32.c
@@ -0,0 +1,278 @@
+#include "cache.h"
+#include "config.h"
+#include "fsmonitor.h"
+#include "fsm-health.h"
+#include "fsmonitor--daemon.h"
+
+/*
+ * Every minute wake up and test our health.
+ */
+#define WAIT_FREQ_MS (60 * 1000)
+
+/*
+ * State machine states for each of the interval functions
+ * used for polling our health.
+ */
+enum interval_fn_ctx {
+	CTX_INIT = 0,
+	CTX_TERM,
+	CTX_TIMER
+};
+
+typedef int (interval_fn)(struct fsmonitor_daemon_state *state,
+			  enum interval_fn_ctx ctx);
+
+struct fsm_health_data
+{
+	HANDLE hEventShutdown;
+
+	HANDLE hHandles[1]; /* the array does not own these handles */
+#define HEALTH_SHUTDOWN 0
+	int nr_handles; /* number of active event handles */
+
+	struct wt_moved
+	{
+		wchar_t wpath[MAX_PATH + 1];
+		BY_HANDLE_FILE_INFORMATION bhfi;
+	} wt_moved;
+};
+
+/*
+ * Lookup the system unique ID for the path.  This is as close as
+ * we get to an inode number, but this also contains volume info,
+ * so it is a little stronger.
+ */
+static int lookup_bhfi(wchar_t *wpath,
+		       BY_HANDLE_FILE_INFORMATION *bhfi)
+{
+	DWORD desired_access = FILE_LIST_DIRECTORY;
+	DWORD share_mode =
+		FILE_SHARE_WRITE | FILE_SHARE_READ | FILE_SHARE_DELETE;
+	HANDLE hDir;
+
+	hDir = CreateFileW(wpath, desired_access, share_mode, NULL,
+			   OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, NULL);
+	if (hDir == INVALID_HANDLE_VALUE) {
+		error(_("[GLE %ld] health thread could not open '%ls'"),
+		      GetLastError(), wpath);
+		return -1;
+	}
+
+	if (!GetFileInformationByHandle(hDir, bhfi)) {
+		error(_("[GLE %ld] health thread getting BHFI for '%ls'"),
+		      GetLastError(), wpath);
+		CloseHandle(hDir);
+		return -1;
+	}
+
+	CloseHandle(hDir);
+	return 0;
+}
+
+/*
+ * Compare the relevant fields from two system unique IDs.
+ * We use this to see if two different handles to the same
+ * path actually refer to the same *instance* of the file
+ * or directory.
+ */
+static int bhfi_eq(const BY_HANDLE_FILE_INFORMATION *bhfi_1,
+		   const BY_HANDLE_FILE_INFORMATION *bhfi_2)
+{
+	return (bhfi_1->dwVolumeSerialNumber == bhfi_2->dwVolumeSerialNumber &&
+		bhfi_1->nFileIndexHigh == bhfi_2->nFileIndexHigh &&
+		bhfi_1->nFileIndexLow == bhfi_2->nFileIndexLow);
+}
+
+/*
+ * Shutdown if the original worktree root directory been deleted,
+ * moved, or renamed?
+ *
+ * Since the main thread did a "chdir(getenv($HOME))" and our CWD
+ * is not in the worktree root directory and because the listener
+ * thread added FILE_SHARE_DELETE to the watch handle, it is possible
+ * for the root directory to be moved or deleted while we are still
+ * watching it.  We want to detect that here and force a shutdown.
+ *
+ * Granted, a delete MAY cause some operations to fail, such as
+ * GetOverlappedResult(), but it is not guaranteed.  And because
+ * ReadDirectoryChangesW() only reports on changes *WITHIN* the
+ * directory, not changes *ON* the directory, our watch will not
+ * receive a delete event for it.
+ *
+ * A move/rename of the worktree root will also not generate an event.
+ * And since the listener thread already has an open handle, it may
+ * continue to receive events for events within the directory.
+ * However, the pathname of the named-pipe was constructed using the
+ * original location of the worktree root.  (Remember named-pipes are
+ * stored in the NPFS and not in the actual file system.)  Clients
+ * trying to talk to the worktree after the move/rename will not
+ * reach our daemon process, since we're still listening on the
+ * pipe with original path.
+ *
+ * Furthermore, if the user does something like:
+ *
+ *   $ mv repo repo.old
+ *   $ git init repo
+ *
+ * A new daemon cannot be started in the new instance of "repo"
+ * because the named-pipe is still being used by the daemon on
+ * the original instance.
+ *
+ * So, detect move/rename/delete and shutdown.  This should also
+ * handle unsafe drive removal.
+ *
+ * We use the file system unique ID to distinguish the original
+ * directory instance from a new instance and force a shutdown
+ * if the unique ID changes.
+ *
+ * Since a worktree move/rename/delete/unmount doesn't happen
+ * that often (and we can't get an immediate event anyway), we
+ * use a timeout and periodically poll it.
+ */
+static int has_worktree_moved(struct fsmonitor_daemon_state *state,
+			      enum interval_fn_ctx ctx)
+{
+	struct fsm_health_data *data = state->health_data;
+	BY_HANDLE_FILE_INFORMATION bhfi;
+	int r;
+
+	switch (ctx) {
+	case CTX_TERM:
+		return 0;
+
+	case CTX_INIT:
+		if (xutftowcs_path(data->wt_moved.wpath,
+				   state->path_worktree_watch.buf) < 0) {
+			error(_("could not convert to wide characters: '%s'"),
+			      state->path_worktree_watch.buf);
+			return -1;
+		}
+
+		/*
+		 * On the first call we lookup the unique sequence ID for
+		 * the worktree root directory.
+		 */
+		return lookup_bhfi(data->wt_moved.wpath, &data->wt_moved.bhfi);
+
+	case CTX_TIMER:
+		r = lookup_bhfi(data->wt_moved.wpath, &bhfi);
+		if (r)
+			return r;
+		if (!bhfi_eq(&data->wt_moved.bhfi, &bhfi)) {
+			error(_("BHFI changed '%ls'"), data->wt_moved.wpath);
+			return -1;
+		}
+		return 0;
+
+	default:
+		die(_("unhandled case in 'has_worktree_moved': %d"),
+		    (int)ctx);
+	}
+
+	return 0;
+}
+
+
+int fsm_health__ctor(struct fsmonitor_daemon_state *state)
+{
+	struct fsm_health_data *data;
+
+	CALLOC_ARRAY(data, 1);
+
+	data->hEventShutdown = CreateEvent(NULL, TRUE, FALSE, NULL);
+
+	data->hHandles[HEALTH_SHUTDOWN] = data->hEventShutdown;
+	data->nr_handles++;
+
+	state->health_data = data;
+	return 0;
+}
+
+void fsm_health__dtor(struct fsmonitor_daemon_state *state)
+{
+	struct fsm_health_data *data;
+
+	if (!state || !state->health_data)
+		return;
+
+	data = state->health_data;
+
+	CloseHandle(data->hEventShutdown);
+
+	FREE_AND_NULL(state->health_data);
+}
+
+/*
+ * A table of the polling functions.
+ */
+static interval_fn *table[] = {
+	has_worktree_moved,
+	NULL, /* must be last */
+};
+
+/*
+ * Call all of the polling functions in the table.
+ * Shortcut and return first error.
+ *
+ * Return 0 if all succeeded.
+ */
+static int call_all(struct fsmonitor_daemon_state *state,
+		    enum interval_fn_ctx ctx)
+{
+	int k;
+
+	for (k = 0; table[k]; k++) {
+		int r = table[k](state, ctx);
+		if (r)
+			return r;
+	}
+
+	return 0;
+}
+
+void fsm_health__loop(struct fsmonitor_daemon_state *state)
+{
+	struct fsm_health_data *data = state->health_data;
+	int r;
+
+	r = call_all(state, CTX_INIT);
+	if (r < 0)
+		goto force_error_stop;
+	if (r > 0)
+		goto force_shutdown;
+
+	for (;;) {
+		DWORD dwWait = WaitForMultipleObjects(data->nr_handles,
+						      data->hHandles,
+						      FALSE, WAIT_FREQ_MS);
+
+		if (dwWait == WAIT_OBJECT_0 + HEALTH_SHUTDOWN)
+			goto clean_shutdown;
+
+		if (dwWait == WAIT_TIMEOUT) {
+			r = call_all(state, CTX_TIMER);
+			if (r < 0)
+				goto force_error_stop;
+			if (r > 0)
+				goto force_shutdown;
+			continue;
+		}
+
+		error(_("health thread wait failed [GLE %ld]"),
+		      GetLastError());
+		goto force_error_stop;
+	}
+
+force_error_stop:
+	state->health_error_code = -1;
+force_shutdown:
+	ipc_server_stop_async(state->ipc_server_data);
+clean_shutdown:
+	call_all(state, CTX_TERM);
+	return;
+}
+
+void fsm_health__stop_async(struct fsmonitor_daemon_state *state)
+{
+	SetEvent(state->health_data->hHandles[HEALTH_SHUTDOWN]);
+}