[PATCH v3] fsmonitor: option to allow fsmonitor to run against network-mounted repos

From: Eric DeCosta <edecosta@mathworks.com>

Though perhaps not common, there are uses cases where users have large, network-mounted repos. Having the ability to run fsmonitor against network paths would benefit those users.

Most modern Samba-based filers have the necessary support to enable fsmonitor on network-mounted repos. As a first step towards enabling fsmonitor to work against network-mounted repos, introduce a configuration option, 'fsmonitor.allowRemote'. Setting this option to true will override the default behavior (erroring-out) when a network-mounted repo is detected by fsmonitor.

Signed-off-by: Eric DeCosta <edecosta@mathworks.com>
---
    Option to allow fsmonitor to run against repos on network file systems
    
    cc: Eric D eric.decosta@gmail.com

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1317%2Fedecosta-mw%2Fmaster-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1317/edecosta-mw/master-v3
Pull-Request: https://github.com/gitgitgadget/git/pull/1317

Range-diff vs v2:

 1:  7e67ce8c944 ! 1:  6c5f176cbee fsmonitor: option to allow fsmonitor to run against network-mounted repos
     @@ Commit message
          true will override the default behavior (erroring-out) when a
          network-mounted repo is detected by fsmonitor.
      
     -    Additionally, as part of this first step, monitoring of network-mounted
     -    repos will be restricted to those mounted over SMB regardless of the
     -    value of 'fsmonitor.allowRemote' until more extensive testing can be
     -    performed.
     -
          Signed-off-by: Eric DeCosta <edecosta@mathworks.com>
      
       ## compat/fsmonitor/fsm-settings-win32.c ##
     @@ compat/fsmonitor/fsm-settings-win32.c: static enum fsmonitor_reason check_vfs4gi
      +/*
      + * Check if monitoring remote working directories is allowed.
      + *
     -+ * By default monitoring remote working directories is not allowed,
     -+ * but users may override this behavior in enviroments where they
     -+ * have proper support.
     -+*/
     -+static enum fsmonitor_reason check_allow_remote(struct repository *r)
     ++ * By default, monitoring remote working directories is
     ++ * disabled unless on a network filesystem that is known to
     ++ * behave well.  Users may override this behavior in enviroments where
     ++ * they have proper support.
     ++ */
     ++static int check_config_allowremote(struct repository *r)
      +{
      +	int allow;
      +
     -+	if (repo_config_get_bool(r, "fsmonitor.allowremote", &allow) || !allow)
     -+		return FSMONITOR_REASON_REMOTE;
     ++	if (!repo_config_get_bool(r, "fsmonitor.allowremote", &allow))
     ++		return allow;
      +
     -+	return FSMONITOR_REASON_OK;
     ++	return -1; /* fsmonitor.allowremote not set */
      +}
      +
      +/*
     -+ * Check if the remote working directory is mounted via SMB
     ++ * Check remote working directory protocol.
      + *
     -+ * For now, remote working directories are only supported via SMB mounts
     -+*/
     -+static enum fsmonitor_reason check_smb(wchar_t *wpath)
     ++ * Error if client machine cannot get remote protocol information.
     ++ */
     ++static void check_remote_protocol(wchar_t *wpath)
      +{
      +	HANDLE h;
      +	FILE_REMOTE_PROTOCOL_INFO proto_info;
      +
      +	h = CreateFileW(wpath, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING,
     -+					FILE_FLAG_BACKUP_SEMANTICS, NULL);
     ++			FILE_FLAG_BACKUP_SEMANTICS, NULL);
      +
      +	if (h == INVALID_HANDLE_VALUE) {
      +		error(_("[GLE %ld] unable to open for read '%ls'"),
      +		      GetLastError(), wpath);
     -+		return FSMONITOR_REASON_ERROR;
     ++		return;
      +	}
      +
      +	if (!GetFileInformationByHandleEx(h, FileRemoteProtocolInfo,
     -+									&proto_info, sizeof(proto_info))) {
     ++		&proto_info, sizeof(proto_info))) {
      +		error(_("[GLE %ld] unable to get protocol information for '%ls'"),
      +		      GetLastError(), wpath);
      +		CloseHandle(h);
     -+		return FSMONITOR_REASON_ERROR;
     ++		return;
      +	}
      +
      +	CloseHandle(h);
      +
     -+	if (proto_info.Protocol == WNNC_NET_SMB)
     -+		return FSMONITOR_REASON_OK;
     ++	trace_printf_key(&trace_fsmonitor,
     ++				"check_remote_protocol('%ls') remote protocol %#8.8lx",
     ++				wpath, proto_info.Protocol);
      +
     -+	return FSMONITOR_REASON_ERROR;
     ++	return;
      +}
      +
       /*
        * Remote working directories are problematic for FSMonitor.
        *
     -@@ compat/fsmonitor/fsm-settings-win32.c: static enum fsmonitor_reason check_vfs4git(struct repository *r)
     -  */
     - static enum fsmonitor_reason check_remote(struct repository *r)
     - {
     -+	enum fsmonitor_reason reason;
     - 	wchar_t wpath[MAX_PATH];
     - 	wchar_t wfullpath[MAX_PATH];
     - 	size_t wlen;
      @@ compat/fsmonitor/fsm-settings-win32.c: static enum fsmonitor_reason check_remote(struct repository *r)
       		trace_printf_key(&trace_fsmonitor,
       				 "check_remote('%s') true",
       				 r->worktree);
     --		return FSMONITOR_REASON_REMOTE;
      +
     -+		reason = check_smb(wfullpath);
     -+		if (reason != FSMONITOR_REASON_OK)
     -+			return reason;
     -+		return check_allow_remote(r);
     ++		check_remote_protocol(wfullpath);
     ++
     ++		switch (check_config_allowremote(r)) {
     ++		case 0: /* config overrides and disables */
     ++			return FSMONITOR_REASON_REMOTE;
     ++		case 1: /* config overrides and enables */
     ++			return FSMONITOR_REASON_OK;
     ++		default:
     ++			break; /* config has no opinion */
     ++		}
     ++
     + 		return FSMONITOR_REASON_REMOTE;
       	}
       
     - 	return FSMONITOR_REASON_OK;
 2:  7a071c9e6be < -:  ----------- fsmonitor.allowRemote now overrides default behavior

 compat/fsmonitor/fsm-settings-win32.c | 66 +++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)