fsmonitor-settings: remote repos on Windows are incompatible
Teach Git to detect remote working directories on Windows and mark them as incompatible with FSMonitor. With this `git fsmonitor--daemon run` will error out with a message like it does for bare repos. Client commands, such as `git status`, will not attempt to start the daemon. Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Jeff Hostetler committed
May 26, 2022 at 21:47 UTC
d989b266c1a7ef47f27cec75e90f3dfefbfa0200
1 file changed
+102
compat/fsmonitor/fsm-settings-win32.c
+102
@@ -2,6 +2,7 @@
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#include "config.h"
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#include "repository.h"
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#include "fsmonitor-settings.h"
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+#include "fsmonitor.h"
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/*
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* VFS for Git is incompatible with FSMonitor.
@@ -23,6 +24,103 @@ static enum fsmonitor_reason check_vfs4git(struct repository *r)
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return FSMONITOR_REASON_OK;
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}
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+/*
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+ * Remote working directories are problematic for FSMonitor.
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+ *
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+ * The underlying file system on the server machine and/or the remote
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+ * mount type dictates whether notification events are available at
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+ * all to remote client machines.
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+ *
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+ * Kernel differences between the server and client machines also
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+ * dictate the how (buffering, frequency, de-dup) the events are
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+ * delivered to client machine processes.
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+ *
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+ * A client machine (such as a laptop) may choose to suspend/resume
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+ * and it is unclear (without lots of testing) whether the watcher can
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+ * resync after a resume. We might be able to treat this as a normal
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+ * "events were dropped by the kernel" event and do our normal "flush
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+ * and resync" --or-- we might need to close the existing (zombie?)
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+ * notification fd and create a new one.
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+ *
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+ * In theory, the above issues need to be addressed whether we are
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+ * using the Hook or IPC API.
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+ *
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+ * So (for now at least), mark remote working directories as
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+ * incompatible.
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+ *
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+ * Notes for testing:
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+ *
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+ * (a) Windows allows a network share to be mapped to a drive letter.
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+ * (This is the normal method to access it.)
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+ *
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+ * $ NET USE Z: \\server\share
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+ * $ git -C Z:/repo status
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+ *
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+ * (b) Windows allows a network share to be referenced WITHOUT mapping
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+ * it to drive letter.
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+ *
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+ * $ NET USE \\server\share\dir
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+ * $ git -C //server/share/repo status
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+ *
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+ * (c) Windows allows "SUBST" to create a fake drive mapping to an
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+ * arbitrary path (which may be remote)
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+ *
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+ * $ SUBST Q: Z:\repo
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+ * $ git -C Q:/ status
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+ *
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+ * (d) Windows allows a directory symlink to be created on a local
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+ * file system that points to a remote repo.
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+ *
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+ * $ mklink /d ./link //server/share/repo
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+ * $ git -C ./link status
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+ */
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+static enum fsmonitor_reason check_remote(struct repository *r)
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+{
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+ wchar_t wpath[MAX_PATH];
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+ wchar_t wfullpath[MAX_PATH];
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+ size_t wlen;
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+ UINT driveType;
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+
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+ /*
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+ * Do everything in wide chars because the drive letter might be
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+ * a multi-byte sequence. See win32_has_dos_drive_prefix().
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+ */
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+ if (xutftowcs_path(wpath, r->worktree) < 0)
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+ return FSMONITOR_REASON_ERROR;
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+
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+ /*
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+ * GetDriveTypeW() requires a final slash. We assume that the
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+ * worktree pathname points to an actual directory.
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+ */
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+ wlen = wcslen(wpath);
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+ if (wpath[wlen - 1] != L'\\' && wpath[wlen - 1] != L'/') {
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+ wpath[wlen++] = L'\\';
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+ wpath[wlen] = 0;
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+ }
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+
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+ /*
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+ * Normalize the path. If nothing else, this converts forward
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+ * slashes to backslashes. This is essential to get GetDriveTypeW()
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+ * correctly handle some UNC "\\server\share\..." paths.
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+ */
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+ if (!GetFullPathNameW(wpath, MAX_PATH, wfullpath, NULL))
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+ return FSMONITOR_REASON_ERROR;
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+
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+ driveType = GetDriveTypeW(wfullpath);
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+ trace_printf_key(&trace_fsmonitor,
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+ "DriveType '%s' L'%ls' (%u)",
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+ r->worktree, wfullpath, driveType);
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+
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+ if (driveType == DRIVE_REMOTE) {
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+ trace_printf_key(&trace_fsmonitor,
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+ "check_remote('%s') true",
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+ r->worktree);
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+ return FSMONITOR_REASON_REMOTE;
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+ }
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+
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+ return FSMONITOR_REASON_OK;
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+}
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+
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enum fsmonitor_reason fsm_os__incompatible(struct repository *r)
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{
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enum fsmonitor_reason reason;
@@ -31,5 +129,9 @@ enum fsmonitor_reason fsm_os__incompatible(struct repository *r)
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if (reason != FSMONITOR_REASON_OK)
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return reason;
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+ reason = check_remote(r);
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+ if (reason != FSMONITOR_REASON_OK)
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+ return reason;
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+
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return FSMONITOR_REASON_OK;
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}