compat/fsmonitor/fsm-settings-win32.c

   1 #include "cache.h"
   2 #include "config.h"
   3 #include "repository.h"
   4 #include "fsmonitor-settings.h"
   5 #include "fsmonitor.h"
   6
   7 /*
   8  * VFS for Git is incompatible with FSMonitor.
   9  *
  10  * Granted, core Git does not know anything about VFS for Git and we
  11  * shouldn't make assumptions about a downstream feature, but users
  12  * can install both versions.  And this can lead to incorrect results
  13  * from core Git commands.  So, without bringing in any of the VFS for
  14  * Git code, do a simple config test for a published config setting.
  15  * (We do not look at the various *_TEST_* environment variables.)
  16  */
  17 static enum fsmonitor_reason check_vfs4git(struct repository *r)
  18 {
  19         const char *const_str;
  20
  21         if (!repo_config_get_value(r, "core.virtualfilesystem", &const_str))
  22                 return FSMONITOR_REASON_VFS4GIT;
  23
  24         return FSMONITOR_REASON_OK;
  25 }
  26
  27 /*
  28  * Remote working directories are problematic for FSMonitor.
  29  *
  30  * The underlying file system on the server machine and/or the remote
  31  * mount type dictates whether notification events are available at
  32  * all to remote client machines.
  33  *
  34  * Kernel differences between the server and client machines also
  35  * dictate the how (buffering, frequency, de-dup) the events are
  36  * delivered to client machine processes.
  37  *
  38  * A client machine (such as a laptop) may choose to suspend/resume
  39  * and it is unclear (without lots of testing) whether the watcher can
  40  * resync after a resume.  We might be able to treat this as a normal
  41  * "events were dropped by the kernel" event and do our normal "flush
  42  * and resync" --or-- we might need to close the existing (zombie?)
  43  * notification fd and create a new one.
  44  *
  45  * In theory, the above issues need to be addressed whether we are
  46  * using the Hook or IPC API.
  47  *
  48  * So (for now at least), mark remote working directories as
  49  * incompatible.
  50  *
  51  * Notes for testing:
  52  *
  53  * (a) Windows allows a network share to be mapped to a drive letter.
  54  *     (This is the normal method to access it.)
  55  *
  56  *     $ NET USE Z: \\server\share
  57  *     $ git -C Z:/repo status
  58  *
  59  * (b) Windows allows a network share to be referenced WITHOUT mapping
  60  *     it to drive letter.
  61  *
  62  *     $ NET USE \\server\share\dir
  63  *     $ git -C //server/share/repo status
  64  *
  65  * (c) Windows allows "SUBST" to create a fake drive mapping to an
  66  *     arbitrary path (which may be remote)
  67  *
  68  *     $ SUBST Q: Z:\repo
  69  *     $ git -C Q:/ status
  70  *
  71  * (d) Windows allows a directory symlink to be created on a local
  72  *     file system that points to a remote repo.
  73  *
  74  *     $ mklink /d ./link //server/share/repo
  75  *     $ git -C ./link status
  76  */
  77 static enum fsmonitor_reason check_remote(struct repository *r)
  78 {
  79         wchar_t wpath[MAX_PATH];
  80         wchar_t wfullpath[MAX_PATH];
  81         size_t wlen;
  82         UINT driveType;
  83
  84         /*
  85          * Do everything in wide chars because the drive letter might be
  86          * a multi-byte sequence.  See win32_has_dos_drive_prefix().
  87          */
  88         if (xutftowcs_path(wpath, r->worktree) < 0)
  89                 return FSMONITOR_REASON_ERROR;
  90
  91         /*
  92          * GetDriveTypeW() requires a final slash.  We assume that the
  93          * worktree pathname points to an actual directory.
  94          */
  95         wlen = wcslen(wpath);
  96         if (wpath[wlen - 1] != L'\\' && wpath[wlen - 1] != L'/') {
  97                 wpath[wlen++] = L'\\';
  98                 wpath[wlen] = 0;
  99         }
 100
 101         /*
 102          * Normalize the path.  If nothing else, this converts forward
 103          * slashes to backslashes.  This is essential to get GetDriveTypeW()
 104          * correctly handle some UNC "\\server\share\..." paths.
 105          */
 106         if (!GetFullPathNameW(wpath, MAX_PATH, wfullpath, NULL))
 107                 return FSMONITOR_REASON_ERROR;
 108
 109         driveType = GetDriveTypeW(wfullpath);
 110         trace_printf_key(&trace_fsmonitor,
 111                          "DriveType '%s' L'%ls' (%u)",
 112                          r->worktree, wfullpath, driveType);
 113
 114         if (driveType == DRIVE_REMOTE) {
 115                 trace_printf_key(&trace_fsmonitor,
 116                                  "check_remote('%s') true",
 117                                  r->worktree);
 118                 return FSMONITOR_REASON_REMOTE;
 119         }
 120
 121         return FSMONITOR_REASON_OK;
 122 }
 123
 124 enum fsmonitor_reason fsm_os__incompatible(struct repository *r)
 125 {
 126         enum fsmonitor_reason reason;
 127
 128         reason = check_vfs4git(r);
 129         if (reason != FSMONITOR_REASON_OK)
 130                 return reason;
 131
 132         reason = check_remote(r);
 133         if (reason != FSMONITOR_REASON_OK)
 134                 return reason;
 135
 136         return FSMONITOR_REASON_OK;
 137 }