vlserver: --enable-ubik-read-while-write configure option

Commit a0f416e3504929b304fefb5ca65e2d6a254ade2e unconditionally turned
on the new ubik_BeginTransReadAnyWrite functionality for the vlserver,
which allows us to read data from ubik during a conflicting ubik write
lock.

This feature is not ready for production use. Make it a build time
option, marked as experimental, until more testing can be done.

Change-Id: If64702e7a7ed2340066df5faf82ce8b0875fc610
Reviewed-on: https://gerrit.openafs.org/12240
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>

diff --git a/acinclude.m4 b/acinclude.m4
index 0a90e16..cacec2e 100644 (file)
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -111,6 +111,11 @@ AC_ARG_ENABLE([pthreaded-ubik],
          enabled)])],
     [],
     [enable_pthreaded_ubik="yes"])
+AC_ARG_ENABLE([ubik-read-while-write],
+    [AS_HELP_STRING([--enable-ubik-read-while-write],
+       [enable vlserver read from db cache during write locks (EXPERIMENTAL)])],
+    [],
+    [enable_ubik_read_while_write="no"])
 
 dnl Kernel module build options.
 AC_ARG_WITH([linux-kernel-headers],
@@ -1409,6 +1414,10 @@ else
 fi
 AC_SUBST(USE_UNIX_SOCKETS)
 
+if test "$enable_ubik_read_while_write" = "yes"; then
+       AC_DEFINE(UBIK_READ_WHILE_WRITE, 1, [define if you want to enable ubik read while write])
+fi
+
 if test "$enable_namei_fileserver" = "yes"; then
        AC_DEFINE(AFS_NAMEI_ENV, 1, [define if you want to want namei fileserver])
        VFSCK=""

diff --git a/src/cf/summary.m4 b/src/cf/summary.m4
index 111b22c..0ac9fc0 100644 (file)
--- a/src/cf/summary.m4
+++ b/src/cf/summary.m4
@@ -69,6 +69,7 @@ options:
   ptserver supergroups   : ${enable_supergroups}
   pthreaded ubik         : ${enable_pthreaded_ubik}
   install kauth          : ${INSTALL_KAUTH}
+  ubik read while write  : ${enable_ubik_read_while_write}
 build:
   scout/afsmonitor       : ${summary_build_scout}
   pam                    : ${HAVE_PAM}

diff --git a/src/vlserver/vlprocs.c b/src/vlserver/vlprocs.c
index 78f9ba6..016ff51 100644 (file)
--- a/src/vlserver/vlprocs.c
+++ b/src/vlserver/vlprocs.c
@@ -206,8 +206,11 @@ Init_VLdbase(struct vl_ctx *ctx,
            code = ubik_BeginTrans(VL_dbase, UBIK_WRITETRANS, &ctx->trans);
            wl = 1;
        } else if (locktype == LOCKREAD) {
-           code =
-               ubik_BeginTransReadAnyWrite(VL_dbase, UBIK_READTRANS, &ctx->trans);
+#ifdef UBIK_READ_WHILE_WRITE
+           code = ubik_BeginTransReadAnyWrite(VL_dbase, UBIK_READTRANS, &ctx->trans);
+#else
+           code = ubik_BeginTransReadAny(VL_dbase, UBIK_READTRANS, &ctx->trans);
+#endif
            wl = 0;
        } else {
            code = ubik_BeginTrans(VL_dbase, UBIK_WRITETRANS, &ctx->trans);