gfs2: Fix atomic bug in gfs2_instantiate

Replace test_bit() + set_bit() with test_and_set_bit() where we need an atomic
operation.  Use clear_and_wake_up_bit() instead of open coding it.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 19f38aee1b618d8355fb7b50cdc3992e6c13ea94..258d8aae7c5355004f987a72b70456c908e3f6c9 100644 (file)
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -496,7 +496,7 @@ again:
         * Since we unlock the lockref lock, we set a flag to indicate
         * instantiate is in progress.
         */
-       if (test_bit(GLF_INSTANTIATE_IN_PROG, &gl->gl_flags)) {
+       if (test_and_set_bit(GLF_INSTANTIATE_IN_PROG, &gl->gl_flags)) {
                wait_on_bit(&gl->gl_flags, GLF_INSTANTIATE_IN_PROG,
                            TASK_UNINTERRUPTIBLE);
                /*
@@ -509,14 +509,10 @@ again:
                goto again;
        }
 
-       set_bit(GLF_INSTANTIATE_IN_PROG, &gl->gl_flags);
-
        ret = glops->go_instantiate(gh);
        if (!ret)
                clear_bit(GLF_INSTANTIATE_NEEDED, &gl->gl_flags);
-       clear_bit(GLF_INSTANTIATE_IN_PROG, &gl->gl_flags);
-       smp_mb__after_atomic();
-       wake_up_bit(&gl->gl_flags, GLF_INSTANTIATE_IN_PROG);
+       clear_and_wake_up_bit(GLF_INSTANTIATE_IN_PROG, &gl->gl_flags);
        return ret;
 }