commit 364b2e413c69 ("sbitmapq: remove struct and member validation
in sbitmapq_init()") lifted the use of the "sbitmapq" command
unconditionally.  Without the patch, the command fails with the
following error on kernels without sbitmap:

   crash> sbitmapq ffff88015796e550

   sbitmapq: invalid structure member offset: sbitmap_queue_sb
             FILE: sbitmap.c  LINE: 385  FUNCTION: sbitmap_queue_context_load()

Now the command supports Linux 4.9 and later kernels since it was
abstracted out, so it can be limited by the non-existence of the
sbitmap structure.

Signed-off-by: Kazuhito Hagio <k-hagio-ab@nec.com>
---
  sbitmap.c | 4 ++++
  1 file changed, 4 insertions(+)

diff --git a/sbitmap.c b/sbitmap.c
index be5d30a8ea88..12d6512a1e4d 100644
--- a/sbitmap.c
+++ b/sbitmap.c
@@ -540,6 +540,10 @@ void sbitmapq_init(void)
        STRUCT_SIZE_INIT(sbitmap_queue, "sbitmap_queue");
        STRUCT_SIZE_INIT(sbq_wait_state, "sbq_wait_state");

+       /* sbitmap was abstracted out by commit 88459642cba4 on Linux 4.9. */
+       if (INVALID_SIZE(sbitmap))
+               command_not_supported();
+
        MEMBER_OFFSET_INIT(sbitmap_word_depth, "sbitmap_word", "depth");
        MEMBER_OFFSET_INIT(sbitmap_word_word, "sbitmap_word", "word");
        MEMBER_OFFSET_INIT(sbitmap_word_cleared, "sbitmap_word", "cleared");
--
2.31.1