sunrpc: remove xpt_pool

The xpt_pool field is only used for reporting BUGs.
And it isn't used correctly.

In particular, when it is cleared in svc_xprt_received before
XPT_BUSY is cleared, there is no guarantee that either the
compiler or the CPU might not re-order to two assignments, just
setting xpt_pool to NULL after XPT_BUSY is cleared.

If a different cpu were running svc_xprt_enqueue at this moment,
it might see XPT_BUSY clear and then xpt_pool non-NULL, and
so BUG.

This could be fixed by calling
  smp_mb__before_clear_bit()
before the clear_bit.  However as xpt_pool isn't really used,
it seems safest to simply remove xpt_pool.

Another alternate would be to change the clear_bit to
clear_bit_unlock, and the test_and_set_bit to test_and_set_bit_lock.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 0 insertions, 1 deletions

diff --git a/include/linux/sunrpc/svc_xprt.h b/include/linux/sunrpc/svc_xprt.h
index aea0d438e3c7..c8f81da15c7e 100644
--- a/include/linux/sunrpc/svc_xprt.h
+++ b/include/linux/sunrpc/svc_xprt.h
@@ -63,7 +63,6 @@ struct svc_xprt {
 #define XPT_LISTENER    11              /* listening endpoint */
 #define XPT_CACHE_AUTH  12              /* cache auth info */
 
-        struct svc_pool         *xpt_pool;      /* current pool iff queued */
         struct svc_serv         *xpt_server;    /* service for transport */
         atomic_t                xpt_reserved;   /* space on outq that is rsvd */
         struct mutex            xpt_mutex;      /* to serialize sending data */