mm: Rename SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU

A group of Linux kernel hackers reported chasing a bug that resulted
from their assumption that SLAB_DESTROY_BY_RCU provided an existence
guarantee, that is, that no block from such a slab would be reallocated
during an RCU read-side critical section.  Of course, that is not the
case.  Instead, SLAB_DESTROY_BY_RCU only prevents freeing of an entire
slab of blocks.

However, there is a phrase for this, namely "type safety".  This commit
therefore renames SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU in order
to avoid future instances of this sort of confusion.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: <linux-mm@kvack.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
[ paulmck: Add comments mentioning the old name, as requested by Eric
  Dumazet, in order to help people familiar with the old name find
  the new one. ]
Acked-by: David Rientjes <rientjes@google.com>

3 files changed, 4 insertions, 4 deletions

diff --git a/net/llc/af_llc.c b/net/llc/af_llc.c
index 06186d608a27..d096ca563054 100644
--- a/net/llc/af_llc.c
+++ b/net/llc/af_llc.c
@@ -142,7 +142,7 @@ static struct proto llc_proto = {
         .name     = "LLC",
         .owner    = THIS_MODULE,
         .obj_size = sizeof(struct llc_sock),
-        .slab_flags = SLAB_DESTROY_BY_RCU,
+        .slab_flags = SLAB_TYPESAFE_BY_RCU,
 };
 
 /**
diff --git a/net/llc/llc_conn.c b/net/llc/llc_conn.c
index 8bc5a1bd2d45..9b02c13d258b 100644
--- a/net/llc/llc_conn.c
+++ b/net/llc/llc_conn.c
@@ -506,7 +506,7 @@ static struct sock *__llc_lookup_established(struct llc_sap *sap,
 again:
         sk_nulls_for_each_rcu(rc, node, laddr_hb) {
                 if (llc_estab_match(sap, daddr, laddr, rc)) {
-                        /* Extra checks required by SLAB_DESTROY_BY_RCU */
+                        /* Extra checks required by SLAB_TYPESAFE_BY_RCU */
                         if (unlikely(!atomic_inc_not_zero(&rc->sk_refcnt)))
                                 goto again;
                         if (unlikely(llc_sk(rc)->sap != sap ||
@@ -565,7 +565,7 @@ static struct sock *__llc_lookup_listener(struct llc_sap *sap,
 again:
         sk_nulls_for_each_rcu(rc, node, laddr_hb) {
                 if (llc_listener_match(sap, laddr, rc)) {
-                        /* Extra checks required by SLAB_DESTROY_BY_RCU */
+                        /* Extra checks required by SLAB_TYPESAFE_BY_RCU */
                         if (unlikely(!atomic_inc_not_zero(&rc->sk_refcnt)))
                                 goto again;
                         if (unlikely(llc_sk(rc)->sap != sap ||
diff --git a/net/llc/llc_sap.c b/net/llc/llc_sap.c
index 5404d0d195cc..63b6ab056370 100644
--- a/net/llc/llc_sap.c
+++ b/net/llc/llc_sap.c
@@ -328,7 +328,7 @@ static struct sock *llc_lookup_dgram(struct llc_sap *sap,
 again:
         sk_nulls_for_each_rcu(rc, node, laddr_hb) {
                 if (llc_dgram_match(sap, laddr, rc)) {
-                        /* Extra checks required by SLAB_DESTROY_BY_RCU */
+                        /* Extra checks required by SLAB_TYPESAFE_BY_RCU */
                         if (unlikely(!atomic_inc_not_zero(&rc->sk_refcnt)))
                                 goto again;
                         if (unlikely(llc_sk(rc)->sap != sap ||