releases/5.15.154/sunrpc-always-treat-sv_nrpools-1-as-not-pooled.patch

   1 From 09497160e5a2af55cefe2a0903fff5ac803cc63a Mon Sep 17 00:00:00 2001
   2 From: Sasha Levin <sashal@kernel.org>
   3 Date: Mon, 29 Nov 2021 15:51:25 +1100
   4 Subject: SUNRPC: always treat sv_nrpools==1 as "not pooled"
   5
   6 From: NeilBrown <neilb@suse.de>
   7
   8 [ Upstream commit 93aa619eb0b42eec2f3a9b4d9db41f5095390aec ]
   9
  10 Currently 'pooled' services hold a reference on the pool_map, and
  11 'unpooled' services do not.
  12 svc_destroy() uses the presence of ->svo_function (via
  13 svc_serv_is_pooled()) to determine if the reference should be dropped.
  14 There is no direct correlation between being pooled and the use of
  15 svo_function, though in practice, lockd is the only non-pooled service,
  16 and the only one not to use svo_function.
  17
  18 This is untidy and would cause problems if we changed lockd to use
  19 svc_set_num_threads(), which requires the use of ->svo_function.
  20
  21 So change the test for "is the service pooled" to "is sv_nrpools > 1".
  22
  23 This means that when svc_pool_map_get() returns 1, it must NOT take a
  24 reference to the pool.
  25
  26 We discard svc_serv_is_pooled(), and test sv_nrpools directly.
  27
  28 Signed-off-by: NeilBrown <neilb@suse.de>
  29 Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
  30 ---
  31  net/sunrpc/svc.c | 54 ++++++++++++++++++++++++++----------------------
  32  1 file changed, 29 insertions(+), 25 deletions(-)
  33
  34 diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
  35 index 8fbfea9f2a04c..fee7a22578b64 100644
  36 --- a/net/sunrpc/svc.c
  37 +++ b/net/sunrpc/svc.c
  38 @@ -37,8 +37,6 @@
  39
  40  static void svc_unregister(const struct svc_serv *serv, struct net *net);
  41
  42 -#define svc_serv_is_pooled(serv)    ((serv)->sv_ops->svo_function)
  43 -
  44  #define SVC_POOL_DEFAULT       SVC_POOL_GLOBAL
  45
  46  /*
  47 @@ -240,8 +238,10 @@ svc_pool_map_init_pernode(struct svc_pool_map *m)
  48
  49  /*
  50   * Add a reference to the global map of cpus to pools (and
  51 - * vice versa).  Initialise the map if we're the first user.
  52 - * Returns the number of pools.
  53 + * vice versa) if pools are in use.
  54 + * Initialise the map if we're the first user.
  55 + * Returns the number of pools. If this is '1', no reference
  56 + * was taken.
  57   */
  58  static unsigned int
  59  svc_pool_map_get(void)
  60 @@ -253,6 +253,7 @@ svc_pool_map_get(void)
  61
  62         if (m->count++) {
  63                 mutex_unlock(&svc_pool_map_mutex);
  64 +               WARN_ON_ONCE(m->npools <= 1);
  65                 return m->npools;
  66         }
  67
  68 @@ -268,29 +269,36 @@ svc_pool_map_get(void)
  69                 break;
  70         }
  71
  72 -       if (npools < 0) {
  73 +       if (npools <= 0) {
  74                 /* default, or memory allocation failure */
  75                 npools = 1;
  76                 m->mode = SVC_POOL_GLOBAL;
  77         }
  78         m->npools = npools;
  79
  80 +       if (npools == 1)
  81 +               /* service is unpooled, so doesn't hold a reference */
  82 +               m->count--;
  83 +
  84         mutex_unlock(&svc_pool_map_mutex);
  85 -       return m->npools;
  86 +       return npools;
  87  }
  88
  89  /*
  90 - * Drop a reference to the global map of cpus to pools.
  91 + * Drop a reference to the global map of cpus to pools, if
  92 + * pools were in use, i.e. if npools > 1.
  93   * When the last reference is dropped, the map data is
  94   * freed; this allows the sysadmin to change the pool
  95   * mode using the pool_mode module option without
  96   * rebooting or re-loading sunrpc.ko.
  97   */
  98  static void
  99 -svc_pool_map_put(void)
 100 +svc_pool_map_put(int npools)
 101  {
 102         struct svc_pool_map *m = &svc_pool_map;
 103
 104 +       if (npools <= 1)
 105 +               return;
 106         mutex_lock(&svc_pool_map_mutex);
 107
 108         if (!--m->count) {
 109 @@ -359,21 +367,18 @@ svc_pool_for_cpu(struct svc_serv *serv, int cpu)
 110         struct svc_pool_map *m = &svc_pool_map;
 111         unsigned int pidx = 0;
 112
 113 -       /*
 114 -        * An uninitialised map happens in a pure client when
 115 -        * lockd is brought up, so silently treat it the
 116 -        * same as SVC_POOL_GLOBAL.
 117 -        */
 118 -       if (svc_serv_is_pooled(serv)) {
 119 -               switch (m->mode) {
 120 -               case SVC_POOL_PERCPU:
 121 -                       pidx = m->to_pool[cpu];
 122 -                       break;
 123 -               case SVC_POOL_PERNODE:
 124 -                       pidx = m->to_pool[cpu_to_node(cpu)];
 125 -                       break;
 126 -               }
 127 +       if (serv->sv_nrpools <= 1)
 128 +               return serv->sv_pools;
 129 +
 130 +       switch (m->mode) {
 131 +       case SVC_POOL_PERCPU:
 132 +               pidx = m->to_pool[cpu];
 133 +               break;
 134 +       case SVC_POOL_PERNODE:
 135 +               pidx = m->to_pool[cpu_to_node(cpu)];
 136 +               break;
 137         }
 138 +
 139         return &serv->sv_pools[pidx % serv->sv_nrpools];
 140  }
 141
 142 @@ -526,7 +531,7 @@ svc_create_pooled(struct svc_program *prog, unsigned int bufsize,
 143                 goto out_err;
 144         return serv;
 145  out_err:
 146 -       svc_pool_map_put();
 147 +       svc_pool_map_put(npools);
 148         return NULL;
 149  }
 150  EXPORT_SYMBOL_GPL(svc_create_pooled);
 151 @@ -561,8 +566,7 @@ svc_destroy(struct kref *ref)
 152
 153         cache_clean_deferred(serv);
 154
 155 -       if (svc_serv_is_pooled(serv))
 156 -               svc_pool_map_put();
 157 +       svc_pool_map_put(serv->sv_nrpools);
 158
 159         kfree(serv->sv_pools);
 160         kfree(serv);
 161 --
 162 2.43.0
 163