LU-6049 obdclass: Add synchro in lu_context_key_degister()

[fs/lustre-release.git] / lustre / obdclass / lu_object.c

diff --git a/lustre/obdclass/lu_object.c b/lustre/obdclass/lu_object.c
index dac8c2a..1ce045d 100644 (file)
--- a/lustre/obdclass/lu_object.c
+++ b/lustre/obdclass/lu_object.c
@@ -1365,6 +1365,7 @@ enum {
 static struct lu_context_key *lu_keys[LU_CONTEXT_KEY_NR] = { NULL, };
 
 static DEFINE_SPINLOCK(lu_keys_guard);
+static atomic_t lu_key_initing_cnt = ATOMIC_INIT(0);
 
 /**
  * Global counter incremented whenever key is registered, unregistered,
@@ -1441,6 +1442,19 @@ void lu_context_key_degister(struct lu_context_key *key)
        ++key_set_version;
        spin_lock(&lu_keys_guard);
        key_fini(&lu_shrink_env.le_ctx, key->lct_index);
+
+       /**
+        * Wait until all transient contexts referencing this key have
+        * run lu_context_key::lct_fini() method.
+        */
+       while (atomic_read(&key->lct_used) > 1) {
+               spin_unlock(&lu_keys_guard);
+               CDEBUG(D_INFO, "lu_context_key_degister: \"%s\" %p, %d\n",
+                      key->lct_owner ? key->lct_owner->name : "", key,
+                      atomic_read(&key->lct_used));
+               schedule();
+               spin_lock(&lu_keys_guard);
+       }
        if (lu_keys[key->lct_index]) {
                lu_keys[key->lct_index] = NULL;
                lu_ref_fini(&key->lct_reference);
@@ -1567,11 +1581,27 @@ void lu_context_key_quiesce(struct lu_context_key *key)
                  * XXX layering violation.
                  */
                 cl_env_cache_purge(~0);
-                key->lct_tags |= LCT_QUIESCENT;
                 /*
                  * XXX memory barrier has to go here.
                  */
                spin_lock(&lu_keys_guard);
+               key->lct_tags |= LCT_QUIESCENT;
+
+               /**
+                * Wait until all lu_context_key::lct_init() methods
+                * have completed.
+                */
+               while (atomic_read(&lu_key_initing_cnt) > 0) {
+                       spin_unlock(&lu_keys_guard);
+                       CDEBUG(D_INFO, "lu_context_key_quiesce: \"%s\""
+                              " %p, %d (%d)\n",
+                              key->lct_owner ? key->lct_owner->name : "",
+                              key, atomic_read(&key->lct_used),
+                              atomic_read(&lu_key_initing_cnt));
+                       schedule();
+                       spin_lock(&lu_keys_guard);
+               }
+
                list_for_each_entry(ctx, &lu_context_remembered,
                                    lc_remember)
                        key_fini(ctx, key->lct_index);
@@ -1604,6 +1634,19 @@ static int keys_fill(struct lu_context *ctx)
 {
        unsigned int i;
 
+       /*
+        * A serialisation with lu_context_key_quiesce() is needed, but some
+        * "key->lct_init()" are calling kernel memory allocation routine and
+        * can't be called while holding a spin_lock.
+        * "lu_keys_guard" is held while incrementing "lu_key_initing_cnt"
+        * to ensure the start of the serialisation.
+        * An atomic_t variable is still used, in order not to reacquire the
+        * lock when decrementing the counter.
+        */
+       spin_lock(&lu_keys_guard);
+       atomic_inc(&lu_key_initing_cnt);
+       spin_unlock(&lu_keys_guard);
+
         LINVRNT(ctx->lc_value != NULL);
         for (i = 0; i < ARRAY_SIZE(lu_keys); ++i) {
                 struct lu_context_key *key;
@@ -1621,13 +1664,19 @@ static int keys_fill(struct lu_context *ctx)
                         LINVRNT(key->lct_init != NULL);
                         LINVRNT(key->lct_index == i);
 
-                        value = key->lct_init(ctx, key);
-                        if (unlikely(IS_ERR(value)))
-                                return PTR_ERR(value);
-
                        LASSERT(key->lct_owner != NULL);
-                       if (!(ctx->lc_tags & LCT_NOREF))
-                               try_module_get(key->lct_owner);
+                       if (!(ctx->lc_tags & LCT_NOREF) &&
+                           try_module_get(key->lct_owner) == 0) {
+                               /* module is unloading, skip this key */
+                               continue;
+                       }
+
+                       value = key->lct_init(ctx, key);
+                       if (unlikely(IS_ERR(value))) {
+                               atomic_dec(&lu_key_initing_cnt);
+                               return PTR_ERR(value);
+                       }
+
                        lu_ref_add_atomic(&key->lct_reference, "ctx", ctx);
                        atomic_inc(&key->lct_used);
                         /*
@@ -1641,6 +1690,7 @@ static int keys_fill(struct lu_context *ctx)
                 }
                 ctx->lc_version = key_set_version;
         }
+       atomic_dec(&lu_key_initing_cnt);
         return 0;
 }