LU-11089 obd: rename lu_keys_guard to lu_context_remembered_guard

The only remaining use of lu_keys_guard is to protect the
lu_context_remembers linked list, and always write_lock()
is used.
So rename it to reflect this, and change to a spinlock.
We move keys_fini() out of the locked region in
lu_context_fini() - once we have removed the context from
the lc_remembers list, there can no longer be a race.

Linux-commit: dc8aaaca0062878c2fbad9df1b9ac3e85cad8630

Change-Id: Id66930e073d5351a96b139f2fc1a8007841de728
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: https://review.whamcloud.com/33673
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Gu Zheng <gzheng@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>

diff --git a/lustre/obdclass/lu_object.c b/lustre/obdclass/lu_object.c
index a236b61..fbe034a 100644 (file)
--- a/lustre/obdclass/lu_object.c
+++ b/lustre/obdclass/lu_object.c
@@ -1351,7 +1351,6 @@ enum {
 
 static struct lu_context_key *lu_keys[LU_CONTEXT_KEY_NR] = { NULL, };
 
-DEFINE_RWLOCK(lu_keys_guard);
 static DECLARE_RWSEM(lu_key_initing);
 
 /**
@@ -1405,7 +1404,7 @@ static void key_fini(struct lu_context *ctx, int index)
                 key = lu_keys[index];
                 LASSERT(key != NULL);
                 LASSERT(key->lct_fini != NULL);
-               LASSERT(atomic_read(&key->lct_used) > 1);
+               LASSERT(atomic_read(&key->lct_used) > 0);
 
                 key->lct_fini(ctx, key, ctx->lc_value[index]);
                 lu_ref_del(&key->lct_reference, "ctx", ctx);
@@ -1545,6 +1544,7 @@ EXPORT_SYMBOL(lu_context_key_get);
  * List of remembered contexts. XXX document me.
  */
 static LIST_HEAD(lu_context_remembered);
+static DEFINE_SPINLOCK(lu_context_remembered_guard);
 
 /**
  * Destroy \a key in all remembered contexts. This is used to destroy key
@@ -1565,13 +1565,13 @@ void lu_context_key_quiesce(struct lu_context_key *key)
                key->lct_tags |= LCT_QUIESCENT;
                up_write(&lu_key_initing);
 
-               write_lock(&lu_keys_guard);
+               spin_lock(&lu_context_remembered_guard);
                list_for_each_entry(ctx, &lu_context_remembered, lc_remember) {
                        spin_until_cond(READ_ONCE(ctx->lc_state) != LCS_LEAVING);
                        key_fini(ctx, key->lct_index);
                }
 
-               write_unlock(&lu_keys_guard);
+               spin_unlock(&lu_context_remembered_guard);
        }
 }
 
@@ -1677,9 +1677,9 @@ int lu_context_init(struct lu_context *ctx, __u32 tags)
        ctx->lc_state = LCS_INITIALIZED;
        ctx->lc_tags = tags;
        if (tags & LCT_REMEMBER) {
-               write_lock(&lu_keys_guard);
+               spin_lock(&lu_context_remembered_guard);
                list_add(&ctx->lc_remember, &lu_context_remembered);
-               write_unlock(&lu_keys_guard);
+               spin_unlock(&lu_context_remembered_guard);
        } else {
                INIT_LIST_HEAD(&ctx->lc_remember);
        }
@@ -1702,14 +1702,13 @@ void lu_context_fini(struct lu_context *ctx)
 
        if ((ctx->lc_tags & LCT_REMEMBER) == 0) {
                LASSERT(list_empty(&ctx->lc_remember));
-               keys_fini(ctx);
-
-       } else { /* could race with key degister */
-               write_lock(&lu_keys_guard);
-               keys_fini(ctx);
+       } else {
+               /* could race with key degister */
+               spin_lock(&lu_context_remembered_guard);
                list_del_init(&ctx->lc_remember);
-               write_unlock(&lu_keys_guard);
+               spin_unlock(&lu_context_remembered_guard);
        }
+       keys_fini(ctx);
 }
 EXPORT_SYMBOL(lu_context_fini);
 
@@ -1788,37 +1787,37 @@ u32 lu_session_tags_default;
 #ifdef HAVE_SERVER_SUPPORT
 void lu_context_tags_update(__u32 tags)
 {
-       write_lock(&lu_keys_guard);
+       spin_lock(&lu_context_remembered_guard);
        lu_context_tags_default |= tags;
        atomic_inc(&key_set_version);
-       write_unlock(&lu_keys_guard);
+       spin_unlock(&lu_context_remembered_guard);
 }
 EXPORT_SYMBOL(lu_context_tags_update);
 
 void lu_context_tags_clear(__u32 tags)
 {
-       write_lock(&lu_keys_guard);
+       spin_lock(&lu_context_remembered_guard);
        lu_context_tags_default &= ~tags;
        atomic_inc(&key_set_version);
-       write_unlock(&lu_keys_guard);
+       spin_unlock(&lu_context_remembered_guard);
 }
 EXPORT_SYMBOL(lu_context_tags_clear);
 
 void lu_session_tags_update(__u32 tags)
 {
-       write_lock(&lu_keys_guard);
+       spin_lock(&lu_context_remembered_guard);
        lu_session_tags_default |= tags;
        atomic_inc(&key_set_version);
-       write_unlock(&lu_keys_guard);
+       spin_unlock(&lu_context_remembered_guard);
 }
 EXPORT_SYMBOL(lu_session_tags_update);
 
 void lu_session_tags_clear(__u32 tags)
 {
-       write_lock(&lu_keys_guard);
+       spin_lock(&lu_context_remembered_guard);
        lu_session_tags_default &= ~tags;
        atomic_inc(&key_set_version);
-       write_unlock(&lu_keys_guard);
+       spin_unlock(&lu_context_remembered_guard);
 }
 EXPORT_SYMBOL(lu_session_tags_clear);
 #endif /* HAVE_SERVER_SUPPORT */