NFSv4: Reduce the chances of an open_owner identifier collision

Currently we just use a 32-bit counter.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 154 insertions, 39 deletions

diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 0f79d56e97f0..ab0b5ab60e60 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -44,6 +44,7 @@
 #include <linux/nfs_idmap.h>
 #include <linux/kthread.h>
 #include <linux/module.h>
+#include <linux/random.h>
 #include <linux/workqueue.h>
 #include <linux/bitops.h>
 
@@ -69,18 +70,14 @@ static int nfs4_init_client(struct nfs_client *clp, struct rpc_cred *cred)
         return status;
 }
 
-u32
-nfs4_alloc_lockowner_id(struct nfs_client *clp)
-{
-        return clp->cl_lockowner_id ++;
-}
-
 struct rpc_cred *nfs4_get_renew_cred(struct nfs_client *clp)
 {
         struct nfs4_state_owner *sp;
+        struct rb_node *pos;
         struct rpc_cred *cred = NULL;
 
-        list_for_each_entry(sp, &clp->cl_state_owners, so_list) {
+        for (pos = rb_first(&clp->cl_state_owners); pos != NULL; pos = rb_next(pos)) {
+                sp = rb_entry(pos, struct nfs4_state_owner, so_client_node);
                 if (list_empty(&sp->so_states))
                         continue;
                 cred = get_rpccred(sp->so_cred);
@@ -92,32 +89,129 @@ struct rpc_cred *nfs4_get_renew_cred(struct nfs_client *clp)
 static struct rpc_cred *nfs4_get_setclientid_cred(struct nfs_client *clp)
 {
         struct nfs4_state_owner *sp;
+        struct rb_node *pos;
 
-        if (!list_empty(&clp->cl_state_owners)) {
-                sp = list_entry(clp->cl_state_owners.next,
-                                struct nfs4_state_owner, so_list);
+        pos = rb_first(&clp->cl_state_owners);
+        if (pos != NULL) {
+                sp = rb_entry(pos, struct nfs4_state_owner, so_client_node);
                 return get_rpccred(sp->so_cred);
         }
         return NULL;
 }
 
+static void nfs_alloc_unique_id(struct rb_root *root, struct nfs_unique_id *new,
+                __u64 minval, int maxbits)
+{
+        struct rb_node **p, *parent;
+        struct nfs_unique_id *pos;
+        __u64 mask = ~0ULL;
+
+        if (maxbits < 64)
+                mask = (1ULL << maxbits) - 1ULL;
+
+        /* Ensure distribution is more or less flat */
+        get_random_bytes(&new->id, sizeof(new->id));
+        new->id &= mask;
+        if (new->id < minval)
+                new->id += minval;
+retry:
+        p = &root->rb_node;
+        parent = NULL;
+
+        while (*p != NULL) {
+                parent = *p;
+                pos = rb_entry(parent, struct nfs_unique_id, rb_node);
+
+                if (new->id < pos->id)
+                        p = &(*p)->rb_left;
+                else if (new->id > pos->id)
+                        p = &(*p)->rb_right;
+                else
+                        goto id_exists;
+        }
+        rb_link_node(&new->rb_node, parent, p);
+        rb_insert_color(&new->rb_node, root);
+        return;
+id_exists:
+        for (;;) {
+                new->id++;
+                if (new->id < minval || (new->id & mask) != new->id) {
+                        new->id = minval;
+                        break;
+                }
+                parent = rb_next(parent);
+                if (parent == NULL)
+                        break;
+                pos = rb_entry(parent, struct nfs_unique_id, rb_node);
+                if (new->id < pos->id)
+                        break;
+        }
+        goto retry;
+}
+
+static void nfs_free_unique_id(struct rb_root *root, struct nfs_unique_id *id)
+{
+        rb_erase(&id->rb_node, root);
+}
+
 static struct nfs4_state_owner *
 nfs4_find_state_owner(struct nfs_client *clp, struct rpc_cred *cred)
 {
+        struct rb_node **p = &clp->cl_state_owners.rb_node,
+                       *parent = NULL;
         struct nfs4_state_owner *sp, *res = NULL;
 
-        list_for_each_entry(sp, &clp->cl_state_owners, so_list) {
-                if (sp->so_cred != cred)
-                        continue;
-                atomic_inc(&sp->so_count);
-                /* Move to the head of the list */
-                list_move(&sp->so_list, &clp->cl_state_owners);
-                res = sp;
-                break;
+        while (*p != NULL) {
+                parent = *p;
+                sp = rb_entry(parent, struct nfs4_state_owner, so_client_node);
+
+                if (cred < sp->so_cred)
+                        p = &parent->rb_left;
+                else if (cred > sp->so_cred)
+                        p = &parent->rb_right;
+                else {
+                        atomic_inc(&sp->so_count);
+                        res = sp;
+                        break;
+                }
         }
         return res;
 }
 
+static struct nfs4_state_owner *
+nfs4_insert_state_owner(struct nfs_client *clp, struct nfs4_state_owner *new)
+{
+        struct rb_node **p = &clp->cl_state_owners.rb_node,
+                       *parent = NULL;
+        struct nfs4_state_owner *sp;
+
+        while (*p != NULL) {
+                parent = *p;
+                sp = rb_entry(parent, struct nfs4_state_owner, so_client_node);
+
+                if (new->so_cred < sp->so_cred)
+                        p = &parent->rb_left;
+                else if (new->so_cred > sp->so_cred)
+                        p = &parent->rb_right;
+                else {
+                        atomic_inc(&sp->so_count);
+                        return sp;
+                }
+        }
+        nfs_alloc_unique_id(&clp->cl_openowner_id, &new->so_owner_id, 1, 64);
+        rb_link_node(&new->so_client_node, parent, p);
+        rb_insert_color(&new->so_client_node, &clp->cl_state_owners);
+        return new;
+}
+
+static void
+nfs4_remove_state_owner(struct nfs_client *clp, struct nfs4_state_owner *sp)
+{
+        if (!RB_EMPTY_NODE(&sp->so_client_node))
+                rb_erase(&sp->so_client_node, &clp->cl_state_owners);
+        nfs_free_unique_id(&clp->cl_openowner_id, &sp->so_owner_id);
+}
+
 /*
  * nfs4_alloc_state_owner(): this is called on the OPEN or CREATE path to
  * create a new state_owner.
@@ -145,10 +239,14 @@ nfs4_alloc_state_owner(void)
 void
 nfs4_drop_state_owner(struct nfs4_state_owner *sp)
 {
-        struct nfs_client *clp = sp->so_client;
-        spin_lock(&clp->cl_lock);
-        list_del_init(&sp->so_list);
-        spin_unlock(&clp->cl_lock);
+        if (!RB_EMPTY_NODE(&sp->so_client_node)) {
+                struct nfs_client *clp = sp->so_client;
+
+                spin_lock(&clp->cl_lock);
+                rb_erase(&sp->so_client_node, &clp->cl_state_owners);
+                RB_CLEAR_NODE(&sp->so_client_node);
+                spin_unlock(&clp->cl_lock);
+        }
 }
 
 /*
@@ -160,22 +258,24 @@ struct nfs4_state_owner *nfs4_get_state_owner(struct nfs_server *server, struct
         struct nfs_client *clp = server->nfs_client;
         struct nfs4_state_owner *sp, *new;
 
-        new = nfs4_alloc_state_owner();
         spin_lock(&clp->cl_lock);
         sp = nfs4_find_state_owner(clp, cred);
-        if (sp == NULL && new != NULL) {
-                list_add(&new->so_list, &clp->cl_state_owners);
-                new->so_client = clp;
-                new->so_id = nfs4_alloc_lockowner_id(clp);
-                new->so_cred = get_rpccred(cred);
-                sp = new;
-                new = NULL;
-        }
         spin_unlock(&clp->cl_lock);
-        kfree(new);
         if (sp != NULL)
                 return sp;
-        return NULL;
+        new = nfs4_alloc_state_owner();
+        if (new == NULL)
+                return NULL;
+        new->so_client = clp;
+        new->so_cred = cred;
+        spin_lock(&clp->cl_lock);
+        sp = nfs4_insert_state_owner(clp, new);
+        spin_unlock(&clp->cl_lock);
+        if (sp == new)
+                get_rpccred(cred);
+        else
+                kfree(new);
+        return sp;
 }
 
 /*
@@ -189,7 +289,7 @@ void nfs4_put_state_owner(struct nfs4_state_owner *sp)
 
         if (!atomic_dec_and_lock(&sp->so_count, &clp->cl_lock))
                 return;
-        list_del(&sp->so_list);
+        nfs4_remove_state_owner(clp, sp);
         spin_unlock(&clp->cl_lock);
         put_rpccred(cred);
         kfree(sp);
@@ -386,12 +486,22 @@ static struct nfs4_lock_state *nfs4_alloc_lock_state(struct nfs4_state *state, f
         atomic_set(&lsp->ls_count, 1);
         lsp->ls_owner = fl_owner;
         spin_lock(&clp->cl_lock);
-        lsp->ls_id = nfs4_alloc_lockowner_id(clp);
+        nfs_alloc_unique_id(&clp->cl_lockowner_id, &lsp->ls_id, 1, 64);
         spin_unlock(&clp->cl_lock);
         INIT_LIST_HEAD(&lsp->ls_locks);
         return lsp;
 }
 
+static void nfs4_free_lock_state(struct nfs4_lock_state *lsp)
+{
+        struct nfs_client *clp = lsp->ls_state->owner->so_client;
+
+        spin_lock(&clp->cl_lock);
+        nfs_free_unique_id(&clp->cl_lockowner_id, &lsp->ls_id);
+        spin_unlock(&clp->cl_lock);
+        kfree(lsp);
+}
+
 /*
  * Return a compatible lock_state. If no initialized lock_state structure
  * exists, return an uninitialized one.
@@ -421,7 +531,8 @@ static struct nfs4_lock_state *nfs4_get_lock_state(struct nfs4_state *state, fl_
                         return NULL;
         }
         spin_unlock(&state->state_lock);
-        kfree(new);
+        if (new != NULL)
+                nfs4_free_lock_state(new);
         return lsp;
 }
 
@@ -442,7 +553,7 @@ void nfs4_put_lock_state(struct nfs4_lock_state *lsp)
         if (list_empty(&state->lock_states))
                 clear_bit(LK_STATE_IN_USE, &state->flags);
         spin_unlock(&state->state_lock);
-        kfree(lsp);
+        nfs4_free_lock_state(lsp);
 }
 
 static void nfs4_fl_copy_lock(struct file_lock *dst, struct file_lock *src)
@@ -719,11 +830,13 @@ out_err:
 static void nfs4_state_mark_reclaim(struct nfs_client *clp)
 {
         struct nfs4_state_owner *sp;
+        struct rb_node *pos;
         struct nfs4_state *state;
         struct nfs4_lock_state *lock;
 
         /* Reset all sequence ids to zero */
-        list_for_each_entry(sp, &clp->cl_state_owners, so_list) {
+        for (pos = rb_first(&clp->cl_state_owners); pos != NULL; pos = rb_next(pos)) {
+                sp = rb_entry(pos, struct nfs4_state_owner, so_client_node);
                 sp->so_seqid.counter = 0;
                 sp->so_seqid.flags = 0;
                 spin_lock(&sp->so_lock);
@@ -742,6 +855,7 @@ static int reclaimer(void *ptr)
 {
         struct nfs_client *clp = ptr;
         struct nfs4_state_owner *sp;
+        struct rb_node *pos;
         struct nfs4_state_recovery_ops *ops;
         struct rpc_cred *cred;
         int status = 0;
@@ -787,7 +901,8 @@ restart_loop:
         /* Mark all delegations for reclaim */
         nfs_delegation_mark_reclaim(clp);
         /* Note: list is protected by exclusive lock on cl->cl_sem */
-        list_for_each_entry(sp, &clp->cl_state_owners, so_list) {
+        for (pos = rb_first(&clp->cl_state_owners); pos != NULL; pos = rb_next(pos)) {
+                sp = rb_entry(pos, struct nfs4_state_owner, so_client_node);
                 status = nfs4_reclaim_open_state(ops, sp);
                 if (status < 0) {
                         if (status == -NFS4ERR_NO_GRACE) {