NFSv4.1: Allow SEQUENCE to resize the slot table on the fly

Instead of an array of slots, use a singly linked list of slots that
can be dynamically appended to or shrunk.

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

3 files changed, 120 insertions, 80 deletions

diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h
index 5d4e82b10c3c..856bc496a210 100644
--- a/fs/nfs/nfs4_fs.h
+++ b/fs/nfs/nfs4_fs.h
@@ -258,10 +258,10 @@ extern int nfs4_proc_get_lease_time(struct nfs_client *clp,
 extern int nfs4_proc_layoutcommit(struct nfs4_layoutcommit_data *data,
                                   bool sync);
 
-extern struct nfs4_slot *nfs4_alloc_slots(struct nfs4_slot_table *table,
-                u32 max_slots, gfp_t gfp_flags);
 extern void nfs41_set_target_slotid(struct nfs4_slot_table *tbl,
                 u32 target_highest_slotid);
+extern int nfs4_resize_slot_table(struct nfs4_slot_table *tbl,
+                u32 max_reqs, u32 ivalue);
 
 static inline bool
 is_ds_only_client(struct nfs_client *clp)
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 1792ece8b53c..fc65300172e1 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -397,6 +397,27 @@ static void renew_lease(const struct nfs_server *server, unsigned long timestamp
 #if defined(CONFIG_NFS_V4_1)
 
 /*
+ * nfs4_shrink_slot_table - free retired slots from the slot table
+ */
+static void nfs4_shrink_slot_table(struct nfs4_slot_table  *tbl, u32 newsize)
+{
+        struct nfs4_slot **p;
+        if (newsize >= tbl->max_slots)
+                return;
+
+        p = &tbl->slots;
+        while (newsize--)
+                p = &(*p)->next;
+        while (*p) {
+                struct nfs4_slot *slot = *p;
+
+                *p = slot->next;
+                kfree(slot);
+                tbl->max_slots--;
+        }
+}
+
+/*
  * nfs4_free_slot - free a slot and efficiently update slot table.
  *
  * freeing a slot is trivially done by clearing its respective bit
@@ -499,7 +520,7 @@ static void nfs41_set_target_slotid_locked(struct nfs4_slot_table *tbl,
         tbl->target_highest_slotid = target_highest_slotid;
         tbl->generation++;
 
-        max_slotid = min(tbl->max_slots - 1, tbl->target_highest_slotid);
+        max_slotid = min(NFS4_MAX_SLOT_TABLE - 1, tbl->target_highest_slotid);
         for (i = tbl->max_slotid + 1; i <= max_slotid; i++)
                 rpc_wake_up_next(&tbl->slot_tbl_waitq);
         tbl->max_slotid = max_slotid;
@@ -516,16 +537,12 @@ void nfs41_set_target_slotid(struct nfs4_slot_table *tbl,
 static void nfs41_set_server_slotid_locked(struct nfs4_slot_table *tbl,
                 u32 highest_slotid)
 {
-        unsigned int max_slotid, i;
-
         if (tbl->server_highest_slotid == highest_slotid)
                 return;
         if (tbl->highest_used_slotid > highest_slotid)
                 return;
-        max_slotid = min(tbl->max_slots - 1, highest_slotid);
-        /* Reset the seq_nr for deallocated slots */
-        for (i = tbl->server_highest_slotid + 1; i <= max_slotid; i++)
-                tbl->slots[i].seq_nr = 1;
+        /* Deallocate slots */
+        nfs4_shrink_slot_table(tbl, highest_slotid + 1);
         tbl->server_highest_slotid = highest_slotid;
 }
 
@@ -612,6 +629,42 @@ static int nfs4_sequence_done(struct rpc_task *task,
         return nfs41_sequence_done(task, res);
 }
 
+static struct nfs4_slot *nfs4_new_slot(struct nfs4_slot_table  *tbl,
+                u32 slotid, u32 seq_init, gfp_t gfp_mask)
+{
+        struct nfs4_slot *slot;
+
+        slot = kzalloc(sizeof(*slot), gfp_mask);
+        if (slot) {
+                slot->table = tbl;
+                slot->slot_nr = slotid;
+                slot->seq_nr = seq_init;
+        }
+        return slot;
+}
+
+static struct nfs4_slot *nfs4_find_or_create_slot(struct nfs4_slot_table  *tbl,
+                u32 slotid, u32 seq_init, gfp_t gfp_mask)
+{
+        struct nfs4_slot **p, *slot;
+
+        p = &tbl->slots;
+        for (;;) {
+                if (*p == NULL) {
+                        *p = nfs4_new_slot(tbl, tbl->max_slots,
+                                        seq_init, gfp_mask);
+                        if (*p == NULL)
+                                break;
+                        tbl->max_slots++;
+                }
+                slot = *p;
+                if (slot->slot_nr == slotid)
+                        return slot;
+                p = &slot->next;
+        }
+        return NULL;
+}
+
 /*
  * nfs4_alloc_slot - efficiently look for a free slot
  *
@@ -628,15 +681,17 @@ static struct nfs4_slot *nfs4_alloc_slot(struct nfs4_slot_table *tbl)
 
         dprintk("--> %s used_slots=%04lx highest_used=%u max_slots=%u\n",
                 __func__, tbl->used_slots[0], tbl->highest_used_slotid,
-                tbl->max_slots);
+                tbl->max_slotid + 1);
         slotid = find_first_zero_bit(tbl->used_slots, tbl->max_slotid + 1);
         if (slotid > tbl->max_slotid)
                 goto out;
+        ret = nfs4_find_or_create_slot(tbl, slotid, 1, GFP_NOWAIT);
+        if (ret == NULL)
+                goto out;
         __set_bit(slotid, tbl->used_slots);
         if (slotid > tbl->highest_used_slotid ||
                         tbl->highest_used_slotid == NFS4_NO_SLOT)
                 tbl->highest_used_slotid = slotid;
-        ret = &tbl->slots[slotid];
         ret->renewal_time = jiffies;
         ret->generation = tbl->generation;
 
@@ -5718,67 +5773,56 @@ int nfs4_proc_get_lease_time(struct nfs_client *clp, struct nfs_fsinfo *fsinfo)
         return status;
 }
 
-struct nfs4_slot *nfs4_alloc_slots(struct nfs4_slot_table *table,
-                u32 max_slots, gfp_t gfp_flags)
+static int nfs4_grow_slot_table(struct nfs4_slot_table *tbl,
+                 u32 max_reqs, u32 ivalue)
 {
-        struct nfs4_slot *tbl;
-        u32 i;
-
-        tbl = kmalloc_array(max_slots, sizeof(*tbl), gfp_flags);
-        if (tbl != NULL) {
-                for (i = 0; i < max_slots; i++) {
-                        tbl[i].table = table;
-                        tbl[i].slot_nr = i;
-                }
-        }
-        return tbl;
+        if (max_reqs <= tbl->max_slots)
+                return 0;
+        if (nfs4_find_or_create_slot(tbl, max_reqs - 1, ivalue, GFP_NOFS))
+                return 0;
+        return -ENOMEM;
 }
 
-static void nfs4_add_and_init_slots(struct nfs4_slot_table *tbl,
-                struct nfs4_slot *new,
-                u32 max_slots,
+static void nfs4_reset_slot_table(struct nfs4_slot_table *tbl,
+                u32 server_highest_slotid,
                 u32 ivalue)
 {
-        struct nfs4_slot *old = NULL;
-        u32 i;
+        struct nfs4_slot **p;
 
-        spin_lock(&tbl->slot_tbl_lock);
-        if (new) {
-                old = tbl->slots;
-                tbl->slots = new;
-                tbl->max_slots = max_slots;
+        nfs4_shrink_slot_table(tbl, server_highest_slotid + 1);
+        p = &tbl->slots;
+        while (*p) {
+                (*p)->seq_nr = ivalue;
+                p = &(*p)->next;
         }
         tbl->highest_used_slotid = NFS4_NO_SLOT;
-        tbl->target_highest_slotid = max_slots - 1;
-        tbl->server_highest_slotid = max_slots - 1;
-        tbl->max_slotid = max_slots - 1;
-        for (i = 0; i < tbl->max_slots; i++)
-                tbl->slots[i].seq_nr = ivalue;
-        spin_unlock(&tbl->slot_tbl_lock);
-        kfree(old);
+        tbl->target_highest_slotid = server_highest_slotid;
+        tbl->server_highest_slotid = server_highest_slotid;
+        tbl->max_slotid = server_highest_slotid;
 }
 
 /*
  * (re)Initialise a slot table
  */
-static int nfs4_realloc_slot_table(struct nfs4_slot_table *tbl, u32 max_reqs,
-                                 u32 ivalue)
+static int nfs4_realloc_slot_table(struct nfs4_slot_table *tbl,
+                u32 max_reqs, u32 ivalue)
 {
-        struct nfs4_slot *new = NULL;
-        int ret = -ENOMEM;
+        int ret;
 
         dprintk("--> %s: max_reqs=%u, tbl->max_slots %d\n", __func__,
                 max_reqs, tbl->max_slots);
 
-        /* Does the newly negotiated max_reqs match the existing slot table? */
-        if (max_reqs != tbl->max_slots) {
-                new = nfs4_alloc_slots(tbl, max_reqs, GFP_NOFS);
-                if (!new)
-                        goto out;
-        }
-        ret = 0;
+        if (max_reqs > NFS4_MAX_SLOT_TABLE)
+                max_reqs = NFS4_MAX_SLOT_TABLE;
+
+        ret = nfs4_grow_slot_table(tbl, max_reqs, ivalue);
+        if (ret)
+                goto out;
+
+        spin_lock(&tbl->slot_tbl_lock);
+        nfs4_reset_slot_table(tbl, max_reqs - 1, ivalue);
+        spin_unlock(&tbl->slot_tbl_lock);
 
-        nfs4_add_and_init_slots(tbl, new, max_reqs, ivalue);
         dprintk("%s: tbl=%p slots=%p max_slots=%d\n", __func__,
                 tbl, tbl->slots, tbl->max_slots);
 out:
@@ -5786,18 +5830,28 @@ out:
         return ret;
 }
 
+int nfs4_resize_slot_table(struct nfs4_slot_table *tbl,
+                 u32 max_reqs, u32 ivalue)
+{
+        int ret;
+
+        if (max_reqs > NFS4_MAX_SLOT_TABLE)
+                max_reqs = NFS4_MAX_SLOT_TABLE;
+        ret = nfs4_grow_slot_table(tbl, max_reqs, ivalue);
+        if (ret)
+                return ret;
+        spin_lock(&tbl->slot_tbl_lock);
+        nfs4_shrink_slot_table(tbl, max_reqs);
+        tbl->max_slotid = max_reqs - 1;
+        spin_unlock(&tbl->slot_tbl_lock);
+        return 0;
+}
+
 /* Destroy the slot table */
 static void nfs4_destroy_slot_tables(struct nfs4_session *session)
 {
-        if (session->fc_slot_table.slots != NULL) {
-                kfree(session->fc_slot_table.slots);
-                session->fc_slot_table.slots = NULL;
-        }
-        if (session->bc_slot_table.slots != NULL) {
-                kfree(session->bc_slot_table.slots);
-                session->bc_slot_table.slots = NULL;
-        }
-        return;
+        nfs4_shrink_slot_table(&session->fc_slot_table, 0);
+        nfs4_shrink_slot_table(&session->bc_slot_table, 0);
 }
 
 /*
diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 1b7fa73c9436..c14b2c7ac8a7 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -2025,29 +2025,15 @@ out:
 static int nfs4_recall_slot(struct nfs_client *clp)
 {
         struct nfs4_slot_table *fc_tbl;
-        struct nfs4_slot *new, *old;
-        int i;
+        u32 new_size;
 
         if (!nfs4_has_session(clp))
                 return 0;
         nfs4_begin_drain_session(clp);
-        fc_tbl = &clp->cl_session->fc_slot_table;
-        new = nfs4_alloc_slots(fc_tbl, fc_tbl->target_highest_slotid + 1, GFP_NOFS);
-        if (!new)
-                return -ENOMEM;
 
-        spin_lock(&fc_tbl->slot_tbl_lock);
-        for (i = 0; i <= fc_tbl->target_highest_slotid; i++)
-                new[i].seq_nr = fc_tbl->slots[i].seq_nr;
-        old = fc_tbl->slots;
-        fc_tbl->slots = new;
-        fc_tbl->max_slots = fc_tbl->target_highest_slotid + 1;
-        fc_tbl->max_slotid = fc_tbl->target_highest_slotid;
-        clp->cl_session->fc_attrs.max_reqs = fc_tbl->max_slots;
-        spin_unlock(&fc_tbl->slot_tbl_lock);
-
-        kfree(old);
-        return 0;
+        fc_tbl = &clp->cl_session->fc_slot_table;
+        new_size = fc_tbl->server_highest_slotid + 1;
+        return nfs4_resize_slot_table(fc_tbl, new_size, 1);
 }
 
 static int nfs4_bind_conn_to_session(struct nfs_client *clp)