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>

1 files changed, 114 insertions, 60 deletions

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);
 }
 
 /*