Re: [PATCH] nfs41: Initialize slot->seq_nr at nfs4_init_slot_table()

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On Tue, 2012-02-14 at 20:50 -0500, Trond Myklebust wrote:
> Hang on... Looking at 3.2, I think you're correct. We used to initialise
> to 1, and now we're initialising to 0.
> 
> Ah... I see what happened.
> 
> commit aacd5537270a752fe12a9914a207284fc2341c6d (NFSv4.1: cleanup init
> and reset of session slot tables) seems to have removed the call to
> nfs4_reset_slot_tables() that was doing that initialisation. OK... So
> this is a Linux 3.3-rcX only regression, and should be treated as
> such...
> 
> How about the following instead so that we ensure we fully share the
> initialisation code between nfs4_reset_slot_tables and
> nfs4_init_slot_tables?
> 

Here's a version 2 that does a few more cleanups by merging the
nfs4_init_slot_table() and nfs4_reset_slot_table() into a single
function.

8<-------------------------------------------------------------------------
>From dea20ac15be192d0b4c4e367b7b61740ceee8dc4 Mon Sep 17 00:00:00 2001
From: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
Date: Tue, 14 Feb 2012 20:33:19 -0500
Subject: [PATCH v2] NFSv4.1: Fix a NFSv4.1 session initialisation regression

Commit aacd553 (NFSv4.1: cleanup init and reset of session slot tables)
introduces a regression in the session initialisation code. New tables
now find their sequence ids initialised to 0, rather than the mandated
value of 1 (see RFC5661).

Fix the problem by merging nfs4_reset_slot_table() and nfs4_init_slot_table().
Since the tbl->max_slots is initialised to 0, the test in
nfs4_reset_slot_table for max_reqs != tbl->max_slots will automatically
pass for an empty table.

Reported-by: Vitaliy Gusev <gusev.vitaliy@xxxxxxxxxxx>
Signed-off-by: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
---
 fs/nfs/nfs4proc.c |  109 ++++++++++++++++++++--------------------------------
 1 files changed, 42 insertions(+), 67 deletions(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index d202e04..1684c9b 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -5008,37 +5008,53 @@ int nfs4_proc_get_lease_time(struct nfs_client *clp, struct nfs_fsinfo *fsinfo)
 	return status;
 }
 
+static struct nfs4_slot *nfs4_alloc_slots(u32 max_slots, gfp_t gfp_flags)
+{
+	return kcalloc(max_slots, sizeof(struct nfs4_slot), gfp_flags);
+}
+
+static void nfs4_add_and_init_slots(struct nfs4_slot_table *tbl,
+		struct nfs4_slot *new,
+		u32 max_slots,
+		u32 ivalue)
+{
+	struct nfs4_slot *old = NULL;
+	u32 i;
+
+	spin_lock(&tbl->slot_tbl_lock);
+	if (new) {
+		old = tbl->slots;
+		tbl->slots = new;
+		tbl->max_slots = max_slots;
+	}
+	tbl->highest_used_slotid = -1;	/* no slot is currently used */
+	for (i = 0; i < tbl->max_slots; i++)
+		tbl->slots[i].seq_nr = ivalue;
+	spin_unlock(&tbl->slot_tbl_lock);
+	kfree(old);
+}
+
 /*
- * Reset a slot table
+ * (re)Initialise a slot table
  */
-static int nfs4_reset_slot_table(struct nfs4_slot_table *tbl, u32 max_reqs,
-				 int ivalue)
+static int nfs4_realloc_slot_table(struct nfs4_slot_table *tbl, u32 max_reqs,
+				 u32 ivalue)
 {
 	struct nfs4_slot *new = NULL;
-	int i;
-	int ret = 0;
+	int ret = -ENOMEM;
 
 	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) {
-		ret = -ENOMEM;
-		new = kmalloc(max_reqs * sizeof(struct nfs4_slot),
-			      GFP_NOFS);
+		new = nfs4_alloc_slots(max_reqs, GFP_NOFS);
 		if (!new)
 			goto out;
-		ret = 0;
-		kfree(tbl->slots);
-	}
-	spin_lock(&tbl->slot_tbl_lock);
-	if (new) {
-		tbl->slots = new;
-		tbl->max_slots = max_reqs;
 	}
-	for (i = 0; i < tbl->max_slots; ++i)
-		tbl->slots[i].seq_nr = ivalue;
-	spin_unlock(&tbl->slot_tbl_lock);
+	ret = 0;
+
+	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:
@@ -5061,36 +5077,6 @@ static void nfs4_destroy_slot_tables(struct nfs4_session *session)
 }
 
 /*
- * Initialize slot table
- */
-static int nfs4_init_slot_table(struct nfs4_slot_table *tbl,
-		int max_slots, int ivalue)
-{
-	struct nfs4_slot *slot;
-	int ret = -ENOMEM;
-
-	BUG_ON(max_slots > NFS4_MAX_SLOT_TABLE);
-
-	dprintk("--> %s: max_reqs=%u\n", __func__, max_slots);
-
-	slot = kcalloc(max_slots, sizeof(struct nfs4_slot), GFP_NOFS);
-	if (!slot)
-		goto out;
-	ret = 0;
-
-	spin_lock(&tbl->slot_tbl_lock);
-	tbl->max_slots = max_slots;
-	tbl->slots = slot;
-	tbl->highest_used_slotid = -1;  /* no slot is currently used */
-	spin_unlock(&tbl->slot_tbl_lock);
-	dprintk("%s: tbl=%p slots=%p max_slots=%d\n", __func__,
-		tbl, tbl->slots, tbl->max_slots);
-out:
-	dprintk("<-- %s: return %d\n", __func__, ret);
-	return ret;
-}
-
-/*
  * Initialize or reset the forechannel and backchannel tables
  */
 static int nfs4_setup_session_slot_tables(struct nfs4_session *ses)
@@ -5101,25 +5087,16 @@ static int nfs4_setup_session_slot_tables(struct nfs4_session *ses)
 	dprintk("--> %s\n", __func__);
 	/* Fore channel */
 	tbl = &ses->fc_slot_table;
-	if (tbl->slots == NULL) {
-		status = nfs4_init_slot_table(tbl, ses->fc_attrs.max_reqs, 1);
-		if (status) /* -ENOMEM */
-			return status;
-	} else {
-		status = nfs4_reset_slot_table(tbl, ses->fc_attrs.max_reqs, 1);
-		if (status)
-			return status;
-	}
+	status = nfs4_realloc_slot_table(tbl, ses->fc_attrs.max_reqs, 1);
+	if (status) /* -ENOMEM */
+		return status;
 	/* Back channel */
 	tbl = &ses->bc_slot_table;
-	if (tbl->slots == NULL) {
-		status = nfs4_init_slot_table(tbl, ses->bc_attrs.max_reqs, 0);
-		if (status)
-			/* Fore and back channel share a connection so get
-			 * both slot tables or neither */
-			nfs4_destroy_slot_tables(ses);
-	} else
-		status = nfs4_reset_slot_table(tbl, ses->bc_attrs.max_reqs, 0);
+	status = nfs4_realloc_slot_table(tbl, ses->bc_attrs.max_reqs, 0);
+	if (status && tbl->slots == NULL)
+		/* Fore and back channel share a connection so get
+		 * both slot tables or neither */
+		nfs4_destroy_slot_tables(ses);
 	return status;
 }
 
@@ -5133,13 +5110,11 @@ struct nfs4_session *nfs4_alloc_session(struct nfs_client *clp)
 		return NULL;
 
 	tbl = &session->fc_slot_table;
-	tbl->highest_used_slotid = -1;
 	spin_lock_init(&tbl->slot_tbl_lock);
 	rpc_init_priority_wait_queue(&tbl->slot_tbl_waitq, "ForeChannel Slot table");
 	init_completion(&tbl->complete);
 
 	tbl = &session->bc_slot_table;
-	tbl->highest_used_slotid = -1;
 	spin_lock_init(&tbl->slot_tbl_lock);
 	rpc_init_wait_queue(&tbl->slot_tbl_waitq, "BackChannel Slot table");
 	init_completion(&tbl->complete);
-- 
1.7.7.6


-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@xxxxxxxxxx
www.netapp.com

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