linux-kernel - [PATCH] Fix computation of SKB size for quota messages

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Message-ID: <20071218180839.GG31091@duck.suse.cz>
Date:	Tue, 18 Dec 2007 19:08:39 +0100
From:	Jan Kara <jack@...e.cz>
To:	linux-kernel@...r.kernel.org
Cc:	Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH] Fix computation of SKB size for quota messages

  Hello,

  attached patch fixes computation of buffer size needed for quota netlink
messages. Otherwise we were getting errors on some architectures. Andrew,
please apply. Thanks.

									Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
---

Fix computation of size of skb needed for quota message. We should use
netlink provided functions and not just an ad-hoc number. Also don't
print the return value from nla_put_foo() as it is always -1.

Signed-off-by: Jan Kara <jack@...e.cz>

diff --git a/fs/dquot.c b/fs/dquot.c
index 686ab63..cee7c6f 100644
--- a/fs/dquot.c
+++ b/fs/dquot.c
@@ -895,9 +903,6 @@ out_lock:
 
 #ifdef CONFIG_QUOTA_NETLINK_INTERFACE
 
-/* Size of quota netlink message - actually an upperbound for buffer size */
-#define QUOTA_NL_MSG_SIZE 32
-
 /* Netlink family structure for quota */
 static struct genl_family quota_genl_family = {
 	.id = GENL_ID_GENERATE,
@@ -914,11 +919,13 @@ static void send_warning(const struct dquot *dquot, const char warntype)
 	struct sk_buff *skb;
 	void *msg_head;
 	int ret;
+	int msg_size = 4 * nla_total_size(sizeof(u32)) +
+		       2 * nla_total_size(sizeof(u64));
 
 	/* We have to allocate using GFP_NOFS as we are called from a
 	 * filesystem performing write and thus further recursion into
 	 * the fs to free some data could cause deadlocks. */
-	skb = genlmsg_new(QUOTA_NL_MSG_SIZE, GFP_NOFS);
+	skb = genlmsg_new(msg_size, GFP_NOFS);
 	if (!skb) {
 		printk(KERN_ERR
 		  "VFS: Not enough memory to send quota warning.\n");
@@ -959,7 +966,7 @@ static void send_warning(const struct dquot *dquot, const char warntype)
 			"VFS: Failed to send notification message: %d\n", ret);
 	return;
 attr_err_out:
-	printk(KERN_ERR "VFS: Failed to compose quota message: %d\n", ret);
+	printk(KERN_ERR "VFS: Not enough space to compose quota message!\n");
 err_out:
 	kfree_skb(skb);
 }
--
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