linux-ext4 - [PATCH -next v2 3/6] ext4: compare to local seq and nodename when check conflict

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Date:   Sat, 11 Sep 2021 17:00:56 +0800
From:   Ye Bin <yebin10@...wei.com>
To:     <tytso@....edu>, <adilger.kernel@...ger.ca>,
        <linux-ext4@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>, <jack@...e.cz>,
        Ye Bin <yebin10@...wei.com>
Subject: [PATCH -next v2 3/6] ext4: compare to local seq and nodename when check conflict

As mmp and check_mmp is point to the same data, so there will never
detect conflict.
To solve this issue just compare to local data.

Signed-off-by: Ye Bin <yebin10@...wei.com>
---
 fs/ext4/mmp.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c
index c781b09a78c9..4433fe7e9e86 100644
--- a/fs/ext4/mmp.c
+++ b/fs/ext4/mmp.c
@@ -154,6 +154,7 @@ static int kmmpd(void *data)
 	unsigned long last_update_time;
 	unsigned long last_check_time;
 	unsigned long diff;
+	char nodename[64];
 	int retval = 0;
 
 	mmp_block = le64_to_cpu(es->s_mmp_block);
@@ -169,8 +170,8 @@ static int kmmpd(void *data)
 	BUILD_BUG_ON(sizeof(mmp->mmp_bdevname) < BDEVNAME_SIZE);
 	bdevname(bh->b_bdev, mmp->mmp_bdevname);
 
-	memcpy(mmp->mmp_nodename, init_utsname()->nodename,
-	       sizeof(mmp->mmp_nodename));
+	memcpy(nodename, init_utsname()->nodename, sizeof(nodename));
+	memcpy(mmp->mmp_nodename, nodename, sizeof(mmp->mmp_nodename));
 	last_check_time = jiffies;
 
 	while (!kthread_should_stop() && !sb_rdonly(sb)) {
@@ -224,8 +225,8 @@ static int kmmpd(void *data)
 			}
 
 			mmp_check = (struct mmp_struct *)(bh_check->b_data);
-			if (mmp->mmp_seq != mmp_check->mmp_seq ||
-			    memcmp(mmp->mmp_nodename, mmp_check->mmp_nodename,
+			if (seq != mmp_check->mmp_seq ||
+			    memcmp(nodename, mmp_check->mmp_nodename,
 				   sizeof(mmp->mmp_nodename))) {
 				dump_mmp_msg(sb, mmp_check,
 					     "Error while updating MMP info. "
-- 
2.31.1