[PATCH -next v4 1/3] ext4: compare to local seq and nodename when check conflict

Ye Bin
2021-10-19T12:27:04Z

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@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
fs/ext4/ext4.h | 5 ++++-
fs/ext4/mmp.c | 9 +++++----
2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 404dd50856e5..9a487a558787 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2601,6 +2601,8 @@ struct ext4_features {
#define EXT4_MMP_SEQ_FSCK 0xE24D4D50U /* mmp_seq value when being fscked */
#define EXT4_MMP_SEQ_MAX 0xE24D4D4FU /* maximum valid mmp_seq value */

+#define EXT4_MMP_NODENAME_LEN 64 /* mmp_nodename length */
+
struct mmp_struct {
__le32 mmp_magic; /* Magic number for MMP */
__le32 mmp_seq; /* Sequence no. updated periodically */
@@ -2610,7 +2612,8 @@ struct mmp_struct {
* purposes and do not affect the correctness of the algorithm
*/
__le64 mmp_time; /* Time last updated */
- char mmp_nodename[64]; /* Node which last updated MMP block */
+ /* Node which last updated MMP block */
+ char mmp_nodename[EXT4_MMP_NODENAME_LEN];
char mmp_bdevname[32]; /* Bdev which last updated MMP block */

/*
diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c
index cebea4270817..97d5a8136eb2 100644
--- a/fs/ext4/mmp.c
+++ b/fs/ext4/mmp.c
@@ -138,6 +138,7 @@ static int kmmpd(void *data)
unsigned mmp_check_interval;
unsigned long last_update_time;
unsigned long diff;
+ char nodename[EXT4_MMP_NODENAME_LEN];
int retval = 0;

mmp_block = le64_to_cpu(es->s_mmp_block);
@@ -153,8 +154,8 @@ 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));

while (!kthread_should_stop() && !sb_rdonly(sb)) {
if (!ext4_has_feature_mmp(sb)) {
@@ -206,8 +207,8 @@ 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