Re: [PATCH -next v3 1/5] ext4: init 'seq' with the value which set in 'ext4_multi_mount_protect'
From: Jan Kara <jack@suse.cz>
Date: 2021-10-19 08:53:26
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lkml
On Tue 19-10-21 14:49:55, Ye Bin wrote:
If two host have the same nodename, and seq start from 0, May cause the detection mechanism to fail. So init 'seq' with the value which set in 'ext4_multi_mount_protect' to accelerate conflict detection. Signed-off-by: Ye Bin <redacted>
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quoted hunk ↗ jump to hunk
@@ -143,6 +143,7 @@ static int kmmpd(void *data) mmp_block = le64_to_cpu(es->s_mmp_block); mmp = (struct mmp_struct *)(bh->b_data); mmp->mmp_time = cpu_to_le64(ktime_get_real_seconds()); + seq = le32_to_cpu(mmp->mmp_seq); /* * Start with the higher mmp_check_interval and reduce it if * the MMP block is being updated on time.
Thanks for the patch. After discussing what MMP guards against and what it does not protect, I don't think this change is actually needed. Under normal conditions we expect kmmpd() to only write to MMP block, checking of MMP block is done only in ext4_multi_mount_protect(). And for checking there to trigger, using 'seq' starting from 1 in kmmpd is enough... Honza -- Jan Kara [off-list ref] SUSE Labs, CR