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Date: Tue, 19 Oct 2021 10:53:19 +0200 From: Jan Kara <jack@...e.cz> To: Ye Bin <yebin10@...wei.com> Cc: tytso@....edu, adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org, jack@...e.cz Subject: Re: [PATCH -next v3 1/5] ext4: init 'seq' with the value which set in 'ext4_multi_mount_protect' 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 <yebin10@...wei.com> ... > @@ -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 <jack@...e.com> SUSE Labs, CR
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