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Date:   Thu, 23 Jan 2020 16:32:17 +0800
From:   Murphy Zhou <jencce.kernel@gmail.com>
To:     linux-xfs@vger.kernel.org, linux-nfs@vger.kernel.org
Subject: A NFS, xfs, reflink and rmapbt story
Message-ID: <20200123083217.flkl6tkyr4b7zwuk@xzhoux.usersys.redhat.com>
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Hi,

Deleting the files left by generic/175 costs too much time when testing
on NFSv4.2 exporting xfs with rmapbt=1.

"./check -nfs generic/175 generic/176" should reproduce it.

My test bed is a 16c8G vm.

NFSv4.2  rmapbt=1   24h+
NFSv4.2  rmapbt=0   1h-2h
xfs      rmapbt=1   10m+

At first I thought it hung, turns out it was just slow when deleting
2 massive reflined files.

It's reproducible using latest Linus tree, and Darrick's deferred-inactivation
branch. Run latest for-next branch xfsprogs.

I'm not sure it's something wrong, just sharing with you guys. I don't
remember I have identified this as a regression. It should be there for
a long time.

Sending to xfs and nfs because it looks like all related. :)

This almost gets lost in my list. Not much information recorded, some
trace-cmd outputs for your info. It's easy to reproduce. If it's
interesting to you and need any info, feel free to ask.

Thanks,


7)   0.279 us    |  xfs_btree_get_block [xfs]();
7)   0.303 us    |  xfs_btree_rec_offset [xfs]();
7)   0.301 us    |  xfs_rmapbt_init_high_key_from_rec [xfs]();
7)   0.356 us    |  xfs_rmapbt_diff_two_keys [xfs]();
7)   0.305 us    |  xfs_rmapbt_init_key_from_rec [xfs]();
7)   0.306 us    |  xfs_rmapbt_diff_two_keys [xfs]();
7)               |  xfs_rmap_query_range_helper [xfs]() {
7)   0.279 us    |    xfs_rmap_btrec_to_irec [xfs]();
7)               |    xfs_rmap_lookup_le_range_helper [xfs]() {
1)   0.786 us    |  _raw_spin_lock_irqsave();
7)               |      /* xfs_rmap_lookup_le_range_candidate: dev 8:34 agno 2 agbno 6416 len 256 owner 67160161 offset 99284480 flags 0x0 */
7)   0.506 us    |    }
7)   1.680 us    |  }