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From: Chris Murphy <lists@colorremedies.com>
To: Nikolay Borisov <nborisov@suse.com>
Cc: "Jürgen Herrmann" <t-5@t-5.eu>,
	"Btrfs BTRFS" <linux-btrfs@vger.kernel.org>
Subject: Re: btrfs send hangs after partial transfer and blocks all IO
Date: Thu, 13 Sep 2018 09:30:35 -0600	[thread overview]
Message-ID: <CAJCQCtQFfGzNrCSVsZXutfx+O5BdNEELieVuHbJ0mLBqATc-cw@mail.gmail.com> (raw)
In-Reply-To: <322267c4-5671-73f3-acca-797dd6fe3572@suse.com>

This is the 2nd or 3rd thread containing hanging btrfs send, with
kernel 4.18.x. The subject of one is "btrfs send hung in pipe_wait"
and the other I can't find at the moment. In that case though the hang
is reproducible in 4.14.x and weirdly it only happens when a snapshot
contains (perhaps many) reflinks. Scrub and check lowmem find nothing
wrong.

I have snapshots with a few reflinks (cp --reflink and also
deduplication), and I see maybe 15-30 second hangs where nothing is
apparently happening (in top or iotop), but I'm also not seeing any
blocked tasks or high CPU usage. Perhaps in my case it's just
recovering quickly.

Are there any kernel config options in "# Debug Lockups and Hangs"
that might hint at what's going on? Some of these are enabled in
Fedora debug kernels, which are built practically daily, e.g. right
now the latest in the build system is 4.19.0-0.rc3.git2.1 - which
translates to git 54eda9df17f3.


Chris Murphy

  reply	other threads:[~2018-09-13 20:40 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-13  8:34 btrfs send hangs after partial transfer and blocks all IO Jürgen Herrmann
2018-09-13  8:40 ` Nikolay Borisov
2018-09-13 10:29   ` Jürgen Herrmann
2018-09-13 10:50     ` Nikolay Borisov
2018-09-13 10:56       ` Jürgen Herrmann
2018-09-13 11:04         ` Nikolay Borisov
2018-09-13 11:50           ` Jürgen Herrmann
2018-09-13 12:02             ` Nikolay Borisov
2018-09-13 12:30               ` Jürgen Herrmann
2018-09-13 12:35                 ` Nikolay Borisov
2018-09-13 15:30                   ` Chris Murphy [this message]
2018-09-13 15:44                     ` Nikolay Borisov
2018-09-13 16:22                       ` Chris Murphy
2018-09-19 19:35                         ` Jürgen Herrmann
2018-09-19 19:41                   ` Jürgen Herrmann
2018-09-20 17:25                     ` Chris Murphy

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