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From: David Sterba <dsterba@suse.cz>
To: Michael Ruiz <michael@mruiz.dev>
Cc: linux-btrfs@vger.kernel.org, osandov@fb.com
Subject: Re: Linux swap file not activating after reboot
Date: Thu, 16 Jan 2020 19:55:39 +0100	[thread overview]
Message-ID: <20200116185539.GZ3929@twin.jikos.cz> (raw)
In-Reply-To: <5318295.DvuYhMxLoT@archlinux>

On Wed, Jan 15, 2020 at 04:34:02PM -0800, Michael Ruiz wrote:
> Hi,
>  I have a //@swap subvolume and i have a swapfile within it. I mount the 
> subvolume like such in fstab:
> 
> `rw,ssd,nofail,noautodefrag,nodatacow,nodatasum,subvolid=1234,subvol=/@swap`
> 
> It mounts correctly, but 1/15/20 4:20 PM kernel I get: 
> 
> `BTRFS warning (device dm-0): swapfile must not be copy-on-write`

There are two reasons why the message is printed, one is when the file
does not have the C attribute and another one when the the existing file
extents need to be COWed (same case as if the file is NOCOW and has been
snapshotted).

Plain reboot will not change the C attribute, so either there's a
snapshot of /@snap or the check of a used swapfile is wrong.

I tested it here, a swapfile that got almost full after a stress test,
followed by reboot and swapon (without any change to the file) was ok.

Doing a snapshot and swapon resulted in the message you saw.

After deleting the snapshot and waiting until it gets cleaned, swapon
did not activate the file anymore. Filefrag or fiemap don't report any
shared extents so here I' expect that the file should be in a valid
state for swapon.

Omar, any ideas?

  parent reply	other threads:[~2020-01-16 18:55 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-16  0:34 Linux swap file not activating after reboot Michael Ruiz
2020-01-16  0:51 ` Qu Wenruo
2020-01-16 18:55 ` David Sterba [this message]
2020-01-16 20:43   ` Omar Sandoval
2020-01-17  0:44     ` Michael Ruiz
2020-01-17 13:47       ` David Sterba

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