On Thu, Jul 20, 2017 at 03:10:35PM -0700, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@xxxxxx>
>
> If a lot of metadata is reserved for outstanding delayed allocations, we
> rely on shrink_delalloc() to reclaim metadata space in order to fulfill
> reservation tickets. However, shrink_delalloc() has a shortcut where if
> it determines that space can be overcommitted, it will stop early. This
> made sense before the ticketed enospc system, but now it means that
> shrink_delalloc() will often not reclaim enough space to fulfill any
> tickets, leading to an early ENOSPC. (Reservation tickets don't care
> about being able to overcommit, they need every byte accounted for.)
>
> Fix it by getting rid of the shortcut so that shrink_delalloc() reclaims
> all of the metadata it is supposed to. This fixes early ENOSPCs we were
> seeing when doing a btrfs receive to populate a new filesystem, as well
> as early ENOSPCs Christoph saw when doing a big cp -r onto Btrfs.
>
> Fixes: 957780eb2788 ("Btrfs: introduce ticketed enospc infrastructure")
> Tested-by: Christoph Anton Mitterer <mail@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Omar Sandoval <osandov@xxxxxx>
Reviewed-by: Josef Bacik <jbacik@xxxxxx>
Thanks,
Josef