Bug#869149: linux: please merge Btrfs: fix early ENOSPC due to delalloc

[Christoph Anton Mitterer <calestyo@scientia.net>]

Source: linux
Version: 4.9.30-2+deb9u2
Severity: normal


Hey Ben, et al.

There seems to be an annoying bug in btrfs, as described here:
https://www.spinics.net/lists/linux-btrfs/msg67479.html

It's not really extremely critical as it causes no direct fs corruption,
but it gives spurious ENOSPC in case of heavy metadata operation,
even though plenty of space is left.

It affects stretch kernels as well as the current 4.12.


It can e.g. easily be hit, when copying a root-fs, as described in the
thread above.

There's a fix, which seems to work:
https://patchwork.kernel.org/patch/9829593/

Omar will mark it for linux-stable, I'm just reporting it here as well
to make sure that it doesn't get lost :-)


Best wishes,
Chris