Merge ~mwhudson/curtin:lp-1918990-dd-ext2 into curtin:master

[Michael Hudson-Doyle]

swap: use dd to allocate swapfiles on ext2 and ext3

LP: #1918990

[Ryan Harper (raharper)]

LGTM, one nit if you're so inclined.

review: Approve

26ae9cf... by Michael Hudson-Doyle on 2021-03-24

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[Michael Hudson-Doyle (mwhudson)]

Thanks, may as well do that. Now I guess I should go and figure out why jenkins isn't running CI jobs...

[Server Team CI bot (server-team-bot)]

PASSED: Continuous integration, rev:5a9000bbd3d0b278135e569cee546e01635965aa
https://jenkins.ubuntu.com/server/job/curtin-ci/103/
Executed test runs:
    SUCCESS: https://jenkins.ubuntu.com/server/job/curtin-ci/nodes=metal-amd64/103/
    SUCCESS: https://jenkins.ubuntu.com/server/job/curtin-ci/nodes=metal-arm64/103/
    SUCCESS: https://jenkins.ubuntu.com/server/job/curtin-ci/nodes=metal-ppc64el/103/
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review: Approve (continuous-integration)

[Server Team CI bot (server-team-bot)]

PASSED: Continuous integration, rev:26ae9cf78c6875f83a197d468eddfe9b3458fb2e
https://jenkins.ubuntu.com/server/job/curtin-ci/105/
Executed test runs:
    SUCCESS: https://jenkins.ubuntu.com/server/job/curtin-ci/nodes=metal-amd64/105/
    SUCCESS: https://jenkins.ubuntu.com/server/job/curtin-ci/nodes=metal-arm64/105/
    SUCCESS: https://jenkins.ubuntu.com/server/job/curtin-ci/nodes=metal-ppc64el/105/
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Click here to trigger a rebuild:
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review: Approve (continuous-integration)

diff --git a/curtin/swap.py b/curtin/swap.py
index 11e95c4..7a0128d 100644
--- a/curtin/swap.py
+++ b/curtin/swap.py
@@ -135,9 +135,10 @@ def setup_swapfile(target, fstab=None, swapfile=None, size=None, maxsize=None,
 
     allocate_cmd = 'fallocate -l "${2}M" "$1"'
     # fallocate uses IOCTLs to allocate space in a filesystem, however it's not
-    # clear (from curtin's POV) that it creates non-sparse files as required by
-    # mkswap so we'll skip fallocate for now and use dd.
-    if fstype in ['btrfs', 'xfs']:
+    # clear (from curtin's POV) that it creates non-sparse files on btrfs or
+    # xfs as required by mkswap so we'll skip fallocate for now and use dd. It
+    # is also plain not supported on ext2 and ext3.
+    if fstype in ['btrfs', 'ext2', 'ext3', 'xfs']:
         allocate_cmd = 'dd if=/dev/zero "of=$1" bs=1M "count=$2"'
 
     mbsize = str(int(size / (2 ** 20)))