Add new L2ARC tests with Compressed ARC enabled/disabled

[allanjude]

Signed-off-by: Allan Jude allanjude@freebsd.org
Sponsored-by: The FreeBSD Foundation

Motivation and Context

Blocks are handled differently depending on the state of the
zfs_compressed_arc_enabled tunable.

If a block is compressed on-disk, and compressed_arc is enabled:

• the block is read from disk
• It is NOT decompressed
• It is added to the ARC in its compressed form
• l2arc_write_buffers() may write it to the L2ARC (as is)
• l2arc_read_done() compares the checksum to the BP (compressed)

However, if compressed_arc is disabled:

• the block is read from disk
• It is decompressed
• It is added to the ARC (uncompressed)
• l2arc_write_buffers() will use l2arc_apply_transforms() to
  recompress the block, before writing it to the L2ARC
• l2arc_read_done() compares the checksum to the BP (compressed)
• l2arc_read_done() will use l2arc_untransform() to uncompress it

Description

This test writes out a test file to a pool consisting of one disk
and one cache device, then randomly reads from it. Since the arc_max
in the tests is low, this will feed the L2ARC, and result in reads
from the L2ARC.

We compare the value of the kstat l2_cksum_bad before and after
to determine if any blocks failed to survive the trip through the
L2ARC.

Note: It is expected for the second test, with compressed ARC disabled to fail. This test found a bug, I'll post the fix as a separate PR. I wanted to be able to show the test failing before, and passing after.

How Has This Been Tested?

The tests have been run on Linux (CentOS 7) and FreeBSD (12.1)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the ZFS on Linux code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• I have run the ZFS Test Suite with this change applied.
• All commit messages are properly formatted and contain Signed-off-by.

[bghira]

#7896

[codecov]

Codecov Report

Merging #10692 into master will increase coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #10692      +/-   ##
==========================================
+ Coverage   79.77%   79.80%   +0.02%     
==========================================
  Files         394      394              
  Lines      124647   124647              
==========================================
+ Hits        99438    99474      +36     
+ Misses      25209    25173      -36     

Flag	Coverage Δ
#kernel	80.35% <ø> (+0.01%)	⬆️
#user	66.33% <ø> (+0.14%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
module/os/linux/spl/spl-zlib.c	55.35% <0.00%> (-28.58%)	⬇️
module/zfs/zio_compress.c	89.74% <0.00%> (-2.57%)	⬇️
module/zfs/dsl_synctask.c	92.40% <0.00%> (-2.54%)	⬇️
lib/libzfs/libzfs_changelist.c	84.26% <0.00%> (-1.88%)	⬇️
cmd/zed/agents/fmd_api.c	88.61% <0.00%> (-1.78%)	⬇️
cmd/ztest/ztest.c	78.88% <0.00%> (-1.60%)	⬇️
cmd/zed/agents/zfs_diagnosis.c	77.55% <0.00%> (-1.17%)	⬇️
module/zfs/dsl_userhold.c	89.17% <0.00%> (-1.12%)	⬇️
cmd/zdb/zdb.c	81.70% <0.00%> (-0.86%)	⬇️
module/zfs/txg.c	93.96% <0.00%> (-0.73%)	⬇️
... and 49 more

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[behlendorf]

You'll need to add both of these new tests to the tests/runfiles/common.run file so they're run by default.

[allanjude]

You'll need to add both of these new tests to the tests/runfiles/common.run file so they're run by default.

Ahh, that explains a lot.

Ok, that is done, lets see what CI things. It should fail the l2arc_compressed_arc_disabled test since that requires the fix from #10693

[behlendorf]

It looks like the test failed as expected. Can you add this change to the fix in #10693, then we can verify it passes and merge both the fix and test in a single commit.

[allanjude]

Pushed