persistent L2ARC minor fixes

[gamanakis]

Minor fixes on persistent L2ARC improving code readability and fixing a typo in zdb.c when byte-swapping a log block. It also improves the pesist_l2arc_007_pos.ksh test by giving it more time to retrieve log blocks on the cache device.

Signed-off-by: George Amanakis [email protected]

Motivation and Context

Description

How Has This Been Tested?

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.

[adamdmoss]

A minor nit, but reviewed and approved. :)

[codecov-io]

Codecov Report

Merging #10210 into master will decrease coverage by 13.75%.
The diff coverage is 0.00%.

@@             Coverage Diff             @@
##           master   #10210       +/-   ##
===========================================
- Coverage   79.23%   65.47%   -13.76%     
===========================================
  Files         388      306       -82     
  Lines      123392   106100    -17292     
===========================================
- Hits        97768    69470    -28298     
- Misses      25624    36630    +11006     

Flag	Coverage Δ
#kernel	?
#user	65.47% <0.00%> (+0.21%)	⬆️

Impacted Files	Coverage Δ
cmd/zdb/zdb.c	80.27% <0.00%> (-0.28%)	⬇️
module/zfs/arc.c	71.59% <0.00%> (-14.36%)	⬇️
module/zfs/objlist.c	0.00% <0.00%> (-100.00%)	⬇️
module/zfs/pathname.c	0.00% <0.00%> (-100.00%)	⬇️
include/sys/dmu_redact.h	0.00% <0.00%> (-100.00%)	⬇️
include/sys/dmu_traverse.h	0.00% <0.00%> (-100.00%)	⬇️
module/zfs/zfs_rlock.c	0.00% <0.00%> (-96.36%)	⬇️
module/lua/ltablib.c	2.34% <0.00%> (-95.32%)	⬇️
module/zfs/bqueue.c	0.00% <0.00%> (-94.45%)	⬇️
module/zcommon/zfs_deleg.c	0.00% <0.00%> (-92.46%)	⬇️
... and 241 more

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