Rework error handling in zpool_trim()

[jgallag88]

Motivation and Context

When a manual trim is run against an entire pool, errors about particular devices which don't support trim are suppressed. However, a non-zero status is returned. Moreover, if a wait was requested it is skipped, as if there had been a fatal error.

Description

This changes zpool_trim() in libzfs so that it doesn't return an error when the only errors are suppressed ones. An exception is made when none of the devices support trim, in which case an error is reported and a non-zero status is returned.

This also fixes how the --wait flag works in the presence of suppressed errors. In particular, suppressed errors no longer cause zpool_trim() to skip the wait.

I did some refactoring that I felt helped make the updated error-handling logic simpler. It also fixes a small memory leak, and a assertion failure that can happen in certain error paths, both related to the errlist nvlist constructed by lzc_trim.

How Has This Been Tested?

Ran zpool trim against a pool with devices which all support trim, against a pool with a mixture of devices that support trim and devices that don't, and against a pool with only devices that don't support trim. I checked that an error was reported in the third scenario, but not the first two.

I repeated the same tests, except specifying the vdevs explicitly instead of just trimming the whole pool. In this case, an error was reported in both of the last two scenarios.

In all cases, I check that a non-zero exit status was returned if and only if and only if an error was reported.

I also checked that in all of the scenarios above, if the wait flag was specified, the wait was performed unless an error was reported.

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.

[behlendorf]

Thanks!

[codecov-commenter]

Codecov Report

Merging #10372 into master will increase coverage by 0.10%.
The diff coverage is 79.06%.

@@            Coverage Diff             @@
##           master   #10372      +/-   ##
==========================================
+ Coverage   79.52%   79.62%   +0.10%     
==========================================
  Files         391      391              
  Lines      123590   123608      +18     
==========================================
+ Hits        98288    98427     +139     
+ Misses      25302    25181     -121     

Flag	Coverage Δ
#kernel	80.01% <ø> (+0.01%)	⬆️
#user	66.10% <79.06%> (+0.17%)	⬆️

Impacted Files	Coverage Δ
lib/libzfs/libzfs_pool.c	73.24% <79.06%> (-0.24%)	⬇️
module/zfs/vdev_raidz.c	88.88% <0.00%> (-4.36%)	⬇️
module/zfs/vdev_raidz_math.c	76.57% <0.00%> (-2.26%)	⬇️
module/zfs/zrlock.c	89.23% <0.00%> (-1.54%)	⬇️
module/os/linux/zfs/vdev_disk.c	83.65% <0.00%> (-0.78%)	⬇️
module/zfs/dsl_scan.c	85.87% <0.00%> (-0.68%)	⬇️
cmd/zed/agents/zfs_mod.c	77.55% <0.00%> (-0.67%)	⬇️
module/zfs/vdev_removal.c	96.55% <0.00%> (-0.58%)	⬇️
module/zfs/vdev_indirect_mapping.c	98.55% <0.00%> (-0.49%)	⬇️
module/os/linux/zfs/zpl_xattr.c	83.26% <0.00%> (-0.43%)	⬇️
... and 49 more

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