du_test: Skip three tests if sparse files are not supported

[arichardson]

Summary

This fixes running the du tests with /tmp as tmpfs (which is what we do in the
CheriBSD CI).

Obtained from: CheriBSD
Co-authored-by: Brooks Davis <[e-mail]>

[ngie]

This isn't the right approach; please use getconf MIN_HOLE_SIZE instead, like the ls tests do

83 create_test_inputs2()
84 {
85         create_test_dir
86 
87         if ! getconf MIN_HOLE_SIZE "$(pwd)"; then
88             echo "getconf MIN_HOLE_SIZE $(pwd) failed; sparse files probably" \
89                  "not supported by file system"
90             mount
91             atf_skip "Test's work directory does not support sparse files;" \
92                      "try with a different TMPDIR?"
93         fi

[arichardson]

In D28398#635444, @ngie wrote:

This isn't the right approach; please use getconf MIN_HOLE_SIZE instead, like the ls tests do

83 create_test_inputs2()
84 {
85         create_test_dir
86 
87         if ! getconf MIN_HOLE_SIZE "$(pwd)"; then
88             echo "getconf MIN_HOLE_SIZE $(pwd) failed; sparse files probably" \
89                  "not supported by file system"
90             mount
91             atf_skip "Test's work directory does not support sparse files;" \
92                      "try with a different TMPDIR?"
93         fi

Thanks, I was not aware of MIN_HOLE_SIZE. Seems to report a sensible value on UFS and fail on tmpfs and smbfs. Will update the patch tomorrow.

[arichardson]

Use MIN_HOLE_SIZE

[arichardson]

correct version of diff

[arichardson]

With this change I now get three skipped tests by default, and if I do env TMPDIR=/root/tmp to run them on UFS all of them pass.

[ngie]

This might be a good thing to add to a general purpose library.