Redacted Send/Receive causes zdb to dump core

[loli10K]

Motivation and Context

When used with verbosity >= 4 zdb fails an assertion in dump_bookmarks() because it expects snprintf() to retun 0 on success.

root@master:~# zdb -ddddddd testpool/fs
Dataset testpool/fs [ZPL], ID 74, cr_txg 6, 24K, 6 objects, rootbp DVA[0]=<0:d000:200> DVA[1]=<0:100d000:200> [L0 DMU objset] fletcher4 lz4 unencrypted LE contiguous unique double size=1000L/200P birth=6L/6P fill=6 cksum=c5e39e0f3:4800b5c0ac7:dab03d77ffcb:1cd8517b60f997

    Deadlist: 0 (0/0 comp)

    mintxg 0 -> obj 77: object 77, 0 blkptrs, 0

    mintxg 1 -> obj 77: object 77, 0 blkptrs, 0

snprintf(buf, sizeof (buf), "%s#%s", osname, attr.za_name) == 0 (0xe == 0)
ASSERT at zdb.c:1943:dump_bookmarks()Aborted (core dumped)

Description

This was the only occurrence of zdb using VERIFY0() on snprintf() results, so i just removed it.

EDIT: gcc 7.3.1 20180303 does not like this (http://build.zfsonlinux.org/builders/Amazon%202%20x86_64%20%28BUILD%29/builds/12443/steps/shell_3/logs/make), change to VERIFY3S() instead.

How Has This Been Tested?

Run patched zdb binary on local builder, successfully use zdb -dddd testpool.

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.
• All new and existing tests passed.
• All commit messages are properly formatted and contain Signed-off-by.

[codecov]

Codecov Report

Merging #8948 into master will increase coverage by 0.03%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #8948      +/-   ##
==========================================
+ Coverage   78.48%   78.52%   +0.03%     
==========================================
  Files         388      388              
  Lines      120013   120013              
==========================================
+ Hits        94197    94239      +42     
+ Misses      25816    25774      -42

Flag	Coverage Δ
#kernel	79.44% <ø> (-0.02%)	⬇️
#user	65.87% <0%> (+0.01%)	⬆️

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[pcd1193182]

Interesting. Not sure how this worked on Illumos, which appears to have the same return semantics, but this is definitely a good change.

[behlendorf]

Do I understand correctly that the change to VERIFY3S resolved the gcc warning?

[loli10K]

@behlendorf yes, the Amazon 2 builder which was failing the build (http://build.zfsonlinux.org/builders/Amazon%202%20x86_64%20%28BUILD%29/builds/12443/steps/shell_3/logs/make) is now happy (http://build.zfsonlinux.org/builders/Amazon%202%20x86_64%20(BUILD)/builds/12447/steps/shell_3/logs/make)