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Fix comparison signedness in arc_is_overflowing() #8873

Merged
merged 1 commit into from
Jun 10, 2019
Merged

Fix comparison signedness in arc_is_overflowing() #8873

merged 1 commit into from
Jun 10, 2019

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amotin
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@amotin amotin commented Jun 8, 2019

Motivation and Context

When ARC size is very small, aggsum_lower_bound(&arc_size) may return
negative values, that due to unsigned comparison caused delays, waiting
for arc_adjust() to "fix" it by calling aggsum_value(&arc_size).

Description

Use of signed comparison there fixes the problem.

How Has This Been Tested?

Debug printf() added to arc_adjust() triggered several times during FreeBSD boot, while obviously should not.

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:

@amotin
Fix comparison signedness in arc_is_overflowing().
65f3718 
When ARC size is very small, aggsum_lower_bound(&arc_size) may return
negative values, that due to unsigned comparison caused delays, waiting
for arc_adjust() to "fix" it by calling aggsum_value(&arc_size).  Use
of signed comparison there fixes the problem.

Signed-off-by:	Alexander Motin <mav@FreeBSD.org>
gmelikov
gmelikov reviewed Jun 10, 2019
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LGTM

@behlendorf behlendorf added the Status: Accepted Ready to integrate (reviewed, tested) label Jun 10, 2019
@behlendorf behlendorf merged commit 5a902f5 into openzfs:master Jun 10, 2019
@amotin amotin deleted the arc_sign branch June 10, 2019 16:54
behlendorf pushed a commit that referenced this pull request Jun 11, 2019
@amotin @behlendorf
Fix comparison signedness in arc_is_overflowing()
7288881 
When ARC size is very small, aggsum_lower_bound(&arc_size) may return
negative values, that due to unsigned comparison caused delays, waiting
for arc_adjust() to "fix" it by calling aggsum_value(&arc_size).  Use
of signed comparison there fixes the problem.

Reviewed-by: Matt Ahrens <mahrens@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by:	Alexander Motin <mav@FreeBSD.org>
Closes #8873
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@gmelikov gmelikov gmelikov approved these changes

@ahrens ahrens ahrens approved these changes

@behlendorf behlendorf behlendorf approved these changes

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@amotin @behlendorf @ahrens @gmelikov