HADOOP-18296. Memory fragmentation in ChecksumFileSystem readVectored() (#7732)

[steveloughran]

Option "fs.file.checksum.verify" disables checksum verification in local FS, so sliced subsets of larger buffers are never returned.

Stream capability "fs.capability.vectoredio.sliced" is true if a filesystem knows that it is returning slices of a larger buffer. This is false if a filesystem doesn't, or against the local FS in releases which lack this feature.

Contributed by Steve Loughran

Description of PR

this is #7732 as cherrypicked from branch-3.4 to trunk

How was this patch tested?

run modified common and hadoop-aws tests; full aws test in progress

For code changes:

• Does the title or this PR starts with the corresponding JIRA issue id (e.g. 'HADOOP-17799. Your PR title ...')?
• Object storage: have the integration tests been executed and the endpoint declared according to the connector-specific documentation?
• If adding new dependencies to the code, are these dependencies licensed in a way that is compatible for inclusion under ASF 2.0?
• If applicable, have you updated the LICENSE, LICENSE-binary, NOTICE-binary files?

[steveloughran]

tested s3 london with -Dparallel-tests -DtestsThreadCount=8 -Dscale

all good except those needing a yarn cluster.

[hadoop-yetus]

🎊 +1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	0m 52s		Docker mode activated.
			_ Prechecks _
+1 💚	dupname	0m 0s		No case conflicting files found.
+0 🆗	codespell	0m 0s		codespell was not available.
+0 🆗	detsecrets	0m 0s		detect-secrets was not available.
+0 🆗	xmllint	0m 0s		xmllint was not available.
+0 🆗	markdownlint	0m 0s		markdownlint was not available.
+1 💚	@author	0m 0s		The patch does not contain any @author tags.
+1 💚	test4tests	0m 0s		The patch appears to include 5 new or modified test files.
			_ trunk Compile Tests _
+0 🆗	mvndep	10m 8s		Maven dependency ordering for branch
+1 💚	mvninstall	39m 23s		trunk passed
+1 💚	compile	18m 57s		trunk passed with JDK Ubuntu-11.0.27+6-post-Ubuntu-0ubuntu120.04
+1 💚	compile	18m 8s		trunk passed with JDK Private Build-1.8.0_452-8u452-gaus1-0ubuntu120.04-b09
+1 💚	checkstyle	4m 59s		trunk passed
+1 💚	mvnsite	2m 45s		trunk passed
+1 💚	javadoc	2m 8s		trunk passed with JDK Ubuntu-11.0.27+6-post-Ubuntu-0ubuntu120.04
+1 💚	javadoc	1m 38s		trunk passed with JDK Private Build-1.8.0_452-8u452-gaus1-0ubuntu120.04-b09
+1 💚	spotbugs	4m 20s		trunk passed
+1 💚	shadedclient	42m 15s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+0 🆗	mvndep	0m 31s		Maven dependency ordering for patch
+1 💚	mvninstall	1m 54s		the patch passed
+1 💚	compile	18m 43s		the patch passed with JDK Ubuntu-11.0.27+6-post-Ubuntu-0ubuntu120.04
+1 💚	javac	18m 43s		the patch passed
+1 💚	compile	17m 29s		the patch passed with JDK Private Build-1.8.0_452-8u452-gaus1-0ubuntu120.04-b09
+1 💚	javac	17m 29s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
-0 ⚠️	checkstyle	5m 26s	/results-checkstyle-root.txt	root: The patch generated 1 new + 142 unchanged - 0 fixed = 143 total (was 142)
+1 💚	mvnsite	3m 4s		the patch passed
+1 💚	javadoc	2m 25s		the patch passed with JDK Ubuntu-11.0.27+6-post-Ubuntu-0ubuntu120.04
+1 💚	javadoc	1m 57s		the patch passed with JDK Private Build-1.8.0_452-8u452-gaus1-0ubuntu120.04-b09
+1 💚	spotbugs	4m 57s		the patch passed
+1 💚	shadedclient	45m 51s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
+1 💚	unit	24m 33s		hadoop-common in the patch passed.
+1 💚	unit	3m 57s		hadoop-aws in the patch passed.
+1 💚	asflicense	1m 19s		The patch does not generate ASF License warnings.
		282m 52s

Subsystem	Report/Notes
Docker	ClientAPI=1.51 ServerAPI=1.51 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-7846/1/artifact/out/Dockerfile
GITHUB PR	#7846
Optional Tests	dupname asflicense compile javac javadoc mvninstall mvnsite unit shadedclient spotbugs checkstyle codespell detsecrets xmllint markdownlint
uname	Linux 863bf91ffcaa 5.15.0-143-generic #153-Ubuntu SMP Fri Jun 13 19:10:45 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / b4e34be
Default Java	Private Build-1.8.0_452-8u452-gaus1-0ubuntu120.04-b09
Multi-JDK versions	/usr/lib/jvm/java-11-openjdk-amd64:Ubuntu-11.0.27+6-post-Ubuntu-0ubuntu120.04 /usr/lib/jvm/java-8-openjdk-amd64:Private Build-1.8.0_452-8u452-gaus1-0ubuntu120.04-b09
Test Results	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-7846/1/testReport/
Max. process+thread count	1295 (vs. ulimit of 5500)
modules	C: hadoop-common-project/hadoop-common hadoop-tools/hadoop-aws U: .
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-7846/1/console
versions	git=2.25.1 maven=3.6.3 spotbugs=4.2.2
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