HDFS-15930: Fix some @param errors in DirectoryScanner.

[zhuqi-lucas]

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[zhuqi-lucas]

@ferhui @Hexiaoqiao @ayushtkn
There are some @param errors fixed in this pr.
Could you help review this?

[hadoop-yetus]

💔 -1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	0m 38s		Docker mode activated.
			_ Prechecks _
+1 💚	dupname	0m 0s		No case conflicting files found.
+0 🆗	codespell	0m 1s		codespell was not available.
+1 💚	@author	0m 0s		The patch does not contain any @author tags.
-1 ❌	test4tests	0m 0s		The patch doesn't appear to include any new or modified tests. Please justify why no new tests are needed for this patch. Also please list what manual steps were performed to verify this patch.
			_ trunk Compile Tests _
+1 💚	mvninstall	32m 44s		trunk passed
+1 💚	compile	1m 21s		trunk passed with JDK Ubuntu-11.0.10+9-Ubuntu-0ubuntu1.20.04
+1 💚	compile	1m 13s		trunk passed with JDK Private Build-1.8.0_282-8u282-b08-0ubuntu1~20.04-b08
+1 💚	checkstyle	1m 1s		trunk passed
+1 💚	mvnsite	1m 23s		trunk passed
+1 💚	javadoc	0m 55s		trunk passed with JDK Ubuntu-11.0.10+9-Ubuntu-0ubuntu1.20.04
+1 💚	javadoc	1m 23s		trunk passed with JDK Private Build-1.8.0_282-8u282-b08-0ubuntu1~20.04-b08
+1 💚	spotbugs	3m 6s		trunk passed
+1 💚	shadedclient	16m 6s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	1m 11s		the patch passed
+1 💚	compile	1m 11s		the patch passed with JDK Ubuntu-11.0.10+9-Ubuntu-0ubuntu1.20.04
+1 💚	javac	1m 11s		the patch passed
+1 💚	compile	1m 8s		the patch passed with JDK Private Build-1.8.0_282-8u282-b08-0ubuntu1~20.04-b08
+1 💚	javac	1m 8s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
+1 💚	checkstyle	0m 52s		the patch passed
+1 💚	mvnsite	1m 11s		the patch passed
+1 💚	javadoc	0m 44s		the patch passed with JDK Ubuntu-11.0.10+9-Ubuntu-0ubuntu1.20.04
+1 💚	javadoc	1m 18s		the patch passed with JDK Private Build-1.8.0_282-8u282-b08-0ubuntu1~20.04-b08
+1 💚	spotbugs	3m 5s		the patch passed
+1 💚	shadedclient	16m 1s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
-1 ❌	unit	230m 12s	/patch-unit-hadoop-hdfs-project_hadoop-hdfs.txt	hadoop-hdfs in the patch passed.
+1 💚	asflicense	0m 45s		The patch does not generate ASF License warnings.
		315m 29s

Reason	Tests
Failed junit tests	hadoop.hdfs.server.namenode.TestAddOverReplicatedStripedBlocks
	hadoop.hdfs.server.datanode.TestBlockRecovery
	hadoop.hdfs.server.namenode.snapshot.TestNestedSnapshots
	hadoop.hdfs.server.balancer.TestBalancer
	hadoop.hdfs.TestRollingUpgrade
	hadoop.hdfs.server.datanode.TestDirectoryScanner

Subsystem	Report/Notes
Docker	ClientAPI=1.41 ServerAPI=1.41 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2829/1/artifact/out/Dockerfile
GITHUB PR	#2829
Optional Tests	dupname asflicense compile javac javadoc mvninstall mvnsite unit shadedclient spotbugs checkstyle codespell
uname	Linux 4cc5786ead65 4.15.0-58-generic #64-Ubuntu SMP Tue Aug 6 11:12:41 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / 464e00a
Default Java	Private Build-1.8.0_282-8u282-b08-0ubuntu1~20.04-b08
Multi-JDK versions	/usr/lib/jvm/java-11-openjdk-amd64:Ubuntu-11.0.10+9-Ubuntu-0ubuntu1.20.04 /usr/lib/jvm/java-8-openjdk-amd64:Private Build-1.8.0_282-8u282-b08-0ubuntu1~20.04-b08
Test Results	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2829/1/testReport/
Max. process+thread count	3044 (vs. ulimit of 5500)
modules	C: hadoop-hdfs-project/hadoop-hdfs U: hadoop-hdfs-project/hadoop-hdfs
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-2829/1/console
versions	git=2.25.1 maven=3.6.3 spotbugs=4.2.2
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[Hexiaoqiao]

+1 from my side.

[ayushtkn]

Thanx @qizhu-lucas for the improvement.
+1

[zhuqi-lucas]

Thanks a lot @Hexiaoqiao @ayushtkn for review.

[zhuqi-lucas]

@umamaheswararao @aajisaka Could you help check this?
Thanks.

[ayushtkn]

Thanx @qizhu-lucas for the contribution, @Hexiaoqiao for the review.

@qizhu-lucas, I missed your message, sorry.

[zhuqi-lucas]

Thanks @ayushtkn for commit and review.