HDFS-16798. SerialNumberMap should decrease current counter if the item exist

[ZanderXu]

Description of PR

During looking into some code related XATTR, I found there is a bug in SerialNumberMap, as bellow:

public int get(T t) {
  if (t == null) {
    return 0;
  }
  Integer sn = t2i.get(t);
  if (sn == null) {
    sn = current.getAndIncrement();
    if (sn > max) {
      current.getAndDecrement();
      throw new IllegalStateException(name + ": serial number map is full");
    }
    Integer old = t2i.putIfAbsent(t, sn);
    if (old != null) {
      // here: if the old is not null, we should decrease the current value.
      return old;
    }
    i2t.put(sn, t);
  }
  return sn;
} 

This bug will only cause that the capacity of serialNumberMap is less than expected, no other impact.

[slfan1989]

@ZanderXu Congratulations on your promotion to committer, very good!

[ZanderXu]

Congratulations on your promotion to committer, very good!

@slfan1989 Thanks, bro. You will get a promotion soon.

[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 1s		codespell was not available.
+0 🆗	detsecrets	0m 1s		detect-secrets 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	41m 51s		trunk passed
+1 💚	compile	1m 37s		trunk passed with JDK Ubuntu-11.0.16+8-post-Ubuntu-0ubuntu120.04
+1 💚	compile	1m 28s		trunk passed with JDK Private Build-1.8.0_342-8u342-b07-0ubuntu1~20.04-b07
+1 💚	checkstyle	1m 16s		trunk passed
+1 💚	mvnsite	1m 37s		trunk passed
+1 💚	javadoc	1m 17s		trunk passed with JDK Ubuntu-11.0.16+8-post-Ubuntu-0ubuntu120.04
+1 💚	javadoc	1m 42s		trunk passed with JDK Private Build-1.8.0_342-8u342-b07-0ubuntu1~20.04-b07
+1 💚	spotbugs	3m 40s		trunk passed
+1 💚	shadedclient	26m 39s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	1m 22s		the patch passed
+1 💚	compile	1m 26s		the patch passed with JDK Ubuntu-11.0.16+8-post-Ubuntu-0ubuntu120.04
+1 💚	javac	1m 26s		the patch passed
+1 💚	compile	1m 18s		the patch passed with JDK Private Build-1.8.0_342-8u342-b07-0ubuntu1~20.04-b07
+1 💚	javac	1m 18s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
+1 💚	checkstyle	1m 0s		the patch passed
+1 💚	mvnsite	1m 25s		the patch passed
+1 💚	javadoc	0m 56s		the patch passed with JDK Ubuntu-11.0.16+8-post-Ubuntu-0ubuntu120.04
+1 💚	javadoc	1m 30s		the patch passed with JDK Private Build-1.8.0_342-8u342-b07-0ubuntu1~20.04-b07
+1 💚	spotbugs	3m 32s		the patch passed
+1 💚	shadedclient	26m 8s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
+1 💚	unit	352m 32s		hadoop-hdfs in the patch passed.
+1 💚	asflicense	0m 54s		The patch does not generate ASF License warnings.
		471m 19s

Subsystem	Report/Notes
Docker	ClientAPI=1.41 ServerAPI=1.41 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-4987/1/artifact/out/Dockerfile
GITHUB PR	#4987
Optional Tests	dupname asflicense compile javac javadoc mvninstall mvnsite unit shadedclient spotbugs checkstyle codespell detsecrets
uname	Linux 1e14947bde23 4.15.0-191-generic #202-Ubuntu SMP Thu Aug 4 01:49:29 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / 1c17673
Default Java	Private Build-1.8.0_342-8u342-b07-0ubuntu1~20.04-b07
Multi-JDK versions	/usr/lib/jvm/java-11-openjdk-amd64:Ubuntu-11.0.16+8-post-Ubuntu-0ubuntu120.04 /usr/lib/jvm/java-8-openjdk-amd64:Private Build-1.8.0_342-8u342-b07-0ubuntu1~20.04-b07
Test Results	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-4987/1/testReport/
Max. process+thread count	2109 (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-4987/1/console
versions	git=2.25.1 maven=3.6.3 spotbugs=4.2.2
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[Hexiaoqiao]

Great catch here. +1 from my side.
IMO, this bug will only cause that the capacity of serialNumberMap is less than expected, no other impact, right? If true, suggest to add detail for the description segment of this PR.

[Hexiaoqiao]

@slfan1989 would you mind to take another check?
BTW please leave one email address for communication offline if possible.

[slfan1989]

Great catch here. +1 from my side. IMO, this bug will only cause that the capacity of serialNumberMap is less than expected, no other impact, right? If true, suggest to add detail for the description segment of this PR.

LGTM.
@ZanderXu Thanks for the contribution!

[slfan1989]

@slfan1989 would you mind to take another check? BTW please leave one email address for communication offline if possible.

my personal email slfan1989@foxmail.com, looking forward to communicating with you @Hexiaoqiao @ZanderXu

[ZanderXu]

@Hexiaoqiao @slfan1989 Thanks for your review.

This bug will only cause that the capacity of serialNumberMap is less than expected, no other impact.

Yes, it is. I have updated the description.

[Hexiaoqiao]

Committed to trunk. Thanks @ZanderXu for your works. Thanks @slfan1989 for your reviews.

[Hexiaoqiao]

@ZanderXu Please let me know if we should backport to other active branches.

[nstang01]

This mr may cause the corresponding relationship between t2i and i2t to be inconsistent? @Hexiaoqiao