After Jenkins upgraded from 2.46.2 to 2.138.4 on Jan 5. 2019,

I started to see many (deleted) open file handles.

Those (deleted) open file handles seem caused by "discard old build" rotate.

The "builds/.${old-build-number}" folder doesn't exist anymore,

but when using "lsof" command to check, it showed up:

sudo lsof -a -p $(pgrep -P $(sudo cat /var/run/jenkins/jenkins.pid)) | grep '(deleted)'

eg

java 34189 jenkins 5199r REG 252,0 1818111 17044616 /var/lib/jenkins/jobs/Projects/jobs/FortiClientEMS/jobs/br_6_Branch_Build/builds/.1394/log (deleted)

java 34189 jenkins 5200r REG 252,0 1813394 17052273 /var/lib/jenkins/jobs/Projects/jobs/FortiClientEMS/jobs/br_6_Branch_Build/builds/.1388/log (deleted)

java 34189 jenkins 5201r REG 252,0 1813394 17052273 /var/lib/jenkins/jobs/Projects/jobs/FortiClientEMS/jobs/br_6_Branch_Build/builds/.1388/log (deleted)

java 34189 jenkins 5212r REG 252,0 1815212 17053470 /var/lib/jenkins/jobs/Projects/jobs/FortiClientEMS/jobs/br_6_Branch_Build/builds/.1398/log (deleted)