fio: X trim entries leaked? messages after trim verify workloads

[mjekdi]

Please acknowledge the following before creating a ticket

• I have read the GitHub issues section of REPORTING-BUGS.

Description of the bug:
For trim verify workloads fio will print a message like "fio: X trim entries leaked?" upon workload completion. I am unsure what this message means but trim verify appears to be working as expected so it may be a bug. Note that it does not seem to reproduce when trim_backlog=1.

Environment: Ubuntu 26.04, Linux 7.0.0-22

fio version: fio-3.42-98-g179f

Reproduction steps

1. Run the following workload:

# fio trim-verify.ini --output=trim-verify.log

[trim-verify]
direct=1
size=10%
bs=16k
rw=randwrite
trim_percentage=2
trim_backlog=1000000
verify=crc32c
verify_backlog=2000000
filename=/dev/nvme0n1

2. Upon completion fio will print a message about trim entries leaked to the console and to the output log (attached):

trim-verify: (g=0): rw=randwrite, bs=(R) 16.0KiB-16.0KiB, (W) 16.0KiB-16.0KiB, (T) 16.0KiB-16.0KiB, ioengine=psync, iodepth=1
fio-3.42-98-g179f
Starting 1 process
fio: 5101 trim entries leaked?
...

trim-verify.log

[vincentkfu]

This message appears when Fio is in the process of exiting but has not fully drained the list of offsets that were saved for trim operations. Try to carry out some experiments with --debug=io,verify on a small job to understand what is happening.