[LU-12460] lli_trunc_sem can lead to a readlock

• Type: Bug
• Resolution: Fixed
• Priority: Major
• Fix Version/s: Lustre 2.14.0
• Affects Version/s: Lustre 2.13.0, Lustre 2.12.2
• Environment: Any lustre client
• Severity: 3
• Assignee: Neil Brown
• Reporter: James A Simmons

Description

Neil Brown discovered during the linux lustre client work a potential read lock condition involving lli_trunc_sem. If you mmap a lustre file, then read into that mapped memory from the file they can shared the same mmap_sem which does is okay since they are down_read() calls. The read lock can happen if truncate is called in between memory mapping the file and reading into the that mapped memory from the file.

Issue Links

• is related to: LU-12511 Prepare lustre for adoption into the linux kernel