[LU-13745] tasks hang with copy_file_range: ll_file_splice_read()

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Severity: 3
• Assignee: Zhenyu Xu
• Reporter: Zhenyu Xu

Description

copy_file_range(2) reads from a Lustre file hang.

With no .copy_file_range VFS API implemented it calls do_splice_direct()->splice_direct_to_actor()->do_splice_to()->ll_file_splice_read().

While the call chain of ll_file_splice_read()->ll_file_io_generic()->generic_file_splice_read()->ll_file_read_iter()->ll_file_io_generic().

And that would try to get LDLM lock twice in ll_file_io_generic(), so that hang ensued.