[Bug 220489] New: copy_file_range glibc user-space emulation in versions 2.27-2.29 only

bugzilla-daemon
2025-08-25T06:40:12Z

Bug ID: 220489
Summary: copy_file_range glibc user-space emulation in versions
2.27-2.29 only
Product: Documentation
Version: unspecified
Hardware: All
OS: Linux
Status: NEW
Severity: low
Priority: P3
Component: man-pages
Assignee: documentation_man-pages@kernel-bugs.osdl.org
Reporter: hvtaifwkbgefbaei@gmail.com
Regression: No

Current version of the man page: "Linux 4.5, but glibc 2.27 provides a
user-space emulation when it is not available."

However, glibc 2.30 changelog:
The copy_file_range function fails with ENOSYS if the kernel does not support
the system call of the same name. Previously, user space emulation was
performed, but its behavior did not match the kernel behavior, which was deemed
too confusing. Applications which use the copy_file_range function can no
longer rely on glibc to provide a fallback on kernels that do not support the
copy_file_range system call, and if this function returns ENOSYS, they will
need to use their own fallback. Support for copy_file_range for most
architectures was added in version 4.5 of the mainline Linux kernel.