internal/poll: CopyFileRange returns EIO on CentOS 7 ( Linux Kernel 3.10.0-1127) when io.Copy in mounted CIFS [1.15 backport]

[gopherbot]

@ianlancetaylor requested issue #42334 to be considered for backport to the next 1.15 minor release.

@gopherbot Please open backport issues for 1.15.

This is an unlikely error, but if it occurs there is no workaround.

[toothrot]

Approved. This is a serious issue with no workaround. This code is new in 1.15.

[gopherbot]

Change https://golang.org/cl/267917 mentions this issue: [release-branch.go1.15] internal/poll: treat copy_file_range EIO as not-handled

[gopherbot]

Closed by merging 1f2e58d to release-branch.go1.15.