cp: fall back to read/write if copy_file_range fails

[asomers]

Summary

cp: fall back to read/write if copy_file_range fails

Even though copy_file_range has a file-system agnostic version, it still
fails on devfs (perhaps because the file descriptor is non-seekable?) In
that case, fallback to old-fashioned read/write. Fixes
"cp /dev/null /tmp/null"

Reported-by: Michael Butler

[imp]

Minor nit, which could report a bad write total in some rare circumstances is the only issue I see.

bin/cp/utils.c

249

if rcount < 0, then this code will execute where before it would not.

[asomers]

bin/cp/utils.c

249

Yeah, I'm aware of that. But I didn't think inaccurate SIGINFO output in the event of an error was a problem. Do you want me to fix it?

[mjg]

This is a serious regression, just please get this in. The SIGINFO nit can be sorted out later.

[mjg]

I think it fails because vn_copy_file_range checks for v_type == VREG while /dev/null is VCHR. There may be other problems.

[jmg]

Might I suggest that you enable NetBSD's cp tests, and add necessary tests to prevent this breakage again?

[allanjude]

head/bin/cp/utils.c

245 ↗

(On Diff #76932)

Is there a reason this isn't juse an else?

[imp]

head/bin/cp/utils.c

245 ↗

(On Diff #76932)

Think first time through