Re: [PATCH] lib/iov_iter: Fix pipe handling in _copy_to_iter_mcsafe

From: Ross Zwisler
Date: Tue Jul 03 2018 - 12:47:49 EST

On Sun, Jul 01, 2018 at 08:52:20AM -0700, Dan Williams wrote:
> By mistake the ITER_PIPE early-exit / warning from copy_from_iter() was
> cargo-culted in _copy_to_iter_mcsafe() rather than a machine-check-safe
> version of copy_to_iter_pipe().
> Implement copy_pipe_to_iter_mcsafe() being careful to return the
> indication of short copies due to a CPU exception.
> Without this regression-fix all splice reads to dax-mode files fail.
> Fixes: 8780356ef630 ("x86/asm/memcpy_mcsafe: Define copy_to_iter_mcsafe()")
> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxxxx>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Tony Luck <tony.luck@xxxxxxxxx>
> Reported-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>

Tested-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>