Re: [PATCH] fs/splice: ignore flag SPLICE_F_GIFT in syscall vmsplice

[Christoph Hellwig]

On Sun, Nov 10, 2019 at 01:01:23PM +0300, Konstantin Khlebnikov wrote:
> Generic support of flag SPLICE_F_MOVE in syscall splice was removed in
> kernel 2.6.21 commit 485ddb4b9741 ("1/2 splice: dont steal").
> Infrastructure stay intact and this feature may came back.
> At least driver or filesystem could provide own implementation.
> 
> But stealing mapped pages from userspace never worked and is very
> unlikely that will ever make sense due to unmapping overhead.
> Also lru handling is broken if gifted anon page spliced into file.
> 
> Let's seal entry point for marking page as a gift in vmsplice.

Please kill off PIPE_BUF_FLAG_GIFT entirely, there is no need to keep
dead code around.  Anyone who cares enough can resurrect it from git
history.