Re: Do we need to unrevert "fs: do not prefault sys_write() user buffer pages"?

David Howells
2021-06-22T17:55:43Z

Linus Torvalds <torvalds@linux-foundation.org> wrote:

> End result: doing the fault_in_readable "unnecessarily" at the
> beginning is likely the better optimization. It's basically free when
> it's not necessary, and it avoids an extra fault (and extra
> lock/unlock and retry) when it does end up faulting pages in.

It may also cause the read in to happen in the background whilst write_begin
is being done.

David