Re: PATCH [2.4.0test10]: Kiobuf#02, fault-in fix

Eric Lowe
2000-11-04T01:28:30Z

Hello,

> Yes. The kernel often has to make these checks the non-intuitive way
> round, because a disk or network read IO actually involves write to
> memory, but a write IO only has to read from memory. The convention
> is that read/write flags which affect IO paths indicate whether we are
> writing from backing store, so we have to invert the sense to decide
> whether it's a write to memory.
>
> > This seems to further imply datain means 'read access':
> > if (((datain) && (!(vma->vm_flags & VM_WRITE))) ||
>
> No, because the next line is
> err = -EACCES;
> so (rw==READ) and !VM_WRITE is an error --- datain does imply write
> access to memory.

That's why I call it write_access in my patches instead:
there's no ambiguity about what we mean. :) But in any
case, it's much better than using (rw==READ) everywhere like
it used to be ...

--
Eric Lowe
Software Engineer, Systran Corporation
elowe@systran.com