Re: Proposal for kernel change

From: Alexander Viro (viro@math.psu.edu)
Date: Mon Jan 24 2000 - 04:36:18 EST


On Sun, 23 Jan 2000, Alan Cox wrote:

> > problem. Normal sys_read() and sys_write() would pass copy_to_user() /
> > copy_from_user() here. For sys_readv() and sys_writev() - well,
> > corresponding function that would copy to/from iovector. IIRC we have
> > something like that either in net/core/* or in net/socket.c...
>
> read and write sometimes lock and DMA from user pages in new driver toys
> using Stephen's rawio and kiovec stuff. You would need to be careful how
> you arranged it to avoid shooting yourself in the foot on future optimisations

Ouch... And what happens if we do write() _not_ from user page? I can't
think of a place that would write to character device from kernel space,
but...

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