Re: PF_MEMALLOC in 2.6

Stephen C. Tweedie
2004-08-20T10:31:53Z

Hi,

On Thu, 2004-08-19 at 13:41, Hugh Dickins wrote:

> Or would it solve the problem at hand, if it made itself PF_MEMALLOC
> just while servicing a request from a PF_MEMALLOC?

It's not the PF_* state of the caller who submitted the IO that matters,
though --- it's the state of all threads _waiting_ on the IO, which may
be different, and which can change even after the IO has begun.

Eg. kswapd does a writepage, the writepage needs to allocate disk space,
and in doing so tries to access a metadata block which is already
undergoing IO from a different thread altogether.

--Stephen