2.2.1{3,4,5pre*} VM bug found

[Stephen C. Tweedie]

Hi,

On Wed, 26 Jan 2000 01:48:43 +0100 (CET), Rik van Riel
<riel en nl.linux.org> said:

> The problem in this case is that schedule() may be called
> from within get_page(GFP_KERNEL). This already was possible
> in 2.2.14 and before (if the task had to wait for I/O on
> try_to_free_pages()), but the explicit schedule() in my
> stuff in 2.2.15pre4 amplified the problem and made it
> visible.

It's not only possible, it is explicitly legal.  It always has been.
You _must_ call it with GFP_ATOMIC if you can't afford to block (or,
alternatively, call it without __GFP_IO, or with the PF_MEMALLOC flag).

> A fix for this problem is in one of my other emails 

It's not a problem.  If callers are expecting GFP_KERNEL to be atomic,
then _that_ is a problem, but it is perfectly all right for GFP_KERNEL
allocations to block.

--Stephen

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