On 03/08/17 16:55, Michal Hocko wrote:

On Thu 03-08-17 15:20:31, Igor Stoppa wrote:

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On 03/08/17 14:48, Michal Hocko wrote:

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On Thu 03-08-17 13:11:45, Igor Stoppa wrote:

[...]

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But, to reply more specifically to your advice, yes, I think I could add
a flag to vm_struct and then retrieve its value, for the address being
processed, by passing through find_vm_area().

... and you can store vm_struct pointer to the struct page there 

"there" as in the new field of the union?
btw, what would be a meaningful name, since "private" is already taken?

For simplicity, I'll use, for now, "private2"

why not explicit vm_area?

ok :-)

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and you won't need to do the slow find_vm_area. I haven't checked

very closely

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but this should be possible in principle. I guess other callers might
benefit from this as well.

I am confused about this: if "private2" is a pointer, but when I get an
address, I do not even know if the address represents a valid pmalloc
page, how can i know when it's ok to dereference "private2"?

because you can make all pages which back vmalloc mappings have vm_area
pointer set.

Ah, now I see, I had missed that the field would be set for *all* pages
backed by vmalloc.

So, given a pointer, I still have to figure out if it refers to a
vmalloc area or not.

However, that is something I need to do anyway, to get the reference to
the corresponding page struct, in case it is indeed a vmalloc address.

--
thanks, igor

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