Hugh Dickins a écrit :

On Thu, 30 Apr 2009, Mel Gorman wrote:

quoted

On Wed, Apr 29, 2009 at 10:09:48PM +0100, Hugh Dickins wrote:

quoted

On an x86_64 with 4GB ram, tcp_init()'s call to alloc_large_system_hash(),
to allocate tcp_hashinfo.ehash, is now triggering an mmotm WARN_ON_ONCE on
order >= MAX_ORDER - it's hoping for order 11.  alloc_large_system_hash()
had better make its own check on the order.

Well, I dont know why, since alloc_large_system_hash() already take
care of retries, halving size between each tries.

quoted

quoted

Signed-off-by: Hugh Dickins <redacted>

Looks good

Reviewed-by: Mel Gorman <redacted>

Thanks.

quoted

As I was looking there, it seemed that alloc_large_system_hash() should be
using alloc_pages_exact() instead of having its own "give back the spare
pages at the end of the buffer" logic. If alloc_pages_exact() was used, then
the check for an order >= MAX_ORDER can be pushed down to alloc_pages_exact()
where it may catch other unwary callers.

How about adding the following patch on top of yours?

Well observed, yes indeed.  In fact, it even looks as if, shock horror,
alloc_pages_exact() was _plagiarized_ from alloc_large_system_hash().
Blessed be the GPL, I'm sure we can skip the lengthy lawsuits!

As a matter of fact, I was planning to call my lawyer, so I'll reconsider
this and save some euros, thanks !

;)

It makes sense to use a helper function if it already exist, of course !

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