Messages in this thread | | | Date | Fri, 01 May 2009 13:46:55 +0200 | From | Eric Dumazet <> | Subject | Re: [PATCH mmotm] mm: alloc_large_system_hash check order |
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Hugh Dickins a écrit : > On Thu, 30 Apr 2009, Mel Gorman wrote: >> On Wed, Apr 29, 2009 at 10:09:48PM +0100, Hugh Dickins wrote: >>> 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.
>>> >>> Signed-off-by: Hugh Dickins <hugh@veritas.com> >> Looks good >> >> Reviewed-by: Mel Gorman <mel@csn.ul.ie> > > Thanks. > >> 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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