Messages in this thread | | | Date | Wed, 22 Mar 2006 08:19:24 -0800 (PST) | From | Linus Torvalds <> | Subject | Re: [PATCH 10 of 20] ipath - support for userspace apps using core driver |
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On Wed, 22 Mar 2006, Bryan O'Sullivan wrote: > > Under 2.6.15, what seems to be actually happening is that vmops->nopage > is being called on each page of a 32K compound page, driving the page > count from 1 (prior to any nopage calls) to 9. By the time I get to my > cleanup code, the page count has gone from 9 to 8 (whereas under 2.6.16, > the page count has gone from 9 back to 1, where it belongs). From this, > it seems fairly clear that the kernel isn't decrementing the use counts > correctly on compound pages in 2.6.15.
Ahh. Isn't this the same problem that the fairly recent "mm: compound release fix" by Nick should fix?
Git commit ID 8519fb30e438f8088b71a94a7d5a660a814d3872, to be exact:
Author: Nick Piggin <npiggin@suse.de> Date: Tue Feb 7 12:58:52 2006 -0800
[PATCH] mm: compound release fix
Compound pages on SMP systems can now often be freed from pagetables via the release_pages path. This uses put_page_testzero which does not handle compound pages at all. Releasing constituent pages from process mappings decrements their count to a large negative number and leaks the reference at the head page - net result is a memory leak.
The problem was hidden because the debug check in put_page_testzero itself actually did take compound pages into consideration.
Fix the bug and the debug check.
Signed-off-by: Nick Piggin <npiggin@suse.de> Acked-by: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
But anything based on 2.6.16-rc6 should be fine (The bug was fixed by 2.6.16-rc3, methinks). You said:
"First of all, it turns out that the BUG I mentioned was reported against the SLES10 2.6.16-rc6 kernel. I haven't had a chance to chase it down yet, but I'm going to have to, because..."
but if that _really_ is 2.6.16-rc6-based, this problem should have been fixed already.
Maybe SLES is based on 2.6._15_-rc6?
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