[Question] ksm: rmap_item pointing to some stale vmas

From: Susheel Khiani
Date: Thu Apr 09 2015 - 10:06:06 EST


We are seeing an issue during try_to_unmap_ksm where in call to try_to_unmap_one is failing.

try_to_unmap_ksm in this particular case is trying to go through vmas associated with each rmap_item->anon_vma. What we see is this that the corresponding page is not mapped to any of the vmas associated with 2 rmap_item.

The associated rmap_item in this case looks like pointing to some valid vma but the said page is not found to be mapped under it. try_to_unmap_one thus fails to find valid ptes for these vmas.

At the same time we can see that the page actually is mapped in 2 separate and different vmas which are not part of rmap_item associated with page.

So whether rmap_item is pointing to some stale vmas and now the mapping has changed? Or there is something else going on here.
Any pointer would be appreciated.

Susheel Khiani

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