Messages in this thread | | | Date | Fri, 21 Feb 2014 11:23:39 -0600 | From | Jay Cornwall <> | Subject | put page on transparent huge page leaks? |
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Hi,
I'm tracking a possible memory leak in iommu/amd. The driver uses this logic to fault a page in response to a PRI from a device:
npages = get_user_pages(fault->state->task, fault->state->mm, fault->address, 1, write, 0, &page, NULL);
if (npages == 1) put_page(page); else ...
This works correctly when get_user_pages returns a 4KB page. When transparent huge pages are enabled any 2MB page returned by this call appears to leak on process exit. The non-cached memory usage stays elevated by the set of faulted 2MB pages. This behavior is not observed when the exception handler demand faults 2MB pages.
I notice there is a difference in reference count between the 4KB/2MB paths.
get_user_pages (4KB): page_count()=3, page_mapcount()=1 put_page (4KB): page_count()=2, page_mapcount()=1
get_user_pages (2MB): page_count()=3, page_mapcount()=1 put_page (2MB): page_count()=3, page_mapcount()=0
I'm concerned that the driver appears to be holding a reference count after put_page(). Am I interpreting this observation correctly?
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