----- Original Message ----- > From: "Mike Kravetz" <mike.kravetz@xxxxxxxxxx> > To: linux-mm@xxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx > Cc: "Aneesh Kumar K . V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx>, "Naoya Horiguchi" <n-horiguchi@xxxxxxxxxxxxx>, "Michal > Hocko" <mhocko@xxxxxxxx>, "Kirill A . Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>, "Hillf Danton" > <hillf.zj@xxxxxxxxxxxxxxx>, "Dave Hansen" <dave.hansen@xxxxxxxxxxxxxxx>, "Jan Stancek" <jstancek@xxxxxxxxxx>, "Mike > Kravetz" <mike.kravetz@xxxxxxxxxx> > Sent: Thursday, 20 October, 2016 5:11:16 AM > Subject: [PATCH 0/1] mm/hugetlb: fix huge page reservation leak in private mapping error paths > > This issue was discovered by Jan Stancek as described in > https://lkml.kernel.org/r/57FF7BB4.1070202@xxxxxxxxxx > > Error paths in hugetlb_cow() and hugetlb_no_page() do not properly clean > up reservation entries when freeing a newly allocated huge page. This > issue was introduced with commit 67961f9db8c4 ("mm/hugetlb: fix huge page > reserve accounting for private mappings). That commit uses the information > in private mapping reserve maps to determine if a reservation was already > consumed. This is important in the case of hole punch and truncate as the > pages are released, but reservation entries are not restored. > > This patch restores the reserve entries in hugetlb_cow and hugetlb_no_page > such that reserve entries are consistent with the global reservation count. > > The huge page reservation code is quite hard to follow, and this patch > makes it even more complex. One thought I had was to change the way > hole punch and truncate work so that private mapping pages are not thrown > away. This would eliminate the need for this patch as well as 67961f9db8c4. > It would change the existing semantics (as seen by the user) in this area, > but I believe the documentation (man pages) say the behavior is unspecified. > This could be a future change as well as rewriting the existing reservation > code to make it easier to understand/maintain. Thoughts? > > In any case, this patch addresses the immediate issue. Mike, Just to confirm, I ran this patch on my setup (without the patch from Aneesh) with libhugetlbfs testsuite in loop for several hours. There were no ENOMEM/OOM failures, I did not observe resv leak after it finished. Regards, Jan > > Mike Kravetz (1): > mm/hugetlb: fix huge page reservation leak in private mapping error > paths > > mm/hugetlb.c | 66 > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 66 insertions(+) > > -- > 2.7.4 > > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>