On 10/20/2016 08:44 AM, Jan Stancek wrote: > > > > > ----- Original Message ----- >> From: "Mike Kravetz" <mike.krav...@oracle.com> >> To: linux...@kvack.org, linux-kernel@vger.kernel.org >> Cc: "Aneesh Kumar K . V" <aneesh.ku...@linux.vnet.ibm.com>, "Naoya >> Horiguchi" <n-horigu...@ah.jp.nec.com>, "Michal >> Hocko" <mho...@suse.com>, "Kirill A . Shutemov" >> <kirill.shute...@linux.intel.com>, "Hillf Danton" >> <hillf...@alibaba-inc.com>, "Dave Hansen" <dave.han...@linux.intel.com>, >> "Jan Stancek" <jstan...@redhat.com>, "Mike >> Kravetz" <mike.krav...@oracle.com> >> 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/57ff7bb4.1070...@redhat.com >> >> 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.
Thanks for the testing Jan. I do not have access to a Power system, so I simulated the condition to test. -- Mike Kravetz > > 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 >> >>
