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authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2015-02-11 15:26:53 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2015-02-11 17:06:04 -0800
commitb30fe6c7ced70f62862c3d09357e7e8084e98d9f (patch)
tree317c0298b2111b342e1ff031b5da5aad2b894c00 /arch/unicore32
parentdc6c9a35b66b520cf67e05d8ca60ebecad3b0479 (diff)
downloadlinux-b30fe6c7ced70f62862c3d09357e7e8084e98d9f.tar.bz2
mm: fix false-positive warning on exit due mm_nr_pmds(mm)
The problem is that we check nr_ptes/nr_pmds in exit_mmap() which happens *before* pgd_free(). And if an arch does pte/pmd allocation in pgd_alloc() and frees them in pgd_free() we see offset in counters by the time of the checks. We tried to workaround this by offsetting expected counter value according to FIRST_USER_ADDRESS for both nr_pte and nr_pmd in exit_mmap(). But it doesn't work in some cases: 1. ARM with LPAE enabled also has non-zero USER_PGTABLES_CEILING, but upper addresses occupied with huge pmd entries, so the trick with offsetting expected counter value will get really ugly: we will have to apply it nr_pmds, but not nr_ptes. 2. Metag has non-zero FIRST_USER_ADDRESS, but doesn't do allocation pte/pmd page tables allocation in pgd_alloc(), just setup a pgd entry which is allocated at boot and shared accross all processes. The proposal is to move the check to check_mm() which happens *after* pgd_free() and do proper accounting during pgd_alloc() and pgd_free() which would bring counters to zero if nothing leaked. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reported-by: Tyler Baker <tyler.baker@linaro.org> Tested-by: Tyler Baker <tyler.baker@linaro.org> Tested-by: Nishanth Menon <nm@ti.com> Cc: Russell King <linux@arm.linux.org.uk> Cc: James Hogan <james.hogan@imgtec.com> Cc: Guan Xuetao <gxt@mprc.pku.edu.cn> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/unicore32')
-rw-r--r--arch/unicore32/mm/pgd.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/unicore32/mm/pgd.c b/arch/unicore32/mm/pgd.c
index 08b8d4295e70..2ade20d8eab3 100644
--- a/arch/unicore32/mm/pgd.c
+++ b/arch/unicore32/mm/pgd.c
@@ -69,6 +69,7 @@ pgd_t *get_pgd_slow(struct mm_struct *mm)
no_pte:
pmd_free(mm, new_pmd);
+ mm_dec_nr_pmds(mm);
no_pmd:
free_pages((unsigned long)new_pgd, 0);
no_pgd:
@@ -96,7 +97,9 @@ void free_pgd_slow(struct mm_struct *mm, pgd_t *pgd)
pte = pmd_pgtable(*pmd);
pmd_clear(pmd);
pte_free(mm, pte);
+ atomic_long_dec(&mm->nr_ptes);
pmd_free(mm, pmd);
+ mm_dec_nr_pmds(mm);
free:
free_pages((unsigned long) pgd, 0);
}