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author | Kirill A. Shutemov <kirill.shutemov@linux.intel.com> | 2015-02-11 15:26:53 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-02-11 17:06:04 -0800 |
commit | b30fe6c7ced70f62862c3d09357e7e8084e98d9f (patch) | |
tree | 317c0298b2111b342e1ff031b5da5aad2b894c00 /arch/arm/mm | |
parent | dc6c9a35b66b520cf67e05d8ca60ebecad3b0479 (diff) | |
download | linux-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/arm/mm')
-rw-r--r-- | arch/arm/mm/pgd.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/arm/mm/pgd.c b/arch/arm/mm/pgd.c index 249379535be2..a3681f11dd9f 100644 --- a/arch/arm/mm/pgd.c +++ b/arch/arm/mm/pgd.c @@ -97,6 +97,7 @@ pgd_t *pgd_alloc(struct mm_struct *mm) no_pte: pmd_free(mm, new_pmd); + mm_dec_nr_pmds(mm); no_pmd: pud_free(mm, new_pud); no_pud: @@ -130,9 +131,11 @@ void pgd_free(struct mm_struct *mm, pgd_t *pgd_base) pte = pmd_pgtable(*pmd); pmd_clear(pmd); pte_free(mm, pte); + atomic_long_dec(&mm->nr_ptes); no_pmd: pud_clear(pud); pmd_free(mm, pmd); + mm_dec_nr_pmds(mm); no_pud: pgd_clear(pgd); pud_free(mm, pud); @@ -152,6 +155,7 @@ no_pgd: pmd = pmd_offset(pud, 0); pud_clear(pud); pmd_free(mm, pmd); + mm_dec_nr_pmds(mm); pgd_clear(pgd); pud_free(mm, pud); } |