Re: [PATCH] mm: memcontrol: Make the walk_page_range() limit obvious
From: Michal Hocko <mhocko@kernel.org>
Date: 2016-08-31 15:17:34
Also in:
linux-mm
On Wed 31-08-16 16:04:57, James Morse wrote:
Trying to walk all of virtual memory requires architecture specific knowledge. On x86_64, addresses must be sign extended from bit 48, whereas on arm64 the top VA_BITS of address space have their own set of page tables. mem_cgroup_count_precharge() and mem_cgroup_move_charge() both call walk_page_range() on the range 0 to ~0UL, neither provide a pte_hole callback, which causes the current implementation to skip non-vma regions. As this call only expects to walk user address space, make it walk 0 to 'highest_vm_end'. Signed-off-by: James Morse <james.morse@arm.com> Cc: Naoya Horiguchi <redacted> --- This is in preparation for a RFC series that allows walk_page_range() to walk kernel page tables too.
OK, so do I get it right that this is only needed with that change? Because AFAICS walk_page_range will be bound to the last vma->vm_end right now. If this is the case this should be mentioned in the changelog because the above might confuse somebody to think this is a bug fix. Other than that this seams reasonable to me.
quoted hunk ↗ jump to hunk
mm/memcontrol.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 2ff0289ad061..bfd54b43beb9 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c@@ -4712,7 +4712,8 @@ static unsigned long mem_cgroup_count_precharge(struct mm_struct *mm) .mm = mm, }; down_read(&mm->mmap_sem); - walk_page_range(0, ~0UL, &mem_cgroup_count_precharge_walk); + walk_page_range(0, mm->highest_vm_end, + &mem_cgroup_count_precharge_walk); up_read(&mm->mmap_sem); precharge = mc.precharge;@@ -5000,7 +5001,8 @@ retry: * When we have consumed all precharges and failed in doing * additional charge, the page walk just aborts. */ - walk_page_range(0, ~0UL, &mem_cgroup_move_charge_walk); + walk_page_range(0, mc.mm->highest_vm_end, &mem_cgroup_move_charge_walk); + up_read(&mc.mm->mmap_sem); atomic_dec(&mc.from->moving_account); }-- 2.8.0.rc3 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
-- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>