The following commit has been merged into the x86/mm branch of tip: Commit-ID: 88993b1627f2a2205b2f3112c4d22448cd863df3 Gitweb: https://git.kernel.org/tip/88993b1627f2a2205b2f3112c4d22448cd863df3 Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx> AuthorDate: Thu, 26 Nov 2020 14:04:46 +01:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Tue, 01 Nov 2022 13:43:59 +01:00 mm: Update ptep_get_lockless()'s comment Improve the comment. Suggested-by: Matthew Wilcox <willy@xxxxxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Link: https://lkml.kernel.org/r/20221022114424.515572025%40infradead.org --- include/linux/pgtable.h | 15 ++++++--------- 1 file changed, 6 insertions(+), 9 deletions(-) diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index a108b60..c0b2900 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -300,15 +300,12 @@ static inline pte_t ptep_get(pte_t *ptep) #ifdef CONFIG_GUP_GET_PTE_LOW_HIGH /* - * WARNING: only to be used in the get_user_pages_fast() implementation. - * - * With get_user_pages_fast(), we walk down the pagetables without taking any - * locks. For this we would like to load the pointers atomically, but sometimes - * that is not possible (e.g. without expensive cmpxchg8b on x86_32 PAE). What - * we do have is the guarantee that a PTE will only either go from not present - * to present, or present to not present or both -- it will not switch to a - * completely different present page without a TLB flush in between; something - * that we are blocking by holding interrupts off. + * For walking the pagetables without holding any locks. Some architectures + * (eg x86-32 PAE) cannot load the entries atomically without using expensive + * instructions. We are guaranteed that a PTE will only either go from not + * present to present, or present to not present -- it will not switch to a + * completely different present page without a TLB flush inbetween; which we + * are blocking by holding interrupts off. * * Setting ptes from not present to present goes: *
|