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SubjectRe: [PATCH 4/4] mm/gup: remove get_user_pages_locked()
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On 1/31/22 05:36, Jason Gunthorpe wrote:
...
>> @@ -968,15 +966,15 @@ static long do_get_mempolicy(int *policy, nodemask_t *nmask,
>> if (flags & MPOL_F_NODE) {
>> if (flags & MPOL_F_ADDR) {
>> /*
>> - * Take a refcount on the mpol, lookup_node()
>> - * will drop the mmap_lock, so after calling
>> - * lookup_node() only "pol" remains valid, "vma"
>> - * is stale.
>> + * Take a refcount on the mpol, because we are about to
>> + * drop the mmap_lock, after which only "pol" remains
>> + * valid, "vma" is stale.
>> */
>> pol_refcount = pol;
>> vma = NULL;
>> mpol_get(pol);
>> err = lookup_node(mm, addr);
>> + mmap_read_unlock(mm);
>
> How about move the mmap_read_unlock up one line and then use
> get_user_pages_fast()
>
> I'm guessing in most cases here the PTE will be present so that should
> be a net win?

Neat, I'll do that.


thanks,
--
John Hubbard
NVIDIA

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