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dkim=pass header.d=Nvidia.com header.s=selector2 header.b=nr6KMwF+; spf=none (imf01.hostedemail.com: domain of jhubbard@nvidia.com has no SPF policy when checking 40.107.237.71) smtp.mailfrom=jhubbard@nvidia.com; dmarc=pass (policy=reject) header.from=nvidia.com X-HE-Tag: 1643659317-720364 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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