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[PATCH] mm: remove unnecessary __get_user_pages_unlocked() calls

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In hva_to_pfn_slow() we are able to replace __get_user_pages_unlocked() with
get_user_pages_unlocked() since we can now pass gup_flags.

In async_pf_execute() we need to pass different tsk, mm arguments so
get_user_pages_remote() is the sane replacement here (having added manual
acquisition and release of mmap_sem.)

Since we pass a NULL pages parameter the subsequent call to
__get_user_pages_locked() will have previously bailed any attempt at
VM_FAULT_RETRY, so we do not change this behaviour by using
get_user_pages_remote() which does not invoke VM_FAULT_RETRY logic at all.

Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
---
 virt/kvm/async_pf.c | 7 ++++---
 virt/kvm/kvm_main.c | 5 ++---
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
index 8035cc1..e8c832c 100644
--- a/virt/kvm/async_pf.c
+++ b/virt/kvm/async_pf.c
@@ -82,10 +82,11 @@ static void async_pf_execute(struct work_struct *work)
 	/*
 	 * This work is run asynchromously to the task which owns
 	 * mm and might be done in another context, so we must
-	 * use FOLL_REMOTE.
+	 * access remotely.
 	 */
-	__get_user_pages_unlocked(NULL, mm, addr, 1, NULL,
-			FOLL_WRITE | FOLL_REMOTE);
+	down_read(&mm->mmap_sem);
+	get_user_pages_remote(NULL, mm, addr, 1, FOLL_WRITE, NULL, NULL);
+	up_read(&mm->mmap_sem);

 	kvm_async_page_present_sync(vcpu, apf);

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 2907b7b..c45d951 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1415,13 +1415,12 @@ static int hva_to_pfn_slow(unsigned long addr, bool *async, bool write_fault,
 		npages = get_user_page_nowait(addr, write_fault, page);
 		up_read(&current->mm->mmap_sem);
 	} else {
-		unsigned int flags = FOLL_TOUCH | FOLL_HWPOISON;
+		unsigned int flags = FOLL_HWPOISON;

 		if (write_fault)
 			flags |= FOLL_WRITE;

-		npages = __get_user_pages_unlocked(current, current->mm, addr, 1,
-						   page, flags);
+		npages = get_user_pages_unlocked(addr, 1, page, flags);
 	}
 	if (npages != 1)
 		return npages;
--
2.10.1

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[PATCH] mm: remove unnecessary __get_user_pages_unlocked() calls Lorenzo Stoakes <lstoakes@gmail.com> - 2016-10-26 01:40 +0200
  Re: [PATCH] mm: remove unnecessary __get_user_pages_unlocked() calls Lorenzo Stoakes <lstoakes@gmail.com> - 2016-10-26 01:50 +0200
    Re: [PATCH] mm: remove unnecessary __get_user_pages_unlocked() calls Michal Hocko <mhocko@kernel.org> - 2016-10-26 11:20 +0200
      Re: [PATCH] mm: remove unnecessary __get_user_pages_unlocked() calls Lorenzo Stoakes <lstoakes@gmail.com> - 2016-10-26 11:40 +0200
        Re: [PATCH] mm: remove unnecessary __get_user_pages_unlocked() calls Michal Hocko <mhocko@kernel.org> - 2016-10-26 12:00 +0200
  Re: [PATCH] mm: remove unnecessary __get_user_pages_unlocked() calls Lorenzo Stoakes <lstoakes@gmail.com> - 2016-10-26 10:10 +0200
    Re: [PATCH] mm: remove unnecessary __get_user_pages_unlocked() calls Michal Hocko <mhocko@kernel.org> - 2016-10-26 11:10 +0200
  Re: [PATCH] mm: remove unnecessary __get_user_pages_unlocked() calls Michal Hocko <mhocko@kernel.org> - 2016-10-26 11:20 +0200
  [PATCH v2] mm: remove unnecessary __get_user_pages_unlocked() calls Lorenzo Stoakes <lstoakes@gmail.com> - 2016-10-26 11:30 +0200
    Re: [PATCH v2] mm: remove unnecessary __get_user_pages_unlocked()  calls Andrew Morton <akpm@linux-foundation.org> - 2016-10-27 02:20 +0200

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