[PATCH] mm: remove unnecessary __get_user_pages_unlocked() calls

[Lorenzo Stoakes]

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 <lstoa...@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