mm: unexport __get_user_pages_unlocked()

Unexport the low-level __get_user_pages_unlocked() function and replaces
invocations with calls to more appropriate higher-level functions.

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() and process_vm_rw_single_vec() we need to pass
different tsk, mm arguments so get_user_pages_remote() is the sane
replacement in these cases (having added manual acquisition and release
of mmap_sem.)

Additionally get_user_pages_remote() reintroduces use of the FOLL_TOUCH
flag.  However, this flag was originally silently dropped by commit
1e9877902dc7 ("mm/gup: Introduce get_user_pages_remote()"), so this
appears to have been unintentional and reintroducing it is therefore not
an issue.

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20161027095141.2569-3-lstoakes@gmail.com
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krcmar <rkrcmar@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

6 files changed, 25 insertions, 21 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index cc154454675a..7b2d14ed3815 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1280,9 +1280,6 @@ long get_user_pages(unsigned long start, unsigned long nr_pages,
                             struct vm_area_struct **vmas);
 long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
                     unsigned int gup_flags, struct page **pages, int *locked);
-long __get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
-                               unsigned long start, unsigned long nr_pages,
-                               struct page **pages, unsigned int gup_flags);
 long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
                     struct page **pages, unsigned int gup_flags);
 int get_user_pages_fast(unsigned long start, int nr_pages, int write,
diff --git a/mm/gup.c b/mm/gup.c
index b64c907aa4f0..55315555489d 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -865,9 +865,10 @@ EXPORT_SYMBOL(get_user_pages_locked);
  * caller if required (just like with __get_user_pages). "FOLL_GET"
  * is set implicitly if "pages" is non-NULL.
  */
-__always_inline long __get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
-                                               unsigned long start, unsigned long nr_pages,
-                                               struct page **pages, unsigned int gup_flags)
+static __always_inline long __get_user_pages_unlocked(struct task_struct *tsk,
+                struct mm_struct *mm, unsigned long start,
+                unsigned long nr_pages, struct page **pages,
+                unsigned int gup_flags)
 {
         long ret;
         int locked = 1;
@@ -879,7 +880,6 @@ __always_inline long __get_user_pages_unlocked(struct task_struct *tsk, struct m
                 up_read(&mm->mmap_sem);
         return ret;
 }
-EXPORT_SYMBOL(__get_user_pages_unlocked);
 
 /*
  * get_user_pages_unlocked() is suitable to replace the form:
diff --git a/mm/nommu.c b/mm/nommu.c
index 9720e0bab029..c299a7fbca70 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -176,9 +176,10 @@ long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
 }
 EXPORT_SYMBOL(get_user_pages_locked);
 
-long __get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
-                               unsigned long start, unsigned long nr_pages,
-                               struct page **pages, unsigned int gup_flags)
+static long __get_user_pages_unlocked(struct task_struct *tsk,
+                        struct mm_struct *mm, unsigned long start,
+                        unsigned long nr_pages, struct page **pages,
+                        unsigned int gup_flags)
 {
         long ret;
         down_read(&mm->mmap_sem);
@@ -187,7 +188,6 @@ long __get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
         up_read(&mm->mmap_sem);
         return ret;
 }
-EXPORT_SYMBOL(__get_user_pages_unlocked);
 
 long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
                              struct page **pages, unsigned int gup_flags)
diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
index be8dc8d1edb9..84d0c7eada2b 100644
--- a/mm/process_vm_access.c
+++ b/mm/process_vm_access.c
@@ -88,7 +88,7 @@ static int process_vm_rw_single_vec(unsigned long addr,
         ssize_t rc = 0;
         unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES
                 / sizeof(struct pages *);
-        unsigned int flags = FOLL_REMOTE;
+        unsigned int flags = 0;
 
         /* Work out address and page range required */
         if (len == 0)
@@ -100,15 +100,19 @@ static int process_vm_rw_single_vec(unsigned long addr,
 
         while (!rc && nr_pages && iov_iter_count(iter)) {
                 int pages = min(nr_pages, max_pages_per_loop);
+                int locked = 1;
                 size_t bytes;
 
                 /*
                  * Get the pages we're interested in.  We must
-                 * add FOLL_REMOTE because task/mm might not
+                 * access remotely because task/mm might not
                  * current/current->mm
                  */
-                pages = __get_user_pages_unlocked(task, mm, pa, pages,
-                                                  process_pages, flags);
+                down_read(&mm->mmap_sem);
+                pages = get_user_pages_remote(task, mm, pa, pages, flags,
+                                              process_pages, NULL, &locked);
+                if (locked)
+                        up_read(&mm->mmap_sem);
                 if (pages <= 0)
                         return -EFAULT;
 
diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
index efeceb0a222d..3815e940fbea 100644
--- a/virt/kvm/async_pf.c
+++ b/virt/kvm/async_pf.c
@@ -76,16 +76,20 @@ static void async_pf_execute(struct work_struct *work)
         struct kvm_vcpu *vcpu = apf->vcpu;
         unsigned long addr = apf->addr;
         gva_t gva = apf->gva;
+        int locked = 1;
 
         might_sleep();
 
         /*
          * 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,
+                        &locked);
+        if (locked)
+                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 823544c166be..de102cae7125 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1418,13 +1418,12 @@ 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;