mm: gup: add __get_user_pages_unlocked to customize gup_flags

Some callers (like KVM) may want to set the gup_flags like FOLL_HWPOSION
to get a proper -EHWPOSION retval instead of -EFAULT to take a more
appropriate action if get_user_pages runs into a memory failure.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Peter Feiner <pfeiner@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/mm.h b/include/linux/mm.h
index fc499e67547566690e88074c5490f6b4325b2d89..3696b3bd1d7e241c5299e17a0ad47aef5b24a464 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1265,6 +1265,10 @@ long get_user_pages_locked(struct task_struct *tsk, struct mm_struct *mm,
                    unsigned long start, unsigned long nr_pages,
                    int write, int force, 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,
+                              int write, int force, struct page **pages,
+                              unsigned int gup_flags);
 long get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
                    unsigned long start, unsigned long nr_pages,
                    int write, int force, struct page **pages);

diff --git a/mm/gup.c b/mm/gup.c
index 71a37738a3269a0dc7cc54eda38d41fa2dfe819f..dad5875fb766b5e1d0f8044fce03826dcd782384 100644 (file)
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -582,9 +582,9 @@ static __always_inline long __get_user_pages_locked(struct task_struct *tsk,
                                                int write, int force,
                                                struct page **pages,
                                                struct vm_area_struct **vmas,
-                                               int *locked, bool notify_drop)
+                                               int *locked, bool notify_drop,
+                                               unsigned int flags)
 {
-       int flags = FOLL_TOUCH;
        long ret, pages_done;
        bool lock_dropped;
 
@@ -698,10 +698,36 @@ long get_user_pages_locked(struct task_struct *tsk, struct mm_struct *mm,
                           int *locked)
 {
        return __get_user_pages_locked(tsk, mm, start, nr_pages, write, force,
-                                      pages, NULL, locked, true);
+                                      pages, NULL, locked, true, FOLL_TOUCH);
 }
 EXPORT_SYMBOL(get_user_pages_locked);
 
+/*
+ * Same as get_user_pages_unlocked(...., FOLL_TOUCH) but it allows to
+ * pass additional gup_flags as last parameter (like FOLL_HWPOISON).
+ *
+ * NOTE: here FOLL_TOUCH is not set implicitly and must be set by the
+ * caller if required (just like with __get_user_pages). "FOLL_GET",
+ * "FOLL_WRITE" and "FOLL_FORCE" are set implicitly as needed
+ * according to the parameters "pages", "write", "force"
+ * respectively.
+ */
+__always_inline long __get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
+                                              unsigned long start, unsigned long nr_pages,
+                                              int write, int force, struct page **pages,
+                                              unsigned int gup_flags)
+{
+       long ret;
+       int locked = 1;
+       down_read(&mm->mmap_sem);
+       ret = __get_user_pages_locked(tsk, mm, start, nr_pages, write, force,
+                                     pages, NULL, &locked, false, gup_flags);
+       if (locked)
+               up_read(&mm->mmap_sem);
+       return ret;
+}
+EXPORT_SYMBOL(__get_user_pages_unlocked);
+
 /*
  * get_user_pages_unlocked() is suitable to replace the form:
  *
@@ -723,14 +749,8 @@ long get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
                             unsigned long start, unsigned long nr_pages,
                             int write, int force, struct page **pages)
 {
-       long ret;
-       int locked = 1;
-       down_read(&mm->mmap_sem);
-       ret = __get_user_pages_locked(tsk, mm, start, nr_pages, write, force,
-                                     pages, NULL, &locked, false);
-       if (locked)
-               up_read(&mm->mmap_sem);
-       return ret;
+       return __get_user_pages_unlocked(tsk, mm, start, nr_pages, write,
+                                        force, pages, FOLL_TOUCH);
 }
 EXPORT_SYMBOL(get_user_pages_unlocked);
 
@@ -794,7 +814,7 @@ long get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                int force, struct page **pages, struct vm_area_struct **vmas)
 {
        return __get_user_pages_locked(tsk, mm, start, nr_pages, write, force,
-                                      pages, vmas, NULL, false);
+                                      pages, vmas, NULL, false, FOLL_TOUCH);
 }
 EXPORT_SYMBOL(get_user_pages);
 

diff --git a/mm/nommu.c b/mm/nommu.c
index bfb690b0f986e54acb0511ac0370104f7f596705..4d1b8a19986770ad56f5ad58dc9d0250745851da 100644 (file)
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -224,9 +224,10 @@ long get_user_pages_locked(struct task_struct *tsk, struct mm_struct *mm,
 }
 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,
-                            int write, int force, struct page **pages)
+long __get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm,
+                              unsigned long start, unsigned long nr_pages,
+                              int write, int force, struct page **pages,
+                              unsigned int gup_flags)
 {
        long ret;
        down_read(&mm->mmap_sem);
@@ -235,6 +236,15 @@ 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(struct task_struct *tsk, struct mm_struct *mm,
+                            unsigned long start, unsigned long nr_pages,
+                            int write, int force, struct page **pages)
+{
+       return __get_user_pages_unlocked(tsk, mm, start, nr_pages, write,
+                                        force, pages, 0);
+}
 EXPORT_SYMBOL(get_user_pages_unlocked);
 
 /**