get rid of separate multipage fault-in primitives

* the only remaining callers of "short" fault-ins are just as happy with generic
variants (both in lib/iov_iter.c); switch them to multipage variants, kill the
"short" ones
* rename the multipage variants to now available plain ones.
* get rid of compat macro defining iov_iter_fault_in_multipage_readable by
expanding it in its only user.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

7 files changed, 9 insertions, 61 deletions

diff --git a/drivers/gpu/drm/armada/armada_gem.c b/drivers/gpu/drm/armada/armada_gem.c
index cb8f0347b934..ff843160c600 100644
--- a/drivers/gpu/drm/armada/armada_gem.c
+++ b/drivers/gpu/drm/armada/armada_gem.c
@@ -387,7 +387,7 @@ int armada_gem_pwrite_ioctl(struct drm_device *dev, void *data,
         if (!access_ok(VERIFY_READ, ptr, args->size))
                 return -EFAULT;
 
-        ret = fault_in_multipages_readable(ptr, args->size);
+        ret = fault_in_pages_readable(ptr, args->size);
         if (ret)
                 return ret;
 
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index a77ce9983f69..ccf56c60e6e8 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -675,7 +675,7 @@ i915_gem_gtt_pread(struct drm_device *dev,
 
         mutex_unlock(&dev->struct_mutex);
         if (likely(!i915.prefault_disable)) {
-                ret = fault_in_multipages_writeable(user_data, remain);
+                ret = fault_in_pages_writeable(user_data, remain);
                 if (ret) {
                         mutex_lock(&dev->struct_mutex);
                         goto out_unpin;
@@ -803,7 +803,7 @@ i915_gem_shmem_pread(struct drm_device *dev,
                 mutex_unlock(&dev->struct_mutex);
 
                 if (likely(!i915.prefault_disable) && !prefaulted) {
-                        ret = fault_in_multipages_writeable(user_data, remain);
+                        ret = fault_in_pages_writeable(user_data, remain);
                         /* Userspace is tricking us, but we've already clobbered
                          * its pages with the prefault and promised to write the
                          * data up to the first fault. Hence ignore any errors
@@ -1267,7 +1267,7 @@ i915_gem_pwrite_ioctl(struct drm_device *dev, void *data,
                 return -EFAULT;
 
         if (likely(!i915.prefault_disable)) {
-                ret = fault_in_multipages_readable(u64_to_user_ptr(args->data_ptr),
+                ret = fault_in_pages_readable(u64_to_user_ptr(args->data_ptr),
                                                    args->size);
                 if (ret)
                         return -EFAULT;
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index b35e5b6475b2..72628edda376 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1048,7 +1048,7 @@ validate_exec_list(struct drm_device *dev,
                         return -EFAULT;
 
                 if (likely(!i915.prefault_disable)) {
-                        if (fault_in_multipages_readable(ptr, length))
+                        if (fault_in_pages_readable(ptr, length))
                                 return -EFAULT;
                 }
         }
diff --git a/fs/ntfs/file.c b/fs/ntfs/file.c
index f548629dfaac..bf72a2c58b75 100644
--- a/fs/ntfs/file.c
+++ b/fs/ntfs/file.c
@@ -1850,7 +1850,7 @@ again:
                  * pages being swapped out between us bringing them into memory
                  * and doing the actual copying.
                  */
-                if (unlikely(iov_iter_fault_in_multipages_readable(i, bytes))) {
+                if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
                         status = -EFAULT;
                         break;
                 }
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 01e84436cddf..cb2e1d06d2e9 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -518,59 +518,10 @@ void page_endio(struct page *page, bool is_write, int err);
 extern void add_page_wait_queue(struct page *page, wait_queue_t *waiter);
 
 /*
- * Fault one or two userspace pages into pagetables.
- * Return -EINVAL if more than two pages would be needed.
- * Return non-zero on a fault.
+ * Fault everything in given userspace address range in.
  */
 static inline int fault_in_pages_writeable(char __user *uaddr, int size)
 {
-        int span, ret;
-
-        if (unlikely(size == 0))
-                return 0;
-
-        span = offset_in_page(uaddr) + size;
-        if (span > 2 * PAGE_SIZE)
-                return -EINVAL;
-        /*
-         * Writing zeroes into userspace here is OK, because we know that if
-         * the zero gets there, we'll be overwriting it.
-         */
-        ret = __put_user(0, uaddr);
-        if (ret == 0 && span > PAGE_SIZE)
-                ret = __put_user(0, uaddr + size - 1);
-        return ret;
-}
-
-static inline int fault_in_pages_readable(const char __user *uaddr, int size)
-{
-        volatile char c;
-        int ret;
-
-        if (unlikely(size == 0))
-                return 0;
-
-        ret = __get_user(c, uaddr);
-        if (ret == 0) {
-                const char __user *end = uaddr + size - 1;
-
-                if (((unsigned long)uaddr & PAGE_MASK) !=
-                                ((unsigned long)end & PAGE_MASK)) {
-                        ret = __get_user(c, end);
-                        (void)c;
-                }
-        }
-        return ret;
-}
-
-/*
- * Multipage variants of the above prefault helpers, useful if more than
- * PAGE_SIZE of data needs to be prefaulted. These are separate from the above
- * functions (which only handle up to PAGE_SIZE) to avoid clobbering the
- * filemap.c hotpaths.
- */
-static inline int fault_in_multipages_writeable(char __user *uaddr, int size)
-{
         char __user *end = uaddr + size - 1;
 
         if (unlikely(size == 0))
@@ -596,8 +547,7 @@ static inline int fault_in_multipages_writeable(char __user *uaddr, int size)
         return 0;
 }
 
-static inline int fault_in_multipages_readable(const char __user *uaddr,
-                                               int size)
+static inline int fault_in_pages_readable(const char __user *uaddr, int size)
 {
         volatile char c;
         const char __user *end = uaddr + size - 1;
diff --git a/include/linux/uio.h b/include/linux/uio.h
index 75b4aaf31a9d..7709f8d4a9cb 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -76,7 +76,6 @@ size_t iov_iter_copy_from_user_atomic(struct page *page,
                 struct iov_iter *i, unsigned long offset, size_t bytes);
 void iov_iter_advance(struct iov_iter *i, size_t bytes);
 int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes);
-#define iov_iter_fault_in_multipages_readable iov_iter_fault_in_readable
 size_t iov_iter_single_seg_count(const struct iov_iter *i);
 size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
                          struct iov_iter *i);
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 7e3138cfc8c9..ce4632002611 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -306,8 +306,7 @@ int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
 
         if (!(i->type & (ITER_BVEC|ITER_KVEC))) {
                 iterate_iovec(i, bytes, v, iov, skip, ({
-                        err = fault_in_multipages_readable(v.iov_base,
-                                        v.iov_len);
+                        err = fault_in_pages_readable(v.iov_base, v.iov_len);
                         if (unlikely(err))
                         return err;
                 0;}))