diff --git a/Documentation/vm/hmm.rst b/Documentation/vm/hmm.rst
index d9b27bdadd1b..61f073215a8d 100644
--- a/Documentation/vm/hmm.rst
+++ b/Documentation/vm/hmm.rst
@@ -190,13 +190,7 @@ When the device driver wants to populate a range of virtual addresses, it can
 use either::
 
   long hmm_range_snapshot(struct hmm_range *range);
-  int hmm_vma_fault(struct vm_area_struct *vma,
-                    struct hmm_range *range,
-                    unsigned long start,
-                    unsigned long end,
-                    hmm_pfn_t *pfns,
-                    bool write,
-                    bool block);
+  long hmm_range_fault(struct hmm_range *range, bool block);
 
 The first one (hmm_range_snapshot()) will only fetch present CPU page table
 entries and will not trigger a page fault on missing or non-present entries.
diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index 32206b0b1bfd..e9afd23c2eac 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -391,7 +391,18 @@ bool hmm_vma_range_done(struct hmm_range *range);
  *
  * See the function description in mm/hmm.c for further documentation.
  */
-int hmm_vma_fault(struct hmm_range *range, bool block);
+long hmm_range_fault(struct hmm_range *range, bool block);
+
+/* This is a temporary helper to avoid merge conflict between trees. */
+static inline int hmm_vma_fault(struct hmm_range *range, bool block)
+{
+	long ret = hmm_range_fault(range, block);
+	if (ret == -EBUSY)
+		ret = -EAGAIN;
+	else if (ret == -EAGAIN)
+		ret = -EBUSY;
+	return ret < 0 ? ret : 0;
+}
 
 /* Below are for HMM internal use only! Not to be used by device driver! */
 void hmm_mm_destroy(struct mm_struct *mm);
diff --git a/mm/hmm.c b/mm/hmm.c
index 91361aa74b8b..7860e63c3ba7 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -336,13 +336,13 @@ static int hmm_vma_do_fault(struct mm_walk *walk, unsigned long addr,
 	flags |= write_fault ? FAULT_FLAG_WRITE : 0;
 	ret = handle_mm_fault(vma, addr, flags);
 	if (ret & VM_FAULT_RETRY)
-		return -EBUSY;
+		return -EAGAIN;
 	if (ret & VM_FAULT_ERROR) {
 		*pfn = range->values[HMM_PFN_ERROR];
 		return -EFAULT;
 	}
 
-	return -EAGAIN;
+	return -EBUSY;
 }
 
 static int hmm_pfns_bad(unsigned long addr,
@@ -368,7 +368,7 @@ static int hmm_pfns_bad(unsigned long addr,
  * @fault: should we fault or not ?
  * @write_fault: write fault ?
  * @walk: mm_walk structure
- * Returns: 0 on success, -EAGAIN after page fault, or page fault error
+ * Returns: 0 on success, -EBUSY after page fault, or page fault error
  *
  * This function will be called whenever pmd_none() or pte_none() returns true,
  * or whenever there is no page directory covering the virtual address range.
@@ -391,12 +391,12 @@ static int hmm_vma_walk_hole_(unsigned long addr, unsigned long end,
 
 			ret = hmm_vma_do_fault(walk, addr, write_fault,
 					       &pfns[i]);
-			if (ret != -EAGAIN)
+			if (ret != -EBUSY)
 				return ret;
 		}
 	}
 
-	return (fault || write_fault) ? -EAGAIN : 0;
+	return (fault || write_fault) ? -EBUSY : 0;
 }
 
 static inline void hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
@@ -527,11 +527,11 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
 	uint64_t orig_pfn = *pfn;
 
 	*pfn = range->values[HMM_PFN_NONE];
-	cpu_flags = pte_to_hmm_pfn_flags(range, pte);
-	hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags,
-			   &fault, &write_fault);
+	fault = write_fault = false;
 
 	if (pte_none(pte)) {
+		hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0,
+				   &fault, &write_fault);
 		if (fault || write_fault)
 			goto fault;
 		return 0;
@@ -570,7 +570,7 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
 				hmm_vma_walk->last = addr;
 				migration_entry_wait(vma->vm_mm,
 						     pmdp, addr);
-				return -EAGAIN;
+				return -EBUSY;
 			}
 			return 0;
 		}
@@ -578,6 +578,10 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
 		/* Report error for everything else */
 		*pfn = range->values[HMM_PFN_ERROR];
 		return -EFAULT;
+	} else {
+		cpu_flags = pte_to_hmm_pfn_flags(range, pte);
+		hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags,
+				   &fault, &write_fault);
 	}
 
 	if (fault || write_fault)
@@ -628,7 +632,7 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
 		if (fault || write_fault) {
 			hmm_vma_walk->last = addr;
 			pmd_migration_entry_wait(vma->vm_mm, pmdp);
-			return -EAGAIN;
+			return -EBUSY;
 		}
 		return 0;
 	} else if (!pmd_present(pmd))
@@ -856,53 +860,34 @@ bool hmm_vma_range_done(struct hmm_range *range)
 EXPORT_SYMBOL(hmm_vma_range_done);
 
 /*
- * hmm_vma_fault() - try to fault some address in a virtual address range
+ * hmm_range_fault() - try to fault some address in a virtual address range
  * @range: range being faulted
  * @block: allow blocking on fault (if true it sleeps and do not drop mmap_sem)
- * Returns: 0 success, error otherwise (-EAGAIN means mmap_sem have been drop)
+ * Returns: number of valid pages in range->pfns[] (from range start
+ *          address). This may be zero. If the return value is negative,
+ *          then one of the following values may be returned:
+ *
+ *           -EINVAL  invalid arguments or mm or virtual address are in an
+ *                    invalid vma (ie either hugetlbfs or device file vma).
+ *           -ENOMEM: Out of memory.
+ *           -EPERM:  Invalid permission (for instance asking for write and
+ *                    range is read only).
+ *           -EAGAIN: If you need to retry and mmap_sem was drop. This can only
+ *                    happens if block argument is false.
+ *           -EBUSY:  If the the range is being invalidated and you should wait
+ *                    for invalidation to finish.
+ *           -EFAULT: Invalid (ie either no valid vma or it is illegal to access
+ *                    that range), number of valid pages in range->pfns[] (from
+ *                    range start address).
  *
  * This is similar to a regular CPU page fault except that it will not trigger
- * any memory migration if the memory being faulted is not accessible by CPUs.
+ * any memory migration if the memory being faulted is not accessible by CPUs
+ * and caller does not ask for migration.
  *
  * On error, for one virtual address in the range, the function will mark the
  * corresponding HMM pfn entry with an error flag.
- *
- * Expected use pattern:
- * retry:
- *   down_read(&mm->mmap_sem);
- *   // Find vma and address device wants to fault, initialize hmm_pfn_t
- *   // array accordingly
- *   ret = hmm_vma_fault(range, write, block);
- *   switch (ret) {
- *   case -EAGAIN:
- *     hmm_vma_range_done(range);
- *     // You might want to rate limit or yield to play nicely, you may
- *     // also commit any valid pfn in the array assuming that you are
- *     // getting true from hmm_vma_range_monitor_end()
- *     goto retry;
- *   case 0:
- *     break;
- *   case -ENOMEM:
- *   case -EINVAL:
- *   case -EPERM:
- *   default:
- *     // Handle error !
- *     up_read(&mm->mmap_sem)
- *     return;
- *   }
- *   // Take device driver lock that serialize device page table update
- *   driver_lock_device_page_table_update();
- *   hmm_vma_range_done(range);
- *   // Commit pfns we got from hmm_vma_fault()
- *   driver_unlock_device_page_table_update();
- *   up_read(&mm->mmap_sem)
- *
- * YOU MUST CALL hmm_vma_range_done() AFTER THIS FUNCTION RETURN SUCCESS (0)
- * BEFORE FREEING THE range struct OR YOU WILL HAVE SERIOUS MEMORY CORRUPTION !
- *
- * YOU HAVE BEEN WARNED !
  */
-int hmm_vma_fault(struct hmm_range *range, bool block)
+long hmm_range_fault(struct hmm_range *range, bool block)
 {
 	struct vm_area_struct *vma = range->vma;
 	unsigned long start = range->start;
@@ -974,7 +959,8 @@ int hmm_vma_fault(struct hmm_range *range, bool block)
 	do {
 		ret = walk_page_range(start, range->end, &mm_walk);
 		start = hmm_vma_walk.last;
-	} while (ret == -EAGAIN);
+		/* Keep trying while the range is valid. */
+	} while (ret == -EBUSY && range->valid);
 
 	if (ret) {
 		unsigned long i;
@@ -984,6 +970,7 @@ int hmm_vma_fault(struct hmm_range *range, bool block)
 			       range->end);
 		hmm_vma_range_done(range);
 		hmm_put(hmm);
+		return ret;
 	} else {
 		/*
 		 * Transfer hmm reference to the range struct it will be drop
@@ -993,9 +980,9 @@ int hmm_vma_fault(struct hmm_range *range, bool block)
 		range->hmm = hmm;
 	}
 
-	return ret;
+	return (hmm_vma_walk.last - range->start) >> PAGE_SHIFT;
 }
-EXPORT_SYMBOL(hmm_vma_fault);
+EXPORT_SYMBOL(hmm_range_fault);
 #endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */
 
 
