[PATCH hmm 5/8] mm/hmm: add missing call to hmm_range_need_fault() before returning EFAULT

[Jason Gunthorpe]

From: Jason Gunthorpe <jgg at mellanox.com>

All return paths that do EFAULT must call hmm_range_need_fault() to
determine if the user requires this page to be valid.

If the page cannot be made valid if the user later requires it, due to vma
flags in this case, then the return should be HMM_PFN_ERROR.

Fixes: a3e0d41c2b1f ("mm/hmm: improve driver API to work and wait over a range")
Signed-off-by: Jason Gunthorpe <jgg at mellanox.com>
---
 mm/hmm.c | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index 5f5ccf13dd1e85..e10cd0adba7b37 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -582,18 +582,15 @@ static int hmm_vma_walk_test(unsigned long start, unsigned long end,
 	struct vm_area_struct *vma = walk->vma;
 
 	/*
-	 * Skip vma ranges that don't have struct page backing them or
-	 * map I/O devices directly.
-	 */
-	if (vma->vm_flags & (VM_IO | VM_PFNMAP | VM_MIXEDMAP))
-		return -EFAULT;
-
-	/*
+	 * Skip vma ranges that don't have struct page backing them or map I/O
+	 * devices directly.
+	 *
 	 * If the vma does not allow read access, then assume that it does not
-	 * allow write access either. HMM does not support architectures
-	 * that allow write without read.
+	 * allow write access either. HMM does not support architectures that
+	 * allow write without read.
 	 */
-	if (!(vma->vm_flags & VM_READ)) {
+	if ((vma->vm_flags & (VM_IO | VM_PFNMAP | VM_MIXEDMAP)) ||
+	    !(vma->vm_flags & VM_READ)) {
 		bool fault, write_fault;
 
 		/*
@@ -607,7 +604,7 @@ static int hmm_vma_walk_test(unsigned long start, unsigned long end,
 		if (fault || write_fault)
 			return -EFAULT;
 
-		hmm_pfns_fill(start, end, range, HMM_PFN_NONE);
+		hmm_pfns_fill(start, end, range, HMM_PFN_ERROR);
 		hmm_vma_walk->last = end;
 
 		/* Skip this vma and continue processing the next vma. */
-- 
2.25.1