[PATCH 1/3] mm/vma: miss to restore vmi.index on expansion failure

[Wei Yang <richard.weiyang@gmail.com>]

On expansion failure, we try to restore vmg state, but we missed to
restore vmi.index. The reason is we have reset vmg->vma before checking.
So let's put the operation before reset vmg->vma.

Also we don't need to do the restore if there is no mergeable adjacent
VMA. Let's take it out to skip the unnecessary operations.

Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
CC: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
---
 mm/vma.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/mm/vma.c b/mm/vma.c
index fb4f1863f88e..c94d953d453c 100644
--- a/mm/vma.c
+++ b/mm/vma.c
@@ -954,23 +954,27 @@ struct vm_area_struct *vma_merge_new_range(struct vma_merge_struct *vmg)
 		vma_prev(vmg->vmi); /* Equivalent to going to the previous range */
 	}
 
+	/* No mergeable adjacent VMA, return */
+	if (!vmg->vma)
+		return NULL;
+
 	/*
 	 * Now try to expand adjacent VMA(s). This takes care of removing the
 	 * following VMA if we have VMAs on both sides.
 	 */
-	if (vmg->vma && !vma_expand(vmg)) {
+	if (!vma_expand(vmg)) {
 		khugepaged_enter_vma(vmg->vma, vmg->flags);
 		vmg->state = VMA_MERGE_SUCCESS;
 		return vmg->vma;
 	}
 
 	/* If expansion failed, reset state. Allows us to retry merge later. */
+	if (vmg->vma == prev)
+		vma_iter_set(vmg->vmi, start);
 	vmg->vma = NULL;
 	vmg->start = start;
 	vmg->end = end;
 	vmg->pgoff = pgoff;
-	if (vmg->vma == prev)
-		vma_iter_set(vmg->vmi, start);
 
 	return NULL;
 }
-- 
2.34.1