mm: report success more often from filemap_map_folio_range()

Even though we had successfully mapped the relevant page, we would rarely
return success from filemap_map_folio_range().  That leads to falling back
from the VMA lock path to the mmap_lock path, which is a speed &
scalability issue.  Found by inspection.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: 617c28e ("filemap: batch PTE mappings")
Signed-off-by: Matthew Wilcox (Oracle) <[email protected]>
Reviewed-by: Yin Fengwei <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: Matthew Wilcox (Oracle)

mm/filemap.c

@@ -3503,7 +3503,7 @@ static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf,
 		if (count) {
 			set_pte_range(vmf, folio, page, count, addr);
 			folio_ref_add(folio, count);
-			if (in_range(vmf->address, addr, count))
+			if (in_range(vmf->address, addr, count * PAGE_SIZE))
 				ret = VM_FAULT_NOPAGE;
 		}
 
@@ -3517,7 +3517,7 @@ static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf,
 	if (count) {
 		set_pte_range(vmf, folio, page, count, addr);
 		folio_ref_add(folio, count);
-		if (in_range(vmf->address, addr, count))
+		if (in_range(vmf->address, addr, count * PAGE_SIZE))
 			ret = VM_FAULT_NOPAGE;
 	}