BACKPORT: FROMGIT: mm: Pass 'address' to map to do_set_pte() and drop FAULT_FLAG_PREFAULT

Rather than modifying the 'address' field of the 'struct vm_fault'
passed to do_set_pte(), leave that to identify the real faulting address
and pass in the virtual address to be mapped by the new pte as a
separate argument.

This makes FAULT_FLAG_PREFAULT redundant, as a prefault entry can be
identified simply by comparing the new address parameter with the
faulting address, so remove the redundant flag at the same time.

Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Will Deacon <will@kernel.org>
Change-Id: I495c06047bac0f4e2241bc47a18b8ee8f97e4af8
Bug: 171278850
(cherry picked from commit 9d3af4b448a119ac81378d3bc775f1c4a2a7ff36
https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/log/?h=for-next/faultaround)
[vinmenon: changes for speculative page fault]
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>

mm/memory.c

@@ -3952,11 +3952,11 @@ vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page)
 }
 #endif
 
-void do_set_pte(struct vm_fault *vmf, struct page *page)
+void do_set_pte(struct vm_fault *vmf, struct page *page, unsigned long addr)
 {
 	struct vm_area_struct *vma = vmf->vma;
 	bool write = vmf->flags & FAULT_FLAG_WRITE;
-	bool prefault = vmf->flags & FAULT_FLAG_PREFAULT;
+	bool prefault = vmf->address != addr;
 	pte_t entry;
 
 	flush_icache_page(vma, page);
@@ -3972,13 +3972,13 @@ void do_set_pte(struct vm_fault *vmf, struct page *page)
 	/* copy-on-write page */
 	if (write && !(vmf->vma_flags & VM_SHARED)) {
 		inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
-		__page_add_new_anon_rmap(page, vma, vmf->address, false);
+		__page_add_new_anon_rmap(page, vma, addr, false);
 		__lru_cache_add_inactive_or_unevictable(page, vmf->vma_flags);
 	} else {
 		inc_mm_counter_fast(vma->vm_mm, mm_counter_file(page));
 		page_add_file_rmap(page, false);
 	}
-	set_pte_at(vma->vm_mm, vmf->address, vmf->pte, entry);
+	set_pte_at(vma->vm_mm, addr, vmf->pte, entry);
 }
 
 /**
@@ -4040,7 +4040,7 @@ vm_fault_t finish_fault(struct vm_fault *vmf)
 	ret = 0;
 	/* Re-check under ptl */
 	if (likely(pte_none(*vmf->pte)))
-		do_set_pte(vmf, page);
+		do_set_pte(vmf, page, vmf->address);
 	else
 		ret = VM_FAULT_NOPAGE;