[PATCH 1/2] mm/hugetlb: Match behavior on read-only private mappings

[Peter Xu]

The default behavior for reading a private file mapping should fill in the
page cache and map the page read-only.  Hugetlb didn't do like it.  Make it
behave the same.

Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
---
 mm/hugetlb.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index a8536349de13..bc3c97c476d2 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -6199,6 +6199,7 @@ static vm_fault_t hugetlb_no_page(struct address_space *mapping,
 	struct folio *folio;
 	pte_t new_pte;
 	bool new_folio, new_pagecache_folio = false;
+	bool is_write = vmf->flags & FAULT_FLAG_WRITE;
 	u32 hash = hugetlb_fault_mutex_hash(mapping, vmf->pgoff);
 
 	/*
@@ -6276,7 +6277,7 @@ static vm_fault_t hugetlb_no_page(struct address_space *mapping,
 		__folio_mark_uptodate(folio);
 		new_folio = true;
 
-		if (vma->vm_flags & VM_MAYSHARE) {
+		if (!is_write || vma->vm_flags & VM_MAYSHARE) {
 			int err = hugetlb_add_to_page_cache(folio, mapping,
 							vmf->pgoff);
 			if (err) {
@@ -6294,6 +6295,7 @@ static vm_fault_t hugetlb_no_page(struct address_space *mapping,
 			}
 			new_pagecache_folio = true;
 		} else {
+			/* Write on a private mapping */
 			folio_lock(folio);
 
 			ret = vmf_anon_prepare(vmf);
@@ -6333,7 +6335,7 @@ static vm_fault_t hugetlb_no_page(struct address_space *mapping,
 	 * any allocations necessary to record that reservation occur outside
 	 * the spinlock.
 	 */
-	if ((vmf->flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED)) {
+	if (is_write && !(vma->vm_flags & VM_SHARED)) {
 		if (vma_needs_reservation(h, vma, vmf->address) < 0) {
 			ret = VM_FAULT_OOM;
 			goto backout_unlocked;
-- 
2.44.0