linux-kernel - [PATCH v2 2/5] hugetlb: Move vm_struct declaration to the top of hugetlb

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Date: Wed, 21 Feb 2024 15:47:29 -0800
From: "Vishal Moola (Oracle)" <vishal.moola@...il.com>
To: linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org,
	muchun.song@...ux.dev,
	willy@...radead.org,
	"Vishal Moola (Oracle)" <vishal.moola@...il.com>
Subject: [PATCH v2 2/5] hugetlb: Move vm_struct declaration to the top of hugetlb_fault()

hugetlb_fault() currently defines a vm_struct to pass to the generic
handle_userfault() function. We can move this definition to the top of
hugetlb_fault() so that it can be used throughout the rest of the
hugetlb fault path.

This will help cleanup a number of excess variables and function
arguments throughout the stack. Also, since vm_fault already has space
to store the page offset, use that instead and get rid of idx.

Signed-off-by: Vishal Moola (Oracle) <vishal.moola@...il.com>
---
 mm/hugetlb.c | 32 +++++++++++++++++++-------------
 1 file changed, 19 insertions(+), 13 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index ed1581b670d4..d792d60ea16c 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -6353,13 +6353,25 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 	spinlock_t *ptl;
 	vm_fault_t ret;
 	u32 hash;
-	pgoff_t idx;
 	struct folio *folio = NULL;
 	struct folio *pagecache_folio = NULL;
 	struct hstate *h = hstate_vma(vma);
 	struct address_space *mapping;
 	int need_wait_lock = 0;
 	unsigned long haddr = address & huge_page_mask(h);
+	struct vm_fault vmf = {
+		.vma = vma,
+		.address = haddr,
+		.real_address = address,
+		.flags = flags,
+		.pgoff = vma_hugecache_offset(h, vma, haddr),
+		/* TODO: Track hugetlb faults using vm_fault */
+
+		/*
+		 * Some fields may not be initialized, be careful as it may
+		 * be hard to debug if called functions make assumptions
+		 */
+	};
 
 	/* TODO: Handle faults under the VMA lock */
 	if (flags & FAULT_FLAG_VMA_LOCK) {
@@ -6373,8 +6385,7 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 	 * the same page in the page cache.
 	 */
 	mapping = vma->vm_file->f_mapping;
-	idx = vma_hugecache_offset(h, vma, haddr);
-	hash = hugetlb_fault_mutex_hash(mapping, idx);
+	hash = hugetlb_fault_mutex_hash(mapping, vmf.pgoff);
 	mutex_lock(&hugetlb_fault_mutex_table[hash]);
 
 	/*
@@ -6408,8 +6419,9 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 		 * hugetlb_no_page will drop vma lock and hugetlb fault
 		 * mutex internally, which make us return immediately.
 		 */
-		return hugetlb_no_page(mm, vma, mapping, idx, address, ptep,
-				      entry, flags);
+
+		return hugetlb_no_page(mm, vma, mapping, vmf.pgoff, address,
+					ptep, entry, flags);
 	}
 
 	ret = 0;
@@ -6455,7 +6467,8 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 		/* Just decrements count, does not deallocate */
 		vma_end_reservation(h, vma, haddr);
 
-		pagecache_folio = filemap_lock_hugetlb_folio(h, mapping, idx);
+		pagecache_folio = filemap_lock_hugetlb_folio(h, mapping,
+							     vmf.pgoff);
 		if (IS_ERR(pagecache_folio))
 			pagecache_folio = NULL;
 	}
@@ -6470,13 +6483,6 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 	if (userfaultfd_wp(vma) && huge_pte_uffd_wp(huge_ptep_get(ptep)) &&
 	    (flags & FAULT_FLAG_WRITE) && !huge_pte_write(entry)) {
 		if (!userfaultfd_wp_async(vma)) {
-			struct vm_fault vmf = {
-				.vma = vma,
-				.address = haddr,
-				.real_address = address,
-				.flags = flags,
-			};
-
 			spin_unlock(ptl);
 			if (pagecache_folio) {
 				folio_unlock(pagecache_folio);
-- 
2.43.0