[PATCH v2 05/19] mm, swap: simplify the code and reduce indention

[Kairui Song <ryncsn@gmail.com>]

From: Kairui Song <kasong@tencent.com>

Now swap cache is always used, multiple swap cache checks are no longer
useful, remove them and reduce the code indention.

No behavior change.

Signed-off-by: Kairui Song <kasong@tencent.com>
---
 mm/memory.c | 89 +++++++++++++++++++++++++++++--------------------------------
 1 file changed, 43 insertions(+), 46 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 806becd6bad5..5bd417ae7f26 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4761,55 +4761,52 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 		goto out_release;
 
 	page = folio_file_page(folio, swp_offset(entry));
-	if (swapcache) {
-		/*
-		 * Make sure folio_free_swap() or swapoff did not release the
-		 * swapcache from under us.  The page pin, and pte_same test
-		 * below, are not enough to exclude that.  Even if it is still
-		 * swapcache, we need to check that the page's swap has not
-		 * changed.
-		 */
-		if (unlikely(!folio_matches_swap_entry(folio, entry)))
-			goto out_page;
-
-		if (unlikely(PageHWPoison(page))) {
-			/*
-			 * hwpoisoned dirty swapcache pages are kept for killing
-			 * owner processes (which may be unknown at hwpoison time)
-			 */
-			ret = VM_FAULT_HWPOISON;
-			goto out_page;
-		}
-
-		/*
-		 * KSM sometimes has to copy on read faults, for example, if
-		 * folio->index of non-ksm folios would be nonlinear inside the
-		 * anon VMA -- the ksm flag is lost on actual swapout.
-		 */
-		folio = ksm_might_need_to_copy(folio, vma, vmf->address);
-		if (unlikely(!folio)) {
-			ret = VM_FAULT_OOM;
-			folio = swapcache;
-			goto out_page;
-		} else if (unlikely(folio == ERR_PTR(-EHWPOISON))) {
-			ret = VM_FAULT_HWPOISON;
-			folio = swapcache;
-			goto out_page;
-		}
-		if (folio != swapcache)
-			page = folio_page(folio, 0);
+	/*
+	 * Make sure folio_free_swap() or swapoff did not release the
+	 * swapcache from under us.  The page pin, and pte_same test
+	 * below, are not enough to exclude that.  Even if it is still
+	 * swapcache, we need to check that the page's swap has not
+	 * changed.
+	 */
+	if (unlikely(!folio_matches_swap_entry(folio, entry)))
+		goto out_page;
 
+	if (unlikely(PageHWPoison(page))) {
 		/*
-		 * If we want to map a page that's in the swapcache writable, we
-		 * have to detect via the refcount if we're really the exclusive
-		 * owner. Try removing the extra reference from the local LRU
-		 * caches if required.
+		 * hwpoisoned dirty swapcache pages are kept for killing
+		 * owner processes (which may be unknown at hwpoison time)
 		 */
-		if ((vmf->flags & FAULT_FLAG_WRITE) && folio == swapcache &&
-		    !folio_test_ksm(folio) && !folio_test_lru(folio))
-			lru_add_drain();
+		ret = VM_FAULT_HWPOISON;
+		goto out_page;
 	}
 
+	/*
+	 * KSM sometimes has to copy on read faults, for example, if
+	 * folio->index of non-ksm folios would be nonlinear inside the
+	 * anon VMA -- the ksm flag is lost on actual swapout.
+	 */
+	folio = ksm_might_need_to_copy(folio, vma, vmf->address);
+	if (unlikely(!folio)) {
+		ret = VM_FAULT_OOM;
+		folio = swapcache;
+		goto out_page;
+	} else if (unlikely(folio == ERR_PTR(-EHWPOISON))) {
+		ret = VM_FAULT_HWPOISON;
+		folio = swapcache;
+		goto out_page;
+	} else if (folio != swapcache)
+		page = folio_page(folio, 0);
+
+	/*
+	 * If we want to map a page that's in the swapcache writable, we
+	 * have to detect via the refcount if we're really the exclusive
+	 * owner. Try removing the extra reference from the local LRU
+	 * caches if required.
+	 */
+	if ((vmf->flags & FAULT_FLAG_WRITE) &&
+	    !folio_test_ksm(folio) && !folio_test_lru(folio))
+		lru_add_drain();
+
 	folio_throttle_swaprate(folio, GFP_KERNEL);
 
 	/*
@@ -4999,7 +4996,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 			pte, pte, nr_pages);
 
 	folio_unlock(folio);
-	if (folio != swapcache && swapcache) {
+	if (unlikely(folio != swapcache)) {
 		/*
 		 * Hold the lock to avoid the swap entry to be reused
 		 * until we take the PT lock for the pte_same() check
@@ -5037,7 +5034,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 	folio_unlock(folio);
 out_release:
 	folio_put(folio);
-	if (folio != swapcache && swapcache) {
+	if (folio != swapcache) {
 		folio_unlock(swapcache);
 		folio_put(swapcache);
 	}

-- 
2.51.2