From b62c71f3c9f8f6b02896d377b816ab23f2678ad1 Mon Sep 17 00:00:00 2001
From: Matheus <matheusuky@gmail.com>
Date: Wed, 22 Apr 2026 19:53:58 -0300
Subject: [PATCH] vmmcache: fix dirty list race

---
 kernel-src/include/kernel/pmm.h |  1 +
 kernel-src/mm/vmmcache.c        | 21 +++++++++++++--------
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/kernel-src/include/kernel/pmm.h b/kernel-src/include/kernel/pmm.h
index fc5b9f6b..23b3d340 100644
--- a/kernel-src/include/kernel/pmm.h
+++ b/kernel-src/include/kernel/pmm.h
@@ -15,6 +15,7 @@
 #define PAGE_FLAGS_DIRTY 8
 #define PAGE_FLAGS_READY 16
 #define PAGE_FLAGS_ERROR 32
+#define PAGE_FLAGS_VNODE_SYNCING 64
 
 typedef struct page_t {
 	struct vnode_t *backing;
diff --git a/kernel-src/mm/vmmcache.c b/kernel-src/mm/vmmcache.c
index e7a3494c..9a5f8988 100644
--- a/kernel-src/mm/vmmcache.c
+++ b/kernel-src/mm/vmmcache.c
@@ -338,7 +338,7 @@ int vmmcache_syncvnode(vnode_t *vnode, uintmax_t offset, size_t size) {
 	page_t *page = vnode->pages;
 	page_t *vnodedirtylist = NULL;
 	for (; page; page = page->vnodenext) {
-		if (page->offset < offset || page->offset >= top || (page->flags & PAGE_FLAGS_DIRTY) == 0)
+		if (page->offset < offset || page->offset >= top || (page->flags & PAGE_FLAGS_DIRTY) == 0 || (page->flags & PAGE_FLAGS_VNODE_SYNCING))
 			continue;
 
 		// remove from write list and add to an internal list using the write pointers
@@ -355,6 +355,7 @@ int vmmcache_syncvnode(vnode_t *vnode, uintmax_t offset, size_t size) {
 
 		page->writenext = vnodedirtylist;
 		page->writeprev = NULL;
+		page->flags |= PAGE_FLAGS_VNODE_SYNCING;
 		vnodedirtylist = page;
 	}
 
@@ -368,6 +369,7 @@ int vmmcache_syncvnode(vnode_t *vnode, uintmax_t offset, size_t size) {
 		page_t *page = vnodedirtylist;
 		vnodedirtylist = vnodedirtylist->writenext;
 		page->writenext = NULL;
+		page->flags &= ~PAGE_FLAGS_VNODE_SYNCING;
 
 		// another thread could already have synced this page, verify if it is still dirty
 		if (page->flags & PAGE_FLAGS_DIRTY) {
@@ -414,14 +416,17 @@ int vmmcache_makedirty(page_t *page) {
 		// page is neither dirty nor truncated, add to dirty list and hold the page and vnode
 		page->flags |= PAGE_FLAGS_DIRTY;
 
-		page->writeprev = NULL;
-		page->writenext = dirtylist;
-		if (dirtylist)
-			dirtylist->writeprev = page;
-		else
-			dirtylistend = page;
+		if ((page->flags & PAGE_FLAGS_VNODE_SYNCING) == 0) {
+			page->writeprev = NULL;
+			page->writenext = dirtylist;
+			if (dirtylist)
+				dirtylist->writeprev = page;
+			else
+				dirtylistend = page;
+
+			dirtylist = page;
+		}
 
-		dirtylist = page;
 		pmm_hold(pmm_getpageaddress(page));
 		__assert(page->backing);
 		VOP_HOLD(page->backing);