From f5c76c5ff8ee166fadea1c0a5de5a7711eb59be9 Mon Sep 17 00:00:00 2001
From: Matheus <matheusuky@gmail.com>
Date: Tue, 18 Apr 2023 23:48:41 -0300
Subject: [PATCH] slab: deallocation

---
 kernel-src/mm/slab.c | 78 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 77 insertions(+), 1 deletion(-)

diff --git a/kernel-src/mm/slab.c b/kernel-src/mm/slab.c
index 34606f59..a63cbc23 100644
--- a/kernel-src/mm/slab.c
+++ b/kernel-src/mm/slab.c
@@ -76,15 +76,54 @@ static void *takeobject(scache_t *cache, slab_t *slab) {
 	if (slab->free == NULL)
 		return NULL;
 
-	void *objend = slab->free;
+	void **objend = slab->free;
 	slab->free = *slab->free;
 	slab->used += 1;
+	*objend = NULL;
 	if (cache->size < SLAB_INDIRECT_CUTOFF)
 		return (void *)((uintptr_t)objend - cache->size);
 	else
 		return (void *)((uintptr_t)slab->base + ((uintptr_t)objend - ROUND_DOWN((uintptr_t)slab, PAGE_SIZE)) / sizeof(void **) * cache->truesize);
 }
 
+// frees an object and returns the slab the object belongs to
+static slab_t *returnobject(scache_t *cache, void *obj) {
+	slab_t *slab = NULL;
+	void **freeptr = NULL;
+	if (cache->size < SLAB_INDIRECT_CUTOFF) {
+		slab = (slab_t *)(ROUND_DOWN((uintptr_t)obj, PAGE_SIZE) + SLAB_PAGE_OFFSET);
+		freeptr = (void **)((uintptr_t)obj + cache->size);
+		__assert(*freeptr == NULL);
+	} else {
+		slab = cache->full;
+		bool partial = false;
+		while (slab) {
+			void *top = (void *)((uintptr_t)slab->base + cache->slabobjcount * cache->truesize);
+			if (obj >= slab->base && obj < top)
+				break;
+			if (slab->next == NULL && partial == false) {
+				slab = cache->partial;
+				partial = true;
+			} else {
+				slab = slab->next;
+			}
+		}
+		__assert(slab);
+		uintmax_t objn = ((uintptr_t)obj - (uintptr_t)slab->base) / cache->truesize;
+		void **base = (void **)ROUND_DOWN((uintptr_t)obj, PAGE_SIZE);
+		freeptr = &base[objn];
+	}
+
+	if (cache->dtor)
+		cache->dtor(cache, obj);
+
+	*freeptr = slab->free;
+	slab->free = freeptr;
+	--slab->used;
+
+	return slab;
+}
+
 void *slab_allocate(scache_t *cache) {
 	// TODO lock
 	slab_t *slab = NULL;
@@ -106,12 +145,20 @@ void *slab_allocate(scache_t *cache) {
 
 	if (slab == cache->empty) {
 		cache->empty = slab->next;
+		if (slab->prev)
+			slab->prev->next = slab->next;
+		if (slab->next)
+			slab->next->prev = slab->prev;
 		slab->next = cache->partial;
 		cache->partial = slab;
 	}
 
 	if (slab->used == cache->slabobjcount) {
 		cache->partial = slab->next;
+		if (slab->prev)
+			slab->prev->next = slab->next;
+		if (slab->next)
+			slab->next->prev = slab->prev;
 		slab->next = cache->full;
 		cache->full = slab;
 	}
@@ -121,6 +168,35 @@ void *slab_allocate(scache_t *cache) {
 	return ret;
 }
 
+void slab_free(scache_t *cache, void *addr) {
+	// TODO lock
+
+	slab_t *slab = returnobject(cache, addr);
+	__assert(slab);
+
+	if (slab->used == 0) {
+		cache->partial = slab->next;
+		if (slab->prev)
+			slab->prev->next = slab->next;
+		if (slab->next)
+			slab->next->prev = slab->prev;
+		slab->next = cache->empty;
+		cache->empty = slab;
+	}
+	
+	if (slab->used == cache->slabobjcount - 1) {
+		cache->full = slab->next;
+		if (slab->prev)
+			slab->prev->next = slab->next;
+		if (slab->next)
+			slab->next->prev = slab->prev;
+		slab->next = cache->empty;
+		cache->empty = slab;
+	}
+
+	// TODO unlock
+}
+
 scache_t *slab_newcache(size_t size, size_t alignment, void (*ctor)(scache_t *, void *), void (*dtor)(scache_t *, void *)) {
 	if (alignment == 0)
 		alignment = 8;