Efficient reallocation of SHM chunks (mostly)

kernel/ds/list.c

@@ -98,6 +98,42 @@ node_t * list_insert_after(list_t * list, node_t * before, void * item) {
 	return node;
 }
 
+void list_append_before(list_t * list, node_t * after, node_t * node) {
+	assert(!(node->next || node->prev) && "Node is already in a list.");
+	node->owner = list;
+	if (!list->length) {
+		list_append(list, node);
+		return;
+	}
+	if (after == NULL) {
+		node->next = NULL;
+		node->prev = list->tail;
+		list->tail->next = node;
+		list->tail = node;
+		list->length++;
+		return;
+	}
+	if (after == list->head) {
+		list->head = node;
+	} else {
+		after->prev->next = node;
+		node->prev = after->prev;
+	}
+	node->next = after;
+	after->prev = node;
+	list->length++;
+}
+
+node_t * list_insert_before(list_t * list, node_t * after, void * item) {
+	node_t * node = malloc(sizeof(node_t));
+	node->value = item;
+	node->next  = NULL;
+	node->prev  = NULL;
+	node->owner = NULL;
+	list_append_before(list, after, node);
+	return node;
+}
+
 list_t * list_create(void) {
 	/* Create a fresh list */
 	list_t * out = malloc(sizeof(list_t));

kernel/include/list.h

@@ -43,6 +43,9 @@ void list_merge(list_t * target, list_t * source);
 void list_append_after(list_t * list, node_t * before, node_t * node);
 node_t * list_insert_after(list_t * list, node_t * before, void * item);
 
+void list_append_before(list_t * list, node_t * after, node_t * node);
+node_t * list_insert_before(list_t * list, node_t * after, void * item);
+
 #define foreach(i, list) for (node_t * i = list->head; i != NULL; i = i->next)
 
 #endif

kernel/mem/shm.c

@@ -163,6 +163,55 @@ static void * map_in (shm_chunk_t * chunk, process_t * proc) {
 	mapping->num_vaddrs = chunk->num_frames;
 	mapping->vaddrs = malloc(sizeof(uintptr_t) * mapping->num_vaddrs);
 
+	debug_print(INFO, "want %d bytes, running through mappings...", mapping->num_vaddrs * 0x1000);
+	uintptr_t last_address = SHM_START;
+	foreach(node, proc->shm_mappings) {
+		shm_mapping_t * m = node->value;
+		if (m->vaddrs[0] > last_address) {
+			size_t gap = (uintptr_t)m->vaddrs[0] - last_address;
+			debug_print(INFO, "gap found at 0x%x of size %d", last_address, gap);
+			if (gap >= mapping->num_vaddrs * 0x1000) {
+				debug_print(INFO, "Gap is sufficient, we can insert here.");
+
+				/* Map the gap */
+				for (unsigned int i = 0; i < chunk->num_frames; ++i) {
+					page_t * page = get_page(last_address + i * 0x1000, 1, proc->thread.page_directory);
+					alloc_frame(page, 0, 1);
+					page->frame = chunk->frames[i];
+					mapping->vaddrs[i] = last_address + i * 0x1000;
+				}
+
+				/* Insert us before this node */
+				list_insert_before(proc->shm_mappings, node, mapping);
+
+				return (void *)mapping->vaddrs[0];
+			}
+		}
+		last_address = m->vaddrs[0] + m->num_vaddrs * 0x1000;
+		debug_print(INFO, "[0x%x:0x%x] %s", m->vaddrs[0], last_address, m->chunk->parent->name);
+	}
+	if (proc->image.shm_heap > last_address) {
+		size_t gap = proc->image.shm_heap - last_address;
+		debug_print(INFO, "gap found at 0x%x of size %d", last_address, gap);
+		if (gap >= mapping->num_vaddrs * 0x1000) {
+			debug_print(INFO, "Gap is sufficient, we can insert here.");
+
+			for (unsigned int i = 0; i < chunk->num_frames; ++i) {
+				page_t * page = get_page(last_address + i * 0x1000, 1, proc->thread.page_directory);
+				alloc_frame(page, 0, 1);
+				page->frame = chunk->frames[i];
+				mapping->vaddrs[i] = last_address + i * 0x1000;
+			}
+
+			list_insert(proc->shm_mappings, mapping);
+
+			return (void *)mapping->vaddrs[0];
+		} else {
+			debug_print(INFO, "should be more efficient here - there is space available, but we are not going to use it");
+		}
+	}
+
+
 	for (uint32_t i = 0; i < chunk->num_frames; i++) {
 		uintptr_t new_vpage = proc_sbrk(1, proc);
 		assert(new_vpage % 0x1000 == 0);
@@ -241,6 +290,10 @@ int shm_release (char * path) {
 	spin_lock(&bsl);
 	process_t * proc = (process_t *)current_process;
 
+	if (proc->group != 0) {
+		proc = process_from_pid(proc->group);
+	}
+
 	/* First, find the right chunk */
 	shm_node_t * _node = get_node(path, 0);
 	if (!_node) {