mm/vmalloc.c: add flags to mark vm_map_ram area

Through vmalloc API, a virtual kernel area is reserved for physical
address mapping. And vmap_area is used to track them, while vm_struct
is allocated to associate with the vmap_area to store more information
and passed out.

However, area reserved via vm_map_ram() is an exception. It doesn't have
vm_struct to associate with vmap_area. And we can't recognize the
vmap_area with '->vm == NULL' as a vm_map_ram() area because the normal
freeing path will set va->vm = NULL before unmapping, please see
function remove_vm_area().

Meanwhile, there are two types of vm_map_ram area. One is the whole
vmap_area being reserved and mapped at one time; the other is the
whole vmap_area with VMAP_BLOCK_SIZE size being reserved, while mapped
into split regions with smaller size several times via vb_alloc().

To mark the area reserved through vm_map_ram(), add flags field into
struct vmap_area. Bit 0 indicates whether it's a vm_map_ram area,
while bit 1 indicates whether it's a vmap_block type of vm_map_ram
area.

This is a preparatoin for later use.

Signed-off-by: Baoquan He <bhe@redhat.com>

include/linux/vmalloc.h

@@ -76,6 +76,7 @@ struct vmap_area {
 		unsigned long subtree_max_size; /* in "free" tree */
 		struct vm_struct *vm;           /* in "busy" tree */
 	};
+	unsigned long flags; /* mark type of vm_map_ram area */
 };
 
 /* archs that select HAVE_ARCH_HUGE_VMAP should override one or more of these */

mm/vmalloc.c

@@ -1827,6 +1827,7 @@ static void free_vmap_area_noflush(struct vmap_area *va)
 
 	spin_lock(&vmap_area_lock);
 	unlink_va(va, &vmap_area_root);
+	va->flags = 0;
 	spin_unlock(&vmap_area_lock);
 
 	nr_lazy = atomic_long_add_return((va->va_end - va->va_start) >>
@@ -1901,6 +1902,10 @@ struct vmap_area *find_vmap_area(unsigned long addr)
 
 #define VMAP_BLOCK_SIZE		(VMAP_BBMAP_BITS * PAGE_SIZE)
 
+#define VMAP_RAM		0x1
+#define VMAP_BLOCK		0x2
+#define VMAP_FLAGS_MASK		0x3
+
 struct vmap_block_queue {
 	spinlock_t lock;
 	struct list_head free;
@@ -1981,6 +1986,9 @@ static void *new_vmap_block(unsigned int order, gfp_t gfp_mask)
 		kfree(vb);
 		return ERR_CAST(va);
 	}
+	spin_lock(&vmap_area_lock);
+	va->flags = VMAP_RAM|VMAP_BLOCK;
+	spin_unlock(&vmap_area_lock);
 
 	vaddr = vmap_block_vaddr(va->va_start, 0);
 	spin_lock_init(&vb->lock);
@@ -2243,8 +2251,12 @@ void vm_unmap_ram(const void *mem, unsigned int count)
 		return;
 	}
 
-	va = find_vmap_area(addr);
+	spin_lock(&vmap_area_lock);
+	va = __find_vmap_area((unsigned long)addr, &vmap_area_root);
 	BUG_ON(!va);
+	if (va)
+		va->flags &= ~VMAP_RAM;
+	spin_unlock(&vmap_area_lock);
 	debug_check_no_locks_freed((void *)va->va_start,
 				    (va->va_end - va->va_start));
 	free_unmap_vmap_area(va);
@@ -2283,6 +2295,10 @@ void *vm_map_ram(struct page **pages, unsigned int count, int node)
 		if (IS_ERR(va))
 			return NULL;
 
+		spin_lock(&vmap_area_lock);
+		va->flags = VMAP_RAM;
+		spin_unlock(&vmap_area_lock);
+
 		addr = va->va_start;
 		mem = (void *)addr;
 	}