Re: [PATCH v3 2/7] mm/vmalloc.c: add flags to mark vm_map_ram area

Baoquan He
2023-01-18T02:14:05Z

On 01/16/23 at 12:23pm, Lorenzo Stoakes wrote:
> On Fri, Jan 13, 2023 at 11:19:16AM +0800, Baoquan He wrote:
> > 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 kinds of handling for vm_map_ram area. One is
> > the whole vmap_area being reserved and mapped at one time through
> > vm_map_area() interface; the other is the whole vmap_area with
> > VMAP_BLOCK_SIZE size being reserved, while mapped into split regions
> > with smaller size via vb_alloc().
> >
> > To mark the area reserved through vm_map_ram(), add flags field into
> > struct vmap_area. Bit 0 indicates this is vm_map_ram area created
> > through vm_map_ram() interface, while bit 1 marks out the type of
> > vm_map_ram area which makes use of vmap_block to manage split regions
> > via vb_alloc/free().
> >
> > This is a preparatoin for later use.
> >
>
> Small typo here :)

Good catch, will fix it.

>
> > Signed-off-by: Baoquan He <bhe@redhat.com>
> > ---
> > include/linux/vmalloc.h | 1 +
> > mm/vmalloc.c | 16 ++++++++++++----
> > 2 files changed, 13 insertions(+), 4 deletions(-)
> >
> > diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> > index 096d48aa3437..69250efa03d1 100644
> > --- a/include/linux/vmalloc.h
> > +++ b/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 */
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index d6ff058ef4d0..ab4825050b5c 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -1589,7 +1589,8 @@ preload_this_cpu_lock(spinlock_t *lock, gfp_t gfp_mask, int node)
> > static struct vmap_area *alloc_vmap_area(unsigned long size,
> > unsigned long align,
> > unsigned long vstart, unsigned long vend,
> > - int node, gfp_t gfp_mask)
> > + int node, gfp_t gfp_mask,
> > + unsigned long va_flags)
> > {
> > struct vmap_area *va;
> > unsigned long freed;
> > @@ -1635,6 +1636,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
> > va->va_start = addr;
> > va->va_end = addr + size;
> > va->vm = NULL;
> > + va->flags = va_flags;
> >
> > spin_lock(&vmap_area_lock);
> > insert_vmap_area(va, &vmap_area_root, &vmap_area_list);
> > @@ -1913,6 +1915,10 @@ static struct vmap_area *find_unlink_vmap_area(unsigned long addr)
> >
> > #define VMAP_BLOCK_SIZE (VMAP_BBMAP_BITS * PAGE_SIZE)
> >
> > +#define VMAP_RAM 0x1 /* indicates vm_map_ram area*/
> > +#define VMAP_BLOCK 0x2 /* mark out the vmap_block sub-type*/
> > +#define VMAP_FLAGS_MASK 0x3
> > +
> > struct vmap_block_queue {
> > spinlock_t lock;
> > struct list_head free;
> > @@ -1988,7 +1994,8 @@ static void *new_vmap_block(unsigned int order, gfp_t gfp_mask)
> >
> > va = alloc_vmap_area(VMAP_BLOCK_SIZE, VMAP_BLOCK_SIZE,
> > VMALLOC_START, VMALLOC_END,
> > - node, gfp_mask);
> > + node, gfp_mask,
> > + VMAP_RAM|VMAP_BLOCK);
> > if (IS_ERR(va)) {
> > kfree(vb);
> > return ERR_CAST(va);
> > @@ -2297,7 +2304,8 @@ void *vm_map_ram(struct page **pages, unsigned int count, int node)
> > } else {
> > struct vmap_area *va;
> > va = alloc_vmap_area(size, PAGE_SIZE,
> > - VMALLOC_START, VMALLOC_END, node, GFP_KERNEL);
> > + VMALLOC_START, VMALLOC_END,
> > + node, GFP_KERNEL, VMAP_RAM);
> > if (IS_ERR(va))
> > return NULL;
> >
> > @@ -2537,7 +2545,7 @@ static struct vm_struct *__get_vm_area_node(unsigned long size,
> > if (!(flags & VM_NO_GUARD))
> > size += PAGE_SIZE;
> >
> > - va = alloc_vmap_area(size, align, start, end, node, gfp_mask);
> > + va = alloc_vmap_area(size, align, start, end, node, gfp_mask, 0);
> > if (IS_ERR(va)) {
> > kfree(area);
> > return NULL;
> > --
> > 2.34.1
> >
>
> Other than that typo,
>
> Reviewed-by: Lorenzo Stoakes <lstoakes@gmail.com>
>