Re: [PATCH v3 1/7] mm/vmalloc.c: add used_map into vmap_block to track space of vmap_block

Uladzislau Rezki
2023-01-16T11:40:01Z

On Fri, Jan 13, 2023 at 11:19:15AM +0800, Baoquan He wrote:
> In one vmap_block area, there could be three types of regions: region
> being used which is allocated through vb_alloc(), dirty region which
> is freed via vb_free() and free region. Among them, only used region
> has available data. While there's no way to track those used regions
> currently.
>
> Here, add bitmap field used_map into vmap_block, and set/clear it during
> allocation or freeing regions of vmap_block area.
>
> This is a preparatoin for later use.
>
> Signed-off-by: Baoquan He <bhe@redhat.com>
> ---
> mm/vmalloc.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 428e0bee5c9c..d6ff058ef4d0 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -1922,6 +1922,7 @@ struct vmap_block {
> spinlock_t lock;
> struct vmap_area *va;
> unsigned long free, dirty;
> + DECLARE_BITMAP(used_map, VMAP_BBMAP_BITS);
> unsigned long dirty_min, dirty_max; /*< dirty range */
> struct list_head free_list;
> struct rcu_head rcu_head;
> @@ -1998,10 +1999,12 @@ static void *new_vmap_block(unsigned int order, gfp_t gfp_mask)
> vb->va = va;
> /* At least something should be left free */
> BUG_ON(VMAP_BBMAP_BITS <= (1UL << order));
> + bitmap_zero(vb->used_map, VMAP_BBMAP_BITS);
> vb->free = VMAP_BBMAP_BITS - (1UL << order);
> vb->dirty = 0;
> vb->dirty_min = VMAP_BBMAP_BITS;
> vb->dirty_max = 0;
> + bitmap_set(vb->used_map, 0, (1UL << order));
> INIT_LIST_HEAD(&vb->free_list);
>
> vb_idx = addr_to_vb_idx(va->va_start);
> @@ -2111,6 +2114,7 @@ static void *vb_alloc(unsigned long size, gfp_t gfp_mask)
> pages_off = VMAP_BBMAP_BITS - vb->free;
> vaddr = vmap_block_vaddr(vb->va->va_start, pages_off);
> vb->free -= 1UL << order;
> + bitmap_set(vb->used_map, pages_off, (1UL << order));
> if (vb->free == 0) {
> spin_lock(&vbq->lock);
> list_del_rcu(&vb->free_list);
> @@ -2144,6 +2148,9 @@ static void vb_free(unsigned long addr, unsigned long size)
> order = get_order(size);
> offset = (addr & (VMAP_BLOCK_SIZE - 1)) >> PAGE_SHIFT;
> vb = xa_load(&vmap_blocks, addr_to_vb_idx(addr));
> + spin_lock(&vb->lock);
> + bitmap_clear(vb->used_map, offset, (1UL << order));
> + spin_unlock(&vb->lock);
>
> vunmap_range_noflush(addr, addr + size);
>
> --
> 2.34.1
>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

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Uladzislau Rezki