zhaoyang.huang <zhaoyang.huang@xxxxxxxxxx> 于2024年5月30日周四 10:52写道：
>
> From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
>
> Broken vbq->free reported on a v6.6 based system which is caused
> by invalid vbq->lock protect over vbq->free in purge_fragmented_block.
> This should be introduced by the Fixes below which ignored vbq->lock
> matter.
>
> Fixes: fc1e0d980037 ("mm/vmalloc: prevent stale TLBs in fully utilized blocks")
>
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
> ---
> mm/vmalloc.c | 11 +++++++----
> 1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 22aa63f4ef63..112b50431725 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2614,9 +2614,10 @@ static void free_vmap_block(struct vmap_block *vb)
> }
>
> static bool purge_fragmented_block(struct vmap_block *vb,
> - struct vmap_block_queue *vbq, struct list_head *purge_list,
> - bool force_purge)
> + struct list_head *purge_list, bool force_purge)
> {
> + struct vmap_block_queue *vbq;
> +
> if (vb->free + vb->dirty != VMAP_BBMAP_BITS ||
> vb->dirty == VMAP_BBMAP_BITS)
> return false;
> @@ -2625,6 +2626,8 @@ static bool purge_fragmented_block(struct vmap_block *vb,
> if (!(force_purge || vb->free < VMAP_PURGE_THRESHOLD))
> return false;
>
> + vbq = container_of(addr_to_vb_xa(vb->va->va_start),
> + struct vmap_block_queue, vmap_blocks);
This seems to be the same as before fix :), the vbq found by
addr_to_vb_xa is still added to the xarray vbq, not necessarily to the
free_list vbq,
These two vbqs may not be the same, we need to find the vbq when added
to free_list.
For example:
We add vb to vbq1's xarray and vbq2's free_list, and we need to find
vbq2 instead of vbq1.
So I feel like this place isn't really fixed？
> /* prevent further allocs after releasing lock */
> WRITE_ONCE(vb->free, 0);
> /* prevent purging it again */
> @@ -2664,7 +2667,7 @@ static void purge_fragmented_blocks(int cpu)
> continue;
>
> spin_lock(&vb->lock);
> - purge_fragmented_block(vb, vbq, &purge, true);
> + purge_fragmented_block(vb, &purge, true);
> spin_unlock(&vb->lock);
> }
> rcu_read_unlock();
> @@ -2801,7 +2804,7 @@ static void _vm_unmap_aliases(unsigned long start, unsigned long end, int flush)
> * not purgeable, check whether there is dirty
> * space to be flushed.
> */
> - if (!purge_fragmented_block(vb, vbq, &purge_list, false) &&
> + if (!purge_fragmented_block(vb, &purge_list, false) &&
> vb->dirty_max && vb->dirty != VMAP_BBMAP_BITS) {
> unsigned long va_start = vb->va->va_start;
> unsigned long s, e;
> --
> 2.25.1
>
>
--
Thanks,
Chuanhua
