On Fri, May 31, 2024 at 9:27 AM hailong liu <hailong.liu@xxxxxxxx> wrote:
>
> On Fri, 31. May 08:50, zhaoyang.huang wrote:
> > From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
> >
> > vmalloc area runs out in our ARM64 system during an erofs test as
> > vm_map_ram failed[1]. By following the debug log, we find that
> > vm_map_ram()->vb_alloc() will allocate new vb->va which corresponding
> > to 4MB vmalloc area as list_for_each_entry_rcu returns immediately
> > when vbq->free->next points to vbq->free. That is to say, 65536 times
> > of page fault after the list's broken will run out of the whole
> > vmalloc area. This should be introduced by one vbq->free->next point to
> > vbq->free which makes list_for_each_entry_rcu can not iterate the list
> > and find the BUG.
> >
> > [1]
> > PID: 1 TASK: ffffff80802b4e00 CPU: 6 COMMAND: "init"
> > #0 [ffffffc08006afe0] __switch_to at ffffffc08111d5cc
> > #1 [ffffffc08006b040] __schedule at ffffffc08111dde0
> > #2 [ffffffc08006b0a0] schedule at ffffffc08111e294
> > #3 [ffffffc08006b0d0] schedule_preempt_disabled at ffffffc08111e3f0
> > #4 [ffffffc08006b140] __mutex_lock at ffffffc08112068c
> > #5 [ffffffc08006b180] __mutex_lock_slowpath at ffffffc08111f8f8
> > #6 [ffffffc08006b1a0] mutex_lock at ffffffc08111f834
> > #7 [ffffffc08006b1d0] reclaim_and_purge_vmap_areas at ffffffc0803ebc3c
> > #8 [ffffffc08006b290] alloc_vmap_area at ffffffc0803e83fc
> > #9 [ffffffc08006b300] vm_map_ram at ffffffc0803e78c0
> >
> > Fixes: fc1e0d980037 ("mm/vmalloc: prevent stale TLBs in fully utilized blocks")
> >
> > Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
> > ---
> > v2: introduce cpu in vmap_block to record the right CPU number
> > ---
> > ---
> > mm/vmalloc.c | 11 +++++++----
> > 1 file changed, 7 insertions(+), 4 deletions(-)
> >
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index 22aa63f4ef63..ca962b554fa0 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -2458,6 +2458,7 @@ struct vmap_block {
> > struct list_head free_list;
> > struct rcu_head rcu_head;
> > struct list_head purge;
> > + unsigned int cpu;
> > };
> >
> > /* Queue of free and dirty vmap blocks, for allocation and flushing purposes */
> > @@ -2574,6 +2575,7 @@ static void *new_vmap_block(unsigned int order, gfp_t gfp_mask)
> > vb->dirty = 0;
> > vb->dirty_min = VMAP_BBMAP_BITS;
> > vb->dirty_max = 0;
> if task migration to other CPU at this time, this may lead to get incorrect vbq.
ok, thanks for the prompt. If this works?
vb->cpu =get_cpu();
...
put_cpu();
return vaddr;
> > + vb->cpu = smp_processor_id();
> > bitmap_set(vb->used_map, 0, (1UL << order));
> > INIT_LIST_HEAD(&vb->free_list);
> >
> > @@ -2614,9 +2616,10 @@ 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 = &per_cpu(vmap_block_queue, vb->cpu);
> > +
> > if (vb->free + vb->dirty != VMAP_BBMAP_BITS ||
> > vb->dirty == VMAP_BBMAP_BITS)
> > return false;
> > @@ -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
> >
> >
>
> --
>
> Best Regards,
> Hailong.
