Re: [PATCH 3/3] swiotlb: use the right nslabs-derived sizes in swiotlb_init_late

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 11 May 2022, Christoph Hellwig wrote:
> nslabs can shrink when allocations or the remap don't succeed, so make
> sure to use it for all sizing.  For that remove the bytes value that
> can get stale and replace it with local calculations and a boolean to
> indicate if the originally requested size could not be allocated.
> 
> Fixes: 6424e31b1c05 ("swiotlb: remove swiotlb_init_with_tbl and 
> swiotlb_init_late_with_tbl")
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
>  kernel/dma/swiotlb.c | 19 +++++++++++--------
>  1 file changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index 113e1e8aaca37..d6e62a6a42ceb 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -297,9 +297,9 @@ int swiotlb_init_late(size_t size, gfp_t gfp_mask,
>  {
>       struct io_tlb_mem *mem = &io_tlb_default_mem;
>       unsigned long nslabs = ALIGN(size >> IO_TLB_SHIFT, IO_TLB_SEGSIZE);
> -     unsigned long bytes;
>       unsigned char *vstart = NULL;
>       unsigned int order;
> +     bool retried = false;
>       int rc = 0;
>  
>       if (swiotlb_force_disable)
> @@ -308,7 +308,6 @@ int swiotlb_init_late(size_t size, gfp_t gfp_mask,
>  retry:
>       order = get_order(nslabs << IO_TLB_SHIFT);
>       nslabs = SLABS_PER_PAGE << order;
> -     bytes = nslabs << IO_TLB_SHIFT;
>  
>       while ((SLABS_PER_PAGE << order) > IO_TLB_MIN_SLABS) {
>               vstart = (void *)__get_free_pages(gfp_mask | __GFP_NOWARN,
> @@ -316,16 +315,13 @@ int swiotlb_init_late(size_t size, gfp_t gfp_mask,
>               if (vstart)
>                       break;
>               order--;
> +             nslabs = SLABS_PER_PAGE << order;
> +             retried = true;
>       }
>  
>       if (!vstart)
>               return -ENOMEM;
>  
> -     if (order != get_order(bytes)) {
> -             pr_warn("only able to allocate %ld MB\n",
> -                     (PAGE_SIZE << order) >> 20);
> -             nslabs = SLABS_PER_PAGE << order;
> -     }
>       if (remap)
>               rc = remap(vstart, nslabs);
>       if (rc) {
> @@ -334,9 +330,15 @@ int swiotlb_init_late(size_t size, gfp_t gfp_mask,
>               nslabs = ALIGN(nslabs >> 1, IO_TLB_SEGSIZE);
>               if (nslabs < IO_TLB_MIN_SLABS)
>                       return rc;
> +             retried = true;
>               goto retry;
>       }
>  
> +     if (retried) {
> +             pr_warn("only able to allocate %ld MB\n",
> +                     (PAGE_SIZE << order) >> 20);
> +     }
> +
>       mem->slots = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
>               get_order(array_size(sizeof(*mem->slots), nslabs)));
>       if (!mem->slots) {
> @@ -344,7 +346,8 @@ int swiotlb_init_late(size_t size, gfp_t gfp_mask,
>               return -ENOMEM;
>       }
>  
> -     set_memory_decrypted((unsigned long)vstart, bytes >> PAGE_SHIFT);
> +     set_memory_decrypted((unsigned long)vstart,
> +                          (nslabs << IO_TLB_SHIFT) >> PAGE_SHIFT);
>       swiotlb_init_io_tlb_mem(mem, virt_to_phys(vstart), nslabs, true);
>  
>       swiotlb_print_info();
> -- 
> 2.30.2
>