swiotlb: do not try to allocate a TLB bigger than MAX_ORDER pages

When allocating a new pool at runtime, reduce the number of slabs so
that the allocation order is at most MAX_ORDER.  This avoids a kernel
warning in __alloc_pages().

The warning is relatively benign, because the pool size is subsequently
reduced when allocation fails, but it is silly to start with a request
that is known to fail, especially since this is the default behavior if
the kernel is built with CONFIG_SWIOTLB_DYNAMIC=y and booted without any
swiotlb= parameter.

Reported-by: Ben Greear <greearb@candelatech.com>
Closes: https://lore.kernel.org/netdev/4f173dd2-324a-0240-ff8d-abf5c191be18@candelatech.com/
Fixes: 1aaa736815eb ("swiotlb: allocate a new memory pool when existing pools are full")
Signed-off-by: Petr Tesarik <petr.tesarik1@huawei-partners.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 0163767..dff067b 100644 (file)
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -678,6 +678,11 @@ static struct io_tlb_pool *swiotlb_alloc_pool(struct device *dev,
        size_t pool_size;
        size_t tlb_size;
 
+       if (nslabs > SLABS_PER_PAGE << MAX_ORDER) {
+               nslabs = SLABS_PER_PAGE << MAX_ORDER;
+               nareas = limit_nareas(nareas, nslabs);
+       }
+
        pool_size = sizeof(*pool) + array_size(sizeof(*pool->areas), nareas);
        pool = kzalloc(pool_size, gfp);
        if (!pool)