[PATCH 6/8] swiotlb: lift the double initialization protection from xen-swiotlb

[Christoph Hellwig <hch@xxxxxx>]

Lift the double initialization protection from xen-swiotlb to the core
code to avoid exposing too many swiotlb internals.  Also upgrade the
check to a warning as it should not happen.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 drivers/xen/swiotlb-xen.c | 7 -------
 kernel/dma/swiotlb.c      | 8 ++++++++
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 6e0f2c5ecd1a2f..e6c8556e879ee6 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -172,12 +172,6 @@ int __ref xen_swiotlb_init(int verbose, bool early)
        bytes = nslabs << IO_TLB_SHIFT;
        order = get_order(bytes);
 
-       /*
-        * IO TLB memory already allocated. Just use it.
-        */
-       if (io_tlb_start != 0)
-               goto end;
-
        /*
         * Get IO TLB memory from any location.
         */
@@ -232,7 +226,6 @@ int __ref xen_swiotlb_init(int verbose, bool early)
        } else
                rc = swiotlb_late_init_with_tbl(start, nslabs);
 
-end:
        if (!rc)
                swiotlb_set_max_segment(PAGE_SIZE);
 
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index adcc3c87e10078..a3737961ae5769 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -224,6 +224,10 @@ int __init swiotlb_init_with_tbl(char *tlb, unsigned long 
nslabs, int verbose)
        unsigned long i, bytes;
        size_t alloc_size;
 
+       /* protect against double initialization */
+       if (WARN_ON_ONCE(io_tlb_start))
+               return -ENOMEM;
+
        bytes = nslabs << IO_TLB_SHIFT;
 
        io_tlb_nslabs = nslabs;
@@ -355,6 +359,10 @@ swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs)
 {
        unsigned long i, bytes;
 
+       /* protect against double initialization */
+       if (WARN_ON_ONCE(io_tlb_start))
+               return -ENOMEM;
+
        bytes = nslabs << IO_TLB_SHIFT;
 
        io_tlb_nslabs = nslabs;
-- 
2.29.2