ARM: DMA: Fix struct page iterator in dma_cache_maint() to work with sparsemem

commit 15653371c67c3fbe359ae37b720639dd4c7b42c5 upstream.

Subhash Jadavani reported this partial backtrace:
  Now consider this call stack from MMC block driver (this is on the ARMv7
  based board):

  [<c001b50c>] (v7_dma_inv_range+0x30/0x48) from [<c0017b8c>] (dma_cache_maint_page+0x1c4/0x24c)
  [<c0017b8c>] (dma_cache_maint_page+0x1c4/0x24c) from [<c0017c28>] (___dma_page_cpu_to_dev+0x14/0x1c)
  [<c0017c28>] (___dma_page_cpu_to_dev+0x14/0x1c) from [<c0017ff8>] (dma_map_sg+0x3c/0x114)

This is caused by incrementing the struct page pointer, and running off
the end of the sparsemem page array.  Fix this by incrementing by pfn
instead, and convert the pfn to a struct page.

Suggested-by: James Bottomley <JBottomley@Parallels.com>
Tested-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index f96d2c7300207ee8bd47b4ba4b19abe49f4bee06..56636504f7e07e7450f827e10c78d884f937dcef 100644 (file)
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -467,25 +467,27 @@ static void dma_cache_maint_page(struct page *page, unsigned long offset,
        size_t size, enum dma_data_direction dir,
        void (*op)(const void *, size_t, int))
 {
+       unsigned long pfn;
+       size_t left = size;
+
+       pfn = page_to_pfn(page) + offset / PAGE_SIZE;
+       offset %= PAGE_SIZE;
+
        /*
         * A single sg entry may refer to multiple physically contiguous
         * pages.  But we still need to process highmem pages individually.
         * If highmem is not configured then the bulk of this loop gets
         * optimized out.
         */
-       size_t left = size;
        do {
                size_t len = left;
                void *vaddr;
 
+               page = pfn_to_page(pfn);
+
                if (PageHighMem(page)) {
-                       if (len + offset > PAGE_SIZE) {
-                               if (offset >= PAGE_SIZE) {
-                                       page += offset / PAGE_SIZE;
-                                       offset %= PAGE_SIZE;
-                               }
+                       if (len + offset > PAGE_SIZE)
                                len = PAGE_SIZE - offset;
-                       }
                        vaddr = kmap_high_get(page);
                        if (vaddr) {
                                vaddr += offset;
@@ -502,7 +504,7 @@ static void dma_cache_maint_page(struct page *page, unsigned long offset,
                        op(vaddr, len, dir);
                }
                offset = 0;
-               page++;
+               pfn++;
                left -= len;
        } while (left);
 }