Commit a0c111c6 authored by Paolo Galtieri's avatar Paolo Galtieri Committed by Linus Torvalds
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[PATCH] ppc highmem fix

I've noticed that the calculations for seg_size and nr_segs in
__dma_sync_page_highmem() (arch/ppc/kernel/dma-mapping.c) are wrong.  The
incorrect calculations can result in either an oops or a panic when running
fsck depending on the size of the partition.

The problem with the seg_size calculation is that it can result in a
negative number if size is offset > size.  The problem with the nr_segs
caculation is returns the wrong number of segments, e.g.  it returns 1 when
size is 200 and offset is 4095, when it should return 2 or more.

Acked-by: default avatarBenjamin Herrenschmidt <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 1bef4003
......@@ -401,10 +401,10 @@ EXPORT_SYMBOL(__dma_sync);
static inline void __dma_sync_page_highmem(struct page *page,
unsigned long offset, size_t size, int direction)
size_t seg_size = min((size_t)PAGE_SIZE, size) - offset;
size_t seg_size = min((size_t)(PAGE_SIZE - offset), size);
size_t cur_size = seg_size;
unsigned long flags, start, seg_offset = offset;
int nr_segs = PAGE_ALIGN(size + (PAGE_SIZE - offset))/PAGE_SIZE;
int nr_segs = 1 + ((size - seg_size) + PAGE_SIZE - 1)/PAGE_SIZE;
int seg_nr = 0;
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