1. 23 10月, 2009 7 次提交
  2. 15 10月, 2009 7 次提交
  3. 13 10月, 2009 1 次提交
    • N
      ARM: force dcache flush if dcache_dirty bit set · 787b2faa
      Nitin Gupta 提交于
      On ARM, update_mmu_cache() does dcache flush for a page only if
      it has a kernel mapping (page_mapping(page) != NULL). The correct
      behavior would be to force the flush based on dcache_dirty bit only.
      
      One of the cases where present logic would be a problem is when
      a RAM based block device[1] is used as a swap disk. In this case,
      we would have in-memory data corruption as shown in steps below:
      
      do_swap_page()
      {
          - Allocate a new page (if not already in swap cache)
          - Issue read from swap disk
              - Block driver issues flush_dcache_page()
              - flush_dcache_page() simply sets PG_dcache_dirty bit and does not
                actually issue a flush since this page has no user space mapping yet.
          - Now, if swap disk is almost full, this newly read page is removed
            from swap cache and corrsponding swap slot is freed.
          - Map this page anonymously in user space.
          - update_mmu_cache()
              - Since this page does not have kernel mapping (its not in page/swap
                cache and is mapped anonymously), it does not issue dcache flush
                even if dcache_dirty bit is set by flush_dcache_page() above.
      
          <user now gets stale data since dcache was never flushed>
      }
      
      Same problem exists on mips too.
      
      [1] example:
       - brd (RAM based block device)
       - ramzswap (RAM based compressed swap device)
      Signed-off-by: NNitin Gupta <ngupta@vflare.org>
      Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>
      787b2faa
  4. 12 10月, 2009 3 次提交
  5. 11 10月, 2009 5 次提交
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  8. 06 10月, 2009 4 次提交