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787b2faadc
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: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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| .. | ||
| abort-ev4.S | ||
| abort-ev4t.S | ||
| abort-ev5t.S | ||
| abort-ev5tj.S | ||
| abort-ev6.S | ||
| abort-ev7.S | ||
| abort-lv4t.S | ||
| abort-macro.S | ||
| abort-nommu.S | ||
| alignment.c | ||
| cache-fa.S | ||
| cache-feroceon-l2.c | ||
| cache-l2x0.c | ||
| cache-v3.S | ||
| cache-v4.S | ||
| cache-v4wb.S | ||
| cache-v4wt.S | ||
| cache-v6.S | ||
| cache-v7.S | ||
| cache-xsc3l2.c | ||
| context.c | ||
| copypage-fa.c | ||
| copypage-feroceon.c | ||
| copypage-v3.c | ||
| copypage-v4mc.c | ||
| copypage-v4wb.c | ||
| copypage-v4wt.c | ||
| copypage-v6.c | ||
| copypage-xsc3.c | ||
| copypage-xscale.c | ||
| discontig.c | ||
| dma-mapping.c | ||
| extable.c | ||
| fault-armv.c | ||
| fault.c | ||
| fault.h | ||
| flush.c | ||
| highmem.c | ||
| init.c | ||
| iomap.c | ||
| ioremap.c | ||
| Kconfig | ||
| Makefile | ||
| mm.h | ||
| mmap.c | ||
| mmu.c | ||
| nommu.c | ||
| pabort-legacy.S | ||
| pabort-v6.S | ||
| pabort-v7.S | ||
| pgd.c | ||
| proc-arm6_7.S | ||
| proc-arm7tdmi.S | ||
| proc-arm9tdmi.S | ||
| proc-arm720.S | ||
| proc-arm740.S | ||
| proc-arm920.S | ||
| proc-arm922.S | ||
| proc-arm925.S | ||
| proc-arm926.S | ||
| proc-arm940.S | ||
| proc-arm946.S | ||
| proc-arm1020.S | ||
| proc-arm1020e.S | ||
| proc-arm1022.S | ||
| proc-arm1026.S | ||
| proc-fa526.S | ||
| proc-feroceon.S | ||
| proc-macros.S | ||
| proc-mohawk.S | ||
| proc-sa110.S | ||
| proc-sa1100.S | ||
| proc-syms.c | ||
| proc-v6.S | ||
| proc-v7.S | ||
| proc-xsc3.S | ||
| proc-xscale.S | ||
| tlb-fa.S | ||
| tlb-v3.S | ||
| tlb-v4.S | ||
| tlb-v4wb.S | ||
| tlb-v4wbi.S | ||
| tlb-v6.S | ||
| tlb-v7.S | ||