• Andrea Arcangeli's avatar
    Fix bounce setting for 64-bit · 00d61e3e
    Andrea Arcangeli authored
    Looking a bit closer into this regression the reason this can't be
    right is that dma_addr common default is BLK_BOUNCE_HIGH and most
    machines have less than 4G. So if you do:
    
        if (b_pfn <= (min_t(u64, 0xffffffff, BLK_BOUNCE_HIGH) >> PAGE_SHIFT))
    	dma = 1
    
    that will translate to:
    
         if (BLK_BOUNCE_HIGH <= BLK_BOUNCE_HIGH)
         	dma = 1
    
    So for 99% of hardware this will trigger unnecessary GFP_DMA
    allocations and isa pooling operations.
    
    Also note how the 32bit code still does b_pfn < blk_max_low_pfn.
    
    I guess this is what you were looking after. I didn't verify but as
    far as I can tell, this will stop the regression with isa dma
    operations at boot for 99% of blkdev/memory combinations out there and
    I guess this fixes the setups with >4G of ram and 32bit pci cards as
    well (this also retains symmetry with the 32bit code).
    Signed-off-by: default avatarAndrea Arcangeli <andrea@qumranet.com>
    Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
    00d61e3e
blk-settings.c 13.2 KB