some questions about block and scatterlist

[loody]

Dear all:
My questions are below:
1. Are all struct page 32-bit aligned?
If so, where is this part of code for handleing struct page be 32-bits aligned?
2. if the page of scatterlist is located at high mem, how does
dma_map_sg mapping the virtual address?
3. in blk_rq_map_sg, it seems we only copy bvec->bv_page to sg->page_link
   why don't we add dma_address in bvec and send the bio directly to
the lower level driver?
4. if I plug a USB HD with 3 partitions, will there be 3 request_queues?


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Regards,