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Subhash Jadavani authored
blk_rq_map_sg() function merges the physically contiguous pages to use same scatter-gather node without checking if their page descriptors are contiguous or not. Now when dma_map_sg() is called on the scatter gather list, it would take the base page pointer from each node (one by one) and iterates through all of the pages in same sg node by keep incrementing the base page pointer with the assumption that physically contiguous pages will have their page descriptor address contiguous which may not be true if SPARSEMEM config is enabled. So here we may end referring to invalid page descriptor. Following table shows the example of physically contiguous pages but their page descriptor addresses non-contiguous. ------------------------------------------- | Page Descriptor | Physical Address | ------------------------------------------ | 0xc1e43fdc | 0xdffff000 | | 0xc2052000 | 0xe0000000 | ------------...
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