Christoph Hellwig <[email protected]> writes: > On Sun, Apr 18, 2021 at 08:14:41AM +0000, Alexander Egorenkov wrote: >> If CONFIG_NEED_SG_DMA_LENGTH is NOT enabled then sg_dma_len() is an alias >> for the length field in a SGL. In that case sg_split() wrongly resets >> the length of split SGLs to zero after it was set correctly before. > > Why is this routine messing with sg_dma_address and > sg_dma_lensg_dma_lensg_dma_len at all? This whole sg_spli() routine > seems rather dangerous because ownership and state of the DMA mapping is > entirely unclear.
If i understood it correctly, then sg_split_phys() creates a new SGL from the given one, so it makes sense to initialize DMA fields of the new SGL. sg_split() allows one to split the given SGL into multiple ones and the original one doesn't have to be dma-mapped which is indicated by the parameter in_mapped_nents > 0. Regards Alex
