On Sat, Sep 10, 2022 at 03:35:42PM +0300, Serge Semin wrote: > Well, both approaches will solve the denoted problem. I am just > wondering why do you think that the kmalloc-ed buffer is more > preferable? Because it clearly documents the intent. Here is one buffer that is just a data buffer, and here is one with kernel internal structure. The concept of embedding on-disk / on-the-wire structures into internal stuctures always seemed rather weird and unexpected to me, as we now need to ensure that the alignment works right on both sides. With the right annotations (as done in this series) this will work, but it feels a little fragile to me. > What would be the best solution if we had a qualifier like this: > #ifdef CONFIG_DMA_NONCOHERENT > #define ____dma_buffer ____cacheline_aligned > #else > #define ____dma_buffer > #endif > and used it instead of the direct ____cacheline_aligned utilization. So independent of my preference for separate allocations, this suggested additional would still be very useful for the places where we need to use the alignment for performance or other reasons. I'd use something like __dma_alligned or similar, though.
