On Thu, 14 Jul 2022 11:25:00 +0800 Liu Song <liusong@xxxxxxxxxxxxxxxxx> wrote: > From: Liu Song <liusong@xxxxxxxxxxxxxxxxx> > > In "dma_direct_alloc", the allocated memory is explicitly set to 0. > If use direct alloc, we need to avoid possible duplicate memset in > dma_pool_alloc. I'm having trouble seeing how this change is safe and correct and maintainable. Please describe the code flow more completely? > --- a/mm/dmapool.c > +++ b/mm/dmapool.c > @@ -21,6 +21,7 @@ > > #include <linux/device.h> > #include <linux/dma-mapping.h> > +#include <linux/dma-map-ops.h> > #include <linux/dmapool.h> > #include <linux/kernel.h> > #include <linux/list.h> > @@ -372,7 +373,7 @@ void *dma_pool_alloc(struct dma_pool *pool, gfp_t mem_flags, > #endif > spin_unlock_irqrestore(&pool->lock, flags); > > - if (want_init_on_alloc(mem_flags)) > + if (want_init_on_alloc(mem_flags) && get_dma_ops(pool->dev)) > memset(retval, 0, pool->size); That DMAPOOL_DEBUG memset a couple of lines earlier could/should be testing the same condition - there's no point in poisoning an area which we're about to zero out.
