On Wed, 27 Mar 2019 12:47:30 +0100, Michal Hocko wrote:
On Wed 27-03-19 10:29:58, Takashi Iwai wrote:
snd_malloc_pages() and snd_free_pages() are merely thin wrappers of the standard page allocator / free functions. Even the arguments are compatible with some standard helpers, so there is little merit of keeping these wrappers.
This patch replaces the all existing callers of snd_malloc_pages() and snd_free_pages() with the direct calls of the standard helper functions. In this version, we use a recently introduced one, alloc_pages_exact(), which suits better than the old snd_malloc_pages() implementation for our purposes. Then we can avoid the waste of pages by alignment to power-of-two.
Since alloc_pages_exact() does split pages, we need no longer __GFP_COMP flag; or better to say, we must not pass __GFP_COMP to alloc_pages_exact(). So the former unconditional addition of __GFP_COMP flag in snd_malloc_pages() is dropped, as well as in most other places.
I haven't checked all the callers but the replacement makes sense to me. I am just wondering whether there is any hard requireemet to have all those requests to be physically contiguous or kvmalloc would suit them better.
Most of callers are supposed to allocate buffers that can be also mmapped to user-space, so kvmalloc() won't work. So, the explicit page allocations are on purpose.
thanks,
Takashi