On Mon, Jun 29, 2020 at 02:48:06PM +0000, Christopher Lameter wrote: > On Sat, 27 Jun 2020, Long Li wrote: > > Environment using the slub allocator, 1G memory in my ARM32. > > kmalloc(1024, GFP_HIGHUSER) can allocate memory normally, > > kmalloc(64*1024, GFP_HIGHUSER) will cause a memory leak, because > > alloc_pages returns highmem physical pages, but it cannot be directly > > converted into a virtual address and return NULL, the pages has not > > been released. Usually driver developers will not use the > > GFP_HIGHUSER flag to allocate memory in kmalloc, but I think this > > memory leak is not perfect, it is best to be fixed. This is the > > first time I have posted a patch, there may be something wrong. > > Highmem is not supported by the slab allocators. Please ensure that there > is a warning generated if someone attempts to do such an allocation. We > used to check for that. Sounds like we need a test somewhere that checks this behaviour. > In order to make such allocations possible one would have to create yet > another kmalloc array for high memory. Not for this case because it goes straight to kmalloc_order(). What does make this particular case impossible is that we can't kmap() a compound page. We could vmap it, but why are we bothering?
