Currently system heap maps its buffers with VM_PFNMAP flag using remap_pfn_range. This results in such buffers not being accounted for in PSS calculations because vm treats this memory as having no page structs. Without page structs there are no counters representing how many processes are mapping a page and therefore PSS calculation is impossible. Historically, ION driver used to map its buffers as VM_PFNMAP areas due to memory carveouts that did not have page structs [1]. That is not the case anymore and it seems there was desire to move away from remap_pfn_range [2]. Dmabuf system heap design inherits this ION behavior and maps its pages using remap_pfn_range even though allocated pages are backed by page structs. Clear VM_IO and VM_PFNMAP flags when mapping memory allocated by the system heap and replace remap_pfn_range with vm_insert_page, following Laura's suggestion in [1]. This would allow correct PSS calculation for dmabufs. [1] https://driverdev-devel.linuxdriverproject.narkive.com/v0fJGpaD/using-ion-memory-for-direct-io [2] http://driverdev.linuxdriverproject.org/pipermail/driverdev-devel/2018-October/127519.html (sorry, could not find lore links for these discussions) Suggested-by: Laura Abbott <labbott@xxxxxxxxxx> Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx> --- drivers/dma-buf/heaps/system_heap.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c index 17e0e9a68baf..0e92e42b2251 100644 --- a/drivers/dma-buf/heaps/system_heap.c +++ b/drivers/dma-buf/heaps/system_heap.c @@ -200,11 +200,13 @@ static int system_heap_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma) struct sg_page_iter piter; int ret; + /* All pages are backed by a "struct page" */ + vma->vm_flags &= ~VM_PFNMAP; + for_each_sgtable_page(table, &piter, vma->vm_pgoff) { struct page *page = sg_page_iter_page(&piter); - ret = remap_pfn_range(vma, addr, page_to_pfn(page), PAGE_SIZE, - vma->vm_page_prot); + ret = vm_insert_page(vma, addr, page); if (ret) return ret; addr += PAGE_SIZE; -- 2.30.0.280.ga3ce27912f-goog
