Jason Gunthorpe <jgg@xxxxxxxxxx> writes: > On Thu, Apr 11, 2024 at 10:57:24AM +1000, Alistair Popple wrote: >> The reference counts for ZONE_DEVICE private pages should be >> initialised by the driver when the page is actually allocated by the >> driver allocator, not when they are first created. This is currently >> the case for MEMORY_DEVICE_PRIVATE and MEMORY_DEVICE_COHERENT pages >> but not MEMORY_DEVICE_PCI_P2PDMA pages so fix that up. >> >> Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx> >> --- >> drivers/pci/p2pdma.c | 2 ++ >> mm/memremap.c | 8 ++++---- >> mm/mm_init.c | 4 +++- >> 3 files changed, 9 insertions(+), 5 deletions(-) >> >> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c >> index fa7370f..ab7ef18 100644 >> --- a/drivers/pci/p2pdma.c >> +++ b/drivers/pci/p2pdma.c >> @@ -128,6 +128,8 @@ static int p2pmem_alloc_mmap(struct file *filp, struct kobject *kobj, >> goto out; >> } >> >> + get_page(virt_to_page(kaddr)); >> + > > Should this be > > set_page_count(page, 1) > > If the refcount is already known to be 0 ? Yeah, that would avoid the obvious warning that calling get_page there will generate. My test setup for p2pdma is pretty clunky, so haven't run it a while. Not sure if there are any good qemu based tests for this. >> @@ -508,15 +508,15 @@ void free_zone_device_page(struct page *page) >> page->mapping = NULL; >> page->pgmap->ops->page_free(page); >> >> - if (page->pgmap->type != MEMORY_DEVICE_PRIVATE && >> - page->pgmap->type != MEMORY_DEVICE_COHERENT) >> + if (page->pgmap->type == MEMORY_DEVICE_PRIVATE || >> + page->pgmap->type == MEMORY_DEVICE_COHERENT) >> + put_dev_pagemap(page->pgmap); > > Not related, but we should really be getting rid of this devmap > refcount traffic too, IMHO.. Absolutely. I think there's a bunch of clean ups for this in mm/gup.c that could be done as well. I plan on doing that as a follow up to this series. We pretty much don't use that for device private/coherent pages anyway. > If an implementation wants this then it should hook the page > free/alloc callbacks and do this, not put it in the core code. > > Jason
