On Thu, 8 Jan 2026 09:59:08 -0600 John Groves <[email protected]> wrote:
> On 26/01/08 11:50AM, Jonathan Cameron wrote: > > On Wed, 7 Jan 2026 09:33:13 -0600 > > John Groves <[email protected]> wrote: > > > > > From: John Groves <[email protected]> > > > > > Hi John > > > > The description should generally make sense without the title. > > Sometimes that means more or less repeating the title. > > > > A few other things inline. > > Will do > > > > > > * These methods are based on pmem_dax_ops from drivers/nvdimm/pmem.c > > > * fsdev_dax_direct_access() returns the hpa, pfn and kva. The kva was > > > newly stored as dev_dax->virt_addr by dev_dax_probe(). > > > * The hpa/pfn are used for mmap (dax_iomap_fault()), and the kva is used > > > for read/write (dax_iomap_rw()) > > > * fsdev_dax_recovery_write() and dev_dax_zero_page_range() have not been > > > tested yet. I'm looking for suggestions as to how to test those. > > > * dax-private.h: add dev_dax->cached_size, which fsdev needs to > > > remember. The dev_dax size cannot change while a driver is bound > > > (dev_dax_resize returns -EBUSY if dev->driver is set). Caching the size > > > at probe time allows fsdev's direct_access path can use it without > > > acquiring dax_dev_rwsem (which isn't exported anyway). > > > > > > Signed-off-by: John Groves <[email protected]> > > > > > diff --git a/drivers/dax/fsdev.c b/drivers/dax/fsdev.c > > > index c5c660b193e5..9e2f83aa2584 100644 > > > --- a/drivers/dax/fsdev.c > > > +++ b/drivers/dax/fsdev.c > > > @@ -27,6 +27,81 @@ > > > * - No mmap support - all access is through fs-dax/iomap > > > */ > > > > > > +static void fsdev_write_dax(void *pmem_addr, struct page *page, > > > + unsigned int off, unsigned int len) > > > +{ > > > + while (len) { > > > + void *mem = kmap_local_page(page); > > > > I guess it's pretty simple, but do we care about HIGHMEM for this > > new feature? Maybe it's just easier to support it than argue about it > > however ;) > > I think this compiles to zero overhead, and is an established pattern - > but I'm ok following a consensus elsewhere... That's fair, probably just keep it. > > > +static long __fsdev_dax_direct_access(struct dax_device *dax_dev, > > > pgoff_t pgoff, > > > + long nr_pages, enum dax_access_mode mode, void **kaddr, > > > + unsigned long *pfn) > > > +{ > > > + struct dev_dax *dev_dax = dax_get_private(dax_dev); > > > + size_t size = nr_pages << PAGE_SHIFT; > > > + size_t offset = pgoff << PAGE_SHIFT; > > > + void *virt_addr = dev_dax->virt_addr + offset; > > > + phys_addr_t phys; > > > + unsigned long local_pfn; > > > + > > > + WARN_ON(!dev_dax->virt_addr); > > > + > > > + phys = dax_pgoff_to_phys(dev_dax, pgoff, nr_pages << PAGE_SHIFT); > > > > Use size given you already computed it. > > Not sure I follow. nr_pages is the size of the access or fault, not the size > of the device. Just above: size_t size = nr_pages << PAGE_SHIFT; Jonathan
