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. > * 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 ;) > + unsigned int chunk = min_t(unsigned int, len, PAGE_SIZE - off); > + > + memcpy_flushcache(pmem_addr, mem + off, chunk); > + kunmap_local(mem); > + len -= chunk; > + off = 0; > + page++; > + pmem_addr += chunk; > + } > +} > + > +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. > + > + if (kaddr) > + *kaddr = virt_addr; > + > + local_pfn = PHYS_PFN(phys); > + if (pfn) > + *pfn = local_pfn; > + > + /* > + * Use cached_size which was computed at probe time. The size cannot > + * change while the driver is bound (resize returns -EBUSY). > + */ > + return PHYS_PFN(min_t(size_t, size, dev_dax->cached_size - offset)); Is the min_t() needed? min() is pretty good at picking right types these days. > +} > + > +static int fsdev_dax_zero_page_range(struct dax_device *dax_dev, > + pgoff_t pgoff, size_t nr_pages) > +{ > + void *kaddr; > + > + WARN_ONCE(nr_pages > 1, "%s: nr_pages > 1\n", __func__); > + __fsdev_dax_direct_access(dax_dev, pgoff, 1, DAX_ACCESS, &kaddr, NULL); > + fsdev_write_dax(kaddr, ZERO_PAGE(0), 0, PAGE_SIZE); > + return 0; > +} > + > +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) > +{ > + return __fsdev_dax_direct_access(dax_dev, pgoff, nr_pages, mode, > + kaddr, pfn); Alignment in this file is a bit random, but I'd at least align this one after the ( > +}
