On Tue, 24 Mar 2026 00:39:04 +0000 John Groves <[email protected]> wrote:
> From: John Groves <[email protected]> > > fsdev: Add dax_operations for use by famfs. > > This replicates the functionality from drivers/nvdimm/pmem.c that > conventional fs-dax file systems (e.g. xfs) use to support dax > read/write/mmap to a daxdev - without which famfs can't sit atop a > daxdev. > > - 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]> The indent of trailing parameter lines is very random in here. Pick a style and stick to it. Few other trivial things inline. Reviewed-by: Jonathan Cameron <[email protected]> > --- > drivers/dax/dax-private.h | 1 + > drivers/dax/fsdev.c | 84 +++++++++++++++++++++++++++++++++++++++ > 2 files changed, 85 insertions(+) > diff --git a/drivers/dax/fsdev.c b/drivers/dax/fsdev.c > index c75478d3d548..be3d2b0e8418 100644 > --- a/drivers/dax/fsdev.c > +++ b/drivers/dax/fsdev.c > +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; > + > + phys = dax_pgoff_to_phys(dev_dax, pgoff, nr_pages << PAGE_SHIFT); > + if (phys == -1) { > + dev_dbg(&dev_dax->dev, > + "pgoff (%#lx) out of range\n", pgoff); > + return -EFAULT; > + } > + > + if (kaddr) > + *kaddr = virt_addr; > + > + local_pfn = PHYS_PFN(phys); Trivial but if !pfn, local_pfn not used so... if (pfn) *pfn = PHYS_PFN(phys); Obviously ignore this if it becomes used in some later patch. > + 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). Might be worth capturing somewhere in code that using the value from probe means you don't need locking. > + */ > + return PHYS_PFN(min(size, dev_dax->cached_size - offset)); > +} > + > +static int fsdev_dax_zero_page_range(struct dax_device *dax_dev, > + pgoff_t pgoff, size_t nr_pages) Three tabs > +{ > + 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, Why that indent? Two tabs and a couple of spaces... Either two tabs, or align after ( > + void **kaddr, unsigned long *pfn) > +{ > + return __fsdev_dax_direct_access(dax_dev, pgoff, nr_pages, mode, > + kaddr, pfn); > +} > + > +static size_t fsdev_dax_recovery_write(struct dax_device *dax_dev, pgoff_t > pgoff, > + void *addr, size_t bytes, struct iov_iter *i) two tabs.... > +{ > + return _copy_from_iter_flushcache(addr, bytes, i); > +} > + > +static const struct dax_operations dev_dax_ops = { > + .direct_access = fsdev_dax_direct_access, > + .zero_page_range = fsdev_dax_zero_page_range, > + .recovery_write = fsdev_dax_recovery_write, > +};
