Notes about this commit:
* These methods are based on pmem_dax_ops from drivers/nvdimm/pmem.c
* dev_dax_direct_access() is 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())
* dev_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.
Signed-off-by: John Groves <john@groves.net>
---
drivers/dax/bus.c | 120 ++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 115 insertions(+), 5 deletions(-)
diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 9d9a4ae7bbc0..61a8d1b3c07a 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -7,6 +7,10 @@
#include <linux/slab.h>
#include <linux/dax.h>
#include <linux/io.h>
+#include <linux/backing-dev.h>
+#include <linux/pfn_t.h>
+#include <linux/range.h>
+#include <linux/uio.h>
#include "dax-private.h"
#include "bus.h"
@@ -1441,6 +1445,105 @@ __weak phys_addr_t dax_pgoff_to_phys(struct dev_dax *dev_dax, pgoff_t pgoff,
}
EXPORT_SYMBOL_GPL(dax_pgoff_to_phys);
+#if IS_ENABLED(CONFIG_DEV_DAX_IOMAP)
+
+static void write_dax(void *pmem_addr, struct page *page,
+ unsigned int off, unsigned int len)
+{
+ unsigned int chunk;
+ void *mem;
+
+ while (len) {
+ mem = kmap_local_page(page);
+ 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 __dev_dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
+ long nr_pages, enum dax_access_mode mode, void **kaddr,
+ pfn_t *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;
+ u64 flags = PFN_DEV|PFN_MAP;
+ phys_addr_t phys;
+ pfn_t local_pfn;
+ size_t dax_size;
+
+ WARN_ON(!dev_dax->virt_addr);
+
+ if (down_read_interruptible(&dax_dev_rwsem))
+ return 0; /* no valid data since we were killed */
+ dax_size = dev_dax_size(dev_dax);
+ up_read(&dax_dev_rwsem);
+
+ phys = dax_pgoff_to_phys(dev_dax, pgoff, nr_pages << PAGE_SHIFT);
+
+ if (kaddr)
+ *kaddr = virt_addr;
+
+ local_pfn = phys_to_pfn_t(phys, flags); /* are flags correct? */
+ if (pfn)
+ *pfn = local_pfn;
+
+ /* This the valid size at the specified address */
+ return PHYS_PFN(min_t(size_t, size, dax_size - offset));
+}
+
+static int dev_dax_zero_page_range(struct dax_device *dax_dev, pgoff_t pgoff,
+ size_t nr_pages)
+{
+ long resid = nr_pages << PAGE_SHIFT;
+ long offset = pgoff << PAGE_SHIFT;
+
+ /* Break into one write per dax region */
+ while (resid > 0) {
+ void *kaddr;
+ pgoff_t poff = offset >> PAGE_SHIFT;
+ long len = __dev_dax_direct_access(dax_dev, poff,
+ nr_pages, DAX_ACCESS, &kaddr, NULL);
+ len = min_t(long, len, PAGE_SIZE);
+ write_dax(kaddr, ZERO_PAGE(0), offset, len);
+
+ offset += len;
+ resid -= len;
+ }
+ return 0;
+}
+
+static long dev_dax_direct_access(struct dax_device *dax_dev,
+ pgoff_t pgoff, long nr_pages, enum dax_access_mode mode,
+ void **kaddr, pfn_t *pfn)
+{
+ return __dev_dax_direct_access(dax_dev, pgoff, nr_pages, mode, kaddr, pfn);
+}
+
+static size_t dev_dax_recovery_write(struct dax_device *dax_dev, pgoff_t pgoff,
+ void *addr, size_t bytes, struct iov_iter *i)
+{
+ size_t off;
+
+ off = offset_in_page(addr);
+
+ return _copy_from_iter_flushcache(addr, bytes, i);
+}
+
+static const struct dax_operations dev_dax_ops = {
+ .direct_access = dev_dax_direct_access,
+ .zero_page_range = dev_dax_zero_page_range,
+ .recovery_write = dev_dax_recovery_write,
+};
+
+#endif /* IS_ENABLED(CONFIG_DEV_DAX_IOMAP) */
+
static struct dev_dax *__devm_create_dev_dax(struct dev_dax_data *data)
{
struct dax_region *dax_region = data->dax_region;
@@ -1496,11 +1599,18 @@ static struct dev_dax *__devm_create_dev_dax(struct dev_dax_data *data)
}
}
- /*
- * No dax_operations since there is no access to this device outside of
- * mmap of the resulting character device.
- */
- dax_dev = alloc_dax(dev_dax, NULL);
+ if (IS_ENABLED(CONFIG_DEV_DAX_IOMAP))
+ /* holder_ops currently populated separately in a slightly
+ * hacky way
+ */
+ dax_dev = alloc_dax(dev_dax, &dev_dax_ops);
+ else
+ /*
+ * No dax_operations since there is no access to this device
+ * outside of mmap of the resulting character device.
+ */
+ dax_dev = alloc_dax(dev_dax, NULL);
+
if (IS_ERR(dax_dev)) {
rc = PTR_ERR(dax_dev);
goto err_alloc_dax;
--
2.49.0On Thu, 3 Jul 2025 13:50:18 -0500
John Groves <John@Groves.net> wrote:
> Notes about this commit:
>
> * These methods are based on pmem_dax_ops from drivers/nvdimm/pmem.c
>
> * dev_dax_direct_access() is 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())
>
> * dev_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.
>
> Signed-off-by: John Groves <john@groves.net>
A few trivial things noticed whilst reading through.
> ---
> drivers/dax/bus.c | 120 ++++++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 115 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
> index 9d9a4ae7bbc0..61a8d1b3c07a 100644
> --- a/drivers/dax/bus.c
> +++ b/drivers/dax/bus.c
> @@ -7,6 +7,10 @@
> #include <linux/slab.h>
> #include <linux/dax.h>
> #include <linux/io.h>
> +#include <linux/backing-dev.h>
> +#include <linux/pfn_t.h>
> +#include <linux/range.h>
> +#include <linux/uio.h>
> #include "dax-private.h"
> #include "bus.h"
>
> @@ -1441,6 +1445,105 @@ __weak phys_addr_t dax_pgoff_to_phys(struct dev_dax *dev_dax, pgoff_t pgoff,
> }
> EXPORT_SYMBOL_GPL(dax_pgoff_to_phys);
>
> +#if IS_ENABLED(CONFIG_DEV_DAX_IOMAP)
> +
> +static void write_dax(void *pmem_addr, struct page *page,
> + unsigned int off, unsigned int len)
> +{
> + unsigned int chunk;
> + void *mem;
I'd move these two into the loop - similar to what you have
in other cases with more local scope.
> +
> + while (len) {
> + mem = kmap_local_page(page);
> + 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 __dev_dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
> + long nr_pages, enum dax_access_mode mode, void **kaddr,
> + pfn_t *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;
> + u64 flags = PFN_DEV|PFN_MAP;
spaces around the |
Though given it's in just one place, just put these inline next
to the question...
> + phys_addr_t phys;
> + pfn_t local_pfn;
> + size_t dax_size;
> +
> + WARN_ON(!dev_dax->virt_addr);
> +
> + if (down_read_interruptible(&dax_dev_rwsem))
> + return 0; /* no valid data since we were killed */
> + dax_size = dev_dax_size(dev_dax);
> + up_read(&dax_dev_rwsem);
> +
> + phys = dax_pgoff_to_phys(dev_dax, pgoff, nr_pages << PAGE_SHIFT);
> +
> + if (kaddr)
> + *kaddr = virt_addr;
> +
> + local_pfn = phys_to_pfn_t(phys, flags); /* are flags correct? */
> + if (pfn)
> + *pfn = local_pfn;
> +
> + /* This the valid size at the specified address */
> + return PHYS_PFN(min_t(size_t, size, dax_size - offset));
> +}
> +static size_t dev_dax_recovery_write(struct dax_device *dax_dev, pgoff_t pgoff,
> + void *addr, size_t bytes, struct iov_iter *i)
> +{
> + size_t off;
> +
> + off = offset_in_page(addr);
Unused.
> +
> + return _copy_from_iter_flushcache(addr, bytes, i);
> +}
On 25/07/04 01:47PM, Jonathan Cameron wrote:
> On Thu, 3 Jul 2025 13:50:18 -0500
> John Groves <John@Groves.net> wrote:
>
> > Notes about this commit:
> >
> > * These methods are based on pmem_dax_ops from drivers/nvdimm/pmem.c
> >
> > * dev_dax_direct_access() is 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())
> >
> > * dev_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.
> >
> > Signed-off-by: John Groves <john@groves.net>
> A few trivial things noticed whilst reading through.
BTW thanks for looking at the dev_dax_iomap part of the series. These are
basically identical to the two standalone-famfs series' I put out last year,
but have IIRC not gotten review comments before this.
>
> > ---
> > drivers/dax/bus.c | 120 ++++++++++++++++++++++++++++++++++++++++++++--
> > 1 file changed, 115 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
> > index 9d9a4ae7bbc0..61a8d1b3c07a 100644
> > --- a/drivers/dax/bus.c
> > +++ b/drivers/dax/bus.c
> > @@ -7,6 +7,10 @@
> > #include <linux/slab.h>
> > #include <linux/dax.h>
> > #include <linux/io.h>
> > +#include <linux/backing-dev.h>
> > +#include <linux/pfn_t.h>
> > +#include <linux/range.h>
> > +#include <linux/uio.h>
> > #include "dax-private.h"
> > #include "bus.h"
> >
> > @@ -1441,6 +1445,105 @@ __weak phys_addr_t dax_pgoff_to_phys(struct dev_dax *dev_dax, pgoff_t pgoff,
> > }
> > EXPORT_SYMBOL_GPL(dax_pgoff_to_phys);
> >
> > +#if IS_ENABLED(CONFIG_DEV_DAX_IOMAP)
> > +
> > +static void write_dax(void *pmem_addr, struct page *page,
> > + unsigned int off, unsigned int len)
> > +{
> > + unsigned int chunk;
> > + void *mem;
>
> I'd move these two into the loop - similar to what you have
> in other cases with more local scope.
Done, thanks.
>
> > +
> > + while (len) {
> > + mem = kmap_local_page(page);
> > + 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 __dev_dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
> > + long nr_pages, enum dax_access_mode mode, void **kaddr,
> > + pfn_t *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;
> > + u64 flags = PFN_DEV|PFN_MAP;
>
> spaces around the |
>
> Though given it's in just one place, just put these inline next
> to the question...
Done and done.
>
>
> > + phys_addr_t phys;
> > + pfn_t local_pfn;
> > + size_t dax_size;
> > +
> > + WARN_ON(!dev_dax->virt_addr);
> > +
> > + if (down_read_interruptible(&dax_dev_rwsem))
> > + return 0; /* no valid data since we were killed */
> > + dax_size = dev_dax_size(dev_dax);
> > + up_read(&dax_dev_rwsem);
> > +
> > + phys = dax_pgoff_to_phys(dev_dax, pgoff, nr_pages << PAGE_SHIFT);
> > +
> > + if (kaddr)
> > + *kaddr = virt_addr;
> > +
> > + local_pfn = phys_to_pfn_t(phys, flags); /* are flags correct? */
> > + if (pfn)
> > + *pfn = local_pfn;
> > +
> > + /* This the valid size at the specified address */
> > + return PHYS_PFN(min_t(size_t, size, dax_size - offset));
> > +}
>
> > +static size_t dev_dax_recovery_write(struct dax_device *dax_dev, pgoff_t pgoff,
> > + void *addr, size_t bytes, struct iov_iter *i)
> > +{
> > + size_t off;
> > +
> > + off = offset_in_page(addr);
>
> Unused.
Righto. Thanks.
> > +
> > + return _copy_from_iter_flushcache(addr, bytes, i);
> > +}
>
>
Thanks!
John
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