From: Jan Kara <jack@suse.cz>
Subject: dax: Make extension of dax_operations transparent
Patch-mainline: Never, kabi
References: bsc#1098782

Provide new alloc_dax_to_iter() function for use by drivers which are aware
that struct dax_operations has a new member and use it.

Signed-off-by: Jan Kara <jack@suse.cz>

---
 drivers/dax/super.c          |   16 ++++++++++++++++
 drivers/md/dm.c              |    2 +-
 drivers/nvdimm/pmem.c        |    2 +-
 drivers/s390/block/dcssblk.c |    2 +-
 include/linux/dax.h          |    4 ++++
 5 files changed, 23 insertions(+), 3 deletions(-)

--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -133,6 +133,8 @@ enum dax_device_flags {
 	DAXDEV_ALIVE,
 	/* gate whether dax_flush() calls the low level flush routine */
 	DAXDEV_WRITE_CACHE,
+	/* set if dax device supports copy_to_iter operation */
+	DAXDEV_TO_ITER,
 };
 
 /**
@@ -274,6 +276,8 @@ size_t dax_copy_to_iter(struct dax_devic
 {
 	if (!dax_alive(dax_dev))
 		return 0;
+	if (!test_bit(DAXDEV_TO_ITER, &dax_dev->flags))
+		return copy_to_iter(addr, bytes, i);
 
 	return dax_dev->ops->copy_to_iter(dax_dev, pgoff, addr, bytes, i);
 }
@@ -499,6 +503,18 @@ struct dax_device *alloc_dax(void *priva
 }
 EXPORT_SYMBOL_GPL(alloc_dax);
 
+struct dax_device *alloc_dax_to_iter(void *private, const char *__host,
+		const struct dax_operations *ops)
+{
+	struct dax_device *dax_dev = alloc_dax(private, __host, ops);
+
+	if (!dax_dev)
+		return NULL;
+	set_bit(DAXDEV_TO_ITER, &dax_dev->flags);
+	return dax_dev;
+}
+EXPORT_SYMBOL_GPL(alloc_dax_to_iter);
+
 void put_dax(struct dax_device *dax_dev)
 {
 	if (!dax_dev)
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1763,7 +1763,7 @@ static struct mapped_device *alloc_dev(i
 	md->disk->private_data = md;
 	sprintf(md->disk->disk_name, "dm-%d", minor);
 
-	dax_dev = alloc_dax(md, md->disk->disk_name, &dm_dax_ops);
+	dax_dev = alloc_dax_to_iter(md, md->disk->disk_name, &dm_dax_ops);
 	if (!dax_dev)
 		goto bad;
 	md->dax_dev = dax_dev;
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -391,7 +391,7 @@ static int pmem_attach_disk(struct devic
 	nvdimm_badblocks_populate(nd_region, &pmem->bb, res);
 	disk->bb = &pmem->bb;
 
-	dax_dev = alloc_dax(pmem, disk->disk_name, &pmem_dax_ops);
+	dax_dev = alloc_dax_to_iter(pmem, disk->disk_name, &pmem_dax_ops);
 	if (!dax_dev) {
 		put_disk(disk);
 		return -ENOMEM;
--- a/drivers/s390/block/dcssblk.c
+++ b/drivers/s390/block/dcssblk.c
@@ -676,7 +676,7 @@ dcssblk_add_store(struct device *dev, st
 	if (rc)
 		goto put_dev;
 
-	dev_info->dax_dev = alloc_dax(dev_info, dev_info->gd->disk_name,
+	dev_info->dax_dev = alloc_dax_to_iter(dev_info, dev_info->gd->disk_name,
 			&dcssblk_dax_ops);
 	if (!dev_info->dax_dev) {
 		rc = -ENOMEM;
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -19,9 +19,11 @@ struct dax_operations {
 	/* copy_from_iter: required operation for fs-dax direct-i/o */
 	size_t (*copy_from_iter)(struct dax_device *, pgoff_t, void *, size_t,
 			struct iov_iter *);
+#ifndef __GENKSYMS__
 	/* copy_to_iter: required operation for fs-dax direct-i/o */
 	size_t (*copy_to_iter)(struct dax_device *, pgoff_t, void *, size_t,
 			struct iov_iter *);
+#endif
 };
 
 extern struct attribute_group dax_attribute_group;
@@ -85,6 +87,8 @@ int dax_read_lock(void);
 void dax_read_unlock(int id);
 struct dax_device *alloc_dax(void *private, const char *host,
 		const struct dax_operations *ops);
+struct dax_device *alloc_dax_to_iter(void *private, const char *host,
+		const struct dax_operations *ops);
 bool dax_alive(struct dax_device *dax_dev);
 void kill_dax(struct dax_device *dax_dev);
 void *dax_get_private(struct dax_device *dax_dev);