libnvdimm: add dax_dev sync flag

This patch adds 'DAXDEV_SYNC' flag which is set
for nd_region doing synchronous flush. This later
is used to disable MAP_SYNC functionality for
ext4 & xfs filesystem for devices don't support
synchronous flush.

Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/dax/bus.c

@@ -388,7 +388,7 @@ struct dev_dax *__devm_create_dev_dax(struct dax_region *dax_region, int id,
 	 * No 'host' or 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, NULL);
+	dax_dev = alloc_dax(dev_dax, NULL, NULL, DAXDEV_F_SYNC);
 	if (!dax_dev)
 		goto err;
 

drivers/dax/super.c

@@ -195,6 +195,8 @@ enum dax_device_flags {
 	DAXDEV_ALIVE,
 	/* gate whether dax_flush() calls the low level flush routine */
 	DAXDEV_WRITE_CACHE,
+	/* flag to check if device supports synchronous flush */
+	DAXDEV_SYNC,
 };
 
 /**
@@ -372,6 +374,18 @@ bool dax_write_cache_enabled(struct dax_device *dax_dev)
 }
 EXPORT_SYMBOL_GPL(dax_write_cache_enabled);
 
+bool __dax_synchronous(struct dax_device *dax_dev)
+{
+	return test_bit(DAXDEV_SYNC, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(__dax_synchronous);
+
+void __set_dax_synchronous(struct dax_device *dax_dev)
+{
+	set_bit(DAXDEV_SYNC, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(__set_dax_synchronous);
+
 bool dax_alive(struct dax_device *dax_dev)
 {
 	lockdep_assert_held(&dax_srcu);
@@ -526,7 +540,7 @@ static void dax_add_host(struct dax_device *dax_dev, const char *host)
 }
 
 struct dax_device *alloc_dax(void *private, const char *__host,
-		const struct dax_operations *ops)
+		const struct dax_operations *ops, unsigned long flags)
 {
 	struct dax_device *dax_dev;
 	const char *host;
@@ -549,6 +563,9 @@ struct dax_device *alloc_dax(void *private, const char *__host,
 	dax_add_host(dax_dev, host);
 	dax_dev->ops = ops;
 	dax_dev->private = private;
+	if (flags & DAXDEV_F_SYNC)
+		set_dax_synchronous(dax_dev);
+
 	return dax_dev;
 
  err_dev:

drivers/md/dm.c

@@ -1991,7 +1991,8 @@ static struct mapped_device *alloc_dev(int minor)
 	sprintf(md->disk->disk_name, "dm-%d", minor);
 
 	if (IS_ENABLED(CONFIG_DAX_DRIVER)) {
-		md->dax_dev = alloc_dax(md, md->disk->disk_name, &dm_dax_ops);
+		md->dax_dev = alloc_dax(md, md->disk->disk_name,
+					&dm_dax_ops, 0);
 		if (!md->dax_dev)
 			goto bad;
 	}

drivers/nvdimm/pmem.c

@@ -376,6 +376,7 @@ static int pmem_attach_disk(struct device *dev,
 	struct gendisk *disk;
 	void *addr;
 	int rc;
+	unsigned long flags = 0UL;
 
 	pmem = devm_kzalloc(dev, sizeof(*pmem), GFP_KERNEL);
 	if (!pmem)
@@ -474,7 +475,9 @@ static int pmem_attach_disk(struct device *dev,
 	nvdimm_badblocks_populate(nd_region, &pmem->bb, &bb_res);
 	disk->bb = &pmem->bb;
 
-	dax_dev = alloc_dax(pmem, disk->disk_name, &pmem_dax_ops);
+	if (is_nvdimm_sync(nd_region))
+		flags = DAXDEV_F_SYNC;
+	dax_dev = alloc_dax(pmem, disk->disk_name, &pmem_dax_ops, flags);
 	if (!dax_dev) {
 		put_disk(disk);
 		return -ENOMEM;

drivers/nvdimm/region_devs.c

@@ -1211,6 +1211,13 @@ int nvdimm_has_cache(struct nd_region *nd_region)
 }
 EXPORT_SYMBOL_GPL(nvdimm_has_cache);
 
+bool is_nvdimm_sync(struct nd_region *nd_region)
+{
+	return is_nd_pmem(&nd_region->dev) &&
+		!test_bit(ND_REGION_ASYNC, &nd_region->flags);
+}
+EXPORT_SYMBOL_GPL(is_nvdimm_sync);
+
 struct conflict_context {
 	struct nd_region *nd_region;
 	resource_size_t start, size;

drivers/s390/block/dcssblk.c

@@ -679,7 +679,7 @@ dcssblk_add_store(struct device *dev, struct device_attribute *attr, const char
 		goto put_dev;
 
 	dev_info->dax_dev = alloc_dax(dev_info, dev_info->gd->disk_name,
-			&dcssblk_dax_ops);
+			&dcssblk_dax_ops, DAXDEV_F_SYNC);
 	if (!dev_info->dax_dev) {
 		rc = -ENOMEM;
 		goto put_dev;

include/linux/dax.h

@@ -7,6 +7,9 @@
 #include <linux/radix-tree.h>
 #include <asm/pgtable.h>
 
+/* Flag for synchronous flush */
+#define DAXDEV_F_SYNC (1UL << 0)
+
 typedef unsigned long dax_entry_t;
 
 struct iomap_ops;
@@ -38,18 +41,28 @@ extern struct attribute_group dax_attribute_group;
 #if IS_ENABLED(CONFIG_DAX)
 struct dax_device *dax_get_by_host(const char *host);
 struct dax_device *alloc_dax(void *private, const char *host,
-		const struct dax_operations *ops);
+		const struct dax_operations *ops, unsigned long flags);
 void put_dax(struct dax_device *dax_dev);
 void kill_dax(struct dax_device *dax_dev);
 void dax_write_cache(struct dax_device *dax_dev, bool wc);
 bool dax_write_cache_enabled(struct dax_device *dax_dev);
+bool __dax_synchronous(struct dax_device *dax_dev);
+static inline bool dax_synchronous(struct dax_device *dax_dev)
+{
+	return  __dax_synchronous(dax_dev);
+}
+void __set_dax_synchronous(struct dax_device *dax_dev);
+static inline void set_dax_synchronous(struct dax_device *dax_dev)
+{
+	__set_dax_synchronous(dax_dev);
+}
 #else
 static inline struct dax_device *dax_get_by_host(const char *host)
 {
 	return NULL;
 }
 static inline struct dax_device *alloc_dax(void *private, const char *host,
-		const struct dax_operations *ops)
+		const struct dax_operations *ops, unsigned long flags)
 {
 	/*
 	 * Callers should check IS_ENABLED(CONFIG_DAX) to know if this
@@ -70,6 +83,13 @@ static inline bool dax_write_cache_enabled(struct dax_device *dax_dev)
 {
 	return false;
 }
+static inline bool dax_synchronous(struct dax_device *dax_dev)
+{
+	return true;
+}
+static inline void set_dax_synchronous(struct dax_device *dax_dev)
+{
+}
 #endif
 
 struct writeback_control;

include/linux/libnvdimm.h

@@ -263,6 +263,7 @@ int generic_nvdimm_flush(struct nd_region *nd_region);
 int nvdimm_has_flush(struct nd_region *nd_region);
 int nvdimm_has_cache(struct nd_region *nd_region);
 int nvdimm_in_overwrite(struct nvdimm *nvdimm);
+bool is_nvdimm_sync(struct nd_region *nd_region);
 
 static inline int nvdimm_ctl(struct nvdimm *nvdimm, unsigned int cmd, void *buf,
 		unsigned int buf_len, int *cmd_rc)