[PATCH v12 5/7] dax: check synchronous mapping is supported

Pankaj Gupta
2019-06-11T16:42:23Z

This patch introduces 'daxdev_mapping_supported' helper
which checks if 'MAP_SYNC' is supported with filesystem
mapping. It also checks if corresponding dax_device is
synchronous. Virtio pmem device is asynchronous and
does not not support VM_SYNC.

Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
---
include/linux/dax.h | 17 +++++++++++++++++
1 file changed, 17 insertions(+)

diff --git a/include/linux/dax.h b/include/linux/dax.h
index 2b106752b1b8..267251a394fa 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -42,6 +42,18 @@ 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);
void set_dax_synchronous(struct dax_device *dax_dev);
+/*
+ * Check if given mapping is supported by the file / underlying device.
+ */
+static inline bool daxdev_mapping_supported(struct vm_area_struct *vma,
+ struct dax_device *dax_dev)
+{
+ if (!(vma->vm_flags & VM_SYNC))
+ return true;
+ if (!IS_DAX(file_inode(vma->vm_file)))
+ return false;
+ return dax_synchronous(dax_dev);
+}
#else
static inline struct dax_device *dax_get_by_host(const char *host)
{
@@ -69,6 +81,11 @@ static inline bool dax_write_cache_enabled(struct dax_device *dax_dev)
{
return false;
}
+static inline bool daxdev_mapping_supported(struct vm_area_struct *vma,
+ struct dax_device *dax_dev)
+{
+ return !(vma->vm_flags & VM_SYNC);
+}
#endif

struct writeback_control;
--
2.20.1