6:25 p.m.
On Wed 10-04-19 09:38:24, Pankaj Gupta wrote:
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(a)suse.cz>
Signed-off-by: Pankaj Gupta <pagupta(a)redhat.com>
---
include/linux/dax.h | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/include/linux/dax.h b/include/linux/dax.h
index b896706a5ee9..4a2a60ffec86 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -38,6 +38,24 @@ 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);
+
+/*
+ * Callers check if synchronous mapping is enabled for DAX file
+ * and attached dax device is also synchronous.
+ *
+ * dax_synchronous function verifies if dax device is synchronous.
+ * Currently, only virtio pmem device supports asynchronous device
+ * flush.
+ */
Thanks for the patch! I'd restructure this comment like:
/*
* 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)
+{
/* Everyone supports non-sync mappings */
+ if (!(vma->vm_flags & VM_SYNC))
+ return true;
/* Sync mappings are supported only for files using DAX */
+ if (!IS_DAX(file_inode(vma->vm_file)))
+ return false;
/* Underlying device must support persisting through CPU
instructions */
> + return dax_synchronous(dax_dev);
> +}
> #else
> static inline struct dax_device *dax_get_by_host(const char *host)
> {
> @@ -69,6 +87,11 @@ static inline bool dax_synchronous(struct dax_device *dax_dev)
> {
> return true;
> }
+static inline bool daxdev_mapping_supported(struct vm_area_struct
*vma,
+ struct dax_device *dax_dev)
+{
> + return true;
This looks wrong. Shouldn't it rather be:
return !(vma->flags & VM_SYNC);
?
Honza
--
Jan Kara <jack(a)suse.com>
SUSE Labs, CR