block: Add bdev_dax_supported() for dax mount checks

[cascardo/linux.git] / fs / block_dev.c

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 91e0ec0..518cde6 100644 (file)
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -509,6 +509,51 @@ long bdev_direct_access(struct block_device *bdev, struct blk_dax_ctl *dax)
 }
 EXPORT_SYMBOL_GPL(bdev_direct_access);
 
+/**
+ * bdev_dax_supported() - Check if the device supports dax for filesystem
+ * @sb: The superblock of the device
+ * @blocksize: The block size of the device
+ *
+ * This is a library function for filesystems to check if the block device
+ * can be mounted with dax option.
+ *
+ * Return: negative errno if unsupported, 0 if supported.
+ */
+int bdev_dax_supported(struct super_block *sb, int blocksize)
+{
+       struct blk_dax_ctl dax = {
+               .sector = 0,
+               .size = PAGE_SIZE,
+       };
+       int err;
+
+       if (blocksize != PAGE_SIZE) {
+               vfs_msg(sb, KERN_ERR, "error: unsupported blocksize for dax");
+               return -EINVAL;
+       }
+
+       err = bdev_direct_access(sb->s_bdev, &dax);
+       if (err < 0) {
+               switch (err) {
+               case -EOPNOTSUPP:
+                       vfs_msg(sb, KERN_ERR,
+                               "error: device does not support dax");
+                       break;
+               case -EINVAL:
+                       vfs_msg(sb, KERN_ERR,
+                               "error: unaligned partition for dax");
+                       break;
+               default:
+                       vfs_msg(sb, KERN_ERR,
+                               "error: dax access failed (%d)", err);
+               }
+               return err;
+       }
+
+       return 0;
+}
+EXPORT_SYMBOL_GPL(bdev_dax_supported);
+
 /*
  * pseudo-fs
  */