[PATCH RFC 6/8] fs/ext4: Update ext4_should_use_dax()

[ira . weiny]

From: Ira Weiny <ira.weiny@xxxxxxxxx>

Change the logic of ext4_should_use_dax() to support using the inode dax
flag OR the overriding tri-state mount option.

While we are at it change the function to ext4_enable_dax() as this
better reflects the ask.

Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>
---
 fs/ext4/inode.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index fa0ff78dc033..e9d582e516bc 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4383,9 +4383,11 @@ int ext4_get_inode_loc(struct inode *inode, struct ext4_iloc *iloc)
 		!ext4_test_inode_state(inode, EXT4_STATE_XATTR));
 }
 
-static bool ext4_should_use_dax(struct inode *inode)
+static bool ext4_enable_dax(struct inode *inode)
 {
-	if (!test_opt(inode->i_sb, DAX))
+	unsigned int flags = EXT4_I(inode)->i_flags;
+
+	if (test_opt2(inode->i_sb, NODAX))
 		return false;
 	if (!S_ISREG(inode->i_mode))
 		return false;
@@ -4397,7 +4399,13 @@ static bool ext4_should_use_dax(struct inode *inode)
 		return false;
 	if (ext4_test_inode_flag(inode, EXT4_INODE_VERITY))
 		return false;
-	return true;
+	if (!bdev_dax_supported(inode->i_sb->s_bdev,
+				inode->i_sb->s_blocksize))
+		return false;
+	if (test_opt(inode->i_sb, DAX))
+		return true;
+
+	return (flags & EXT4_DAX_FL) == EXT4_DAX_FL;
 }
 
 void ext4_set_inode_flags(struct inode *inode)
@@ -4415,7 +4423,7 @@ void ext4_set_inode_flags(struct inode *inode)
 		new_fl |= S_NOATIME;
 	if (flags & EXT4_DIRSYNC_FL)
 		new_fl |= S_DIRSYNC;
-	if (ext4_should_use_dax(inode))
+	if (ext4_enable_dax(inode))
 		new_fl |= S_DAX;
 	if (flags & EXT4_ENCRYPT_FL)
 		new_fl |= S_ENCRYPTED;
-- 
2.25.1