[PATCH V3 4/8] fs/ext4: Update ext4_should_use_dax()

[ira . weiny]

From: Ira Weiny <ira.we...@intel.com>

S_DAX should only be enabled when the underlying block device supports
dax.

Change ext4_should_use_dax() to check for device support prior to the
over riding mount option.

While we are at it change the function to ext4_should_enable_dax() as
this better reflects the ask as well as matches xfs.

Reviewed-by: Jan Kara <j...@suse.cz>
Signed-off-by: Ira Weiny <ira.we...@intel.com>

---
Changes from RFC
        Change function name to 'should enable'
        Clean up bool conversion
        Reorder this for better bisect-ability
---
 fs/ext4/inode.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index a10ff12194db..d3a4c2ed7a1c 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4398,10 +4398,8 @@ 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_should_enable_dax(struct inode *inode)
 {
-       if (!test_opt(inode->i_sb, DAX_ALWAYS))
-               return false;
        if (!S_ISREG(inode->i_mode))
                return false;
        if (ext4_should_journal_data(inode))
@@ -4412,7 +4410,13 @@ 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_ALWAYS))
+               return true;
+
+       return false;
 }
 
 void ext4_set_inode_flags(struct inode *inode)
@@ -4430,7 +4434,7 @@ 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_should_enable_dax(inode))
                new_fl |= S_DAX;
        if (flags & EXT4_ENCRYPT_FL)
                new_fl |= S_ENCRYPTED;
-- 
2.25.1