ext4: allow the dax flag to be set and cleared on inline directories

This is needed to allow generic/607 to pass for file systems with the
inline data_feature enabled, and it allows the use of file systems
where the directories use inline_data, while the files are accessed
via DAX.

Cc: stable@kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/ialloc.c

@@ -1292,7 +1292,8 @@ got:
 
 	ei->i_extra_isize = sbi->s_want_extra_isize;
 	ei->i_inline_off = 0;
-	if (ext4_has_feature_inline_data(sb))
+	if (ext4_has_feature_inline_data(sb) &&
+	    (!(ei->i_flags & EXT4_DAX_FL) || S_ISDIR(mode)))
 		ext4_set_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA);
 	ret = inode;
 	err = dquot_alloc_inode(inode);

fs/ext4/ioctl.c

@@ -315,6 +315,12 @@ static void ext4_dax_dontcache(struct inode *inode, unsigned int flags)
 static bool dax_compatible(struct inode *inode, unsigned int oldflags,
 			   unsigned int flags)
 {
+	/* Allow the DAX flag to be changed on inline directories */
+	if (S_ISDIR(inode->i_mode)) {
+		flags &= ~EXT4_INLINE_DATA_FL;
+		oldflags &= ~EXT4_INLINE_DATA_FL;
+	}
+
 	if (flags & EXT4_DAX_FL) {
 		if ((oldflags & EXT4_DAX_MUT_EXCL) ||
 		     ext4_test_inode_state(inode,