Re: [PATCH V4 7/8] fs/ext4: Introduce DAX inode flag

From: Jan Kara
Date: Mon May 25 2020 - 03:28:49 EST

On Sun 24-05-20 21:39:10, Ira Weiny wrote:
> On Fri, May 22, 2020 at 01:48:48PM +0200, Jan Kara wrote:
> > And then we should check conflicts with the journal flag as well, as I
> > mentioned in reply to the first patch. There it is more complicated by the
> > fact that we should disallow setting of both EXT4_INODE_DAX_FL and
> > EXT4_JOURNAL_DATA_FL at the same time so the checks will be somewhat more
> > complicated.
> I'm confused by jflag. Why is EXT4_JOURNAL_DATA_FL stored in jflag?

It isn't just EXT4_JOURNAL_DATA_FL. It is:

jflag = flags & EXT4_JOURNAL_DATA_FL;

so it is EXT4_JOURNAL_DATA_FL if it should be set by the current ioctl and 0
otherwise. But I agree that since we mostly do

(jflag ^ oldflags) & EXT4_JOURNAL_DATA_FL

jflags is mostly useless as we could do just

(flags ^ oldflags) & EXT4_JOURNAL_DATA_FL

I guess it's mostly a relict from the past...

Jan Kara <jack@xxxxxxxx>