On Tue, Mar 30, 2021 at 01:15:08PM -0400, Theodore Ts'o wrote:
> On Tue, Mar 30, 2021 at 09:32:23AM -0700, Darrick J. Wong wrote:
> > Why not make discarding the journal part of FITRIM then?
>
> Unfortunately, the fstrim_range structure doesn't have a place for a
> flags field, and FITRIM works by specifying a range of LBA's:
>
> struct fstrim_range {
> __u64 start;
> __u64 len;
> __u64 minlen;
> };
>
> I suppose we could do something where some combination of start/len
> means "also checkpoint and discard the journal", but that seems rather
> kludgy.
>
> > It occurred to me overnight that another way to look at this ioctl
> > proposal is that it checkpoints the filesystem and has a flag to discard
> > the journal blocks too. Given that we're now only two days away from
> > my traditional bootfs[1] drum-banging day, and there's real user
> > demand[2] for bootloaders to be able to force a journal checkpoint,
>
> How about if we have an ioctl which is "checkpoint journal", which can
> be file system independent (e.g., defined in include/uapi/linux/fs.h)
> which takes a u32 flags field, where we define a flag bit to mean
> "also discard the unused part of the journal after the checkpoint"?
>
> It seems that would also solve your bootfs() use case.
Yeah, that's where I was going with this. I just sent a new review for
the other patch with that level of focus. :)
--D
> - Ted
