On Mon, Dec 30, 2019 at 06:33:52PM +0100, David Sterba wrote:
> On Fri, Dec 13, 2019 at 04:22:28PM -0800, Dennis Zhou wrote:
> > Keep track of how much we are discarding and how often we are reusing
> > with async discard.
> >
> > Signed-off-by: Dennis Zhou <dennis@xxxxxxxxxx>
> > Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
> > ---
> > fs/btrfs/ctree.h | 3 +++
> > fs/btrfs/discard.c | 7 +++++++
> > fs/btrfs/free-space-cache.c | 14 ++++++++++++++
> > fs/btrfs/sysfs.c | 36 ++++++++++++++++++++++++++++++++++++
> > 4 files changed, 60 insertions(+)
> >
> > diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> > index dddf51e27bed..edfbe6060e8d 100644
> > --- a/fs/btrfs/ctree.h
> > +++ b/fs/btrfs/ctree.h
> > @@ -474,6 +474,9 @@ struct btrfs_discard_ctl {
> > u32 delay;
> > u32 iops_limit;
> > u64 bps_limit;
> > + u64 discard_extent_bytes;
> > + u64 discard_bitmap_bytes;
> > + atomic64_t discard_bytes_saved;
> > };
> >
> > /* delayed seq elem */
> > diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c
> > index 55ad357e65f3..fe73814526ef 100644
> > --- a/fs/btrfs/discard.c
> > +++ b/fs/btrfs/discard.c
> > @@ -419,11 +419,15 @@ static void btrfs_discard_workfn(struct work_struct *work)
> > block_group->discard_cursor,
> > btrfs_block_group_end(block_group),
> > minlen, maxlen, true);
> > + WRITE_ONCE(discard_ctl->discard_bitmap_bytes,
> > + discard_ctl->discard_bitmap_bytes + trimmed);
>
> The same argument is used for read and write, this does not seem to be a
> clear usage pattern for WRITE_ONCE, is there are cleaner way to do that?
>
Yeah that doesn't really make any sense. I think we are okay here anyway
as btrfs_discard_workfn() provides synchronization by being a single
work item. So, I've removed the WRITE_ONCE.
> > } else {
> > btrfs_trim_block_group_extents(block_group, &trimmed,
> > block_group->discard_cursor,
> > btrfs_block_group_end(block_group),
> > minlen, true);
> > + WRITE_ONCE(discard_ctl->discard_extent_bytes,
> > + discard_ctl->discard_extent_bytes + trimmed);
