Hi Jan,
> Hi Jan,
> > Hum, these games with several callbacks, lists, etc. look awkward and
> > unnecessary. It think they mostly come from the fact that we call separate
> > freeing callback for each extent to free which doesn't fit the needs of
> > async discard well.
> > So instead of adding post_cb_list and several callback functions, it would
> > seem easier to have just one callback structure instead of one for every
> > extent. Then the structure would contain a list of extents that need to be
> > freed freed. So something like:
> > struct ext4_free_data {
> > struct ext4_journal_cb_entry efd_jce;
> > struct list_head efd_extents;
> > }
> > struct ext4_freed_extent {
> > struct list_head efe_list;
> > struct rb_node efe_node;
> > ext4_group_t efe_group;
> > ext4_grpblk_t efe_start_cluster;
> > ext4_grpblk_t efe_count;
> > tid_t efe_tid;
> > }
> > When commit happens, we can just walk the efd_extents list while efe_tid is
> > equal tid of the transaction for which the callback was called and submit all
> > discard requests. You can use bio chaining implemented in
> > __blkdev_issue_discard() which XFS already uses and so the result of all
> > the discards you submit will be just one bio. Then you walk the list of
> > extents again and free them in the buddy bitmaps. And finally, you wait for
> > the bio to complete. All will be then happening in one function and it will
> > be much easier to understand.
> It's right. the patch didn't look neat because of a few callbacks and the
> post callback list. I will modify the patch as your suggestion. It will
> look better.
> Thank you very much. :-)
It's a little difficult to decide when we have to add new ext4_free_data entry for
a transaction for the first time and how do we know whether the ext4_free_data entry
for a transaction is already added or not? I think that it is a bad idea to search in
t_private_list of the transaction for that, because there might be the different
type of callback entries in the future.
And how do we find the exact ext4_free_data entry for a newly created ext4_freed_extent?
We only know which transcation is related to the ext4_freed_extent, so we could use this
but I don't have any good idea for that.
Do you have any idea?
Thank you.
