Excerpts from Chris Mason's message of 2011-03-27 14:10:46 -0400:

Excerpts from Li Dongyang's message of 2011-03-24 06:24:24 -0400:

quoted

Dear list,
This is V4 of batched discard support, now we will get full mapping of
the free space on each device for RAID0/1/10/DUP instead of just a single
stripe length, and tested with xfsstests 251, Thanks.

I've pushed this out into the for-linus branch, along with a full merge
to 2.6.39 current git.

Please take a look and make sure I've merged it correctly.

Hmmm, this was doing mod operations on 64 bit numbers, so it didn't
compile at all on 32 bit machines.  I've fixed it up and pushed the
result out to for-linus.  Please check the math ;)

-chris

Thanks!

-chris

quoted

Changelog V4:
    *make btrfs_map_block() return full mapping.
Changelog V3:
    *fix style problems.
    *rebase to 2.6.38-rc7.
Changelog V2:
    *Check if we have devices support trim before trying to trim the fs, also adjust
      minlen according to the discard_granularity.
    *Update reserved extent calculations in btrfs_trim_block_group().
    *Call cond_resched() without checking need_resched()
    *Use bitmap_clear_bits() and unlink_free_space() instead of btrfs_remove_free_space(),
      so we won't search the same extent for twice.
    *Try harder in btrfs_discard_extent(), now we won't report errors
     if it's not a EOPNOTSUPP.
    *make sure the block group is cached before trimming it,or we'll see an empty caching
     tree if the block group is not cached.
    *Minor return value fix in btrfs_discard_block_group().