tree 9f21dfa02d5a64a860e4cc392b534c2720785950
parent e4faab844a55edb9b628bf1f982fbc30f07b9700
author Dennis Zhou <dennis@kernel.org> 1576282940 -0800
committer David Sterba <dsterba@suse.com> 1579534858 +0100

btrfs: track discardable extents for async discard

The number of discardable extents will serve as the rate limiting metric
for how often we should discard. This keeps track of discardable extents
in the free space caches by maintaining deltas and propagating them to
the global count.

The deltas are calculated from 2 values stored in PREV and CURR entries,
then propagated up to the global discard ctl.  The current counter value
becomes the previous counter value after update.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>