btrfs: only keep track of data extents for async discard

As mentioned earlier, discarding data can be done either by issuing an
explicit discard or implicitly by reusing the LBA. Metadata block_groups
see much more frequent reuse due to well it being metadata. So instead
of explicitly discarding metadata block_groups, just leave them be and
let the latter implicit discarding be done for them.

For mixed block_groups, block_groups which contain both metadata and
data, we let them be as higher fragmentation is expected.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/block-group.h b/fs/btrfs/block-group.h
index a8d2edcd8760b7207d4e1224a4f6565602954181..5cf1ea33f284e32679e468e5f92478470d62c688 100644 (file)
--- a/fs/btrfs/block-group.h
+++ b/fs/btrfs/block-group.h
@@ -182,6 +182,17 @@ static inline u64 btrfs_block_group_end(struct btrfs_block_group *block_group)
        return (block_group->start + block_group->length);
 }
 
+static inline bool btrfs_is_block_group_data_only(
+                                       struct btrfs_block_group *block_group)
+{
+       /*
+        * In mixed mode the fragmentation is expected to be high, lowering the
+        * efficiency, so only proper data block groups are considered.
+        */
+       return (block_group->flags & BTRFS_BLOCK_GROUP_DATA) &&
+              !(block_group->flags & BTRFS_BLOCK_GROUP_METADATA);
+}
+
 #ifdef CONFIG_BTRFS_DEBUG
 static inline int btrfs_should_fragment_free_space(
                struct btrfs_block_group *block_group)

diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c
index 0299981d0c62b88306e0c6ede6b7cba16fabfb2a..5af42e0317b7d95dbd6f5777f3beab84668ac3bc 100644 (file)
--- a/fs/btrfs/discard.c
+++ b/fs/btrfs/discard.c
@@ -57,6 +57,9 @@ static void __add_to_discard_list(struct btrfs_discard_ctl *discard_ctl,
 static void add_to_discard_list(struct btrfs_discard_ctl *discard_ctl,
                                struct btrfs_block_group *block_group)
 {
+       if (!btrfs_is_block_group_data_only(block_group))
+               return;
+
        spin_lock(&discard_ctl->lock);
        __add_to_discard_list(discard_ctl, block_group);
        spin_unlock(&discard_ctl->lock);
@@ -169,7 +172,10 @@ again:
        if (block_group && now > block_group->discard_eligible_time) {
                if (block_group->discard_index == BTRFS_DISCARD_INDEX_UNUSED &&
                    block_group->used != 0) {
-                       __add_to_discard_list(discard_ctl, block_group);
+                       if (btrfs_is_block_group_data_only(block_group))
+                               __add_to_discard_list(discard_ctl, block_group);
+                       else
+                               list_del_init(&block_group->discard_list);
                        goto again;
                }
                if (block_group->discard_state == BTRFS_DISCARD_RESET_CURSOR) {
@@ -507,7 +513,9 @@ void btrfs_discard_update_discardable(struct btrfs_block_group *block_group,
        s32 extents_delta;
        s64 bytes_delta;
 
-       if (!block_group || !btrfs_test_opt(block_group->fs_info, DISCARD_ASYNC))
+       if (!block_group ||
+           !btrfs_test_opt(block_group->fs_info, DISCARD_ASYNC) ||
+           !btrfs_is_block_group_data_only(block_group))
                return;
 
        discard_ctl = &block_group->fs_info->discard_ctl;