[PATCH 7/9] btrfs: fix may_commit_transaction to deal with no partial filling

[Josef Bacik]

Now that we aren't partially filling tickets we may have some slack
space left in the space_info.  We need to account for this in
may_commit_transaction, otherwise we may choose to not commit the
transaction despite it actually having enough space to satisfy our
ticket.

Calculate the free space we have in the space_info, if any, and subtract
this from the ticket we have and use that amount to determine if we will
need to commit to reclaim enough space.

Signed-off-by: Josef Bacik <jo...@toxicpanda.com>
---
 fs/btrfs/space-info.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
index dd4adfa75a71..cec6db0c41cc 100644
--- a/fs/btrfs/space-info.c
+++ b/fs/btrfs/space-info.c
@@ -473,12 +473,19 @@ static int may_commit_transaction(struct btrfs_fs_info 
*fs_info,
        struct btrfs_trans_handle *trans;
        u64 bytes_needed;
        u64 reclaim_bytes = 0;
+       u64 cur_free_bytes = 0;
 
        trans = (struct btrfs_trans_handle *)current->journal_info;
        if (trans)
                return -EAGAIN;
 
        spin_lock(&space_info->lock);
+       cur_free_bytes = btrfs_space_info_used(space_info, true);
+       if (cur_free_bytes < space_info->total_bytes)
+               cur_free_bytes = space_info->total_bytes - cur_free_bytes;
+       else
+               cur_free_bytes = 0;
+
        if (!list_empty(&space_info->priority_tickets))
                ticket = list_first_entry(&space_info->priority_tickets,
                                          struct reserve_ticket, list);
@@ -486,6 +493,11 @@ static int may_commit_transaction(struct btrfs_fs_info 
*fs_info,
                ticket = list_first_entry(&space_info->tickets,
                                          struct reserve_ticket, list);
        bytes_needed = (ticket) ? ticket->bytes : 0;
+
+       if (bytes_needed > cur_free_bytes)
+               bytes_needed -= cur_free_bytes;
+       else
+               bytes_needed = 0;
        spin_unlock(&space_info->lock);
 
        if (!bytes_needed)
-- 
2.21.0