Btrfs: fill relocation block rsv after allocation

Since we set the reloc control before we've reserved our space for relocation we
could race with a root being dirtied and not actually have space to do our init
reloc root.  So once we've allocated it and set it up go ahead and make our
reservation before setting the relocate control, that way anybody who tries to
do the reloc root init has space to use.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 0bf3bc87950373c46325668fefb40bff0b06a0be..23e16de52e23b83046a98d8b96f1d99599b1923f 100644 (file)
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -3871,6 +3871,7 @@ static noinline_for_stack
 int prepare_to_relocate(struct reloc_control *rc)
 {
        struct btrfs_trans_handle *trans;
+       int ret;
 
        rc->block_rsv = btrfs_alloc_block_rsv(rc->extent_root,
                                              BTRFS_BLOCK_RSV_TEMP);
@@ -3885,6 +3886,11 @@ int prepare_to_relocate(struct reloc_control *rc)
        rc->reserved_bytes = 0;
        rc->block_rsv->size = rc->extent_root->nodesize *
                              RELOCATION_RESERVED_NODES;
+       ret = btrfs_block_rsv_refill(rc->extent_root,
+                                    rc->block_rsv, rc->block_rsv->size,
+                                    BTRFS_RESERVE_FLUSH_ALL);
+       if (ret)
+               return ret;
 
        rc->create_reloc_tree = 1;
        set_reloc_control(rc);