btrfs: take into account global rsv in need_preemptive_reclaim

Global rsv can't be used for normal allocations, and for very full file
systems we can decide to try and async flush constantly even though
there's really not a lot of space to reclaim.  Deal with this by
including the global block rsv size in the "total used" calculation.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
index 33edab17af0d3066b3373fc93809e641f44d67ea..e341f995a7dd49bbd0f089c99f779d4d236fd167 100644 (file)
--- a/fs/btrfs/space-info.c
+++ b/fs/btrfs/space-info.c
@@ -792,12 +792,14 @@ btrfs_calc_reclaim_metadata_size(struct btrfs_fs_info *fs_info,
 static bool need_preemptive_reclaim(struct btrfs_fs_info *fs_info,
                                    struct btrfs_space_info *space_info)
 {
+       u64 global_rsv_size = fs_info->global_block_rsv.reserved;
        u64 ordered, delalloc;
        u64 thresh = div_factor_fine(space_info->total_bytes, 98);
        u64 used;
 
        /* If we're just plain full then async reclaim just slows us down. */
-       if ((space_info->bytes_used + space_info->bytes_reserved) >= thresh)
+       if ((space_info->bytes_used + space_info->bytes_reserved +
+            global_rsv_size) >= thresh)
                return false;
 
        /*