From: Josef Bacik <josef@toxicpanda.com>
Date: Wed, 28 Apr 2021 13:38:44 -0400
Subject: btrfs: take into account global rsv in need_preemptive_reclaim
Git-commit: 610a6ef44ea83ef1c1e10b8270bbd157fbde3181
Patch-mainline: v5.14-rc1
References: bsc#1202528

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>
Acked-by: Nikolay Borisov <nborisov@suse.com>
---
 fs/btrfs/space-info.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
index 33edab17af0d..e341f995a7dd 100644
--- 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;
 
 	/*