btrfs: make BTRFS_RESERVE_FLUSH_EVICT use the global rsv stealing code

I forgot to convert this over when I introduced the global reserve
stealing code to the space flushing code.  Evict was simply trying to
make its reservation and then if it failed it would steal from the
global rsv, which is racey because it's outside of the normal ticketing
code.

Fix this by setting ticket->steal if we are BTRFS_RESERVE_FLUSH_EVICT,
and then make the priority flushing path do the steal for us.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 13 insertions, 3 deletions

diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
index 20f6c0858410..a546cd411de4 100644
--- a/fs/btrfs/space-info.c
+++ b/fs/btrfs/space-info.c
@@ -1289,13 +1289,17 @@ static void priority_reclaim_metadata_space(struct btrfs_fs_info *fs_info,
 		}
 	}
 
+	/* Attempt to steal from the global rsv if we can. */
+	if (!steal_from_global_rsv(fs_info, space_info, ticket)) {
+		ticket->error = -ENOSPC;
+		remove_ticket(space_info, ticket);
+	}
+
 	/*
 	 * We must run try_granting_tickets here because we could be a large
 	 * ticket in front of a smaller ticket that can now be satisfied with
 	 * the available space.
 	 */
-	ticket->error = -ENOSPC;
-	remove_ticket(space_info, ticket);
 	btrfs_try_granting_tickets(fs_info, space_info);
 	spin_unlock(&space_info->lock);
 }
@@ -1449,6 +1453,12 @@ static inline void maybe_clamp_preempt(struct btrfs_fs_info *fs_info,
 		space_info->clamp = min(space_info->clamp + 1, 8);
 }
 
+static inline bool can_steal(enum btrfs_reserve_flush_enum flush)
+{
+	return (flush == BTRFS_RESERVE_FLUSH_ALL_STEAL ||
+		flush == BTRFS_RESERVE_FLUSH_EVICT);
+}
+
 /**
  * Try to reserve bytes from the block_rsv's space
  *
@@ -1522,7 +1532,7 @@ static int __reserve_bytes(struct btrfs_fs_info *fs_info,
 		ticket.error = 0;
 		space_info->reclaim_size += ticket.bytes;
 		init_waitqueue_head(&ticket.wait);
-		ticket.steal = (flush == BTRFS_RESERVE_FLUSH_ALL_STEAL);
+		ticket.steal = can_steal(flush);
 		if (trace_btrfs_reserve_ticket_enabled())
 			start_ns = ktime_get_ns();