From: Josef Bacik <josef@toxicpanda.com>
Date: Tue, 21 Jul 2020 10:22:26 -0400
Subject: btrfs: use ticketing for data space reservations
Git-commit: 1004f6860f8c64f8d959051d6299981c09046cbe
Patch-mainline: v5.10-rc1
References: bsc#1135481

Now that we have all the infrastructure in place, use the ticketing
infrastructure to make data allocations.  This still maintains the exact
same flushing behavior, but now we're using tickets to get our
reservations satisfied.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Tested-by: Nikolay Borisov <nborisov@suse.com>
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 |  129 +++++++++++++++++++++++++-------------------------
 1 file changed, 65 insertions(+), 64 deletions(-)

--- a/fs/btrfs/space-info.c
+++ b/fs/btrfs/space-info.c
@@ -945,6 +945,53 @@ static void priority_reclaim_metadata_sp
 	} while (flush_state < states_nr);
 }
 
+static void priority_reclaim_data_space(struct btrfs_fs_info *fs_info,
+					struct btrfs_space_info *space_info,
+					struct reserve_ticket *ticket,
+					const enum btrfs_flush_state *states,
+					int states_nr)
+{
+	int flush_state = 0;
+	int commit_cycles = 2;
+
+	while (!space_info->full) {
+		flush_space(fs_info, space_info, U64_MAX, ALLOC_CHUNK_FORCE);
+		spin_lock(&space_info->lock);
+		if (ticket->bytes == 0) {
+			spin_unlock(&space_info->lock);
+			return;
+		}
+		spin_unlock(&space_info->lock);
+	}
+again:
+	while (flush_state < states_nr) {
+		u64 flush_bytes = U64_MAX;
+
+		if (!commit_cycles) {
+			if (states[flush_state] == FLUSH_DELALLOC_WAIT) {
+				flush_state++;
+				continue;
+			}
+			if (states[flush_state] == COMMIT_TRANS)
+				flush_bytes = ticket->bytes;
+		}
+
+		flush_space(fs_info, space_info, flush_bytes, states[flush_state]);
+		spin_lock(&space_info->lock);
+		if (ticket->bytes == 0) {
+			spin_unlock(&space_info->lock);
+			return;
+		}
+		spin_unlock(&space_info->lock);
+		flush_state++;
+	}
+	if (commit_cycles) {
+		commit_cycles--;
+		flush_state = 0;
+		goto again;
+	}
+}
+
 static void wait_reserve_ticket(struct btrfs_fs_info *fs_info,
 				struct btrfs_space_info *space_info,
 				struct reserve_ticket *ticket)
@@ -1011,6 +1058,13 @@ static int handle_reserve_ticket(struct
 						evict_flush_states,
 						ARRAY_SIZE(evict_flush_states));
 		break;
+	case BTRFS_RESERVE_FLUSH_DATA:
+		priority_reclaim_data_space(fs_info, space_info, ticket,
+				data_flush_states, ARRAY_SIZE(data_flush_states));
+		break;
+	case BTRFS_RESERVE_FLUSH_FREE_SPACE_INODE:
+		priority_reclaim_data_space(fs_info, space_info, ticket, NULL, 0);
+		break;
 	default:
 		ASSERT(0);
 		break;
@@ -1218,84 +1272,31 @@ int btrfs_reserve_data_bytes(struct btrf
 			     enum btrfs_reserve_flush_enum flush)
 {
 	struct btrfs_space_info *data_sinfo = fs_info->data_sinfo;
-	const enum btrfs_flush_state *states = NULL;
 	u64 used;
-	int states_nr = 0;
-	int commit_cycles = 2;
 	int ret = -ENOSPC;
 
 	ASSERT(!current->journal_info || flush != BTRFS_RESERVE_FLUSH_DATA);
 
-	if (flush == BTRFS_RESERVE_FLUSH_DATA) {
-		states = data_flush_states;
-		states_nr = ARRAY_SIZE(data_flush_states);
-	}
-
 	spin_lock(&data_sinfo->lock);
-again:
 	used = btrfs_space_info_used(data_sinfo, true);
 
 	if (used + bytes > data_sinfo->total_bytes) {
-		u64 prev_total_bytes = data_sinfo->total_bytes;
-		int flush_state = 0;
+		struct reserve_ticket ticket;
 
-		spin_unlock(&data_sinfo->lock);
+		init_waitqueue_head(&ticket.wait);
+		ticket.bytes = bytes;
+		ticket.error = 0;
+		list_add_tail(&ticket.list, &data_sinfo->priority_tickets);
+		data_sinfo->reclaim_size += bytes;
 
-		/*
-		 * Everybody can force chunk allocation, so try this first to
-		 * see if we can just bail here and make our reservation.
-		 */
-		flush_space(fs_info, data_sinfo, bytes, ALLOC_CHUNK_FORCE);
-		spin_lock(&data_sinfo->lock);
-		if (prev_total_bytes < data_sinfo->total_bytes)
-			goto again;
 		spin_unlock(&data_sinfo->lock);
 
-		/*
-		 * Cycle through the rest of the flushing options for our flush
-		 * type, then try again.
-		 */
-		while (flush_state < states_nr) {
-			u64 flush_bytes = U64_MAX;
-
-			/*
-			 * Previously we unconditionally committed the
-			 * transaction twice before finally checking against
-			 * pinned space before committing the final time.  We
-			 * also skipped flushing delalloc the final pass
-			 * through.
-			 */
-			if (!commit_cycles) {
-				if (states[flush_state] == FLUSH_DELALLOC_WAIT) {
-					flush_state++;
-					continue;
-				}
-				if (states[flush_state] == COMMIT_TRANS)
-					flush_bytes = bytes;
-			}
-
-			if (states[flush_state] == COMMIT_TRANS &&
-			    atomic_read(&fs_info->open_ioctl_trans)) {
-				flush_state++;
-				continue;
-			}
-
-			flush_space(fs_info, data_sinfo, flush_bytes,
-				    states[flush_state]);
-			flush_state++;
-		}
-
-		if (!commit_cycles)
-			goto out;
-
-		commit_cycles--;
-		spin_lock(&data_sinfo->lock);
-		goto again;
+		ret = handle_reserve_ticket(fs_info, data_sinfo, &ticket, flush);
+	} else {
+		btrfs_space_info_update_bytes_may_use(fs_info, data_sinfo, bytes);
+		ret = 0;
+		spin_unlock(&data_sinfo->lock);
 	}
-	btrfs_space_info_update_bytes_may_use(fs_info, data_sinfo, bytes);
-	ret = 0;
-	spin_unlock(&data_sinfo->lock);
-out:
 	if (ret)
 		trace_btrfs_space_reservation(fs_info,
 					      "space_info:enospc",