7 files changed, 46 insertions, 42 deletions

diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index 696f47103cfc..233c5663f233 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -1175,7 +1175,7 @@ struct btrfs_trans_handle *btrfs_start_trans_remove_block_group(
 	free_extent_map(em);
 
 	return btrfs_start_transaction_fallback_global_rsv(fs_info->extent_root,
-							   num_items, 1);
+							   num_items);
 }
 
 /*
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 01b03e8a671f..c322568231a4 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2512,6 +2512,7 @@ enum btrfs_reserve_flush_enum {
 	BTRFS_RESERVE_FLUSH_LIMIT,
 	BTRFS_RESERVE_FLUSH_EVICT,
 	BTRFS_RESERVE_FLUSH_ALL,
+	BTRFS_RESERVE_FLUSH_ALL_STEAL,
 };
 
 enum btrfs_flush_state {
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 320d1062068d..259239b33370 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3618,7 +3618,7 @@ static struct btrfs_trans_handle *__unlink_start_trans(struct inode *dir)
 	 * 1 for the inode ref
 	 * 1 for the inode
 	 */
-	return btrfs_start_transaction_fallback_global_rsv(root, 5, 5);
+	return btrfs_start_transaction_fallback_global_rsv(root, 5);
 }
 
 static int btrfs_unlink(struct inode *dir, struct dentry *dentry)
diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
index ff17a4420358..f5ec50e6c48e 100644
--- a/fs/btrfs/space-info.c
+++ b/fs/btrfs/space-info.c
@@ -856,6 +856,34 @@ static inline int need_do_async_reclaim(struct btrfs_fs_info *fs_info,
 		!test_bit(BTRFS_FS_STATE_REMOUNTING, &fs_info->fs_state));
 }
 
+static bool steal_from_global_rsv(struct btrfs_fs_info *fs_info,
+				  struct btrfs_space_info *space_info,
+				  struct reserve_ticket *ticket)
+{
+	struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
+	u64 min_bytes;
+
+	if (global_rsv->space_info != space_info)
+		return false;
+
+	spin_lock(&global_rsv->lock);
+	min_bytes = div_factor(global_rsv->size, 5);
+	if (global_rsv->reserved < min_bytes + ticket->bytes) {
+		spin_unlock(&global_rsv->lock);
+		return false;
+	}
+	global_rsv->reserved -= ticket->bytes;
+	ticket->bytes = 0;
+	list_del_init(&ticket->list);
+	wake_up(&ticket->wait);
+	space_info->tickets_id++;
+	if (global_rsv->reserved < global_rsv->size)
+		global_rsv->full = 0;
+	spin_unlock(&global_rsv->lock);
+
+	return true;
+}
+
 /*
  * maybe_fail_all_tickets - we've exhausted our flushing, start failing tickets
  * @fs_info - fs_info for this fs
@@ -888,6 +916,10 @@ static bool maybe_fail_all_tickets(struct btrfs_fs_info *fs_info,
 		ticket = list_first_entry(&space_info->tickets,
 					  struct reserve_ticket, list);
 
+		if (ticket->steal &&
+		    steal_from_global_rsv(fs_info, space_info, ticket))
+			return true;
+
 		/*
 		 * may_commit_transaction will avoid committing the transaction
 		 * if it doesn't feel like the space reclaimed by the commit
@@ -1104,6 +1136,7 @@ static int handle_reserve_ticket(struct btrfs_fs_info *fs_info,
 
 	switch (flush) {
 	case BTRFS_RESERVE_FLUSH_ALL:
+	case BTRFS_RESERVE_FLUSH_ALL_STEAL:
 		wait_reserve_ticket(fs_info, space_info, ticket);
 		break;
 	case BTRFS_RESERVE_FLUSH_LIMIT:
@@ -1203,7 +1236,9 @@ static int __reserve_metadata_bytes(struct btrfs_fs_info *fs_info,
 		ticket.error = 0;
 		space_info->reclaim_size += ticket.bytes;
 		init_waitqueue_head(&ticket.wait);
-		if (flush == BTRFS_RESERVE_FLUSH_ALL) {
+		ticket.steal = (flush == BTRFS_RESERVE_FLUSH_ALL_STEAL);
+		if (flush == BTRFS_RESERVE_FLUSH_ALL ||
+		    flush == BTRFS_RESERVE_FLUSH_ALL_STEAL) {
 			list_add_tail(&ticket.list, &space_info->tickets);
 			if (!space_info->flush) {
 				space_info->flush = 1;
diff --git a/fs/btrfs/space-info.h b/fs/btrfs/space-info.h
index 0a5001ef1481..c3c64019950a 100644
--- a/fs/btrfs/space-info.h
+++ b/fs/btrfs/space-info.h
@@ -78,6 +78,7 @@ struct btrfs_space_info {
 struct reserve_ticket {
 	u64 bytes;
 	int error;
+	bool steal;
 	struct list_head list;
 	wait_queue_head_t wait;
 };
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 2d5498136e5e..b5da5d8342dc 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -563,7 +563,8 @@ start_transaction(struct btrfs_root *root, unsigned int num_items,
 		 * refill that amount for whatever is missing in the reserve.
 		 */
 		num_bytes = btrfs_calc_insert_metadata_size(fs_info, num_items);
-		if (delayed_refs_rsv->full == 0) {
+		if (flush == BTRFS_RESERVE_FLUSH_ALL &&
+		    delayed_refs_rsv->full == 0) {
 			delayed_refs_bytes = num_bytes;
 			num_bytes <<= 1;
 		}
@@ -699,43 +700,10 @@ struct btrfs_trans_handle *btrfs_start_transaction(struct btrfs_root *root,
 
 struct btrfs_trans_handle *btrfs_start_transaction_fallback_global_rsv(
 					struct btrfs_root *root,
-					unsigned int num_items,
-					int min_factor)
+					unsigned int num_items)
 {
-	struct btrfs_fs_info *fs_info = root->fs_info;
-	struct btrfs_trans_handle *trans;
-	u64 num_bytes;
-	int ret;
-
-	/*
-	 * We have two callers: unlink and block group removal.  The
-	 * former should succeed even if we will temporarily exceed
-	 * quota and the latter operates on the extent root so
-	 * qgroup enforcement is ignored anyway.
-	 */
-	trans = start_transaction(root, num_items, TRANS_START,
-				  BTRFS_RESERVE_FLUSH_ALL, false);
-	if (!IS_ERR(trans) || PTR_ERR(trans) != -ENOSPC)
-		return trans;
-
-	trans = btrfs_start_transaction(root, 0);
-	if (IS_ERR(trans))
-		return trans;
-
-	num_bytes = btrfs_calc_insert_metadata_size(fs_info, num_items);
-	ret = btrfs_cond_migrate_bytes(fs_info, &fs_info->trans_block_rsv,
-				       num_bytes, min_factor);
-	if (ret) {
-		btrfs_end_transaction(trans);
-		return ERR_PTR(ret);
-	}
-
-	trans->block_rsv = &fs_info->trans_block_rsv;
-	trans->bytes_reserved = num_bytes;
-	trace_btrfs_space_reservation(fs_info, "transaction",
-				      trans->transid, num_bytes, 1);
-
-	return trans;
+	return start_transaction(root, num_items, TRANS_START,
+				 BTRFS_RESERVE_FLUSH_ALL_STEAL, false);
 }
 
 struct btrfs_trans_handle *btrfs_join_transaction(struct btrfs_root *root)
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index 31ae8d273065..bf102e64bfb2 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -193,8 +193,7 @@ struct btrfs_trans_handle *btrfs_start_transaction(struct btrfs_root *root,
 						   unsigned int num_items);
 struct btrfs_trans_handle *btrfs_start_transaction_fallback_global_rsv(
 					struct btrfs_root *root,
-					unsigned int num_items,
-					int min_factor);
+					unsigned int num_items);
 struct btrfs_trans_handle *btrfs_join_transaction(struct btrfs_root *root);
 struct btrfs_trans_handle *btrfs_join_transaction_spacecache(struct btrfs_root *root);
 struct btrfs_trans_handle *btrfs_join_transaction_nostart(struct btrfs_root *root);