btrfs: do not allow reservations if we have pending tickets (ef1317a1) · Commits · 戴 / test

If we already have tickets on the list we don't want to steal their reservations. This is a preparation patch for upcoming changes, technically this shouldn't happen today because of the way we add bytes to tickets before adding them to the space_info in most cases. This does not change the FIFO nature of reserve tickets, it simply allows us to enforce it in a different way. Previously it was enforced because any new space would be added to the first ticket on the list, which would result in new reservations getting a reserve ticket. This replaces that mechanism by simply checking to see if we have outstanding reserve tickets and skipping straight to adding a ticket for our reservation. Reviewed-by:

Nikolay Borisov <nborisov@suse.com> Signed-off-by:

Josef Bacik <josef@toxicpanda.com> Signed-off-by:

David Sterba <dsterba@suse.com>

fs/btrfs/space-info.c

+7 −3

Original line number	Diff line number	Diff line
		@@ -993,6 +993,7 @@ static int __reserve_metadata_bytes(struct btrfs_fs_info *fs_info,
		struct reserve_ticket ticket;
		u64 used;
		int ret = 0;
		bool pending_tickets;

		ASSERT(orig_bytes);
		ASSERT(!current->journal_info \|\| flush != BTRFS_RESERVE_FLUSH_ALL);
		@@ -1000,14 +1001,17 @@ static int __reserve_metadata_bytes(struct btrfs_fs_info *fs_info,
		spin_lock(&space_info->lock);
		ret = -ENOSPC;
		used = btrfs_space_info_used(space_info, true);
		pending_tickets = !list_empty(&space_info->tickets) \|\|
		!list_empty(&space_info->priority_tickets);

		/*
		* Carry on if we have enough space (short-circuit) OR call
		* can_overcommit() to ensure we can overcommit to continue.
		*/
		if ((used + orig_bytes <= space_info->total_bytes) \|\|
		if (!pending_tickets &&
		((used + orig_bytes <= space_info->total_bytes) \|\|
		can_overcommit(fs_info, space_info, orig_bytes, flush,
		system_chunk)) {
		system_chunk))) {
		btrfs_space_info_update_bytes_may_use(fs_info, space_info,
		orig_bytes);
		trace_btrfs_space_reservation(fs_info, "space_info",

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