From: Josef Bacik <josef@toxicpanda.com>
Date: Thu, 22 Aug 2019 15:10:54 -0400
Subject: btrfs: do not allow reservations if we have pending tickets
Git-commit: ef1317a1b9a347cdc3967a2048046e8fb4db94ba
Patch-mainline: v5.4-rc1
References: bsc#1165949
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>
Acked-by: Nikolay Borisov <nborisov@suse.com>
---
fs/btrfs/space-info.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)
--- a/fs/btrfs/space-info.c
+++ b/fs/btrfs/space-info.c
@@ -1002,6 +1002,7 @@ static int __reserve_metadata_bytes(stru
struct reserve_ticket ticket;
u64 used;
int ret = 0;
+ bool pending_tickets;
ASSERT(orig_bytes);
ASSERT(!current->journal_info || flush != BTRFS_RESERVE_FLUSH_ALL);
@@ -1009,19 +1010,17 @@ static int __reserve_metadata_bytes(stru
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);
/*
* If we have enough space then hooray, make our reservation and carry
* on. If not see if we can overcommit, and if we can, hooray carry on.
* If not things get more complicated.
*/
- if (used + orig_bytes <= space_info->total_bytes) {
- btrfs_space_info_update_bytes_may_use(fs_info, space_info,
- orig_bytes);
- trace_btrfs_space_reservation(fs_info, "space_info",
- space_info->flags, orig_bytes, 1);
- ret = 0;
- } else if (can_overcommit(fs_info, space_info, orig_bytes, flush)) {
+ if (!pending_tickets &&
+ ((used + orig_bytes <= space_info->total_bytes) ||
+ can_overcommit(fs_info, space_info, orig_bytes, flush))) {
btrfs_space_info_update_bytes_may_use(fs_info, space_info,
orig_bytes);
trace_btrfs_space_reservation(fs_info, "space_info",