For FLUSH_LIMIT flushers (think evict, truncate) we can deadlock when
running delalloc because we may be holding a tree lock. We can also
deadlock with delayed refs rsv's that are running via the committing
mechanism. The only safe operations for FLUSH_LIMIT is to run the
delayed operations and to allocate chunks, everything else has the
potential to deadlock. Future proof this by explicitly specifying the
states that FLUSH_LIMIT is allowed to use. This will keep us from
introducing bugs later on when adding new flush states.
Signed-off-by: Josef Bacik <jo...@toxicpanda.com>
---
fs/btrfs/extent-tree.c | 21 ++++++++++-----------
1 file changed, 10 insertions(+), 11 deletions(-)
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 0e1a499035ac..ab9d915d9289 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -5123,12 +5123,18 @@ void btrfs_init_async_reclaim_work(struct work_struct
*work)
INIT_WORK(work, btrfs_async_reclaim_metadata_space);
}
+static const enum btrfs_flush_state priority_flush_states[] = {
+ FLUSH_DELAYED_ITEMS_NR,
+ FLUSH_DELAYED_ITEMS,
+ ALLOC_CHUNK,
+};
+
static void priority_reclaim_metadata_space(struct btrfs_fs_info *fs_info,
struct btrfs_space_info *space_info,
struct reserve_ticket *ticket)
{
u64 to_reclaim;
- int flush_state = FLUSH_DELAYED_ITEMS_NR;
+ int flush_state = 0;
spin_lock(&space_info->lock);
to_reclaim = btrfs_calc_reclaim_metadata_size(fs_info, space_info,
@@ -5140,7 +5146,8 @@ static void priority_reclaim_metadata_space(struct
btrfs_fs_info *fs_info,
spin_unlock(&space_info->lock);
do {
- flush_space(fs_info, space_info, to_reclaim, flush_state);
+ flush_space(fs_info, space_info, to_reclaim,
+ priority_flush_states[flush_state]);
flush_state++;
spin_lock(&space_info->lock);
if (ticket->bytes == 0) {
@@ -5148,15 +5155,7 @@ static void priority_reclaim_metadata_space(struct
btrfs_fs_info *fs_info,
return;
}
spin_unlock(&space_info->lock);
-
- /*
- * Priority flushers can't wait on delalloc without
- * deadlocking.
- */
- if (flush_state == FLUSH_DELALLOC ||
- flush_state == FLUSH_DELALLOC_WAIT)
- flush_state = ALLOC_CHUNK;
- } while (flush_state < COMMIT_TRANS);
+ } while (flush_state < ARRAY_SIZE(priority_flush_states));
}
static int wait_reserve_ticket(struct btrfs_fs_info *fs_info,
--
2.14.3
