On 4/15/21 9:58 AM, Johannes Thumshirn wrote:
When a file gets deleted on a zoned file system, the space freed is not
returned back into the block group's free space, but is migrated to
zone_unusable.
As this zone_unusable space is behind the current write pointer it is not
possible to use it for new allocations. In the current implementation a
zone is reset once all of the block group's space is accounted as zone
unusable.
This behaviour can lead to premature ENOSPC errors on a busy file system.
Instead of only reclaiming the zone once it is completely unusable,
kick off a reclaim job once the amount of unusable bytes exceeds a user
configurable threshold between 51% and 100%. It can be set per mounted
filesystem via the sysfs tunable bg_reclaim_threshold which is set to 75%
per default.
Similar to reclaiming unused block groups, these dirty block groups are
added to a to_reclaim list and then on a transaction commit, the reclaim
process is triggered but after we deleted unused block groups, which will
free space for the relocation process.
Signed-off-by: Johannes Thumshirn <johannes.thumsh...@wdc.com>
---
fs/btrfs/block-group.c | 96 ++++++++++++++++++++++++++++++++++++
fs/btrfs/block-group.h | 3 ++
fs/btrfs/ctree.h | 6 +++
fs/btrfs/disk-io.c | 13 +++++
fs/btrfs/free-space-cache.c | 9 +++-
fs/btrfs/sysfs.c | 35 +++++++++++++
fs/btrfs/volumes.c | 2 +-
fs/btrfs/volumes.h | 1 +
include/trace/events/btrfs.h | 12 +++++
9 files changed, 175 insertions(+), 2 deletions(-)
diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index bbb5a6e170c7..3f06ea42c013 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -1485,6 +1485,92 @@ void btrfs_mark_bg_unused(struct btrfs_block_group *bg)
spin_unlock(&fs_info->unused_bgs_lock);
}
+void btrfs_reclaim_bgs_work(struct work_struct *work)
+{
+ struct btrfs_fs_info *fs_info =
+ container_of(work, struct btrfs_fs_info, reclaim_bgs_work);
+ struct btrfs_block_group *bg;
+ struct btrfs_space_info *space_info;
+ int ret = 0;
+
+ if (!test_bit(BTRFS_FS_OPEN, &fs_info->flags))
+ return;
+
+ if (!btrfs_exclop_start(fs_info, BTRFS_EXCLOP_BALANCE))
+ return;
+
+ mutex_lock(&fs_info->reclaim_bgs_lock);
+ spin_lock(&fs_info->unused_bgs_lock);
+ while (!list_empty(&fs_info->reclaim_bgs)) {
+ bg = list_first_entry(&fs_info->reclaim_bgs,
+ struct btrfs_block_group,
+ bg_list);
+ list_del_init(&bg->bg_list);
+
+ space_info = bg->space_info;
+ spin_unlock(&fs_info->unused_bgs_lock);
+
+ /* Don't want to race with allocators so take the groups_sem */
+ down_write(&space_info->groups_sem);
+
+ spin_lock(&bg->lock);
+ if (bg->reserved || bg->pinned || bg->ro) {
+ /*
+ * We want to bail if we made new allocations or have
+ * outstanding allocations in this block group. We do
+ * the ro check in case balance is currently acting on
+ * this block group.
+ */
+ spin_unlock(&bg->lock);
+ up_write(&space_info->groups_sem);
+ goto next;
+ }
+ spin_unlock(&bg->lock);
+
Here I think we want a
if (btrfs_fs_closing())
goto next;
so we don't block out a umount for all eternity. Thanks,
Josef
