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); + + ret = inc_block_group_ro(bg, 0); + up_write(&space_info->groups_sem); + if (ret < 0) { + ret = 0; + goto next; + } + + btrfs_info(fs_info, "reclaiming chunk %llu", bg->start); + trace_btrfs_reclaim_block_group(bg); + ret = btrfs_relocate_chunk(fs_info, bg->start); + if (ret) + btrfs_err(fs_info, "error relocating chunk %llu", + bg->start); + +next: + btrfs_put_block_group(bg); + spin_lock(&fs_info->unused_bgs_lock); + } + spin_unlock(&fs_info->unused_bgs_lock); + mutex_unlock(&fs_info->reclaim_bgs_lock); + btrfs_exclop_finish(fs_info); +} + +void btrfs_reclaim_bgs(struct btrfs_fs_info *fs_info) +{ + spin_lock(&fs_info->unused_bgs_lock); + if (!list_empty(&fs_info->reclaim_bgs)) + queue_work(system_unbound_wq, &fs_info->reclaim_bgs_work); + spin_unlock(&fs_info->unused_bgs_lock); +} + +void btrfs_mark_bg_to_reclaim(struct btrfs_block_group *bg) +{ + struct btrfs_fs_info *fs_info = bg->fs_info; + + spin_lock(&fs_info->unused_bgs_lock); + if (list_empty(&bg->bg_list)) { + btrfs_get_block_group(bg); + trace_btrfs_add_reclaim_block_group(bg); + list_add_tail(&bg->bg_list, &fs_info->reclaim_bgs); + } + spin_unlock(&fs_info->unused_bgs_lock); +} + static int read_bg_from_eb(struct btrfs_fs_info *fs_info, struct btrfs_key *key, struct btrfs_path *path) { @@ -3446,6 +3532,16 @@ int btrfs_free_block_groups(struct btrfs_fs_info *info) } spin_unlock(&info->unused_bgs_lock); + spin_lock(&info->unused_bgs_lock); + while (!list_empty(&info->reclaim_bgs)) { + block_group = list_first_entry(&info->reclaim_bgs, + struct btrfs_block_group, + bg_list); + list_del_init(&block_group->bg_list); + btrfs_put_block_group(block_group); + } + spin_unlock(&info->unused_bgs_lock); + spin_lock(&info->block_group_cache_lock); while ((n = rb_last(&info->block_group_cache_tree)) != NULL) { block_group = rb_entry(n, struct btrfs_block_group, diff --git a/fs/btrfs/block-group.h b/fs/btrfs/block-group.h index 3ecc3372a5ce..7b927425dc71 100644 --- a/fs/btrfs/block-group.h +++ b/fs/btrfs/block-group.h @@ -264,6 +264,9 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans, u64 group_start, struct extent_map *em); void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info); void btrfs_mark_bg_unused(struct btrfs_block_group *bg); +void btrfs_reclaim_bgs_work(struct work_struct *work); +void btrfs_reclaim_bgs(struct btrfs_fs_info *fs_info); +void btrfs_mark_bg_to_reclaim(struct btrfs_block_group *bg); int btrfs_read_block_groups(struct btrfs_fs_info *info); int btrfs_make_block_group(struct btrfs_trans_handle *trans, u64 bytes_used, u64 type, u64 chunk_offset, u64 size); diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index c80302564e6b..88531c1fbcdf 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -954,10 +954,14 @@ struct btrfs_fs_info { struct work_struct async_data_reclaim_work; struct work_struct preempt_reclaim_work; + /* Used to reclaim data space in the background */ + struct work_struct reclaim_bgs_work; + spinlock_t unused_bgs_lock; struct list_head unused_bgs; struct mutex unused_bg_unpin_mutex; struct mutex reclaim_bgs_lock; + struct list_head reclaim_bgs; /* Cached block sizes */ u32 nodesize; @@ -998,6 +1002,8 @@ struct btrfs_fs_info { spinlock_t treelog_bg_lock; u64 treelog_bg; + int bg_reclaim_threshold; + #ifdef CONFIG_BTRFS_FS_REF_VERIFY spinlock_t ref_verify_lock; struct rb_root block_tree; diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index e52b89ad0a61..942d894ec175 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -1898,6 +1898,13 @@ static int cleaner_kthread(void *arg) * unused block groups. */ btrfs_delete_unused_bgs(fs_info); + + /* + * Reclaim block groups in the reclaim_bgs list after we deleted + * all unused block_groups. This possibly gives us some more free + * space. + */ + btrfs_reclaim_bgs(fs_info); sleep: clear_and_wake_up_bit(BTRFS_FS_CLEANER_RUNNING, &fs_info->flags); if (kthread_should_park()) @@ -2886,6 +2893,7 @@ void btrfs_init_fs_info(struct btrfs_fs_info *fs_info) INIT_LIST_HEAD(&fs_info->space_info); INIT_LIST_HEAD(&fs_info->tree_mod_seq_list); INIT_LIST_HEAD(&fs_info->unused_bgs); + INIT_LIST_HEAD(&fs_info->reclaim_bgs); #ifdef CONFIG_BTRFS_DEBUG INIT_LIST_HEAD(&fs_info->allocated_roots); INIT_LIST_HEAD(&fs_info->allocated_ebs); @@ -2974,6 +2982,9 @@ void btrfs_init_fs_info(struct btrfs_fs_info *fs_info) fs_info->swapfile_pins = RB_ROOT; fs_info->send_in_progress = 0; + + fs_info->bg_reclaim_threshold = 75; + INIT_WORK(&fs_info->reclaim_bgs_work, btrfs_reclaim_bgs_work); } static int init_mount_fs_info(struct btrfs_fs_info *fs_info, struct super_block *sb) @@ -4332,6 +4343,8 @@ void __cold close_ctree(struct btrfs_fs_info *fs_info) cancel_work_sync(&fs_info->async_data_reclaim_work); cancel_work_sync(&fs_info->preempt_reclaim_work); + cancel_work_sync(&fs_info->reclaim_bgs_work); + /* Cancel or finish ongoing discard work */ btrfs_discard_cleanup(fs_info); diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c index 9988decd5717..e54466fc101f 100644 --- a/fs/btrfs/free-space-cache.c +++ b/fs/btrfs/free-space-cache.c @@ -11,6 +11,7 @@ #include <linux/ratelimit.h> #include <linux/error-injection.h> #include <linux/sched/mm.h> +#include "misc.h" #include "ctree.h" #include "free-space-cache.h" #include "transaction.h" @@ -2539,6 +2540,7 @@ int __btrfs_add_free_space(struct btrfs_fs_info *fs_info, static int __btrfs_add_free_space_zoned(struct btrfs_block_group *block_group, u64 bytenr, u64 size, bool used) { + struct btrfs_fs_info *fs_info = block_group->fs_info; struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl; u64 offset = bytenr - block_group->start; u64 to_free, to_unusable; @@ -2569,8 +2571,13 @@ static int __btrfs_add_free_space_zoned(struct btrfs_block_group *block_group, } /* All the region is now unusable. Mark it as unused and reclaim */ - if (block_group->zone_unusable == block_group->length) + if (block_group->zone_unusable == block_group->length) { btrfs_mark_bg_unused(block_group); + } else if (block_group->zone_unusable >= + div_factor_fine(block_group->length, + fs_info->bg_reclaim_threshold)) { + btrfs_mark_bg_to_reclaim(block_group); + } return 0; } diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c index a99d1f415a7f..436ac7b4b334 100644 --- a/fs/btrfs/sysfs.c +++ b/fs/btrfs/sysfs.c @@ -980,6 +980,40 @@ static ssize_t btrfs_read_policy_store(struct kobject *kobj, } BTRFS_ATTR_RW(, read_policy, btrfs_read_policy_show, btrfs_read_policy_store); +static ssize_t btrfs_bg_reclaim_threshold_show(struct kobject *kobj, + struct kobj_attribute *a, + char *buf) +{ + struct btrfs_fs_info *fs_info = to_fs_info(kobj); + ssize_t ret; + + ret = scnprintf(buf, PAGE_SIZE, "%d\n", fs_info->bg_reclaim_threshold); + + return ret; +} + +static ssize_t btrfs_bg_reclaim_threshold_store(struct kobject *kobj, + struct kobj_attribute *a, + const char *buf, size_t len) +{ + struct btrfs_fs_info *fs_info = to_fs_info(kobj); + int thresh; + int ret; + + ret = kstrtoint(buf, 10, &thresh); + if (ret) + return ret; + + if (thresh <= 50 || thresh > 100) + return -EINVAL; + + fs_info->bg_reclaim_threshold = thresh; + + return len; +} +BTRFS_ATTR_RW(, bg_reclaim_threshold, btrfs_bg_reclaim_threshold_show, + btrfs_bg_reclaim_threshold_store); + static const struct attribute *btrfs_attrs[] = { BTRFS_ATTR_PTR(, label), BTRFS_ATTR_PTR(, nodesize), @@ -991,6 +1025,7 @@ static const struct attribute *btrfs_attrs[] = { BTRFS_ATTR_PTR(, exclusive_operation), BTRFS_ATTR_PTR(, generation), BTRFS_ATTR_PTR(, read_policy), + BTRFS_ATTR_PTR(, bg_reclaim_threshold), NULL, }; diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index a2a7f5ab0a3e..527324154e3e 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -3098,7 +3098,7 @@ int btrfs_remove_chunk(struct btrfs_trans_handle *trans, u64 chunk_offset) return ret; } -static int btrfs_relocate_chunk(struct btrfs_fs_info *fs_info, u64 chunk_offset) +int btrfs_relocate_chunk(struct btrfs_fs_info *fs_info, u64 chunk_offset) { struct btrfs_root *root = fs_info->chunk_root; struct btrfs_trans_handle *trans; diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h index d4c3e0dd32b8..9c0d84e5ec06 100644 --- a/fs/btrfs/volumes.h +++ b/fs/btrfs/volumes.h @@ -484,6 +484,7 @@ void btrfs_describe_block_groups(u64 flags, char *buf, u32 size_buf); int btrfs_resume_balance_async(struct btrfs_fs_info *fs_info); int btrfs_recover_balance(struct btrfs_fs_info *fs_info); int btrfs_pause_balance(struct btrfs_fs_info *fs_info); +int btrfs_relocate_chunk(struct btrfs_fs_info *fs_info, u64 chunk_offset); int btrfs_cancel_balance(struct btrfs_fs_info *fs_info); int btrfs_create_uuid_tree(struct btrfs_fs_info *fs_info); int btrfs_uuid_scan_kthread(void *data); diff --git a/include/trace/events/btrfs.h b/include/trace/events/btrfs.h index 0551ea65374f..a41dd8a0c730 100644 --- a/include/trace/events/btrfs.h +++ b/include/trace/events/btrfs.h @@ -1903,6 +1903,18 @@ DEFINE_EVENT(btrfs__block_group, btrfs_add_unused_block_group, TP_ARGS(bg_cache) ); +DEFINE_EVENT(btrfs__block_group, btrfs_add_reclaim_block_group, + TP_PROTO(const struct btrfs_block_group *bg_cache), + + TP_ARGS(bg_cache) +); + +DEFINE_EVENT(btrfs__block_group, btrfs_reclaim_block_group, + TP_PROTO(const struct btrfs_block_group *bg_cache), + + TP_ARGS(bg_cache) +); + DEFINE_EVENT(btrfs__block_group, btrfs_skip_unused_block_group, TP_PROTO(const struct btrfs_block_group *bg_cache), -- 2.30.0