From: Johannes Thumshirn <jth@kernel.org>
To: linux-btrfs@vger.kernel.org
Cc: Damien Le Moal <dlemoal@kernel.org>,
Naohiro Aota <naohiro.aota@wdc.com>,
Johannes Thumshirn <johannes.thumshirn@wdc.com>
Subject: [PATCH v2 2/3] btrfs: zoned: get rid of treelog_bg_lock
Date: Tue, 24 Jun 2025 11:37:09 +0200 [thread overview]
Message-ID: <20250624093710.18685-3-jth@kernel.org> (raw)
In-Reply-To: <20250624093710.18685-1-jth@kernel.org>
From: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Lockstat analysis of benchmark workloads shows a very high contention on
treelog_bg_lock. But the lock only protects a single field in
'struct btrfs_fs_info', namely 'u64 treelog_bg'.
Use READ_ONCE()/WRITE_ONCE() to access 'btrfs_fs_info::treelog_bg'.
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
---
fs/btrfs/disk-io.c | 1 -
fs/btrfs/extent-tree.c | 49 ++++++++++--------------------------------
fs/btrfs/fs.h | 1 -
fs/btrfs/zoned.c | 2 +-
fs/btrfs/zoned.h | 6 ++----
5 files changed, 14 insertions(+), 45 deletions(-)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 24896322376d..a54218717cb4 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2789,7 +2789,6 @@ void btrfs_init_fs_info(struct btrfs_fs_info *fs_info)
spin_lock_init(&fs_info->defrag_inodes_lock);
spin_lock_init(&fs_info->super_lock);
spin_lock_init(&fs_info->unused_bgs_lock);
- spin_lock_init(&fs_info->treelog_bg_lock);
spin_lock_init(&fs_info->zone_active_bgs_lock);
rwlock_init(&fs_info->tree_mod_log_lock);
rwlock_init(&fs_info->global_root_lock);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 80ceca89a9ef..39d3984153a2 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3809,22 +3809,6 @@ static int do_allocation_clustered(struct btrfs_block_group *block_group,
return find_free_extent_unclustered(block_group, ffe_ctl);
}
-/*
- * Tree-log block group locking
- * ============================
- *
- * fs_info::treelog_bg_lock protects the fs_info::treelog_bg which
- * indicates the starting address of a block group, which is reserved only
- * for tree-log metadata.
- *
- * Lock nesting
- * ============
- *
- * space_info::lock
- * block_group::lock
- * fs_info::treelog_bg_lock
- */
-
/*
* Simple allocator for sequential-only block group. It only allows sequential
* allocation. No need to play with trees. This function also reserves the
@@ -3841,9 +3825,7 @@ static int do_allocation_zoned(struct btrfs_block_group *block_group,
u64 num_bytes = ffe_ctl->num_bytes;
u64 avail;
u64 bytenr = block_group->start;
- u64 log_bytenr;
int ret = 0;
- bool skip = false;
ASSERT(btrfs_is_zoned(block_group->fs_info));
@@ -3851,13 +3833,9 @@ static int do_allocation_zoned(struct btrfs_block_group *block_group,
* Do not allow non-tree-log blocks in the dedicated tree-log block
* group, and vice versa.
*/
- spin_lock(&fs_info->treelog_bg_lock);
- log_bytenr = fs_info->treelog_bg;
- if (log_bytenr && ((ffe_ctl->for_treelog && bytenr != log_bytenr) ||
- (!ffe_ctl->for_treelog && bytenr == log_bytenr)))
- skip = true;
- spin_unlock(&fs_info->treelog_bg_lock);
- if (skip)
+ if (READ_ONCE(fs_info->treelog_bg) &&
+ ((ffe_ctl->for_treelog && bytenr != READ_ONCE(fs_info->treelog_bg)) ||
+ (!ffe_ctl->for_treelog && bytenr == READ_ONCE(fs_info->treelog_bg))))
return 1;
/*
@@ -3892,14 +3870,13 @@ static int do_allocation_zoned(struct btrfs_block_group *block_group,
spin_lock(&space_info->lock);
spin_lock(&block_group->lock);
- spin_lock(&fs_info->treelog_bg_lock);
if (ret)
goto out;
ASSERT(!ffe_ctl->for_treelog ||
- block_group->start == fs_info->treelog_bg ||
- fs_info->treelog_bg == 0);
+ block_group->start == READ_ONCE(fs_info->treelog_bg) ||
+ READ_ONCE(fs_info->treelog_bg) == 0);
ASSERT(!ffe_ctl->for_data_reloc ||
block_group->start == READ_ONCE(fs_info->data_reloc_bg) ||
READ_ONCE(fs_info->data_reloc_bg) == 0);
@@ -3915,7 +3892,7 @@ static int do_allocation_zoned(struct btrfs_block_group *block_group,
* Do not allow currently using block group to be tree-log dedicated
* block group.
*/
- if (ffe_ctl->for_treelog && !fs_info->treelog_bg &&
+ if (ffe_ctl->for_treelog && READ_ONCE(fs_info->treelog_bg) == 0 &&
(block_group->used || block_group->reserved)) {
ret = 1;
goto out;
@@ -3946,8 +3923,8 @@ static int do_allocation_zoned(struct btrfs_block_group *block_group,
goto out;
}
- if (ffe_ctl->for_treelog && !fs_info->treelog_bg)
- fs_info->treelog_bg = block_group->start;
+ if (ffe_ctl->for_treelog && READ_ONCE(fs_info->treelog_bg) == 0)
+ WRITE_ONCE(fs_info->treelog_bg, block_group->start);
if (ffe_ctl->for_data_reloc) {
if (READ_ONCE(fs_info->data_reloc_bg) == 0)
@@ -3985,10 +3962,9 @@ static int do_allocation_zoned(struct btrfs_block_group *block_group,
out:
if (ret && ffe_ctl->for_treelog)
- fs_info->treelog_bg = 0;
+ WRITE_ONCE(fs_info->treelog_bg, 0);
if (ret && ffe_ctl->for_data_reloc)
WRITE_ONCE(fs_info->data_reloc_bg, 0);
- spin_unlock(&fs_info->treelog_bg_lock);
spin_unlock(&block_group->lock);
spin_unlock(&space_info->lock);
return ret;
@@ -4290,11 +4266,8 @@ static int prepare_allocation_clustered(struct btrfs_fs_info *fs_info,
static int prepare_allocation_zoned(struct btrfs_fs_info *fs_info,
struct find_free_extent_ctl *ffe_ctl)
{
- if (ffe_ctl->for_treelog) {
- spin_lock(&fs_info->treelog_bg_lock);
- if (fs_info->treelog_bg)
- ffe_ctl->hint_byte = fs_info->treelog_bg;
- spin_unlock(&fs_info->treelog_bg_lock);
+ if (ffe_ctl->for_treelog && READ_ONCE(fs_info->treelog_bg)) {
+ ffe_ctl->hint_byte = READ_ONCE(fs_info->treelog_bg);
} else if (ffe_ctl->for_data_reloc &&
READ_ONCE(fs_info->data_reloc_bg)) {
ffe_ctl->hint_byte = READ_ONCE(fs_info->data_reloc_bg);
diff --git a/fs/btrfs/fs.h b/fs/btrfs/fs.h
index 570f4b85096c..a388af40a251 100644
--- a/fs/btrfs/fs.h
+++ b/fs/btrfs/fs.h
@@ -846,7 +846,6 @@ struct btrfs_fs_info {
u64 max_zone_append_size;
struct mutex zoned_meta_io_lock;
- spinlock_t treelog_bg_lock;
u64 treelog_bg;
/* Start of the dedicated data relocation block group */
diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
index 421afdb6eb39..98f483def77d 100644
--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c
@@ -1948,7 +1948,7 @@ static bool check_bg_is_active(struct btrfs_eb_write_context *ctx,
if (test_bit(BLOCK_GROUP_FLAG_ZONE_IS_ACTIVE, &block_group->runtime_flags))
return true;
- if (fs_info->treelog_bg == block_group->start) {
+ if (READ_ONCE(fs_info->treelog_bg) == block_group->start) {
if (!btrfs_zone_activate(block_group)) {
int ret_fin = btrfs_zone_finish_one_bg(fs_info);
diff --git a/fs/btrfs/zoned.h b/fs/btrfs/zoned.h
index 6e11533b8e14..f71026b6c100 100644
--- a/fs/btrfs/zoned.h
+++ b/fs/btrfs/zoned.h
@@ -387,10 +387,8 @@ static inline void btrfs_clear_treelog_bg(struct btrfs_block_group *bg)
if (!btrfs_is_zoned(fs_info))
return;
- spin_lock(&fs_info->treelog_bg_lock);
- if (fs_info->treelog_bg == bg->start)
- fs_info->treelog_bg = 0;
- spin_unlock(&fs_info->treelog_bg_lock);
+ if (READ_ONCE(fs_info->treelog_bg) == bg->start)
+ WRITE_ONCE(fs_info->treelog_bg, 0);
}
static inline void btrfs_zoned_data_reloc_lock(struct btrfs_inode *inode)
--
2.49.0
next prev parent reply other threads:[~2025-06-24 9:37 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-24 9:37 [PATCH v2 0/3] btrfs: zoned: reduce lock contention in zoned extent allocator Johannes Thumshirn
2025-06-24 9:37 ` [PATCH v2 1/3] btrfs: zoned: get rid of relocation_bg_lock Johannes Thumshirn
2025-06-24 12:32 ` Naohiro Aota
2025-06-25 10:28 ` Johannes Thumshirn
2025-06-24 9:37 ` Johannes Thumshirn [this message]
2025-06-24 9:37 ` [PATCH v2 3/3] btrfs: zoned: don't hold space_info lock on zoned allocation Johannes Thumshirn
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