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 1/3] btrfs: zoned: get rid of relocation_bg_lock
Date: Tue, 24 Jun 2025 11:37:08 +0200 [thread overview]
Message-ID: <20250624093710.18685-2-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
relocation_bg_lock. But the lock only protects a single field in
'struct btrfs_fs_info', namely 'u64 data_reloc_bg'.
Use READ_ONCE()/WRITE_ONCE() to access 'btrfs_fs_info::data_reloc_bg'.
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
---
fs/btrfs/disk-io.c | 1 -
fs/btrfs/extent-tree.c | 34 ++++++++++++----------------------
fs/btrfs/fs.h | 6 +-----
fs/btrfs/zoned.c | 10 ++++------
4 files changed, 17 insertions(+), 34 deletions(-)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index ee3cdd7035cc..24896322376d 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2791,7 +2791,6 @@ void btrfs_init_fs_info(struct btrfs_fs_info *fs_info)
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);
- spin_lock_init(&fs_info->relocation_bg_lock);
rwlock_init(&fs_info->tree_mod_log_lock);
rwlock_init(&fs_info->global_root_lock);
mutex_init(&fs_info->unused_bg_unpin_mutex);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 10f50c725313..80ceca89a9ef 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3842,7 +3842,6 @@ static int do_allocation_zoned(struct btrfs_block_group *block_group,
u64 avail;
u64 bytenr = block_group->start;
u64 log_bytenr;
- u64 data_reloc_bytenr;
int ret = 0;
bool skip = false;
@@ -3865,14 +3864,9 @@ static int do_allocation_zoned(struct btrfs_block_group *block_group,
* Do not allow non-relocation blocks in the dedicated relocation block
* group, and vice versa.
*/
- spin_lock(&fs_info->relocation_bg_lock);
- data_reloc_bytenr = fs_info->data_reloc_bg;
- if (data_reloc_bytenr &&
- ((ffe_ctl->for_data_reloc && bytenr != data_reloc_bytenr) ||
- (!ffe_ctl->for_data_reloc && bytenr == data_reloc_bytenr)))
- skip = true;
- spin_unlock(&fs_info->relocation_bg_lock);
- if (skip)
+ if (READ_ONCE(fs_info->data_reloc_bg) &&
+ ((ffe_ctl->for_data_reloc && bytenr != READ_ONCE(fs_info->data_reloc_bg)) ||
+ (!ffe_ctl->for_data_reloc && bytenr == READ_ONCE(fs_info->data_reloc_bg))))
return 1;
/* Check RO and no space case before trying to activate it */
@@ -3899,7 +3893,6 @@ 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);
- spin_lock(&fs_info->relocation_bg_lock);
if (ret)
goto out;
@@ -3908,8 +3901,8 @@ static int do_allocation_zoned(struct btrfs_block_group *block_group,
block_group->start == fs_info->treelog_bg ||
fs_info->treelog_bg == 0);
ASSERT(!ffe_ctl->for_data_reloc ||
- block_group->start == fs_info->data_reloc_bg ||
- fs_info->data_reloc_bg == 0);
+ block_group->start == READ_ONCE(fs_info->data_reloc_bg) ||
+ READ_ONCE(fs_info->data_reloc_bg) == 0);
if (block_group->ro ||
(!ffe_ctl->for_data_reloc &&
@@ -3932,7 +3925,7 @@ static int do_allocation_zoned(struct btrfs_block_group *block_group,
* Do not allow currently used block group to be the data relocation
* dedicated block group.
*/
- if (ffe_ctl->for_data_reloc && !fs_info->data_reloc_bg &&
+ if (ffe_ctl->for_data_reloc && READ_ONCE(fs_info->data_reloc_bg) == 0 &&
(block_group->used || block_group->reserved)) {
ret = 1;
goto out;
@@ -3957,8 +3950,8 @@ static int do_allocation_zoned(struct btrfs_block_group *block_group,
fs_info->treelog_bg = block_group->start;
if (ffe_ctl->for_data_reloc) {
- if (!fs_info->data_reloc_bg)
- fs_info->data_reloc_bg = block_group->start;
+ if (READ_ONCE(fs_info->data_reloc_bg) == 0)
+ WRITE_ONCE(fs_info->data_reloc_bg, block_group->start);
/*
* Do not allow allocations from this block group, unless it is
* for data relocation. Compared to increasing the ->ro, setting
@@ -3994,8 +3987,7 @@ static int do_allocation_zoned(struct btrfs_block_group *block_group,
if (ret && ffe_ctl->for_treelog)
fs_info->treelog_bg = 0;
if (ret && ffe_ctl->for_data_reloc)
- fs_info->data_reloc_bg = 0;
- spin_unlock(&fs_info->relocation_bg_lock);
+ 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);
@@ -4303,11 +4295,9 @@ static int prepare_allocation_zoned(struct btrfs_fs_info *fs_info,
if (fs_info->treelog_bg)
ffe_ctl->hint_byte = fs_info->treelog_bg;
spin_unlock(&fs_info->treelog_bg_lock);
- } else if (ffe_ctl->for_data_reloc) {
- spin_lock(&fs_info->relocation_bg_lock);
- if (fs_info->data_reloc_bg)
- ffe_ctl->hint_byte = fs_info->data_reloc_bg;
- spin_unlock(&fs_info->relocation_bg_lock);
+ } 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);
} else if (ffe_ctl->flags & BTRFS_BLOCK_GROUP_DATA) {
struct btrfs_block_group *block_group;
diff --git a/fs/btrfs/fs.h b/fs/btrfs/fs.h
index b239e4b8421c..570f4b85096c 100644
--- a/fs/btrfs/fs.h
+++ b/fs/btrfs/fs.h
@@ -849,11 +849,7 @@ struct btrfs_fs_info {
spinlock_t treelog_bg_lock;
u64 treelog_bg;
- /*
- * Start of the dedicated data relocation block group, protected by
- * relocation_bg_lock.
- */
- spinlock_t relocation_bg_lock;
+ /* Start of the dedicated data relocation block group */
u64 data_reloc_bg;
struct mutex zoned_data_reloc_io_lock;
diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
index bd987c90a05c..421afdb6eb39 100644
--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c
@@ -2496,10 +2496,8 @@ void btrfs_clear_data_reloc_bg(struct btrfs_block_group *bg)
{
struct btrfs_fs_info *fs_info = bg->fs_info;
- spin_lock(&fs_info->relocation_bg_lock);
- if (fs_info->data_reloc_bg == bg->start)
- fs_info->data_reloc_bg = 0;
- spin_unlock(&fs_info->relocation_bg_lock);
+ if (READ_ONCE(fs_info->data_reloc_bg) == bg->start)
+ WRITE_ONCE(fs_info->data_reloc_bg, 0);
}
void btrfs_zoned_reserve_data_reloc_bg(struct btrfs_fs_info *fs_info)
@@ -2518,7 +2516,7 @@ void btrfs_zoned_reserve_data_reloc_bg(struct btrfs_fs_info *fs_info)
if (!btrfs_is_zoned(fs_info))
return;
- if (fs_info->data_reloc_bg)
+ if (READ_ONCE(fs_info->data_reloc_bg))
return;
if (sb_rdonly(fs_info->sb))
@@ -2539,7 +2537,7 @@ void btrfs_zoned_reserve_data_reloc_bg(struct btrfs_fs_info *fs_info)
continue;
}
- fs_info->data_reloc_bg = bg->start;
+ WRITE_ONCE(fs_info->data_reloc_bg, bg->start);
set_bit(BLOCK_GROUP_FLAG_ZONED_DATA_RELOC, &bg->runtime_flags);
btrfs_zone_activate(bg);
--
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 ` Johannes Thumshirn [this message]
2025-06-24 12:32 ` [PATCH v2 1/3] btrfs: zoned: get rid of relocation_bg_lock Naohiro Aota
2025-06-25 10:28 ` Johannes Thumshirn
2025-06-24 9:37 ` [PATCH v2 2/3] btrfs: zoned: get rid of treelog_bg_lock Johannes Thumshirn
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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