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[2003:f6:f719:b200:5a9e:6e27:159b:eb3]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a892e5966csm2152556f8f.72.2025.06.27.02.19.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 Jun 2025 02:19:24 -0700 (PDT) From: Johannes Thumshirn To: linux-btrfs@vger.kernel.org Cc: Damien Le Moal , Naohiro Aota , David Sterba , Josef Bacik , Boris Burkov , Filipe Manana , Johannes Thumshirn Subject: [PATCH RFC 2/9] btrfs: zoned: get rid of relocation_bg_lock Date: Fri, 27 Jun 2025 11:19:07 +0200 Message-ID: <20250627091914.100715-3-jth@kernel.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250627091914.100715-1-jth@kernel.org> References: <20250627091914.100715-1-jth@kernel.org> Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Johannes Thumshirn Lockstat analysis of benchmark workloads shows a very high contention of the relocation_bg_lock. But the relocation_bg_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'. This is safe in the allocator path, as relocation I/O is only going to block groups in the relocation sub-space_info and at the moment, there is only one relocation block group in this space info. Signed-off-by: Johannes Thumshirn --- fs/btrfs/disk-io.c | 1 - fs/btrfs/extent-tree.c | 28 +++++++++++----------------- fs/btrfs/fs.h | 6 +----- fs/btrfs/zoned.c | 11 +++++------ 4 files changed, 17 insertions(+), 29 deletions(-) diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index 6ac5be02dce7..9a13f5b1ed43 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..a9bda68a1883 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -3865,14 +3865,10 @@ 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; + data_reloc_bytenr = READ_ONCE(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) return 1; /* Check RO and no space case before trying to activate it */ @@ -3899,7 +3895,6 @@ 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 +3903,8 @@ 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 == data_reloc_bytenr || + data_reloc_bytenr == 0); if (block_group->ro || (!ffe_ctl->for_data_reloc && @@ -3932,7 +3927,7 @@ 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 && data_reloc_bytenr == 0 && (block_group->used || block_group->reserved)) { ret = 1; goto out; @@ -3957,8 +3952,8 @@ 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 +3989,7 @@ 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); @@ -4304,10 +4298,10 @@ static int prepare_allocation_zoned(struct btrfs_fs_info *fs_info, 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); + u64 data_reloc_bg = READ_ONCE(fs_info->data_reloc_bg); + + if (data_reloc_bg) + ffe_ctl->hint_byte = 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 0d5d6db72b62..388c277a84d3 100644 --- a/fs/btrfs/zoned.c +++ b/fs/btrfs/zoned.c @@ -2495,11 +2495,10 @@ void btrfs_schedule_zone_finish_bg(struct btrfs_block_group *bg, void btrfs_clear_data_reloc_bg(struct btrfs_block_group *bg) { struct btrfs_fs_info *fs_info = bg->fs_info; + u64 data_reloc_bg = READ_ONCE(fs_info->data_reloc_bg); - 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 (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 +2517,7 @@ 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 +2538,7 @@ 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