linux-kernel - [PATCH v2] btrfs: zoned: remove redundant space_info lock and variable in do_allocation

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Message-Id: <20260112202227.37626-1-jiashengjiangcool@gmail.com>
Date: Mon, 12 Jan 2026 20:22:27 +0000
From: Jiasheng Jiang <jiashengjiangcool@...il.com>
To: boris@....io
Cc: clm@...com,
	dsterba@...e.com,
	jiashengjiangcool@...il.com,
	linux-btrfs@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2] btrfs: zoned: remove redundant space_info lock and variable in do_allocation_zoned

In do_allocation_zoned(), the code acquires space_info->lock before
block_group->lock. However, the critical section does not access or
modify any members of the space_info structure. Thus, the lock is
redundant as it provides no necessary synchronization here.

This change simplifies the locking logic and aligns the function with
other zoned paths, such as __btrfs_add_free_space_zoned(), which only
rely on block_group->lock. Since the 'space_info' local variable is
no longer used after removing the lock calls, it is also removed.

Removing this unnecessary lock reduces contention on the global
space_info lock, improving concurrency in the zoned allocation path.

Signed-off-by: Jiasheng Jiang <jiashengjiangcool@...il.com>
---
Changelog:

v1 -> v2:

1. Removed the description about avoiding deadlocks.
---
 fs/btrfs/extent-tree.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index e4cae34620d1..43d78056c274 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3839,7 +3839,6 @@ static int do_allocation_zoned(struct btrfs_block_group *block_group,
 			       struct btrfs_block_group **bg_ret)
 {
 	struct btrfs_fs_info *fs_info = block_group->fs_info;
-	struct btrfs_space_info *space_info = block_group->space_info;
 	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
 	u64 start = block_group->start;
 	u64 num_bytes = ffe_ctl->num_bytes;
@@ -3900,7 +3899,6 @@ 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);
@@ -4002,7 +4000,6 @@ static int do_allocation_zoned(struct btrfs_block_group *block_group,
 	spin_unlock(&fs_info->relocation_bg_lock);
 	spin_unlock(&fs_info->treelog_bg_lock);
 	spin_unlock(&block_group->lock);
-	spin_unlock(&space_info->lock);
 	return ret;
 }
 
-- 
2.25.1