[PATCH v2] btrfs: free unlinked replace target on initialization failure

[Guanghui Yang <3497809730@qq.com>]

btrfs_init_dev_replace_tgtdev() allocates the replacement target
before looking up its dev_t and initializing its zoned device
information. If either lookup_bdev() or btrfs_get_dev_zone_info()
fails, the device has not been linked into fs_devices->devices yet,
but the error path only drops the block device file reference.

Free the allocated device on this error path to release its name,
allocation state, zone info, and the device itself.

The issue was found by a failure-path metadata residual analyzer and
verified with targeted failure injection on v6.14.

Assisted-by: Codex:gpt-5
Signed-off-by: Guanghui Yang <3497809730@qq.com>
---
 fs/btrfs/dev-replace.c | 10 +++++++---
 fs/btrfs/volumes.c     |  2 +-
 fs/btrfs/volumes.h     |  1 +
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index 318ddb790..3762429b5 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -235,7 +235,8 @@ static int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
 				  struct btrfs_device **device_out)
 {
 	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
-	struct btrfs_device *device;
+	struct btrfs_device *device = NULL;
+	struct btrfs_device *tmp_device;
 	struct file *bdev_file;
 	struct block_device *bdev;
 	u64 devid = BTRFS_DEV_REPLACE_DEVID;
@@ -264,8 +265,8 @@ static int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
 
 	sync_blockdev(bdev);
 
-	list_for_each_entry(device, &fs_devices->devices, dev_list) {
-		if (device->bdev == bdev) {
+	list_for_each_entry(tmp_device, &fs_devices->devices, dev_list) {
+		if (tmp_device->bdev == bdev) {
 			btrfs_err(fs_info,
 				  "target device is in the filesystem!");
 			ret = -EEXIST;
@@ -285,6 +286,7 @@ static int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
 	device = btrfs_alloc_device(NULL, &devid, NULL, device_path);
 	if (IS_ERR(device)) {
 		ret = PTR_ERR(device);
+		device = NULL;
 		goto error;
 	}
 
@@ -327,6 +329,8 @@ static int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
 	return 0;
 
 error:
+	if (device)
+		btrfs_free_device(device);
 	bdev_fput(bdev_file);
 	return ret;
 }
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index a8e27db8e..c479f268a 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -402,7 +402,7 @@ static struct btrfs_fs_devices *alloc_fs_devices(const u8 *fsid)
 	return fs_devs;
 }
 
-static void btrfs_free_device(struct btrfs_device *device)
+void btrfs_free_device(struct btrfs_device *device)
 {
 	WARN_ON(!list_empty(&device->post_commit_list));
 	/*
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index eaf23c0dc..ecab3ce3c 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -795,6 +795,7 @@ int btrfs_run_dev_stats(struct btrfs_trans_handle *trans);
 void btrfs_rm_dev_replace_remove_srcdev(struct btrfs_device *srcdev);
 void btrfs_rm_dev_replace_free_srcdev(struct btrfs_device *srcdev);
 void btrfs_destroy_dev_replace_tgtdev(struct btrfs_device *tgtdev);
+void btrfs_free_device(struct btrfs_device *device);
 unsigned long btrfs_full_stripe_len(struct btrfs_fs_info *fs_info,
 				    u64 logical);
 u64 btrfs_calc_stripe_length(const struct btrfs_chunk_map *map);
-- 
2.53.0