btrfs: move device->name RCU allocation and assign to btrfs_alloc_device()

There is a repeating code section in the parent function after calling
btrfs_alloc_device(), as below:

      name = rcu_string_strdup(path, GFP_...);
      if (!name) {
              btrfs_free_device(device);
              return ERR_PTR(-ENOMEM);
      }
      rcu_assign_pointer(device->name, name);

Except in add_missing_dev() for obvious reasons.

This patch consolidates that repeating code into the btrfs_alloc_device()
itself so that the parent function doesn't have to duplicate code.
This consolidation also helps to review issues regarding RCU lock
violation with device->name.

Parent function device_list_add() and add_missing_dev() use GFP_NOFS for
the allocation, whereas the rest of the parent functions use GFP_KERNEL,
so bring the NOFS allocation context using memalloc_nofs_save() in the
function device_list_add() and add_missing_dev() is already doing it.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 1 insertions, 9 deletions

diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index 84af2010fae2..9c4a8649a0f4 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -249,7 +249,6 @@ static int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
 	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
 	struct btrfs_device *device;
 	struct block_device *bdev;
-	struct rcu_string *name;
 	u64 devid = BTRFS_DEV_REPLACE_DEVID;
 	int ret = 0;
 
@@ -293,19 +292,12 @@ static int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
 	}
 
 
-	device = btrfs_alloc_device(NULL, &devid, NULL);
+	device = btrfs_alloc_device(NULL, &devid, NULL, device_path);
 	if (IS_ERR(device)) {
 		ret = PTR_ERR(device);
 		goto error;
 	}
 
-	name = rcu_string_strdup(device_path, GFP_KERNEL);
-	if (!name) {
-		btrfs_free_device(device);
-		ret = -ENOMEM;
-		goto error;
-	}
-	rcu_assign_pointer(device->name, name);
 	ret = lookup_bdev(device_path, &device->devt);
 	if (ret)
 		goto error;