btrfs: dev-replace: avoid useless lock on error handling path

The exit sequence in btrfs_dev_replace_start does not allow to simply
add a label to the right place so the error handling after starting
transaction failure jumps there. Currently there's a lock that pairs
with the unlock in the section, which is unnecessary and only raises
questions.  Add a variable to track the locking status and avoid the
extra locking.

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

1 files changed, 6 insertions, 1 deletions

diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index 264105a26e7e..c7f2d6b91a6f 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -400,6 +400,7 @@ int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info,
         int ret;
         struct btrfs_device *tgt_device = NULL;
         struct btrfs_device *src_device = NULL;
+        bool need_unlock;
 
         src_device = btrfs_find_device_by_devspec(fs_info, srcdevid,
                                                   srcdev_name);
@@ -424,6 +425,7 @@ int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info,
                 return PTR_ERR(trans);
         }
 
+        need_unlock = true;
         btrfs_dev_replace_write_lock(dev_replace);
         switch (dev_replace->replace_state) {
         case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
@@ -463,6 +465,7 @@ int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info,
         atomic64_set(&dev_replace->num_write_errors, 0);
         atomic64_set(&dev_replace->num_uncorrectable_read_errors, 0);
         btrfs_dev_replace_write_unlock(dev_replace);
+        need_unlock = false;
 
         ret = btrfs_sysfs_add_device_link(tgt_device->fs_devices, tgt_device);
         if (ret)
@@ -474,6 +477,7 @@ int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info,
         trans = btrfs_start_transaction(root, 0);
         if (IS_ERR(trans)) {
                 ret = PTR_ERR(trans);
+                need_unlock = true;
                 btrfs_dev_replace_write_lock(dev_replace);
                 dev_replace->replace_state =
                         BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED;
@@ -500,7 +504,8 @@ int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info,
         return ret;
 
 leave:
-        btrfs_dev_replace_write_unlock(dev_replace);
+        if (need_unlock)
+                btrfs_dev_replace_write_unlock(dev_replace);
         btrfs_destroy_dev_replace_tgtdev(tgt_device);
         return ret;
 }