[PATCH 05/11] btrfs: dev-replace: avoid useless lock on error handling path

[David Sterba]

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.

Signed-off-by: David Sterba <dste...@suse.com>
---
 fs/btrfs/dev-replace.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index 8b512dddf727..0a49843b2ee6 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;
 
        ret = btrfs_find_device_by_devspec(fs_info, srcdevid,
                                            srcdev_name, &src_device);
@@ -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:
@@ -462,6 +464,7 @@ 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)
@@ -473,7 +476,6 @@ 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);
-               btrfs_dev_replace_write_lock(dev_replace);
                goto leave;
        }
 
@@ -497,7 +499,8 @@ int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info,
 leave:
        dev_replace->srcdev = NULL;
        dev_replace->tgtdev = NULL;
-       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;
 }
-- 
2.18.0