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>

diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index 264105a26e7ede0a6eefb8e4d73c182e1a5d6b24..c7f2d6b91a6f795bfdd615376c48c9351d2e2fd2 100644 (file)
--- 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;
 }