btrfs: device delete to get errors from the kernel

when user runs command btrfs dev del the raid requisite error if any
goes to the /var/log/messages, its not good idea to clutter messages
with these user (knowledge) errors, further user don't have to review
the system messages to know problem with the cli it should be dropped
to the user as part of the cli return.

to bring this feature created a set of the ERROR defined
BTRFS_ERROR_DEV* error codes and created their error string.

I expect this enum to be added with other error which we might
want to communicate to the user land

v3:
moved the code with in the file no logical change

v1->v2:
introduce error codes for the device mgmt usage

v1:
adds a parameter in the ioctl arg struct to carry the error string

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

2 files changed, 18 insertions, 30 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 1f50fe2..015689a 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2360,14 +2360,6 @@ static long btrfs_ioctl_rm_dev(struct file *file, void __user *arg)
 	if (ret)
 		return ret;
 
-	if (atomic_xchg(&root->fs_info->mutually_exclusive_operation_running,
-			1)) {
-		pr_info("btrfs: dev add/delete/balance/replace/resize operation in progress\n");
-		mnt_drop_write_file(file);
-		return -EINVAL;
-	}
-
-	mutex_lock(&root->fs_info->volume_mutex);
 	vol_args = memdup_user(arg, sizeof(*vol_args));
 	if (IS_ERR(vol_args)) {
 		ret = PTR_ERR(vol_args);
@@ -2375,12 +2367,20 @@ static long btrfs_ioctl_rm_dev(struct file *file, void __user *arg)
 	}
 
 	vol_args->name[BTRFS_PATH_NAME_MAX] = '\0';
-	ret = btrfs_rm_device(root, vol_args->name);
 
-	kfree(vol_args);
-out:
+	if (atomic_xchg(&root->fs_info->mutually_exclusive_operation_running,
+			1)) {
+		ret = BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS;
+		goto out;
+	}
+
+	mutex_lock(&root->fs_info->volume_mutex);
+	ret = btrfs_rm_device(root, vol_args->name);
 	mutex_unlock(&root->fs_info->volume_mutex);
 	atomic_set(&root->fs_info->mutually_exclusive_operation_running, 0);
+
+out:
+	kfree(vol_args);
 	mnt_drop_write_file(file);
 	return ret;
 }
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 440de70..b1446c0 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1462,31 +1462,23 @@ int btrfs_rm_device(struct btrfs_root *root, char *device_path)
 	btrfs_dev_replace_unlock(&root->fs_info->dev_replace);
 
 	if ((all_avail & BTRFS_BLOCK_GROUP_RAID10) && num_devices <= 4) {
-		printk(KERN_ERR "btrfs: unable to go below four devices "
-		       "on raid10\n");
-		ret = -EINVAL;
+		ret = BTRFS_ERROR_DEV_RAID10_MIN_NOT_MET;
 		goto out;
 	}
 
 	if ((all_avail & BTRFS_BLOCK_GROUP_RAID1) && num_devices <= 2) {
-		printk(KERN_ERR "btrfs: unable to go below two "
-		       "devices on raid1\n");
-		ret = -EINVAL;
+		ret = BTRFS_ERROR_DEV_RAID1_MIN_NOT_MET;
 		goto out;
 	}
 
 	if ((all_avail & BTRFS_BLOCK_GROUP_RAID5) &&
 	    root->fs_info->fs_devices->rw_devices <= 2) {
-		printk(KERN_ERR "btrfs: unable to go below two "
-		       "devices on raid5\n");
-		ret = -EINVAL;
+		ret = BTRFS_ERROR_DEV_RAID5_MIN_NOT_MET;
 		goto out;
 	}
 	if ((all_avail & BTRFS_BLOCK_GROUP_RAID6) &&
 	    root->fs_info->fs_devices->rw_devices <= 3) {
-		printk(KERN_ERR "btrfs: unable to go below three "
-		       "devices on raid6\n");
-		ret = -EINVAL;
+		ret = BTRFS_ERROR_DEV_RAID6_MIN_NOT_MET;
 		goto out;
 	}
 
@@ -1512,8 +1504,7 @@ int btrfs_rm_device(struct btrfs_root *root, char *device_path)
 		bh = NULL;
 		disk_super = NULL;
 		if (!device) {
-			printk(KERN_ERR "btrfs: no missing devices found to "
-			       "remove\n");
+			ret = BTRFS_ERROR_DEV_MISSING_NOT_FOUND;
 			goto out;
 		}
 	} else {
@@ -1535,15 +1526,12 @@ int btrfs_rm_device(struct btrfs_root *root, char *device_path)
 	}
 
 	if (device->is_tgtdev_for_dev_replace) {
-		pr_err("btrfs: unable to remove the dev_replace target dev\n");
-		ret = -EINVAL;
+		ret = BTRFS_ERROR_DEV_TGT_REPLACE;
 		goto error_brelse;
 	}
 
 	if (device->writeable && root->fs_info->fs_devices->rw_devices == 1) {
-		printk(KERN_ERR "btrfs: unable to remove the only writeable "
-		       "device\n");
-		ret = -EINVAL;
+		ret = BTRFS_ERROR_DEV_ONLY_WRITABLE;
 		goto error_brelse;
 	}