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 <[email protected]>
---
 fs/btrfs/ioctl.c           | 22 +++++++++++-----------
 fs/btrfs/volumes.c         | 26 +++++++-------------------
 include/uapi/linux/btrfs.h | 36 ++++++++++++++++++++++++++++++++++++
 3 files changed, 54 insertions(+), 30 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 898c572..e6d21ec 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2347,14 +2347,6 @@ 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);
@@ -2362,12 +2354,20 @@ 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 5989a92..22c702e 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1461,31 +1461,23 @@ 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;
        }
 
@@ -1511,8 +1503,7 @@ 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 {
@@ -1534,15 +1525,12 @@ 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;
        }
 
diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index fa3a5f9..dcde338 100644
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -511,4 +511,40 @@ struct btrfs_ioctl_send_args {
 #define BTRFS_IOC_DEV_REPLACE _IOWR(BTRFS_IOCTL_MAGIC, 53, \
                                    struct btrfs_ioctl_dev_replace_args)
 
+enum btrfs_err_code {
+       notused,
+       BTRFS_ERROR_DEV_RAID1_MIN_NOT_MET,
+       BTRFS_ERROR_DEV_RAID10_MIN_NOT_MET,
+       BTRFS_ERROR_DEV_RAID5_MIN_NOT_MET,
+       BTRFS_ERROR_DEV_RAID6_MIN_NOT_MET,
+       BTRFS_ERROR_DEV_TGT_REPLACE,
+       BTRFS_ERROR_DEV_MISSING_NOT_FOUND,
+       BTRFS_ERROR_DEV_ONLY_WRITABLE,
+       BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS
+};
+
+static inline char *btrfs_err_str(enum btrfs_err_code err_code)
+{
+       switch (err_code) {
+               case BTRFS_ERROR_DEV_RAID1_MIN_NOT_MET:
+                       return "unable to go below two devices on raid1";
+               case BTRFS_ERROR_DEV_RAID10_MIN_NOT_MET:
+                       return "unable to go below four devices on raid10";
+               case BTRFS_ERROR_DEV_RAID5_MIN_NOT_MET:
+                       return "unable to go below two devices on raid5";
+               case BTRFS_ERROR_DEV_RAID6_MIN_NOT_MET:
+                       return "unable to go below three devices on raid6";
+               case BTRFS_ERROR_DEV_TGT_REPLACE:
+                       return "unable to remove the dev_replace target dev";
+               case BTRFS_ERROR_DEV_MISSING_NOT_FOUND:
+                       return "no missing devices found to remove";
+               case BTRFS_ERROR_DEV_ONLY_WRITABLE:
+                       return "unable to remove the only writeable device";
+               case BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS:
+                       return "add/delete/balance/replace/resize operation "\
+                               "in progress";
+               default:
+                       return NULL;
+       }
+}
 #endif /* _UAPI_LINUX_BTRFS_H */
-- 
1.8.1.227.g44fe835

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