Btrfs: don't write any data into a readonly device when scrub

We should not write data into a readonly device especially seed device when
doing scrub, skip those devices.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Reviewed-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index b6d198f5181e..23d3f6e6a482 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -2904,6 +2904,7 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
         struct scrub_ctx *sctx;
         int ret;
         struct btrfs_device *dev;
+        struct rcu_string *name;
 
         if (btrfs_fs_closing(fs_info))
                 return -EINVAL;
@@ -2965,6 +2966,16 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
                 return -ENODEV;
         }
 
+        if (!is_dev_replace && !readonly && !dev->writeable) {
+                mutex_unlock(&fs_info->fs_devices->device_list_mutex);
+                rcu_read_lock();
+                name = rcu_dereference(dev->name);
+                btrfs_err(fs_info, "scrub: device %s is not writable",
+                          name->str);
+                rcu_read_unlock();
+                return -EROFS;
+        }
+
         mutex_lock(&fs_info->scrub_lock);
         if (!dev->in_fs_metadata || dev->is_tgtdev_for_dev_replace) {
                 mutex_unlock(&fs_info->scrub_lock);