btrfs: mount failure return value fix

I happened to pass swap partition as root partition in cmdline,
then kernel panic and tell me about "Cannot open root device".
It is not correct, in fact it is a fs type mismatch instead of 'no device'.

Eventually I found btrfs mounting failed with -EIO, it should be -EINVAL.
The logic in init/do_mounts.c:
        for (p = fs_names; *p; p += strlen(p)+1) {
                int err = do_mount_root(name, p, flags, root_mount_data);
                switch (err) {
                        case 0:
                                goto out;
                        case -EACCES:
                                flags |= MS_RDONLY;
                                goto retry;
                        case -EINVAL:
                                continue;
                }
		print "Cannot open root device"
		panic
	}
SO fs type after btrfs will have no chance to mount

Here fix the return value as -EINVAL

Signed-off-by: Dave Young <hidave.darkstar@gmail.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

2 files changed, 8 insertions, 4 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index f88eb2ce791..f9efb68fc2e 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1713,8 +1713,10 @@ struct btrfs_root *open_ctree(struct super_block *sb,
                      fs_info, BTRFS_ROOT_TREE_OBJECTID);
 
         bh = btrfs_read_dev_super(fs_devices->latest_bdev);
-        if (!bh)
+        if (!bh) {
+                err = -EINVAL;
                 goto fail_iput;
+        }
 
         memcpy(&fs_info->super_copy, bh->b_data, sizeof(fs_info->super_copy));
         memcpy(&fs_info->super_for_commit, &fs_info->super_copy,
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 0c7f478cf64..e8be478178a 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -600,8 +600,10 @@ static int __btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
                 set_blocksize(bdev, 4096);
 
                 bh = btrfs_read_dev_super(bdev);
-                if (!bh)
+                if (!bh) {
+                        ret = -EINVAL;
                         goto error_close;
+                }
 
                 disk_super = (struct btrfs_super_block *)bh->b_data;
                 devid = btrfs_stack_device_id(&disk_super->dev_item);
@@ -702,7 +704,7 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
                 goto error_close;
         bh = btrfs_read_dev_super(bdev);
         if (!bh) {
-                ret = -EIO;
+                ret = -EINVAL;
                 goto error_close;
         }
         disk_super = (struct btrfs_super_block *)bh->b_data;
@@ -1302,7 +1304,7 @@ int btrfs_rm_device(struct btrfs_root *root, char *device_path)
                 set_blocksize(bdev, 4096);
                 bh = btrfs_read_dev_super(bdev);
                 if (!bh) {
-                        ret = -EIO;
+                        ret = -EINVAL;
                         goto error_close;
                 }
                 disk_super = (struct btrfs_super_block *)bh->b_data;