On 2017/9/5 下午2:43, Christoph Hellwig wrote:

On Tue, Sep 05, 2017 at 01:30:04AM +0800, Coly Li wrote:

quoted

When you mentioned "whole chunk of code", do you mean the following
block of code ?


1960         if (IS_ERR(bdev)) {
========= start of whole chunk of code ============
1961                 if (bdev == ERR_PTR(-EBUSY)) {
1962                         bdev = lookup_bdev(strim(path));
1963                         mutex_lock(&bch_register_lock);
1964                         if (!IS_ERR(bdev) && bch_is_open(bdev))
1965                                 err = "device already registered";
1966                         else
1967                                 err = "device busy";
1968                         mutex_unlock(&bch_register_lock);
1969                         if (!IS_ERR(bdev))
1970                                 bdput(bdev);
1971                         if (attr == &ksysfs_register_quiet)
1972                                 goto out;
1973                 }
========= end of whole chunk of code ============
1974                 goto err;
1975         }

I don't mind to remove it, just double check I don't misunderstand what
you meant.

Yes, that's the problematic block.

Hi Christoph,

I tested the code, and my patch which removes the above code. The result
is, I feel the above chunk of code is useful. When I tried to register a
device and it was already registered. Without the above code, I only saw
"failed to open device", didn't realize it was because this device is
registered already. After adding the above code back, I knew where the
problem was.

The above chunk of code improves user experience and provides more
detailed diagnose information, it is useful. Then I suggest to keep the
code here and pick up Jan's patch.

Thanks.

-- 
Coly Li