[5/5] btrfs: remove final BUG_ON() in close_fs_devices()
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Message ID 20191112122416.30672-6-jthumshirn@suse.de
State New
Headers show
Series
  • [1/5] btrfs: decrement number of open devices after closing the device not before
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Commit Message

Johannes Thumshirn Nov. 12, 2019, 12:24 p.m. UTC
Now that the preparation work is done, remove the temporary BUG_ON() in
close_fs_devices() and return an error instead.

Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
---
 fs/btrfs/volumes.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

Comments

Qu Wenruo Nov. 12, 2019, 12:41 p.m. UTC | #1
On 2019/11/12 下午8:24, Johannes Thumshirn wrote:
> Now that the preparation work is done, remove the temporary BUG_ON() in
> close_fs_devices() and return an error instead.
>
> Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
> ---
>  fs/btrfs/volumes.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index be1fd935edf7..844333b96075 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -1128,7 +1128,12 @@ static int close_fs_devices(struct btrfs_fs_devices *fs_devices)
>  	mutex_lock(&fs_devices->device_list_mutex);
>  	list_for_each_entry_safe(device, tmp, &fs_devices->devices, dev_list) {
>  		ret = btrfs_close_one_device(device);
> -		BUG_ON(ret); /* -ENOMEM */
> +		if (ret) {
> +			mutex_unlock(&fs_devices->device_list_mutex);
> +			return ret;
> +		}
> +		fs_devices->opened--;
> +		fs_devices->seeding--;

This seeding-- doesn't look safe to me.

From what I see, fs_devices->seeding seems to be bool value (0 or 1).

Wouldn't this seeding-- underflow?

Thanks,
Qu

>  	}
>  	mutex_unlock(&fs_devices->device_list_mutex);
>
>
David Sterba Nov. 12, 2019, 12:55 p.m. UTC | #2
On Tue, Nov 12, 2019 at 08:41:50PM +0800, Qu Wenruo wrote:
> 
> 
> On 2019/11/12 下午8:24, Johannes Thumshirn wrote:
> > Now that the preparation work is done, remove the temporary BUG_ON() in
> > close_fs_devices() and return an error instead.
> >
> > Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
> > ---
> >  fs/btrfs/volumes.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> > index be1fd935edf7..844333b96075 100644
> > --- a/fs/btrfs/volumes.c
> > +++ b/fs/btrfs/volumes.c
> > @@ -1128,7 +1128,12 @@ static int close_fs_devices(struct btrfs_fs_devices *fs_devices)
> >  	mutex_lock(&fs_devices->device_list_mutex);
> >  	list_for_each_entry_safe(device, tmp, &fs_devices->devices, dev_list) {
> >  		ret = btrfs_close_one_device(device);
> > -		BUG_ON(ret); /* -ENOMEM */
> > +		if (ret) {
> > +			mutex_unlock(&fs_devices->device_list_mutex);
> > +			return ret;
> > +		}
> > +		fs_devices->opened--;
> > +		fs_devices->seeding--;
> 
> This seeding-- doesn't look safe to me.

Yeah, same here, it could be correct in the sense that it's 1 -> 0
exactly once, but otherwise its a bool, and handled in a special way.
Johannes Thumshirn Nov. 12, 2019, 12:59 p.m. UTC | #3
On 12/11/2019 13:55, David Sterba wrote:
> On Tue, Nov 12, 2019 at 08:41:50PM +0800, Qu Wenruo wrote:
>>
>>
>> On 2019/11/12 下午8:24, Johannes Thumshirn wrote:
>>> Now that the preparation work is done, remove the temporary BUG_ON() in
>>> close_fs_devices() and return an error instead.
>>>
>>> Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
>>> ---
>>>  fs/btrfs/volumes.c | 7 ++++++-
>>>  1 file changed, 6 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
>>> index be1fd935edf7..844333b96075 100644
>>> --- a/fs/btrfs/volumes.c
>>> +++ b/fs/btrfs/volumes.c
>>> @@ -1128,7 +1128,12 @@ static int close_fs_devices(struct btrfs_fs_devices *fs_devices)
>>>  	mutex_lock(&fs_devices->device_list_mutex);
>>>  	list_for_each_entry_safe(device, tmp, &fs_devices->devices, dev_list) {
>>>  		ret = btrfs_close_one_device(device);
>>> -		BUG_ON(ret); /* -ENOMEM */
>>> +		if (ret) {
>>> +			mutex_unlock(&fs_devices->device_list_mutex);
>>> +			return ret;
>>> +		}
>>> +		fs_devices->opened--;
>>> +		fs_devices->seeding--;
>>
>> This seeding-- doesn't look safe to me.
> 
> Yeah, same here, it could be correct in the sense that it's 1 -> 0
> exactly once, but otherwise its a bool, and handled in a special way.

Yeah it looks like an overlook on my side, I'll correct it in the next
revision.

Patch
diff mbox series

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index be1fd935edf7..844333b96075 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1128,7 +1128,12 @@  static int close_fs_devices(struct btrfs_fs_devices *fs_devices)
 	mutex_lock(&fs_devices->device_list_mutex);
 	list_for_each_entry_safe(device, tmp, &fs_devices->devices, dev_list) {
 		ret = btrfs_close_one_device(device);
-		BUG_ON(ret); /* -ENOMEM */
+		if (ret) {
+			mutex_unlock(&fs_devices->device_list_mutex);
+			return ret;
+		}
+		fs_devices->opened--;
+		fs_devices->seeding--;
 	}
 	mutex_unlock(&fs_devices->device_list_mutex);