Re: [PATCH 2/2] libblkid: reopen floppy without O_NONBLOCK

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

16.12.2021 11:47, Vladimir Sementsov-Ogievskiy wrote:
> 15.12.2021 15:56, Karel Zak wrote:
>> On Tue, Dec 14, 2021 at 05:24:44PM +0300, Vladimir Sementsov-Ogievskiy wrote:
>>>> What does it mean didn't help?
>>>
>>> I tried it, but the bug remains as it was.. As I understand,
>>> dropping O_NONBLOCK by fcntl just removes this flag, to change
>>> further behavior of device to non-blocking. But it doesn't do any
>>> additional actions in driver.
>>
>> Hmm ...
>>
>>>> The solution based on blkid_safe_open() means that we have to modify
>>>> many applications. For example, systemd/udevd uses
>>>>
>>>>       fd = open(devnode, O_RDONLY|O_CLOEXEC|O_NONBLOCK);
>>>>       r = blkid_probe_set_device(pr, fd, offset, 0);
>>>
>>> Hmm, yes, that's not very good :(
>>>
>>>>
>>>> The same is probably in many other places (mkfs-like programs, etc.).
>>>>
>>>> What do you think?
>>>>
>>>
>>> Maybe be we can get filename from fd reading it from /proc, then do
>>> open() and than dup() to old fd.. But that's even more dirty to do
>>> in a library call.
>>
>> Yes, re-open() sounds like a possible way.
>>
>> The dup() is not necessary. The library already support private FD for
>> probing. See blkid_new_probe_from_filename() and BLKID_FL_PRIVATE_FD.
>>
>> It's also often used when the library probe whole-disk device (when you
>> probe sda1 than it also reads data from partition table on sda). In
>> this case it opens a separate FD.
>>
>> It's for floppies (0.001% of all cases). IMHO re-open is good enough and
>> better than force changes in all applications :-)> I'll try to prepare a patch and ask you for test/review. Thanks!
>>
> 
> Great!
> 

Hi! Are you working on this? If not I can try to make a v2.

-- 
Best regards,
Vladimir