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From: "\"Kai Mäkisara (Kolumbus)\"" <kai.makisara@kolumbus.fi>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>,
	linux-fsdevel@vger.kernel.org,
	Octavian Purdila <octavian.purdila@intel.com>,
	Pantelis Antoniou <pantelis.antoniou@konsulko.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-scsi@vger.kernel.org
Subject: Re: [RFC] Re: broken userland ABI in configfs binary attributes
Date: Mon, 26 Aug 2019 21:34:37 +0300	[thread overview]
Message-ID: <B35B5EA9-939C-49F5-BF65-491D70BCA8D4@kolumbus.fi> (raw)
In-Reply-To: <20190826162949.GA9980@ZenIV.linux.org.uk>



> On 26 Aug 2019, at 19.29, Al Viro <viro@zeniv.linux.org.uk> wrote:
> 
> On Mon, Aug 26, 2019 at 03:48:38AM +0100, Al Viro wrote:
> 
>> 	We might be able to paper over that mess by doing what /dev/st does -
>> checking that file_count(file) == 1 in ->flush() instance and doing commit
>> there in such case.  It's not entirely reliable, though, and it's definitely
>> not something I'd like to see spreading.
> 
> 	This "not entirely reliable" turns out to be an understatement.
> If you have /proc/*/fdinfo/* being read from at the time of final close(2),
> you'll get file_count(file) > 1 the last time ->flush() is called.  In other
> words, we'd get the data not committed at all.
> 
...
> PS: just dropping the check in st_flush() is probably a bad idea -
> as it is, it can't overlap with st_write() and after such change it
> will…
Yes, don’t just drop it. The tape semantics require that a file mark is written when the last opener closes this sequential device. This is why the check is there. Of course, it is good if someone finds a better solution for this.

Thanks,
Kai


  parent reply	other threads:[~2019-08-26 18:40 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-26  2:48 broken userland ABI in configfs binary attributes Al Viro
2019-08-26 16:29 ` [RFC] " Al Viro
2019-08-26 18:20   ` Matthew Wilcox
2019-08-26 19:28     ` Al Viro
2019-08-27  8:51       ` Miklos Szeredi
2019-08-27 11:58         ` Al Viro
2019-08-27 12:21           ` Miklos Szeredi
2019-08-27 12:53             ` Al Viro
2019-08-31  8:32       ` Christoph Hellwig
2019-08-31 13:35         ` Al Viro
2019-08-31 14:44           ` Christoph Hellwig
2019-08-31 15:58             ` Al Viro
2019-08-26 18:34   ` "Kai Mäkisara (Kolumbus)" [this message]
2019-08-26 19:32     ` Al Viro
2019-08-27 15:01       ` Boaz Harrosh
2019-08-27 17:27         ` Al Viro
2019-08-27 17:59           ` Boaz Harrosh
2019-08-29 22:22           ` Al Viro
2019-08-29 23:32             ` Al Viro
2019-08-30  4:10             ` Dave Chinner
2019-08-30  4:44               ` Al Viro
2019-08-31  8:28                 ` Christoph Hellwig

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