From: Matthew Wilcox <willy@infradead.org>
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>,
"Kai Mäkisara" <Kai.Makisara@kolumbus.fi>,
linux-scsi@vger.kernel.org
Subject: Re: [RFC] Re: broken userland ABI in configfs binary attributes
Date: Mon, 26 Aug 2019 11:20:17 -0700 [thread overview]
Message-ID: <20190826182017.GE15933@bombadil.infradead.org> (raw)
In-Reply-To: <20190826162949.GA9980@ZenIV.linux.org.uk>
On Mon, Aug 26, 2019 at 05:29:49PM +0100, Al Viro 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.
How about always doing the write in ->flush instead of ->release?
Yes, that means that calling close(dup(fd)) is going to flush the
write, but you shouldn't be doing that. I think there'll also be
extra flushes done if you fork() during one of these writes ... but,
again, don't do that. It's not like these are common things.
Why does the prototype of file_operations::release suggest that it can
return an int? __fput doesn't pay any attention to the return value.
Changing that to return void might help some future programmers avoid
this mistake.
next prev parent reply other threads:[~2019-08-26 18:20 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 [this message]
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)"
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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