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Date: Thu, 14 Jan 2016 20:07:35 +0100
From: Felix Janda <felix.janda@posteo.de>
Subject: Re: [PATCH 2/6] libxfs/linux.c: Replace use of ustat by stat
Message-ID: <20160114190735.GB627@nyan>
References: <cover.1452627740.git.felix.janda@posteo.de>
	<20160112195945.GC568@nyan> <20160113075501.GC21939@infradead.org>
	<20160113174241.GC10942@nyan>
	<20160114102009.GD27644@infradead.org>
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To: Christoph Hellwig <hch@infradead.org>
Cc: xfs@oss.sgi.com

Christoph Hellwig wrote:
> On Wed, Jan 13, 2016 at 06:42:41PM +0100, Felix Janda wrote:
> > Is this really performance relevant?
> 
> I'm not entirely sure.  There are systems with giant amounts of mounted
> file systems, in which case iterating each of them and requiring
> multiple syscalls each might not be a good idea.

Of course, it is not very elegant...

> > Hmm, so we couldn't we use for linux just something like
> > 
> > int
> > platform_check_ismounted(char *name, char *block, struct stat64 *s, int verbose)
> > {
> > 	int fd = open(block, O_EXCL);
> > 	int e = errno;
> > 	
> > 	if (fd != -1) close(fd);
> > 	if (e == EBUSY) {
> > 		if (verbose)
> > 			fprintf(stderr, _("%s: %s contains a mounted filesystem\n"), progname, name);
> > 		return 1;
> > 	}
> > 
> > 	return 0;
> 
> Please give me a couple of days to come up with an idea to use O_EXCL
> on Linux and work around it on other platforms in a more integrated way.

No problem. Thank you!

Felix

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