Christoph Hellwig wrote:
> On Tue, Jan 12, 2016 at 08:59:45PM +0100, Felix Janda wrote:
> > ustat has been used to check whether a device file is mounted.
> > The function is deprecated and not supported by uclibc and musl.
> > Now do the check using the *mntent functions.
> >
> > Based on patch by Natanael Copa <ncopa@xxxxxxxxxxxxxxx>.
> >
> > Signed-off-by: Felix Janda <felix.janda@xxxxxxxxx>
>
> ustat is a lot more efficient in checking for the mountedness
> than this loop, so I'd really prefer not to do this unconditionally.
Is this really performance relevant?
Notice that linux's platform_check_iswritable does something very
similar. I've tried to make it consistent with the version from
freebsd.c.
> As far as Linux is concerned the best thing we could do is to use
> O_EXCL for any open of a device file, as Linux overloadds O_EXCL
> behavior for block devices so that any other O_EXCL open will
> be rejected if one has the file open.
>
> But that might be a major pain to find into the cross platform
> framework..
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;
}
Felix
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