On Tue, Mar 17, 2015 at 06:14:00PM +0100, Ruediger Meier wrote:
> On Tuesday 17 March 2015, Karel Zak wrote:
> > On Tue, Mar 17, 2015 at 04:08:58PM +0100, Ruediger Meier wrote:
> > > Hi,
> > >
> > > I wonder what is the correct way to find a mount which is mounted
> > > to a certain target directory. findmnt --target will also find a
> > > mount if you specify a subdirectory of a mountpoint:
> > >
> > > $ mkdir /tmp/bla
> > > $ findmnt --target /tmp/bla
> > > TARGET SOURCE FSTYPE OPTIONS
> > > /tmp /dev/mapper/vg0-tmpdirs[/tmp] ext4 ....
> > >
> > > The man page let me think that --target should not find the parent
> > > directory.
> >
> > No, it's expected behavior since:
> >
> > commit b215d8e9a71ca8d22df6111ddc9d28bd896febb1
> > Author: Dave Reisner <dreisner@xxxxxxxxxxxxx>
> > Date: Wed Apr 25 20:30:52 2012 -0400
>
> Ok, but this was a regression for a common use case. I guess to late to
> revert. Even you liked this old behavior:
Well, the common use-case is to not use --target :-) But I agree that
the feature is questionable. The mistake is that the original (non-df)
behavior has not been covered by test.
> commit 1f42e1089aadbe537bb59143502ebd1767d3f7ea
> Author: Karel Zak <kzak@xxxxxxxxxx>
> Date: Sun Jan 2 22:56:31 2011 +0100
>
> tests: use findmnt(8) for mount --move test
>
>
> > and the current git tree contains:
> >
> > -T, --target path
> > Explicitly define the mount target (mountpoint
> > directory). If the path is not a mountpoint file
> > or directory than findmnt checks path elements in
> > reverse order for get the mountpoint (this
> > feature is supported only if search in kernel
> > files and unsupported for --fstab).
>
> Ah ok, but IMO because of this regression we should make it even more
> clear. Probably the first sentence should not contain "mount target"
> and "mountpoint" without also using the term "parent directory" or
> similar.
>
> I think for df(1) it's written nicely:
>
> df [OPTION]... [FILE]...
> Show information about the file system on which each FILE resides, or
> all file systems by default.
OK.
> > > $TS_CMD_MOUNT --move $DIR_A $DIR_B
> > >
> > > # check the move
> > > $TS_CMD_FINDMNT --kernel --target "$DIR_B" &> /dev/null
> > > [ "$?" == "0" ] || ts_die "Cannot find binded $DIR_B"
> > > [...]
> > >
> > > This findmnt line will never fail I guess.
> >
> > Right, this is mistake, solution is to remove --target:
> >
> > TS_CMD_FINDMNT --kernel "$DIR_B" &> /dev/null
>
> >
> > The disadvantage is that without --source/target findmnt(8) tries
> > to use the path as source and then as target. It's bad in same cases.
> >
> > Maybe we need a new option to disable the evaluation of the target
> > path elements. (--strict-target)
>
> What about "findmnt --target /bla/xyz --no-parents" instead
> of --strict-target?
No problem.
> I have to admint that I don't really like the current behavior
> of --target and the default case without --source/target. Of course we
> can't change it anymore.
Yes, after 3 years it's better to keep the current behavior and
provide an option to disable the "smart" target evaluation. Do you
want to send a patch? (or I can do that tomorrow.)
Karel
--
Karel Zak <kzak@xxxxxxxxxx>
http://karelzak.blogspot.com
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