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[debbugs-tracker] bug#21372: closed (df prioritizes some bind mounts ove


From: GNU bug Tracking System
Subject: [debbugs-tracker] bug#21372: closed (df prioritizes some bind mounts over real ones.)
Date: Mon, 21 Sep 2015 22:45:04 +0000

Your message dated Mon, 21 Sep 2015 23:44:53 +0100
with message-id <address@hidden>
and subject line Re: bug#21372: [PATCH v4] df: fix prioritize real mounts over 
bind mounts
has caused the debbugs.gnu.org bug report #21372,
regarding df prioritizes some bind mounts over real ones.
to be marked as done.

(If you believe you have received this mail in error, please contact
address@hidden)


-- 
21372: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=21372
GNU Bug Tracking System
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--- Begin Message --- Subject: df prioritizes some bind mounts over real ones. Date: Fri, 28 Aug 2015 15:42:44 -0500
With the recent move to /proc/self/mountinfo `df` now returns bind mounts
instead of the original mount when the directory being bound to is shorter than
the original mount destination.

For example:
 * $ mount
<snip>
192.168.1.2:/raid on /raid type nfs
/dev/sdc5 on /data type ext4 (rw)
<snip>

$ mount -o bind /data/a on /a type none (rw,bind)
$ mount -o bind /raid/temp on /b type none (rw,bind)

$df
Filesystem 1K-blocks Used Available Use% Mounted on
<snip>
192.168.1.2:/raid 449830616 229975284 196982196 54% /a
/dev/sdc5 7752072192 5581343744 1780023296 76% /b
</snip>

I'd expect to see the original mount prioritized over the bind mount. Like so.
$ df
Filesystem 1K-blocks Used Available Use% Mounted on
<snip>
/dev/sdc5 449830616 229975284 196982196 54% /data
192.168.1.2:/raid 7752072192 5581438976 1779929088 76% /raid
<snip>

This is both mildly incorrect and misleading.  As the source device in both
cases isn't exactly what is being mounted at the destination directory.
Instead it is a subdir of the filesystem that is being mounted there.

I'm submitting patches to both gnulib and coreutils to correct this issue.

Thank you,
Dave Chiluk




--- End Message ---
--- Begin Message --- Subject: Re: bug#21372: [PATCH v4] df: fix prioritize real mounts over bind mounts Date: Mon, 21 Sep 2015 23:44:53 +0100 User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0
On 21/09/15 21:04, Dave Chiluk wrote:
> Fixes an issue where bind mounts with shorter mount directories than the
> original mount are prioritized when running df.  The root cause of this
> is that /proc/self/mountinfo now lists the filesystem device with bind
> mounts rather than the source directory. With /etc/mtab the source
> device was listed as the originating directory so this was not an issue.
> 
> More information is available here.
> https://bugs.launchpad.net/ubuntu/+source/coreutils/+bug/1432871
> ---
>  src/df.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/src/df.c b/src/df.c
> index 2e541b9..4a3afa2 100644
> --- a/src/df.c
> +++ b/src/df.c
> @@ -652,9 +652,14 @@ filter_mount_list (bool devices_only)
>                else if ((strchr (me->me_devname, '/')
>                         /* let "real" devices with '/' in the name win.  */
>                          && ! strchr (devlist->me->me_devname, '/'))
> -                       /* let a shorter mountdir win.  */
> -                       || (strlen (devlist->me->me_mountdir)
> +                       /* let a shorter mountdir win. If it's mntroot is */
> +                       /* also shorter. i.e. not a bind mount. */
> +                       || ((strlen (devlist->me->me_mountdir)
>                             > strlen (me->me_mountdir))
> +                          && (devlist->me->me_mntroot == NULL
> +                             || me->me_mntroot == NULL
> +                             || (strlen (devlist->me->me_mntroot)
> +                                 >= strlen(me->me_mntroot))))
>                         /* let an entry overmounted on a new device win...  */
>                         || (! STREQ (devlist->me->me_devname, me->me_devname)
>                             /* ... but only when matching an existing mnt 
> point,
> 

This logic looks correct thanks.
I'll adjust the comment a bit and maybe refactor
all the conditions to a single nearer_device_root boolean.

I'll push this later on,
with the associated gnulib update.

thanks,
Pádraig.


--- End Message ---

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