1 From: Pádraig Brady <[email protected]>

     2 Date: Mon, 18 Aug 2014 16:59:26 +0000 (+0100)

     3 Subject: df: improve mount point selection with inaccurate mount list

     4 X-Git-Url: http://git.savannah.gnu.org/gitweb/?p=coreutils.git;a=commitdiff_plain;h=ed1a495b

     5 

     6 df: improve mount point selection with inaccurate mount list

     7 

     8 v8.23 has a test failure on Fedora rawhide build servers

     9 in tests/df/skip-duplicate.sh.  This was due to no '/'

    10 entry being output by df.  That was due to an inaccurate

    11 /proc/mounts on the build environment as stat(/mnt/point)

    12 identified all these /proc/mounts entries as having the

    13 same device id:

    14 

    15   /                    rootfs

    16   /                    /dev/md1

    17   /dev                 devtmpfs

    18   /run                 tmpfs

    19   /boot                /dev/md0

    20   /proc/filesystems    /dev/md1

    21 

    22 Since the device name on the right changes for a given id,

    23 that causes the entries to be continually replaced, thus

    24 resulting in no '/' entry.  I'm guessing this is due to

    25 the mock environment bind mounting unneeded or sensitive

    26 items to a dummy file on the host / (/dev/md1) though

    27 have not looked into those details.

    28 

    29 So rather than relying on an accurate /proc/mounts,

    30 the attached patch takes a more conservative replacement

    31 approach and only swaps a new device entry when the

    32 mount point matches.  That should handle all practical

    33 cases while also avoiding this situation.

    34 

    35 * src/df.c (filter_mount_list): Only replace entries with

    36 different device names when the mount point also matches.

    37 ---

    38 

    39 diff --git a/src/df.c b/src/df.c

    40 index 3ef5d33..e907b94 100644

    41 --- src/df.c

    42 +++ src/df.c

    43 @@ -640,13 +640,18 @@ filter_mount_list (bool devices_only)

    44  

    45            if (devlist)

    46              {

    47 -              /* ...let the shorter mountdir win.  */

    48 +                  /* let "real" devices with '/' in the name win.  */

    49                if ((strchr (me->me_devname, '/')

    50                     && ! strchr (devlist->me->me_devname, '/'))

    51 +                  /* let a shorter mountdir win.  */

    52                    || (strlen (devlist->me->me_mountdir)

    53                        > strlen (me->me_mountdir))

    54 -                  /* or one overmounted on a different device.  */

    55 -                  || ! STREQ (devlist->me->me_devname, me->me_devname))

    56 +                  /* let an entry overmounted on a different device win...  */

    57 +                  || (! STREQ (devlist->me->me_devname, me->me_devname)

    58 +                      /* ... but only when matching an exsiting mount point, to

    59 +                      avoid problematic replacement when given inaccurate mount

    60 +                      lists, seen with some chroot environments for example.  */

    61 +                      && STREQ (me->me_mountdir, devlist->me->me_mountdir)))

    62                  {

    63                    /* Discard mount entry for existing device.  */

    64                    discard_me = devlist->me;