linux-ext4 - Re: [PATCH] resize2fs : resize2fs failed due to the same name of tmpfs

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Message-ID: <YcI/xt1IiJKLN/Bw@mit.edu>
Date:   Tue, 21 Dec 2021 15:57:42 -0500
From:   "Theodore Ts'o" <tytso@....edu>
To:     zhanchengbin <zhanchengbin1@...wei.com>
Cc:     linux-ext4@...r.kernel.org, liuzhiqiang26@...wei.com,
        linfeilong@...wei.com
Subject: Re: [PATCH] resize2fs : resize2fs failed due to the same name of
 tmpfs

On Tue, Nov 30, 2021 at 12:04:48PM +0800, zhanchengbin wrote:
> If there is a tmpfs with the same name as the disk, and mount before the
> disk,example:
> 	/dev/sdd /root/tmp tmpfs rw,seclabel,relatime 0 0
> 	/dev/sdd /root/mnt ext4 rw,seclabel,relatime 0 0

This should already be fixed e2fsprogs 1.45.5+ via this commit:

commit ea4d53b7b9079fd6e2cc34cf569a993a183bfbd2
Author: Theodore Ts'o <tytso@....edu>
Date:   Sun Nov 10 12:11:49 2019 -0500

    libext2fs/ismounted.c: check device id in advance to skip false device names
    
    If there is a trickster which tries to use device names as the mount
    device for pseudo-file systems, the resulting /proc/mounts can confuse
    ext2fs_check_mount_point().  (So far as I can tell, there's no good
    reason to do this, but sysadmins do the darnest things.)
    
    An example of this might be the following /proc/mounts excerpt:
    
    /dev/sdb /mnt2 tmpfs rw,relatime 0 0
    /dev/sdb /mnt ext4 rw,relatime 0 0
    
    This is created via "mount -t tmpfs /dev/sdb /mnt2" followed via
    "mount -t ext4 /dev/sdb /mnt".  (Normally, a sane mount of tmpfs would
    use something like "mount -t tmpfs tmpfs /mnt2".)
    
    Fix this by double checking the st_rdev of the claimed mountpoint and
    match it with the dev_t of the device.  (Note that the GNU HURD
    doesn't support st_rdev, so we can't solve this problem for the HURD.)
    
    Reported-by: GuiYao <guiyao@...wei.com>
    Signed-off-by: Theodore Ts'o <tytso@....edu>

I've tested via tst_ismounted and I can't replicate the issue you've described.

% cd /build/e2fsprogs-maint/lib/ext2fs
% make tst_ismounted
% sudo ./tst_ismounted /dev/dm-7
Bogus entry in /proc/mounts!  (/dev/dm-7 is not mounted on /root/tmp)
Device /dev/dm-7 reports flags 11
        /dev/dm-7 is apparently in use.
        /dev/dm-7 is mounted.
        /dev/dm-7 is mounted on /root/mnt.

Cheers,

							- Ted