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

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Date:   Fri, 31 Dec 2021 16:15:04 +0800
From:   zhanchengbin <zhanchengbin1@...wei.com>
To:     Theodore Ts'o <tytso@....edu>
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

To clarify, commit ea4d53b7b9079fd6e2cc34cf569a993a183bfbd2  does
solve the problem for mounting a disk with the same name as file
  system "tmpfs". However, after mounting it, "ln" command (creating
  a hard link) and "resize2fs" command still report an error.

example:
dev_name="/dev/sdc" (ps: a disk in you self)
mkdir /root/tmp
mkdir /root/mnt
mkfs.ext4 -F -b 1024 -E "resize=10000000" "${dev_name}" 32768
mount -t tmpfs "${dev_name}" /root/tmp
mount "${dev_name}" /root/mnt
ln "${dev_name}" "${dev_name}"-ln
resize2fs "${dev_name}"-ln 6G

You can see the disk is mounted on /root/tmp, but it should be
mounted on /root/mnt actually. I will modify the commit message
  and submit the v2 patch to solve this problem.

在 2021/12/22 4:57, Theodore Ts'o 写道:
> 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
> .
>