Re: mnt_count accounting broken

From: Alexander Viro (viro@math.psu.edu)
Date: Fri May 05 2000 - 13:02:26 EDT

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    On Fri, 5 May 2000, Tigran Aivazian wrote:

    > Hi,
    >
    > Ok, here is the promised "consistent reproducible picture" and, btw,
    > the "-o noatime" observation seemed to be bogus (i.e. some small changes
    > I made distorted the picture). Below is a session with a clean
    > 2.3.99-pre7-5 (with a tiny debug patch below):
    >
    > # mount -t ramfs none /mnt/m3
    > # cd /mnt/m3
    > # touch new
    > # l
    > total 0
    > -rw-r--r-- 1 root root 0 May 5 17:33 new
    > # cd
    > # umount /mnt/m3
    > C: count!=2 (3)
    > umount: /mnt/m3: device is busy

    ACK. It's not ->mnt_count, it's an extra dentry reference that holds the
    ramfs objects in dcache. Solution:
            ramfs_umount_begin() that would do equivalent of rm -rf.
    With the changes I'm doing right now we will catch busy filesystems
    without dentry scan, thus we are safe here.
            Linus, are you OK with such variant?
                                                            Cheers,
                                                                    Al

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