linux-kernel - Re: [REGRESSION 4.11] Commit d8514d8edb5b ("ovl: copy up regular file using O

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Date:   Thu, 30 Mar 2017 07:53:37 +0200
From:   Ralph Sennhauser <ralph.sennhauser@...il.com>
To:     Richard Weinberger <richard@....at>
Cc:     Amir Goldstein <amir73il@...il.com>,
        Miklos Szeredi <miklos@...redi.hu>,
        linux-unionfs@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-mtd@...ts.infradead.org, regressions@...mhuis.info,
        Artem Bityutskiy <dedekind1@...il.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        David Oberhollenzer <goliath@...ma-star.at>
Subject: Re: [REGRESSION 4.11] Commit d8514d8edb5b ("ovl: copy up regular
 file using O_TMPFILE") breaks ubifs

Hi Richard,

On Thu, 30 Mar 2017 00:15:31 +0200
Richard Weinberger <richard@....at> wrote:

> Ralph,
> 
> Am 29.03.2017 um 23:26 schrieb Ralph Sennhauser:
> >> # create and link a tmpfile - then remove it
> >> sudo rm -rf foo; sudo xfs_io -T -c "flink foo" . ; ls -l foo; sudo
> >> rm foo  
> > 
> > next-20170328, obviously without your patch:
> > 
> >   # xfs_io -T -c "flink foo" .
> >   .: Not supported  
> 
> -T tells xfs_io to create a tmpfile but you have it disabled in UBIFS.

Bash history says I booted the other partition than I flashed (uname
just happened to match), the downside of the dual boot layout. :)

  # rm -rf foo
  # xfs_io -T -c "flink foo" .
  # ls -l foo
  -rw-------    1 root     root             0 Mar 30 02:00 foo
  # rm foo
  [  305.001436] UBIFS error (ubi0:0 pid 2493): ubifs_add_orphan: orphaned twice

However, unlike with the overlay setup the filesystem can be mounted
just fine without imediatly visible side effects.

> 
> Anyway, can you please test the attached patch?
> Amir was right, UBIFS misses a corner case in ubifs_link(). ;-\
> 
> I think I understand also why we never noticed this in xfstests,
> UBIFS prints only a non-fatal error while umounting the filesystem in
> this case. But will test tomorrow in more detail, need some sleep now.
> 
> diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
> index 30825d882aa9..95e348a2da29 100644
> --- a/fs/ubifs/dir.c
> +++ b/fs/ubifs/dir.c
> @@ -748,6 +748,9 @@ static int ubifs_link(struct dentry *old_dentry,
> struct inode *dir, goto out_fname;
> 
>  	lock_2_inodes(dir, inode);
> +	if (inode->i_nlink == 0)
> +		ubifs_delete_orphan(c, inode->i_ino);
> +
>  	inc_nlink(inode);
>  	ihold(inode);
>  	inode->i_ctime = ubifs_current_time(inode);
> 
> Thanks,
> //richard

With this patch I'm no longer able to reproduce _this_ issue, however,
rename no longer works either:

  # mv /etc/config/wireless /etc/config/wireless.back
  mv: can't rename '/etc/config/wireless': Invalid argument
  # ls /etc/config/wireless
  /etc/config/wireless
  # rm /etc/config/wireless
  # ls /etc/config/wireless
  ls: /etc/config/wireless: No such file or directory


Thanks
Ralph