Re: [PATCH] xfsdump: handle bind mount targets

[Brian Foster <bfoster@redhat.com>]

On Wed, Jan 04, 2017 at 01:42:02PM -0600, Eric Sandeen wrote:
> Today, xfsdump looks at the mount point it was handed, gets
> the inode of that directory, and assumes that it is the
> filesystem's root inode.
> 
> This doesn't work if we have bind-mounted a subdirectory
> somewhere, and point xfsdump at that.  The inode number retrieved
> is not the filesystem's root inode number, and because this
> goes into the dump header and gets checked on restore, things
> go badly when the root inode found in the dump does not match
> the root inode in the dump header:
> 
> # mkfs.xfs -dfile,name=fsfile,size=16g
> # mkdir mnt
> # mount -o loop fsfile mnt
> # mkdir -p mnt/dir
> # mkdir -p mnt2/dir
> # mount -o bind mnt/dir mnt2/dir
> # xfsdump -v trace -J -F -l 0 -  `pwd`/mnt2/dir | xfsdump/restore/xfsrestore -v trace -t - 
> ...
> xfsrestore: tree.c:759: tree_begindir: Assertion `ino != persp->p_rootino || hardh == persp->p_rooth' failed.
> #
> 
> Fix this by using bulkstat to get the first valid inode in the filesystem.
> Compare this to the inode number of the mounted directory, and if they
> differ, issue a notice that this may be a bind mount (which means that
> more than just the tree under the mount will be dumped; the whole
> filesystem is dumped by default).
> 
> Reported-by: Jason L Tibbitts III <tibbs@math.uh.edu>
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
> ---

Reviewed-by: Brian Foster <bfoster@redhat.com>

> 
> This passes xfstests dump group, FWIW, as well as the
> testcase above (which probably should get turned into a test)
> 
> diff --git a/dump/content.c b/dump/content.c
> index 1e86292..5a3c02f 100644
> --- a/dump/content.c
> +++ b/dump/content.c
> @@ -1381,10 +1381,17 @@ baseuuidbypass:
>  	}
>  
>  	/* figure out the ino for the root directory of the fs
> -	 * and get its xfs_bstat_t for inomap_build()
> +	 * and get its xfs_bstat_t for inomap_build().  This could
> +	 * be a bind mount; don't ask for the mount point inode,
> +	 * find the actual lowest inode number in the filesystem.
>  	 */
>  	{
>  		stat64_t rootstat;
> +		xfs_ino_t lastino = 0;
> +		int ocount = 0;
> +		xfs_fsop_bulkreq_t bulkreq;
> +
> +		/* Get the inode of the mount point */
>  		rval = fstat64( sc_fsfd, &rootstat );
>  		if ( rval ) {
>  			mlog( MLOG_NORMAL, _(
> @@ -1396,11 +1403,21 @@ baseuuidbypass:
>  			( xfs_bstat_t * )calloc( 1, sizeof( xfs_bstat_t ));
>  		assert( sc_rootxfsstatp );
>  
> -		if ( bigstat_one( sc_fsfd, rootstat.st_ino, sc_rootxfsstatp) < 0 ) {
> +		/* Get the first valid (i.e. root) inode in this fs */
> +		bulkreq.lastip = (__u64 *)&lastino;
> +		bulkreq.icount = 1;
> +		bulkreq.ubuffer = sc_rootxfsstatp;
> +		bulkreq.ocount = &ocount;
> +		if (ioctl(sc_fsfd, XFS_IOC_FSBULKSTAT, &bulkreq) < 0) {
>  			mlog( MLOG_ERROR,
>  			      _("failed to get bulkstat information for root inode\n"));
>  			return BOOL_FALSE;
>  		}
> +
> +		if (sc_rootxfsstatp->bs_ino != rootstat.st_ino)
> +			mlog ( MLOG_NORMAL | MLOG_NOTE,
> +			       _("root ino %lld differs from mount dir ino %lld, bind mount?\n"),
> +			         sc_rootxfsstatp->bs_ino, rootstat.st_ino);
>  	}
>  	
>  	/* alloc a file system handle, to be used with the jdm_open()
> 
> 
> 
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