Re: [PATCH 7/8] xfs_repair: bump the irec on-disk nlink when adding lost+found

[Bill O'Donnell <billodo@redhat.com>]

On Wed, Dec 19, 2018 at 11:30:17AM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> We increment the nlink of the root directory inode when creating a
> "lost+found" directory during phase 6, but we don't update the irec copy
> of the root dir nlink.  This normally gets papered over by phase 7, but
> this can fail badly if:
> 
> 1) The root directory had an entry to a busted subdirectory, so
>    that root directory will have nlink == 3, but in the ino_tree,
>    counted_nlinks == 2 and disk_nlinks == 3.
> 
> 2) Phase 6 creates lost+found to root the files that were in the busted
>    directory, we'll set nlink = 4 and counted_nlinks = 3.  The correct
>    nlink is 3 ('.', '..', 'lost+found'), not 4.
> 
> 3) During phase 7, we see that counted_nlinks == disk_nlinks and so we
>    totally fail to correct the on-disk inode.
> 
> 4) A subsequent run of xfs_repair complains about the nlink being 4
>    instead of 3.
> 
> To fix this, we have to adjust the irec's disk_nlinks in step 2 so that
> phase 7 seeds that counted_nlinks < disk_nlinks and resets nlink to
> counted_nlinks.  This can be reproduced somewhat frequently by xfs/117.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---

Makes sense.
Reviewed-by: Bill O'Donnell <billodo@redhat.com>

>  repair/phase6.c |   14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
> 
> 
> diff --git a/repair/phase6.c b/repair/phase6.c
> index 8a50b350..194cfdbf 100644
> --- a/repair/phase6.c
> +++ b/repair/phase6.c
> @@ -1019,6 +1019,7 @@ mk_orphanage(xfs_mount_t *mp)
>  	 */
>  	set_inode_used(irec, ino_offset);
>  	add_inode_ref(irec, ino_offset);
> +	add_inode_reached(irec, ino_offset);
>  
>  	/*
>  	 * now that we know the transaction will stay around,
> @@ -1037,14 +1038,14 @@ mk_orphanage(xfs_mount_t *mp)
>  
>  	/*
>  	 * bump up the link count in the root directory to account
> -	 * for .. in the new directory
> +	 * for .. in the new directory, and update the irec copy of the
> +	 * on-disk nlink so we don't fail the link count check later.
>  	 */
>  	inc_nlink(VFS_I(pip));
> -	add_inode_ref(find_inode_rec(mp,
> -				XFS_INO_TO_AGNO(mp, mp->m_sb.sb_rootino),
> -				XFS_INO_TO_AGINO(mp, mp->m_sb.sb_rootino)), 0);
> -
> -
> +	irec = find_inode_rec(mp, XFS_INO_TO_AGNO(mp, mp->m_sb.sb_rootino),
> +				  XFS_INO_TO_AGINO(mp, mp->m_sb.sb_rootino));
> +	add_inode_ref(irec, 0);
> +	set_inode_disk_nlinks(irec, 0, get_inode_disk_nlinks(irec, 0) + 1);
>  
>  	libxfs_trans_log_inode(tp, pip, XFS_ILOG_CORE);
>  	libxfs_dir_init(tp, ip, pip);
> @@ -1056,7 +1057,6 @@ mk_orphanage(xfs_mount_t *mp)
>  	}
>  	libxfs_irele(ip);
>  	libxfs_irele(pip);
> -	add_inode_reached(irec,ino_offset);
>  
>  	return(ino);
>  }
>