Re: [PATCH 5/7] xfs: remove XFS_IFBROOT

[Brian Foster <bfoster@redhat.com>]

On Mon, Apr 12, 2021 at 03:38:17PM +0200, Christoph Hellwig wrote:
> Just check for a btree format fork instead of the using the equivalent
> in-memory XFS_IFBROOT flag.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/xfs/libxfs/xfs_bmap.c          | 16 +++++++---------
>  fs/xfs/libxfs/xfs_btree_staging.c |  1 -
>  fs/xfs/libxfs/xfs_inode_fork.c    |  4 +---
>  fs/xfs/libxfs/xfs_inode_fork.h    |  1 -
>  4 files changed, 8 insertions(+), 14 deletions(-)
> 
...
> diff --git a/fs/xfs/libxfs/xfs_btree_staging.c b/fs/xfs/libxfs/xfs_btree_staging.c
> index f464a7c7cf2246..aa8dc9521c3942 100644
> --- a/fs/xfs/libxfs/xfs_btree_staging.c
> +++ b/fs/xfs/libxfs/xfs_btree_staging.c
> @@ -387,7 +387,6 @@ xfs_btree_bload_prep_block(
>  		new_size = bbl->iroot_size(cur, nr_this_block, priv);
>  		ifp->if_broot = kmem_zalloc(new_size, 0);
>  		ifp->if_broot_bytes = (int)new_size;
> -		ifp->if_flags |= XFS_IFBROOT;
>  
>  		/* Initialize it and send it out. */
>  		xfs_btree_init_block_int(cur->bc_mp, ifp->if_broot,

IIRC, these bits are used in xfsprogs for efficient btree repair. Taking
a closer look, I see AG metadata btree repair implementations, but
nothing that seems to use the ifake variant. Am I missing something or
is this code currently unused?

In any event, the comments for xfs_btree_stage_ifakeroot() suggest that
->if_format should be initialized properly when a fake inode fork is
transferred to a cursor and the rest of the patch looks fine to me:

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

> diff --git a/fs/xfs/libxfs/xfs_inode_fork.c b/fs/xfs/libxfs/xfs_inode_fork.c
> index 73eea7939b55e4..02ad722004d3f4 100644
> --- a/fs/xfs/libxfs/xfs_inode_fork.c
> +++ b/fs/xfs/libxfs/xfs_inode_fork.c
> @@ -60,7 +60,7 @@ xfs_init_local_fork(
>  	}
>  
>  	ifp->if_bytes = size;
> -	ifp->if_flags &= ~(XFS_IFEXTENTS | XFS_IFBROOT);
> +	ifp->if_flags &= ~XFS_IFEXTENTS;
>  	ifp->if_flags |= XFS_IFINLINE;
>  }
>  
> @@ -214,7 +214,6 @@ xfs_iformat_btree(
>  	xfs_bmdr_to_bmbt(ip, dfp, XFS_DFORK_SIZE(dip, ip->i_mount, whichfork),
>  			 ifp->if_broot, size);
>  	ifp->if_flags &= ~XFS_IFEXTENTS;
> -	ifp->if_flags |= XFS_IFBROOT;
>  
>  	ifp->if_bytes = 0;
>  	ifp->if_u1.if_root = NULL;
> @@ -433,7 +432,6 @@ xfs_iroot_realloc(
>  			XFS_BMBT_BLOCK_LEN(ip->i_mount));
>  	} else {
>  		new_broot = NULL;
> -		ifp->if_flags &= ~XFS_IFBROOT;
>  	}
>  
>  	/*
> diff --git a/fs/xfs/libxfs/xfs_inode_fork.h b/fs/xfs/libxfs/xfs_inode_fork.h
> index 06682ff49a5bfc..8ffaa7cc1f7c3f 100644
> --- a/fs/xfs/libxfs/xfs_inode_fork.h
> +++ b/fs/xfs/libxfs/xfs_inode_fork.h
> @@ -32,7 +32,6 @@ struct xfs_ifork {
>   */
>  #define	XFS_IFINLINE	0x01	/* Inline data is read in */
>  #define	XFS_IFEXTENTS	0x02	/* All extent pointers are read in */
> -#define	XFS_IFBROOT	0x04	/* i_broot points to the bmap b-tree root */
>  
>  /*
>   * Worst-case increase in the fork extent count when we're adding a single
> -- 
> 2.30.1
>