Re: [PATCH v3 1/4] xfs: track active state of allocation btree cursors

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Thu, Aug 15, 2019 at 08:55:35AM -0400, Brian Foster wrote:
> The upcoming allocation algorithm update searches multiple
> allocation btree cursors concurrently. As such, it requires an
> active state to track when a particular cursor should continue
> searching. While active state will be modified based on higher level
> logic, we can define base functionality based on the result of
> allocation btree lookups.
> 
> Define an active flag in the private area of the btree cursor.
> Update it based on the result of lookups in the existing allocation
> btree helpers. Finally, provide a new helper to query the current
> state.
> 
> Signed-off-by: Brian Foster <bfoster@redhat.com>
> ---
>  fs/xfs/libxfs/xfs_alloc.c       | 24 +++++++++++++++++++++---
>  fs/xfs/libxfs/xfs_alloc_btree.c |  1 +
>  fs/xfs/libxfs/xfs_btree.h       |  3 +++
>  3 files changed, 25 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
> index 372ad55631fc..6340f59ac3f4 100644
> --- a/fs/xfs/libxfs/xfs_alloc.c
> +++ b/fs/xfs/libxfs/xfs_alloc.c
> @@ -146,9 +146,13 @@ xfs_alloc_lookup_eq(
>  	xfs_extlen_t		len,	/* length of extent */
>  	int			*stat)	/* success/failure */
>  {
> +	int			error;
> +
>  	cur->bc_rec.a.ar_startblock = bno;
>  	cur->bc_rec.a.ar_blockcount = len;
> -	return xfs_btree_lookup(cur, XFS_LOOKUP_EQ, stat);
> +	error = xfs_btree_lookup(cur, XFS_LOOKUP_EQ, stat);
> +	cur->bc_private.a.priv.abt.active = *stat;

<urk> Not really a fan of mixing types (even if they are bool and int),
how hard would it be to convert some of these *stat to bool?

Does abt.active have a use outside of the struct xfs_alloc_cur in the
next patch?

--D

> +	return error;
>  }
>  
>  /*
> @@ -162,9 +166,13 @@ xfs_alloc_lookup_ge(
>  	xfs_extlen_t		len,	/* length of extent */
>  	int			*stat)	/* success/failure */
>  {
> +	int			error;
> +
>  	cur->bc_rec.a.ar_startblock = bno;
>  	cur->bc_rec.a.ar_blockcount = len;
> -	return xfs_btree_lookup(cur, XFS_LOOKUP_GE, stat);
> +	error = xfs_btree_lookup(cur, XFS_LOOKUP_GE, stat);
> +	cur->bc_private.a.priv.abt.active = *stat;
> +	return error;
>  }
>  
>  /*
> @@ -178,9 +186,19 @@ xfs_alloc_lookup_le(
>  	xfs_extlen_t		len,	/* length of extent */
>  	int			*stat)	/* success/failure */
>  {
> +	int			error;
>  	cur->bc_rec.a.ar_startblock = bno;
>  	cur->bc_rec.a.ar_blockcount = len;
> -	return xfs_btree_lookup(cur, XFS_LOOKUP_LE, stat);
> +	error = xfs_btree_lookup(cur, XFS_LOOKUP_LE, stat);
> +	cur->bc_private.a.priv.abt.active = *stat;
> +	return error;
> +}
> +
> +static inline bool
> +xfs_alloc_cur_active(
> +	struct xfs_btree_cur	*cur)
> +{
> +	return cur && cur->bc_private.a.priv.abt.active;
>  }
>  
>  /*
> diff --git a/fs/xfs/libxfs/xfs_alloc_btree.c b/fs/xfs/libxfs/xfs_alloc_btree.c
> index 2a94543857a1..279694d73e4e 100644
> --- a/fs/xfs/libxfs/xfs_alloc_btree.c
> +++ b/fs/xfs/libxfs/xfs_alloc_btree.c
> @@ -507,6 +507,7 @@ xfs_allocbt_init_cursor(
>  
>  	cur->bc_private.a.agbp = agbp;
>  	cur->bc_private.a.agno = agno;
> +	cur->bc_private.a.priv.abt.active = false;
>  
>  	if (xfs_sb_version_hascrc(&mp->m_sb))
>  		cur->bc_flags |= XFS_BTREE_CRC_BLOCKS;
> diff --git a/fs/xfs/libxfs/xfs_btree.h b/fs/xfs/libxfs/xfs_btree.h
> index fa3cd8ab9aba..a66063c356cc 100644
> --- a/fs/xfs/libxfs/xfs_btree.h
> +++ b/fs/xfs/libxfs/xfs_btree.h
> @@ -183,6 +183,9 @@ union xfs_btree_cur_private {
>  		unsigned long	nr_ops;		/* # record updates */
>  		int		shape_changes;	/* # of extent splits */
>  	} refc;
> +	struct {
> +		bool		active;		/* allocation cursor state */
> +	} abt;
>  };
>  
>  /*
> -- 
> 2.20.1
>