Re: [PATCH 06/21] xfs: Add xfs_attr_set_deferred and xfs_attr_remove_deferred

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

On Sun, May 06, 2018 at 10:24:39AM -0700, Allison Henderson wrote:
> These routines set up set and start a new deferred attribute
> operation.  These functions are meant to be called by other
> code needing to initiate a deferred attribute operation.  We
> will use these routines later in the parent pointer patches.
> 
> Signed-off-by: Allison Henderson <allison.henderson@oracle.com>
> ---
>  fs/xfs/libxfs/xfs_attr.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++++
>  fs/xfs/libxfs/xfs_attr.h |  5 ++++
>  2 files changed, 74 insertions(+)
> 
> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> index 2f295ca..adbcef2 100644
> --- a/fs/xfs/libxfs/xfs_attr.c
> +++ b/fs/xfs/libxfs/xfs_attr.c
> @@ -468,6 +468,42 @@ xfs_attr_set(
>  	return error;
>  }
>  
> +/* Sets an attribute for an inode as a deferred operation */
> +int
> +xfs_attr_set_deferred(
> +	struct xfs_inode	*dp,
> +	struct xfs_defer_ops    *dfops,
> +	void			*name,
> +	unsigned int		namelen,
> +	void			*value,
> +	unsigned int		valuelen,
> +	int			flags)
> +{
> +
> +	struct xfs_attr_item	*new;
> +	char			*name_value;
> +
> +	if (!namelen || !valuelen) {
> +		ASSERT(0);
> +		return -EFSCORRUPTED;
> +	}
> +
> +	new = kmem_alloc(XFS_ATTR_ITEM_SIZEOF(namelen, valuelen),
> +			 KM_SLEEP|KM_NOFS);
> +	name_value = ((char *)new) + sizeof(struct xfs_attr_item);
> +	memset(new, 0, XFS_ATTR_ITEM_SIZEOF(namelen, valuelen));
> +	new->xattri_ip = dp;
> +	new->xattri_op_flags = XFS_ATTR_OP_FLAGS_SET;
> +	new->xattri_name_len = namelen;
> +	new->xattri_value_len = valuelen;
> +	new->xattri_flags = flags;
> +	memcpy(&name_value[0], name, namelen);
> +	memcpy(&name_value[namelen], value, valuelen);

If we're going to keep the inode locked across _defer_finish rolls then
we need to xfs_defer_ijoin the inode to the dfops so that the inode is
relogged in each transaction, which prevents the log tail from being
pinned unnecessarily.  xfs_bmap.c does a similar thing with the deferred
map/unmap intents.

> +
> +	xfs_defer_add(dfops, XFS_DEFER_OPS_TYPE_ATTR, &new->xattri_list);
> +
> +	return 0;
> +}
>  
>  /*
>   * Generic handler routine to remove a name from an attribute list.
> @@ -560,6 +596,39 @@ xfs_attr_remove(
>  	return error;
>  }
>  
> +/* Removes an attribute for an inode as a deferred operation */
> +int
> +xfs_attr_remove_deferred(
> +	struct xfs_inode        *dp,
> +	struct xfs_defer_ops    *dfops,
> +	void			*name,
> +	unsigned int		namelen,
> +	int                     flags)
> +{
> +
> +	struct xfs_attr_item	*new;
> +	char			*name_value;
> +
> +	if (!namelen) {
> +		ASSERT(0);
> +		return -EFSCORRUPTED;
> +	}
> +
> +	new = kmem_alloc(XFS_ATTR_ITEM_SIZEOF(namelen, 0), KM_SLEEP|KM_NOFS);
> +	name_value = ((char *)new) + sizeof(struct xfs_attr_item);
> +	memset(new, 0, XFS_ATTR_ITEM_SIZEOF(namelen, 0));
> +	new->xattri_ip = dp;
> +	new->xattri_op_flags = XFS_ATTR_OP_FLAGS_REMOVE;
> +	new->xattri_name_len = namelen;
> +	new->xattri_value_len = 0;
> +	new->xattri_flags = flags;
> +	memcpy(name_value, name, namelen);

Same here.

--D

> +	xfs_defer_add(dfops, XFS_DEFER_OPS_TYPE_ATTR, &new->xattri_list);
> +
> +	return 0;
> +}
> +
>  /*========================================================================
>   * External routines when attribute list is inside the inode
>   *========================================================================*/
> diff --git a/fs/xfs/libxfs/xfs_attr.h b/fs/xfs/libxfs/xfs_attr.h
> index 33b33d3..ec26565 100644
> --- a/fs/xfs/libxfs/xfs_attr.h
> +++ b/fs/xfs/libxfs/xfs_attr.h
> @@ -183,5 +183,10 @@ int xfs_attr_list(struct xfs_inode *dp, char *buffer, int bufsize,
>  int xfs_attr_args_init(struct xfs_da_args *args, struct xfs_inode *dp,
>  		       const unsigned char *name, int flags);
>  int xfs_attr_calc_size(struct xfs_da_args *args, int *local);
> +int xfs_attr_set_deferred(struct xfs_inode *dp, struct xfs_defer_ops *dfops,
> +			  void *name, unsigned int name_len, void *value,
> +			  unsigned int valuelen, int flags);
> +int xfs_attr_remove_deferred(struct xfs_inode *dp, struct xfs_defer_ops *dfops,
> +			    void *name, unsigned int namelen, int flags);
>  
>  #endif	/* __XFS_ATTR_H__ */
> -- 
> 2.7.4
> 
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