Re: [PATCH v22 16/16] xfs: Add helper function xfs_attr_leaf_addname

Darrick J. Wong
2021-07-28T19:52:28Z

On Mon, Jul 26, 2021 at 11:20:53PM -0700, Allison Henderson wrote:
> This patch adds a helper function xfs_attr_leaf_addname. While this
> does help to break down xfs_attr_set_iter, it does also hoist out some
> of the state management. This patch has been moved to the end of the
> clean up series for further discussion.
>
> Suggested-by: Darrick J. Wong <djwong@kernel.org>
> Signed-off-by: Allison Henderson <allison.henderson@oracle.com>
> Reviewed-by: Darrick J. Wong <djwong@kernel.org>
> ---
> fs/xfs/libxfs/xfs_attr.c | 108 ++++++++++++++++++++++++++---------------------
> fs/xfs/xfs_trace.h | 1 +
> 2 files changed, 61 insertions(+), 48 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> index 811288d..acb995b 100644
> --- a/fs/xfs/libxfs/xfs_attr.c
> +++ b/fs/xfs/libxfs/xfs_attr.c
> @@ -285,6 +285,65 @@ xfs_attr_sf_addname(
> return -EAGAIN;
> }
>
> +STATIC int
> +xfs_attr_leaf_addname(
> + struct xfs_attr_item *attr)
> +{
> + struct xfs_da_args *args = attr->xattri_da_args;
> + struct xfs_buf *leaf_bp = attr->xattri_leaf_bp;
> + struct xfs_inode *dp = args->dp;
> + int error;
> +
> + if (xfs_attr_is_leaf(dp)) {
> + error = xfs_attr_leaf_try_add(args, leaf_bp);
> + if (error == -ENOSPC) {
> + error = xfs_attr3_leaf_to_node(args);
> + if (error)
> + return error;
> +
> + /*
> + * Finish any deferred work items and roll the
> + * transaction once more. The goal here is to call
> + * node_addname with the inode and transaction in the
> + * same state (inode locked and joined, transaction
> + * clean) no matter how we got to this step.
> + *
> + * At this point, we are still in XFS_DAS_UNINIT, but
> + * when we come back, we'll be a node, so we'll fall
> + * down into the node handling code below
> + */
> + trace_xfs_attr_set_iter_return(
> + attr->xattri_dela_state, args->dp);
> + return -EAGAIN;
> + }
> +
> + if (error)
> + return error;
> +
> + attr->xattri_dela_state = XFS_DAS_FOUND_LBLK;

Hmm. I know I reviewed this once before, but on second thought it's a
little strange to be calling the node addname function from the leaf
addname function. Can you reduce the leaf addname function's scope like
this:

STATIC int
xfs_attr_leaf_addname(
struct xfs_attr_item *attr)

struct xfs_da_args *args = attr->xattri_da_args;
struct xfs_buf *leaf_bp = attr->xattri_leaf_bp;
struct xfs_inode *dp = args->dp;
int error;

error = xfs_attr_leaf_try_add(args, leaf_bp);
if (error == 0) {
attr->xattri_dela_state = XFS_DAS_FOUND_LBLK;
trace_xfs_attr_leaf_addname_return(attr->xattri_dela_state,
args->dp);
return -EAGAIN;
}
if (error != -ENOSPC)
return error;

/* No room in leaf; convert to node format and try again. */
error = xfs_attr3_leaf_to_node(args);
if (error)
return error;

/*
* Finish any deferred work items and roll the transaction once
* more. The goal here is to call node_addname with the inode
* and transaction in the same state (inode locked and joined,
* transaction clean) no matter how we got to this step.
*
* At this point, we are still in XFS_DAS_UNINIT, but when we
* come back, we'll be a node, so we'll fall down into the node
* handling code below
*/
trace_xfs_attr_set_iter_return(attr->xattri_dela_state,
args->dp);
return -EAGAIN;
}

Then the callsite up in xfs_attr_set_iter looks like:

case XFS_DAS_UNINIT:
if (xfs_attr_is_shortform(dp))
return xfs_attr_sf_addname(dac, leaf_bp);
if (*leaf_bp != NULL) {
xfs_trans_bhold_release(args->trans, *leaf_bp);
*leaf_bp = NULL;
}

if (xfs_attr_is_leaf(dp))
return xfs_attr_leaf_addname(...);

/* node format */
error = xfs_attr_node_addname_find_attr(attr);
if (error)
return error;

error = xfs_attr_node_addname(attr);
if (error)
return error;

dac->dela_state = XFS_DAS_FOUND_NBLK;
return -EAGAIN;

case XFS_DAS_FOUND_LBLK:

--D

> + } else {
> + error = xfs_attr_node_addname_find_attr(attr);
> + if (error)
> + return error;
> +
> + error = xfs_attr_node_addname(attr);
> + if (error)
> + return error;
> +
> + /*
> + * If addname was successful, and we dont need to alloc or
> + * remove anymore blks, we're done.
> + */
> + if (!args->rmtblkno && !args->rmtblkno2)
> + return 0;
> +
> + attr->xattri_dela_state = XFS_DAS_FOUND_NBLK;
> + }
> +
> + trace_xfs_attr_leaf_addname_return(attr->xattri_dela_state, args->dp);
> + return -EAGAIN;
> +}
> +
> /*
> * Set the attribute specified in @args.
> * This routine is meant to function as a delayed operation, and may return
> @@ -320,55 +379,8 @@ xfs_attr_set_iter(
> *leaf_bp = NULL;
> }
>
> - if (xfs_attr_is_leaf(dp)) {
> - error = xfs_attr_leaf_try_add(args, *leaf_bp);
> - if (error == -ENOSPC) {
> - error = xfs_attr3_leaf_to_node(args);
> - if (error)
> - return error;
> -
> - /*
> - * Finish any deferred work items and roll the
> - * transaction once more. The goal here is to
> - * call node_addname with the inode and
> - * transaction in the same state (inode locked
> - * and joined, transaction clean) no matter how
> - * we got to this step.
> - *
> - * At this point, we are still in
> - * XFS_DAS_UNINIT, but when we come back, we'll
> - * be a node, so we'll fall down into the node
> - * handling code below
> - */
> - trace_xfs_attr_set_iter_return(
> - attr->xattri_dela_state, args->dp);
> - return -EAGAIN;
> - } else if (error) {
> - return error;
> - }
> -
> - attr->xattri_dela_state = XFS_DAS_FOUND_LBLK;
> - } else {
> - error = xfs_attr_node_addname_find_attr(attr);
> - if (error)
> - return error;
> + return xfs_attr_leaf_addname(attr);
>
> - error = xfs_attr_node_addname(attr);
> - if (error)
> - return error;
> -
> - /*
> - * If addname was successful, and we dont need to alloc
> - * or remove anymore blks, we're done.
> - */
> - if (!args->rmtblkno && !args->rmtblkno2)
> - return 0;
> -
> - attr->xattri_dela_state = XFS_DAS_FOUND_NBLK;
> - }
> - trace_xfs_attr_set_iter_return(attr->xattri_dela_state,
> - args->dp);
> - return -EAGAIN;
> case XFS_DAS_FOUND_LBLK:
> /*
> * If there was an out-of-line value, allocate the blocks we
> diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
> index f9840dd..cf8bd3a 100644
> --- a/fs/xfs/xfs_trace.h
> +++ b/fs/xfs/xfs_trace.h
> @@ -4008,6 +4008,7 @@ DEFINE_EVENT(xfs_das_state_class, name, \
> TP_ARGS(das, ip))
> DEFINE_DAS_STATE_EVENT(xfs_attr_sf_addname_return);
> DEFINE_DAS_STATE_EVENT(xfs_attr_set_iter_return);
> +DEFINE_DAS_STATE_EVENT(xfs_attr_leaf_addname_return);
> DEFINE_DAS_STATE_EVENT(xfs_attr_node_addname_return);
> DEFINE_DAS_STATE_EVENT(xfs_attr_remove_iter_return);
> DEFINE_DAS_STATE_EVENT(xfs_attr_rmtval_remove_return);
> --
> 2.7.4
>