[PATCH v9 08/29] libmultipath: Add sysfs helpers

[sashiko-bot at kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Low] libmultipath: duplicate parser and ambiguous return in
  mpath_iopolicy_store()
--

commit 12aacc0c8ac98ed4ae873a73979622db40d4f52b
Author: John Garry <john.garry at linux.dev>

libmultipath: Add sysfs helpers

This commit adds sysfs helpers and attribute group definitions for showing
and updating the multipath I/O policy and displaying per-NUMA-node device
paths.

> diff --git a/lib/multipath.c b/lib/multipath.c
> index cdf8fbc5105b3..ae5a73d570b33 100644
> --- a/lib/multipath.c
> +++ b/lib/multipath.c
> @@ -620,6 +620,100 @@ void mpath_device_set_live(struct mpath_device *mpath_device)

[ ... ]

> +static void mpath_iopolicy_update(enum mpath_iopolicy_e *iopolicy,
> +		int new)
> +{
> +	int old = READ_ONCE(*iopolicy);
> +
> +	if (old == new)
> +		return;
> +
> +	WRITE_ONCE(*iopolicy, new);
> +
> +	pr_info("iopolicy changed from %s to %s\n",
> +		mpath_iopolicy_names[old],
> +		mpath_iopolicy_names[new]);
> +}
> +
> +bool mpath_iopolicy_store(enum mpath_iopolicy_e *iopolicy, const char *buf)
> +{
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(mpath_iopolicy_names); i++) {
> +		if (sysfs_streq(buf, mpath_iopolicy_names[i])) {
> +			mpath_iopolicy_update(iopolicy, i);
> +			return true;
> +		}
> +	}
> +
> +	return false;
> +}
> +EXPORT_SYMBOL_GPL(mpath_iopolicy_store);

[Severity: Low]
Can mpath_iopolicy_store() reuse mpath_iopolicy_parse(), and how can callers
tell whether the policy actually changed?

lib/multipath.c already defines mpath_iopolicy_parse() using
__sysfs_match_string() to match against mpath_iopolicy_names[].  Also,
because mpath_iopolicy_store() returns a bool that is true for any valid
policy name even when old == new in mpath_iopolicy_update(), a sysfs store
caller cannot both reject invalid strings with -EINVAL and avoid clearing
cached paths and flushing requeue_work when the existing policy is written
again.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261108204733.557995-1-john.garry@linux.dev?part=8