[PATCH 2/2] xfs: expose the current zonegc required status in sysfs

[Niklas Cassel <cassel@kernel.org>]

The current zonegc required status is currently available in
/proc/<pid>/mountstats (which contains stats for all mounted zoned XFS
filesystems), under "RT GC required:".

Add a sysfs attribute /sys/fs/xfs/<dev>/zoned/zonegc_required for the same.
This makes it trivial for monitoring software to read the value, for a
specific filesystem, without any complex parsing.

Signed-off-by: Niklas Cassel <cassel@kernel.org>
---
 Documentation/admin-guide/xfs.rst |  4 ++++
 fs/xfs/xfs_sysfs.c                | 11 +++++++++++
 2 files changed, 15 insertions(+)

diff --git a/Documentation/admin-guide/xfs.rst b/Documentation/admin-guide/xfs.rst
index be0d3f5e8b4c4..87ead41aa86c4 100644
--- a/Documentation/admin-guide/xfs.rst
+++ b/Documentation/admin-guide/xfs.rst
@@ -565,3 +565,7 @@ For zoned file systems, the following attributes are exposed in:
 	bursts at the cost of increased write amplification.  Regardless
 	of this value, garbage collection will always aim to free a minimum
 	amount of blocks to keep max_open_zones open for data placement purposes.
+
+  zonegc_required		(Min:  0  Default:  Varies  Max:  1)
+	This read-only attribute exposes if GC is currently required by the file
+	system.
diff --git a/fs/xfs/xfs_sysfs.c b/fs/xfs/xfs_sysfs.c
index 312bae4cf70fd..1e1ee020df001 100644
--- a/fs/xfs/xfs_sysfs.c
+++ b/fs/xfs/xfs_sysfs.c
@@ -777,11 +777,22 @@ zonegc_low_space_show(
 }
 XFS_SYSFS_ATTR_RW(zonegc_low_space);
 
+static ssize_t
+zonegc_required_show(
+	struct kobject		*kobj,
+	char			*buf)
+{
+	return sysfs_emit(buf, "%d\n",
+			xfs_zoned_need_gc(zoned_to_mp(kobj)));
+}
+XFS_SYSFS_ATTR_RO(zonegc_required);
+
 static struct attribute *xfs_zoned_attrs[] = {
 	ATTR_LIST(max_open_zones),
 	ATTR_LIST(nr_free_zones),
 	ATTR_LIST(nr_open_zones),
 	ATTR_LIST(zonegc_low_space),
+	ATTR_LIST(zonegc_required),
 	NULL,
 };
 ATTRIBUTE_GROUPS(xfs_zoned);
-- 
2.53.0