xfs: export zone stats in /proc/*/mountstats

Add the per-zone life time hint and the used block distribution
for fully written zones, grouping reclaimable zones in fixed-percentage
buckets spanning 0..9%, 10..19% and full zones as 100% used as well as a
few statistics about the zone allocator and open and reclaimable zones
in /proc/*/mountstats.

This gives good insight into data fragmentation and data placement
success rate.

Signed-off-by: Hans Holmberg <hans.holmberg@wdc.com>
Co-developed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

Author: yhr

fs/xfs/Makefile

@@ -140,6 +140,7 @@ xfs-$(CONFIG_XFS_QUOTA)		+= xfs_dquot.o \
 xfs-$(CONFIG_XFS_RT)		+= xfs_rtalloc.o \
 				   xfs_zone_alloc.o \
 				   xfs_zone_gc.o \
+				   xfs_zone_info.o \
 				   xfs_zone_space_resv.o
 
 xfs-$(CONFIG_XFS_POSIX_ACL)	+= xfs_acl.o

fs/xfs/xfs_super.c

@@ -1263,6 +1263,10 @@ xfs_fs_show_stats(
 	struct seq_file		*m,
 	struct dentry		*root)
 {
+	struct xfs_mount	*mp = XFS_M(root->d_sb);
+
+	if (xfs_has_zoned(mp) && IS_ENABLED(CONFIG_XFS_RT))
+		xfs_zoned_show_stats(m, mp);
 	return 0;
 }
 

fs/xfs/xfs_zone_alloc.h

@@ -44,6 +44,7 @@ void xfs_mark_rtg_boundary(struct iomap_ioend *ioend);
 
 uint64_t xfs_zoned_default_resblks(struct xfs_mount *mp,
 		enum xfs_free_counter ctr);
+void xfs_zoned_show_stats(struct seq_file *m, struct xfs_mount *mp);
 
 #ifdef CONFIG_XFS_RT
 int xfs_mount_zones(struct xfs_mount *mp);

fs/xfs/xfs_zone_info.c

@@ -0,0 +1,105 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2023-2025 Christoph Hellwig.
+ * Copyright (c) 2024-2025, Western Digital Corporation or its affiliates.
+ */
+#include "xfs.h"
+#include "xfs_shared.h"
+#include "xfs_format.h"
+#include "xfs_trans_resv.h"
+#include "xfs_mount.h"
+#include "xfs_inode.h"
+#include "xfs_rtgroup.h"
+#include "xfs_zone_alloc.h"
+#include "xfs_zone_priv.h"
+
+static const char xfs_write_hint_shorthand[6][16] = {
+	"NOT_SET", "NONE", "SHORT", "MEDIUM", "LONG", "EXTREME"};
+
+static inline const char *
+xfs_write_hint_to_str(
+	uint8_t			write_hint)
+{
+	if (write_hint > WRITE_LIFE_EXTREME)
+		return "UNKNOWN";
+	return xfs_write_hint_shorthand[write_hint];
+}
+
+static void
+xfs_show_open_zone(
+	struct seq_file		*m,
+	struct xfs_open_zone	*oz)
+{
+	seq_printf(m, "\t  zone %d, wp %u, written %u, used %u, hint %s\n",
+		rtg_rgno(oz->oz_rtg),
+		oz->oz_write_pointer, oz->oz_written,
+		rtg_rmap(oz->oz_rtg)->i_used_blocks,
+		xfs_write_hint_to_str(oz->oz_write_hint));
+}
+
+static void
+xfs_show_full_zone_used_distribution(
+	struct seq_file         *m,
+	struct xfs_mount        *mp)
+{
+	struct xfs_zone_info	*zi = mp->m_zone_info;
+	unsigned int		reclaimable = 0, full, i;
+
+	spin_lock(&zi->zi_used_buckets_lock);
+	for (i = 0; i < XFS_ZONE_USED_BUCKETS; i++) {
+		unsigned int entries = zi->zi_used_bucket_entries[i];
+
+		seq_printf(m, "\t  %2u..%2u%%: %u\n",
+				i * (100 / XFS_ZONE_USED_BUCKETS),
+				(i + 1) * (100 / XFS_ZONE_USED_BUCKETS) - 1,
+				entries);
+		reclaimable += entries;
+	}
+	spin_unlock(&zi->zi_used_buckets_lock);
+
+	full = mp->m_sb.sb_rgcount;
+	if (zi->zi_open_gc_zone)
+		full--;
+	full -= zi->zi_nr_open_zones;
+	full -= atomic_read(&zi->zi_nr_free_zones);
+	full -= reclaimable;
+
+	seq_printf(m, "\t     100%%: %u\n", full);
+}
+
+void
+xfs_zoned_show_stats(
+	struct seq_file		*m,
+	struct xfs_mount	*mp)
+{
+	struct xfs_zone_info	*zi = mp->m_zone_info;
+	struct xfs_open_zone	*oz;
+
+	seq_puts(m, "\n");
+
+	seq_printf(m, "\tuser free RT blocks: %lld\n",
+		xfs_sum_freecounter(mp, XC_FREE_RTEXTENTS));
+	seq_printf(m, "\treserved free RT blocks: %lld\n",
+		mp->m_free[XC_FREE_RTEXTENTS].res_avail);
+	seq_printf(m, "\tuser available RT blocks: %lld\n",
+		xfs_sum_freecounter(mp, XC_FREE_RTAVAILABLE));
+	seq_printf(m, "\treserved available RT blocks: %lld\n",
+		mp->m_free[XC_FREE_RTAVAILABLE].res_avail);
+	seq_printf(m, "\tRT reservations required: %d\n",
+		!list_empty_careful(&zi->zi_reclaim_reservations));
+	seq_printf(m, "\tRT GC required: %d\n",
+		xfs_zoned_need_gc(mp));
+
+	seq_printf(m, "\tfree zones: %d\n", atomic_read(&zi->zi_nr_free_zones));
+	seq_puts(m, "\topen zones:\n");
+	spin_lock(&zi->zi_open_zones_lock);
+	list_for_each_entry(oz, &zi->zi_open_zones, oz_entry)
+		xfs_show_open_zone(m, oz);
+	if (zi->zi_open_gc_zone) {
+		seq_puts(m, "\topen gc zone:\n");
+		xfs_show_open_zone(m, zi->zi_open_gc_zone);
+	}
+	spin_unlock(&zi->zi_open_zones_lock);
+	seq_puts(m, "\tused blocks distribution (fully written zones):\n");
+	xfs_show_full_zone_used_distribution(m, mp);
+}