[15/26] xfs: create a per-mount shrinker for verity inodes merkle tree blocks

Commit Message

Darrick J. Wong April 30, 2024, 3:28 a.m. UTC

From: Darrick J. Wong <[e-mail]>

Create a shrinker for an entire filesystem that will walk the inodes
looking for inodes that are caching merkle tree blocks, and invoke
shrink functions on that cache.  The actual details of shrinking merkle
tree caches are left for subsequent patches.

Signed-off-by: Darrick J. Wong <[e-mail]>
---
 fs/xfs/xfs_fsverity.c |   58 +++++++++++++++++++++++++++++++++++++++++++++++++
 fs/xfs/xfs_mount.h    |    6 +++++
 fs/xfs/xfs_trace.h    |   20 +++++++++++++++++
 3 files changed, 84 insertions(+)

Patch

diff --git a/fs/xfs/xfs_fsverity.c b/fs/xfs/xfs_fsverity.c
index e0f54acd4f786..ae3d1bdac2876 100644
--- a/fs/xfs/xfs_fsverity.c
+++ b/fs/xfs/xfs_fsverity.c
@@ -21,6 +21,7 @@ 
 #include "xfs_quota.h"
 #include "xfs_ag.h"
 #include "xfs_fsverity.h"
+#include "xfs_icache.h"
 #include <linux/fsverity.h>
 
 /*
@@ -182,6 +183,7 @@  xfs_fsverity_drop_cache(
 	}
 
 	xfs_perag_put(pag);
+	percpu_counter_sub(&mp->m_verity_blocks, freed);
 }
 
 /*
@@ -283,6 +285,7 @@  xfs_fsverity_cache_store(
 		refcount_inc(&mk->refcount);
 		spin_unlock(&pag->pagi_merkle_lock);
 		xfs_perag_put(pag);
+		percpu_counter_add(&mp->m_verity_blocks, 1);
 
 		trace_xfs_fsverity_cache_store(mp, &mk->key, _RET_IP_);
 		return mk;
@@ -300,6 +303,38 @@  xfs_fsverity_cache_store(
 	return old;
 }
 
+/* Count the merkle tree blocks that we might be able to reclaim. */
+static unsigned long
+xfs_fsverity_shrinker_count(
+	struct shrinker		*shrink,
+	struct shrink_control	*sc)
+{
+	struct xfs_mount	*mp = shrink->private_data;
+	s64			count;
+
+	if (!xfs_has_verity(mp))
+		return SHRINK_EMPTY;
+
+	count = percpu_counter_sum_positive(&mp->m_verity_blocks);
+
+	trace_xfs_fsverity_shrinker_count(mp, count, _RET_IP_);
+	return min_t(u64, ULONG_MAX, count);
+}
+
+/* Actually try to reclaim merkle tree blocks. */
+static unsigned long
+xfs_fsverity_shrinker_scan(
+	struct shrinker		*shrink,
+	struct shrink_control	*sc)
+{
+	struct xfs_mount	*mp = shrink->private_data;
+
+	if (!xfs_has_verity(mp))
+		return SHRINK_STOP;
+
+	return 0;
+}
+
 /* Set up fsverity for this mount. */
 int
 xfs_fsverity_mount(
@@ -312,6 +347,10 @@  xfs_fsverity_mount(
 	if (!xfs_has_verity(mp))
 		return 0;
 
+	error = percpu_counter_init(&mp->m_verity_blocks, 0, GFP_KERNEL);
+	if (error)
+		return error;
+
 	for_each_perag(mp, agno, pag) {
 		spin_lock_init(&pag->pagi_merkle_lock);
 		error = rhashtable_init(&pag->pagi_merkle_blobs,
@@ -323,6 +362,20 @@  xfs_fsverity_mount(
 		set_bit(XFS_AGSTATE_MERKLE, &pag->pag_opstate);
 	}
 
+	mp->m_verity_shrinker = shrinker_alloc(0, "xfs-verity:%s",
+			mp->m_super->s_id);
+	if (!mp->m_verity_shrinker) {
+		error = -ENOMEM;
+		goto out_perag;
+	}
+
+	mp->m_verity_shrinker->count_objects = xfs_fsverity_shrinker_count;
+	mp->m_verity_shrinker->scan_objects = xfs_fsverity_shrinker_scan;
+	mp->m_verity_shrinker->seeks = 0;
+	mp->m_verity_shrinker->private_data = mp;
+
+	shrinker_register(mp->m_verity_shrinker);
+
 	return 0;
 out_perag:
 	for_each_perag(mp, agno, pag) {
@@ -405,11 +458,16 @@  xfs_fsverity_unmount(
 	if (!xfs_has_verity(mp))
 		return;
 
+	shrinker_free(mp->m_verity_shrinker);
+
 	for_each_perag(mp, agno, pag) {
 		if (test_and_clear_bit(XFS_AGSTATE_MERKLE, &pag->pag_opstate))
 			rhashtable_free_and_destroy(&pag->pagi_merkle_blobs,
 					xfs_merkle_blob_destroy, &fu);
 	}
+
+	ASSERT(percpu_counter_sum(&mp->m_verity_blocks) == fu.freed);
+	percpu_counter_destroy(&mp->m_verity_blocks);
 }
 
 /*
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index 78284e91244a8..dd6d33deed030 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -271,6 +271,12 @@  typedef struct xfs_mount {
 
 	/* Hook to feed dirent updates to an active online repair. */
 	struct xfs_hooks	m_dir_update_hooks;
+
+#ifdef CONFIG_FS_VERITY
+	/* shrinker and cached blocks count for merkle trees */
+	struct shrinker		*m_verity_shrinker;
+	struct percpu_counter	m_verity_blocks;
+#endif
 } xfs_mount_t;
 
 #define M_IGEO(mp)		(&(mp)->m_ino_geo)
diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
index 3e44d38fd871a..3810e20b9ee9b 100644
--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h
@@ -5959,6 +5959,26 @@  DEFINE_XFS_FSVERITY_CACHE_EVENT(xfs_fsverity_cache_store);
 DEFINE_XFS_FSVERITY_CACHE_EVENT(xfs_fsverity_cache_drop);
 DEFINE_XFS_FSVERITY_CACHE_EVENT(xfs_fsverity_cache_unmount);
 DEFINE_XFS_FSVERITY_CACHE_EVENT(xfs_fsverity_cache_reclaim);
+
+TRACE_EVENT(xfs_fsverity_shrinker_count,
+	TP_PROTO(struct xfs_mount *mp, unsigned long long count,
+		 unsigned long caller_ip),
+	TP_ARGS(mp, count, caller_ip),
+	TP_STRUCT__entry(
+		__field(dev_t, dev)
+		__field(unsigned long long, count)
+		__field(void *, caller_ip)
+	),
+	TP_fast_assign(
+		__entry->dev = mp->m_super->s_dev;
+		__entry->count = count;
+		__entry->caller_ip = (void *)caller_ip;
+	),
+	TP_printk("dev %d:%d count %llu caller %pS",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  __entry->count,
+		  __entry->caller_ip)
+)
 #endif /* CONFIG_XFS_VERITY */
 
 #endif /* _TRACE_XFS_H */