[PATCH v3 1/3] mm/vmscan: introduce drop_sb_dentry_inode() helper

[Ye Bin <yebin@huaweicloud.com>]

From: Ye Bin <yebin10@huawei.com>

This patch is prepare for support drop_caches for specify file system.

Signed-off-by: Ye Bin <yebin10@huawei.com>
---
 include/linux/mm.h |  1 +
 mm/internal.h      |  3 +++
 mm/shrinker.c      |  4 ++--
 mm/vmscan.c        | 50 ++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 56 insertions(+), 2 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 5be3d8a8f806..5bab9472a758 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -4470,6 +4470,7 @@ static inline int in_gate_area(struct mm_struct *mm, unsigned long addr)
 bool process_shares_mm(const struct task_struct *p, const struct mm_struct *mm);
 
 void drop_slab(void);
+void drop_sb_dentry_inode(struct super_block *sb);
 
 #ifndef CONFIG_MMU
 #define randomize_va_space 0
diff --git a/mm/internal.h b/mm/internal.h
index cb0af847d7d9..4690a58c4820 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -1662,6 +1662,9 @@ void __meminit __init_page_from_nid(unsigned long pfn, int nid);
 unsigned long shrink_slab(gfp_t gfp_mask, int nid, struct mem_cgroup *memcg,
 			  int priority);
 
+unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
+			     struct shrinker *shrinker, int priority);
+
 int shmem_add_to_page_cache(struct folio *folio,
 			    struct address_space *mapping,
 			    pgoff_t index, void *expected, gfp_t gfp);
diff --git a/mm/shrinker.c b/mm/shrinker.c
index 4a93fd433689..075e4393da9c 100644
--- a/mm/shrinker.c
+++ b/mm/shrinker.c
@@ -368,8 +368,8 @@ static long add_nr_deferred(long nr, struct shrinker *shrinker,
 
 #define SHRINK_BATCH 128
 
-static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
-				    struct shrinker *shrinker, int priority)
+unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
+			     struct shrinker *shrinker, int priority)
 {
 	unsigned long freed = 0;
 	unsigned long long delta;
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 01d3364fe506..310bed25df78 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -455,6 +455,56 @@ void drop_slab(void)
 	} while ((freed >> shift++) > 1);
 }
 
+static unsigned long drop_shrinker_node(int nid, struct shrinker *shrinker)
+{
+	unsigned long freed = 0;
+	struct mem_cgroup *memcg = NULL;
+
+	memcg = mem_cgroup_iter(NULL, NULL, NULL);
+	do {
+		unsigned long ret;
+
+		struct shrink_control sc = {
+			.gfp_mask = GFP_KERNEL,
+			.nid = nid,
+			.memcg = memcg,
+		};
+
+		if (!mem_cgroup_disabled() &&
+		    !mem_cgroup_is_root(memcg) &&
+		    !mem_cgroup_online(memcg))
+			continue;
+
+		ret = do_shrink_slab(&sc, shrinker, 0);
+		if (ret == SHRINK_EMPTY)
+			ret = 0;
+		freed += ret;
+		cond_resched();
+	} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
+
+	return freed;
+}
+
+void drop_sb_dentry_inode(struct super_block *sb)
+{
+	int nid;
+	int shift = 0;
+	unsigned long freed;
+
+	if (!sb || !sb->s_shrink)
+		return;
+
+	do {
+		freed = 0;
+
+		for_each_online_node(nid) {
+			if (fatal_signal_pending(current))
+				return;
+			freed += drop_shrinker_node(nid, sb->s_shrink);
+		}
+	} while ((freed >> shift++) > 1);
+}
+
 #define CHECK_RECLAIMER_OFFSET(type)					\
 	do {								\
 		BUILD_BUG_ON(PGSTEAL_##type - PGSTEAL_KSWAPD !=		\
-- 
2.34.1