[PATCH] NFSv4.2: fix wrong shrinker_id

[Qi Zheng <qi.zheng@linux.dev>]

From: Qi Zheng <zhengqi.arch@bytedance.com>

Currently, the list_lru::shrinker_id corresponding to the nfs4_xattr
shrinkers is wrong:

>>> prog["nfs4_xattr_cache_lru"].shrinker_id
(int)0
>>> prog["nfs4_xattr_entry_lru"].shrinker_id
(int)0
>>> prog["nfs4_xattr_large_entry_lru"].shrinker_id
(int)0
>>> prog["nfs4_xattr_cache_shrinker"].id
(int)18
>>> prog["nfs4_xattr_entry_shrinker"].id
(int)19
>>> prog["nfs4_xattr_large_entry_shrinker"].id
(int)20

This is not what we expect, which will cause these shrinkers
not to be found in shrink_slab_memcg().

We should assign shrinker::id before calling list_lru_init_memcg(),
so that the corresponding list_lru::shrinker_id will be assigned
the correct value like below:

>>> prog["nfs4_xattr_cache_lru"].shrinker_id
(int)16
>>> prog["nfs4_xattr_entry_lru"].shrinker_id
(int)17
>>> prog["nfs4_xattr_large_entry_lru"].shrinker_id
(int)18
>>> prog["nfs4_xattr_cache_shrinker"].id
(int)16
>>> prog["nfs4_xattr_entry_shrinker"].id
(int)17
>>> prog["nfs4_xattr_large_entry_shrinker"].id
(int)18

So just do it.

Fixes: 95ad37f90c33 ("NFSv4.2: add client side xattr caching.")
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
---
 fs/nfs/nfs42xattr.c | 83 ++++++++++++++++++++++++++-------------------
 1 file changed, 48 insertions(+), 35 deletions(-)

diff --git a/fs/nfs/nfs42xattr.c b/fs/nfs/nfs42xattr.c
index 76ae11834206..e3dab0131e4c 100644
--- a/fs/nfs/nfs42xattr.c
+++ b/fs/nfs/nfs42xattr.c
@@ -991,6 +991,33 @@ static void nfs4_xattr_cache_init_once(void *p)
 	INIT_LIST_HEAD(&cache->dispose);
 }
 
+static int nfs4_xattr_shrinker_init(struct shrinker *shrinker,
+				    struct list_lru *lru, const char *name)
+{
+	int ret = 0;
+
+	ret = prealloc_shrinker(shrinker, name);
+	if (ret)
+		return ret;
+
+	ret = list_lru_init_memcg(lru, shrinker);
+	if (ret) {
+		free_prealloced_shrinker(shrinker);
+		return ret;
+	}
+
+	register_shrinker_prepared(shrinker);
+
+	return 0;
+}
+
+static void nfs4_xattr_shrinker_destroy(struct shrinker *shrinker,
+					struct list_lru *lru)
+{
+	unregister_shrinker(shrinker);
+	list_lru_destroy(lru);
+}
+
 int __init nfs4_xattr_cache_init(void)
 {
 	int ret = 0;
@@ -1002,44 +1029,30 @@ int __init nfs4_xattr_cache_init(void)
 	if (nfs4_xattr_cache_cachep == NULL)
 		return -ENOMEM;
 
-	ret = list_lru_init_memcg(&nfs4_xattr_large_entry_lru,
-	    &nfs4_xattr_large_entry_shrinker);
-	if (ret)
-		goto out4;
-
-	ret = list_lru_init_memcg(&nfs4_xattr_entry_lru,
-	    &nfs4_xattr_entry_shrinker);
-	if (ret)
-		goto out3;
-
-	ret = list_lru_init_memcg(&nfs4_xattr_cache_lru,
-	    &nfs4_xattr_cache_shrinker);
-	if (ret)
-		goto out2;
-
-	ret = register_shrinker(&nfs4_xattr_cache_shrinker, "nfs-xattr_cache");
+	ret = nfs4_xattr_shrinker_init(&nfs4_xattr_cache_shrinker,
+				       &nfs4_xattr_cache_lru,
+				       "nfs-xattr_cache");
 	if (ret)
 		goto out1;
 
-	ret = register_shrinker(&nfs4_xattr_entry_shrinker, "nfs-xattr_entry");
+	ret = nfs4_xattr_shrinker_init(&nfs4_xattr_entry_shrinker,
+				       &nfs4_xattr_entry_lru,
+				       "nfs-xattr_entry");
 	if (ret)
-		goto out;
+		goto out2;
 
-	ret = register_shrinker(&nfs4_xattr_large_entry_shrinker,
-				"nfs-xattr_large_entry");
+	ret = nfs4_xattr_shrinker_init(&nfs4_xattr_large_entry_shrinker,
+				       &nfs4_xattr_large_entry_lru,
+				       "nfs-xattr_large_entry");
 	if (!ret)
 		return 0;
 
-	unregister_shrinker(&nfs4_xattr_entry_shrinker);
-out:
-	unregister_shrinker(&nfs4_xattr_cache_shrinker);
-out1:
-	list_lru_destroy(&nfs4_xattr_cache_lru);
+	nfs4_xattr_shrinker_destroy(&nfs4_xattr_entry_shrinker,
+				    &nfs4_xattr_entry_lru);
 out2:
-	list_lru_destroy(&nfs4_xattr_entry_lru);
-out3:
-	list_lru_destroy(&nfs4_xattr_large_entry_lru);
-out4:
+	nfs4_xattr_shrinker_destroy(&nfs4_xattr_cache_shrinker,
+				    &nfs4_xattr_cache_lru);
+out1:
 	kmem_cache_destroy(nfs4_xattr_cache_cachep);
 
 	return ret;
@@ -1047,11 +1060,11 @@ int __init nfs4_xattr_cache_init(void)
 
 void nfs4_xattr_cache_exit(void)
 {
-	unregister_shrinker(&nfs4_xattr_large_entry_shrinker);
-	unregister_shrinker(&nfs4_xattr_entry_shrinker);
-	unregister_shrinker(&nfs4_xattr_cache_shrinker);
-	list_lru_destroy(&nfs4_xattr_large_entry_lru);
-	list_lru_destroy(&nfs4_xattr_entry_lru);
-	list_lru_destroy(&nfs4_xattr_cache_lru);
+	nfs4_xattr_shrinker_destroy(&nfs4_xattr_large_entry_shrinker,
+				    &nfs4_xattr_large_entry_lru);
+	nfs4_xattr_shrinker_destroy(&nfs4_xattr_entry_shrinker,
+				    &nfs4_xattr_entry_lru);
+	nfs4_xattr_shrinker_destroy(&nfs4_xattr_cache_shrinker,
+				    &nfs4_xattr_cache_lru);
 	kmem_cache_destroy(nfs4_xattr_cache_cachep);
 }
-- 
2.30.2