[PATCH] NFSv4.2: fix wrong shrinker_id

Qi Zheng
2023-06-14T07:32:52Z

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