[PATCH v2 18/21] nfsd: initialize DRC hash table before registering shrinker

shrinker_register() precedes the INIT_LIST_HEAD loop and the
drc_hashsize store. On weakly-ordered architectures (arm64, ppc),
a shrinker scan can observe drc_hashsize before the bucket list
heads are initialized, causing a NULL deref in the DRC shrinker
callback.

Move bucket initialization and the drc_hashsize store before
shrinker_register() so the hash table is fully initialized before
it becomes visible to the shrinker.

Fixes: 8eea99a81c6f ("nfsd: dynamically allocate the nfsd-reply shrinker")
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Jeff Layton <[email protected]>
---
 fs/nfsd/nfscache.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
index 154468ceccdc..18f8556d33dd 100644
--- a/fs/nfsd/nfscache.c
+++ b/fs/nfsd/nfscache.c
@@ -200,14 +200,14 @@ int nfsd_reply_cache_init(struct nfsd_net *nn)
 	nn->nfsd_reply_cache_shrinker->seeks = 1;
 	nn->nfsd_reply_cache_shrinker->private_data = nn;
 
-	shrinker_register(nn->nfsd_reply_cache_shrinker);
-
 	for (i = 0; i < hashsize; i++) {
 		INIT_LIST_HEAD(&nn->drc_hashtbl[i].lru_head);
 		spin_lock_init(&nn->drc_hashtbl[i].cache_lock);
 	}
 	nn->drc_hashsize = hashsize;
 
+	shrinker_register(nn->nfsd_reply_cache_shrinker);
+
 	return 0;
 out_shrinker:
 	kvfree(nn->drc_hashtbl);

-- 
2.54.0