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Subject: [PATCH 1/8] NFSD: Refactor nfsd_reply_cache_free_locked()
From: Chuck Lever <cel@kernel.org>
To: stable@vger.kernel.org
Cc: linux-nfs@vger.kernel.org
Date: Tue, 28 Nov 2023 16:59:38 -0500
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From: Chuck Lever <chuck.lever@oracle.com>

[ Upstream commit 35308e7f0fc3942edc87d9c6dc78c4a096428957 ]

To reduce contention on the bucket locks, we must avoid calling
kfree() while each bucket lock is held.

Start by refactoring nfsd_reply_cache_free_locked() into a helper
that removes an entry from the bucket (and must therefore run under
the lock) and a second helper that frees the entry (which does not
need to hold the lock).

For readability, rename the helpers nfsd_cacherep_<verb>.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 fs/nfsd/nfscache.c |   27 ++++++++++++++++++++-------
 1 file changed, 20 insertions(+), 7 deletions(-)

diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
index 1ad4f30d5f85..e197756b5454 100644
--- a/fs/nfsd/nfscache.c
+++ b/fs/nfsd/nfscache.c
@@ -110,21 +110,33 @@ nfsd_reply_cache_alloc(struct svc_rqst *rqstp, __wsum csum,
 	return rp;
 }
 
+static void nfsd_cacherep_free(struct svc_cacherep *rp)
+{
+	if (rp->c_type == RC_REPLBUFF)
+		kfree(rp->c_replvec.iov_base);
+	kmem_cache_free(drc_slab, rp);
+}
+
 static void
-nfsd_reply_cache_free_locked(struct nfsd_drc_bucket *b, struct svc_cacherep *rp,
-				struct nfsd_net *nn)
+nfsd_cacherep_unlink_locked(struct nfsd_net *nn, struct nfsd_drc_bucket *b,
+			    struct svc_cacherep *rp)
 {
-	if (rp->c_type == RC_REPLBUFF && rp->c_replvec.iov_base) {
+	if (rp->c_type == RC_REPLBUFF && rp->c_replvec.iov_base)
 		nfsd_stats_drc_mem_usage_sub(nn, rp->c_replvec.iov_len);
-		kfree(rp->c_replvec.iov_base);
-	}
 	if (rp->c_state != RC_UNUSED) {
 		rb_erase(&rp->c_node, &b->rb_head);
 		list_del(&rp->c_lru);
 		atomic_dec(&nn->num_drc_entries);
 		nfsd_stats_drc_mem_usage_sub(nn, sizeof(*rp));
 	}
-	kmem_cache_free(drc_slab, rp);
+}
+
+static void
+nfsd_reply_cache_free_locked(struct nfsd_drc_bucket *b, struct svc_cacherep *rp,
+				struct nfsd_net *nn)
+{
+	nfsd_cacherep_unlink_locked(nn, b, rp);
+	nfsd_cacherep_free(rp);
 }
 
 static void
@@ -132,8 +144,9 @@ nfsd_reply_cache_free(struct nfsd_drc_bucket *b, struct svc_cacherep *rp,
 			struct nfsd_net *nn)
 {
 	spin_lock(&b->cache_lock);
-	nfsd_reply_cache_free_locked(b, rp, nn);
+	nfsd_cacherep_unlink_locked(nn, b, rp);
 	spin_unlock(&b->cache_lock);
+	nfsd_cacherep_free(rp);
 }
 
 int nfsd_drc_slab_create(void)