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Subject: [PATCH v7 11/14] NFSD: Clean up find_or_add_file()
From:   Chuck Lever <chuck.lever@oracle.com>
To:     linux-nfs@vger.kernel.org
Cc:     neilb@suse.de, jlayton@redhat.com
Date:   Fri, 28 Oct 2022 10:47:41 -0400
Message-ID: <166696846122.106044.14636201700548704756.stgit@klimt.1015granger.net>
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References: <166696812922.106044.679812521105874329.stgit@klimt.1015granger.net>
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Remove the call to find_file_locked() in insert_nfs4_file(). Tracing
shows that over 99% of these calls return NULL. Thus it is not worth
the expense of the extra bucket list traversal. insert_file() already
deals correctly with the case where the item is already in the hash
bucket.

Since nfsd4_file_hash_insert() is now just a wrapper around
insert_file(), move the meat of insert_file() into
nfsd4_file_hash_insert() and get rid of it.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: NeilBrown <neilb@suse.de>
---
 fs/nfsd/nfs4state.c |   64 ++++++++++++++++++++++-----------------------------
 1 file changed, 28 insertions(+), 36 deletions(-)

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 504455cb80e9..b1988a46fb9b 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -4683,24 +4683,42 @@ find_file_locked(const struct svc_fh *fh, unsigned int hashval)
 	return NULL;
 }
 
-static struct nfs4_file *insert_file(struct nfs4_file *new, struct svc_fh *fh,
-				     unsigned int hashval)
+static struct nfs4_file * find_file(struct svc_fh *fh)
 {
 	struct nfs4_file *fp;
+	unsigned int hashval = file_hashval(fh);
+
+	rcu_read_lock();
+	fp = find_file_locked(fh, hashval);
+	rcu_read_unlock();
+	return fp;
+}
+
+/*
+ * On hash insertion, identify entries with the same inode but
+ * distinct filehandles. They will all be in the same hash bucket
+ * because nfs4_file's are hashed by the address in the fi_inode
+ * field.
+ */
+static noinline_for_stack struct nfs4_file *
+nfsd4_file_hash_insert(struct nfs4_file *new, const struct svc_fh *fhp)
+{
+	unsigned int hashval = file_hashval(fhp);
 	struct nfs4_file *ret = NULL;
 	bool alias_found = false;
+	struct nfs4_file *fi;
 
 	spin_lock(&state_lock);
-	hlist_for_each_entry_rcu(fp, &file_hashtbl[hashval], fi_hash,
+	hlist_for_each_entry_rcu(fi, &file_hashtbl[hashval], fi_hash,
 				 lockdep_is_held(&state_lock)) {
-		if (fh_match(&fp->fi_fhandle, &fh->fh_handle)) {
-			if (refcount_inc_not_zero(&fp->fi_ref))
-				ret = fp;
-		} else if (d_inode(fh->fh_dentry) == fp->fi_inode)
-			fp->fi_aliased = alias_found = true;
+		if (fh_match(&fi->fi_fhandle, &fhp->fh_handle)) {
+			if (refcount_inc_not_zero(&fi->fi_ref))
+				ret = fi;
+		} else if (d_inode(fhp->fh_dentry) == fi->fi_inode)
+			fi->fi_aliased = alias_found = true;
 	}
 	if (likely(ret == NULL)) {
-		nfsd4_file_init(fh, new);
+		nfsd4_file_init(fhp, new);
 		hlist_add_head_rcu(&new->fi_hash, &file_hashtbl[hashval]);
 		new->fi_aliased = alias_found;
 		ret = new;
@@ -4709,32 +4727,6 @@ static struct nfs4_file *insert_file(struct nfs4_file *new, struct svc_fh *fh,
 	return ret;
 }
 
-static struct nfs4_file * find_file(struct svc_fh *fh)
-{
-	struct nfs4_file *fp;
-	unsigned int hashval = file_hashval(fh);
-
-	rcu_read_lock();
-	fp = find_file_locked(fh, hashval);
-	rcu_read_unlock();
-	return fp;
-}
-
-static struct nfs4_file *
-find_or_add_file(struct nfs4_file *new, struct svc_fh *fh)
-{
-	struct nfs4_file *fp;
-	unsigned int hashval = file_hashval(fh);
-
-	rcu_read_lock();
-	fp = find_file_locked(fh, hashval);
-	rcu_read_unlock();
-	if (fp)
-		return fp;
-
-	return insert_file(new, fh, hashval);
-}
-
 static noinline_for_stack void nfsd4_file_hash_remove(struct nfs4_file *fi)
 {
 	hlist_del_rcu(&fi->fi_hash);
@@ -5625,7 +5617,7 @@ nfsd4_process_open2(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nf
 	 * and check for delegations in the process of being recalled.
 	 * If not found, create the nfs4_file struct
 	 */
-	fp = find_or_add_file(open->op_file, current_fh);
+	fp = nfsd4_file_hash_insert(open->op_file, current_fh);
 	if (fp != open->op_file) {
 		status = nfs4_check_deleg(cl, open, &dp);
 		if (status)