linux-ext4 - [PATCH 14/20] cache: add a "get only if incore" flag to cache_node

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Message-ID: <175573713060.20753.7102446050470625029.stgit@frogsfrogsfrogs>
Date: Wed, 20 Aug 2025 18:11:31 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: tytso@....edu
Cc: John@...ves.net, bernd@...ernd.com, linux-fsdevel@...r.kernel.org,
 linux-ext4@...r.kernel.org, miklos@...redi.hu, amir73il@...il.com,
 joannelkoong@...il.com, neal@...pa.dev
Subject: [PATCH 14/20] cache: add a "get only if incore" flag to
 cache_node_get

From: Darrick J. Wong <djwong@...nel.org>

Add a new flag to cache_node_get so that callers can specify that they
only want the cache to return an existing cache node, and not create a
new one.

Signed-off-by: "Darrick J. Wong" <djwong@...nel.org>
---
 lib/support/cache.h |    5 ++++-
 lib/support/cache.c |    7 +++++++
 2 files changed, 11 insertions(+), 1 deletion(-)


diff --git a/lib/support/cache.h b/lib/support/cache.h
index 8d39ca5c02a285..98b2182d49a6e0 100644
--- a/lib/support/cache.h
+++ b/lib/support/cache.h
@@ -134,7 +134,10 @@ void cache_walk(struct cache *cache, cache_walk_t fn, void *data);
 void cache_purge(struct cache *);
 bool cache_flush(struct cache *cache);
 
-int cache_node_get(struct cache *, cache_key_t, struct cache_node **);
+/* don't allocate a new node */
+#define CACHE_GET_INCORE	(1U << 0)
+int cache_node_get(struct cache *c, cache_key_t key, unsigned int cgflags,
+		   struct cache_node **nodep);
 void cache_node_put(struct cache *, struct cache_node *);
 void cache_node_set_priority(struct cache *, struct cache_node *, int);
 int cache_node_get_priority(struct cache_node *);
diff --git a/lib/support/cache.c b/lib/support/cache.c
index fa07b4ad8222d2..9da6c59b3b6391 100644
--- a/lib/support/cache.c
+++ b/lib/support/cache.c
@@ -403,6 +403,7 @@ int
 cache_node_get(
 	struct cache		*cache,
 	cache_key_t		key,
+	unsigned int		cgflags,
 	struct cache_node	**nodep)
 {
 	struct cache_hash	*hash;
@@ -456,6 +457,12 @@ cache_node_get(
 			continue;	/* what the hell, gcc? */
 		}
 		pthread_mutex_unlock(&hash->ch_mutex);
+
+		if (cgflags & CACHE_GET_INCORE) {
+			*nodep = NULL;
+			return 0;
+		}
+
 		/*
 		 * not found, allocate a new entry
 		 */