[PATCH 1/4] fuse: Make the fuse_send_one request counter atomic

[Bernd Schubert <bschubert@ddn.com>]

No need to take lock, we can have that in atomic way.
fuse-io-uring and virtiofs especially benefit from it
as they don't need the fiq lock at all.

Signed-off-by: Bernd Schubert <bschubert@ddn.com>
---
 fs/fuse/dev.c        | 24 +++---------------------
 fs/fuse/fuse_dev_i.h |  4 ----
 fs/fuse/fuse_i.h     | 18 +++++++++++++-----
 3 files changed, 16 insertions(+), 30 deletions(-)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 51e31df4c54613280a9c295f530b18e1d461a974..e9592ab092b948bacb5034018bd1f32c917d5c9f 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -204,24 +204,6 @@ unsigned int fuse_len_args(unsigned int numargs, struct fuse_arg *args)
 }
 EXPORT_SYMBOL_GPL(fuse_len_args);
 
-static u64 fuse_get_unique_locked(struct fuse_iqueue *fiq)
-{
-	fiq->reqctr += FUSE_REQ_ID_STEP;
-	return fiq->reqctr;
-}
-
-u64 fuse_get_unique(struct fuse_iqueue *fiq)
-{
-	u64 ret;
-
-	spin_lock(&fiq->lock);
-	ret = fuse_get_unique_locked(fiq);
-	spin_unlock(&fiq->lock);
-
-	return ret;
-}
-EXPORT_SYMBOL_GPL(fuse_get_unique);
-
 unsigned int fuse_req_hash(u64 unique)
 {
 	return hash_long(unique & ~FUSE_INT_REQ_BIT, FUSE_PQ_HASH_BITS);
@@ -278,7 +260,7 @@ static void fuse_dev_queue_req(struct fuse_iqueue *fiq, struct fuse_req *req)
 	spin_lock(&fiq->lock);
 	if (fiq->connected) {
 		if (req->in.h.opcode != FUSE_NOTIFY_REPLY)
-			req->in.h.unique = fuse_get_unique_locked(fiq);
+			req->in.h.unique = fuse_get_unique(fiq);
 		list_add_tail(&req->list, &fiq->pending);
 		fuse_dev_wake_and_unlock(fiq);
 	} else {
@@ -1177,7 +1159,7 @@ __releases(fiq->lock)
 	struct fuse_in_header ih = {
 		.opcode = FUSE_FORGET,
 		.nodeid = forget->forget_one.nodeid,
-		.unique = fuse_get_unique_locked(fiq),
+		.unique = fuse_get_unique(fiq),
 		.len = sizeof(ih) + sizeof(arg),
 	};
 
@@ -1208,7 +1190,7 @@ __releases(fiq->lock)
 	struct fuse_batch_forget_in arg = { .count = 0 };
 	struct fuse_in_header ih = {
 		.opcode = FUSE_BATCH_FORGET,
-		.unique = fuse_get_unique_locked(fiq),
+		.unique = fuse_get_unique(fiq),
 		.len = sizeof(ih) + sizeof(arg),
 	};
 
diff --git a/fs/fuse/fuse_dev_i.h b/fs/fuse/fuse_dev_i.h
index 3b2bfe1248d3573abe3b144a6d4bf6a502f56a40..e0afd837a8024450bab77312c7eebdcc7a39bd36 100644
--- a/fs/fuse/fuse_dev_i.h
+++ b/fs/fuse/fuse_dev_i.h
@@ -8,10 +8,6 @@
 
 #include <linux/types.h>
 
-/* Ordinary requests have even IDs, while interrupts IDs are odd */
-#define FUSE_INT_REQ_BIT (1ULL << 0)
-#define FUSE_REQ_ID_STEP (1ULL << 1)
-
 struct fuse_arg;
 struct fuse_args;
 struct fuse_pqueue;
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index fee96fe7887b30cd57b8a6bbda11447a228cf446..8aea23ffaf2fa44b284d4efef1e009fb1ca876a0 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -44,6 +44,10 @@
 /** Number of dentries for each connection in the control filesystem */
 #define FUSE_CTL_NUM_DENTRIES 5
 
+/* Ordinary requests have even IDs, while interrupts IDs are odd */
+#define FUSE_INT_REQ_BIT (1ULL << 0)
+#define FUSE_REQ_ID_STEP (1ULL << 1)
+
 /** Maximum of max_pages received in init_out */
 extern unsigned int fuse_max_pages_limit;
 
@@ -490,7 +494,7 @@ struct fuse_iqueue {
 	wait_queue_head_t waitq;
 
 	/** The next unique request id */
-	u64 reqctr;
+	atomic64_t reqctr;
 
 	/** The list of pending requests */
 	struct list_head pending;
@@ -1065,6 +1069,14 @@ static inline void fuse_sync_bucket_dec(struct fuse_sync_bucket *bucket)
 	rcu_read_unlock();
 }
 
+/**
+ * Get the next unique ID for a request
+ */
+static inline u64 fuse_get_unique(struct fuse_iqueue *fiq)
+{
+	return atomic64_add_return(FUSE_REQ_ID_STEP, &fiq->reqctr);
+}
+
 /** Device operations */
 extern const struct file_operations fuse_dev_operations;
 
@@ -1415,10 +1427,6 @@ int fuse_readdir(struct file *file, struct dir_context *ctx);
  */
 unsigned int fuse_len_args(unsigned int numargs, struct fuse_arg *args);
 
-/**
- * Get the next unique ID for a request
- */
-u64 fuse_get_unique(struct fuse_iqueue *fiq);
 void fuse_free_conn(struct fuse_conn *fc);
 
 /* dax.c */

-- 
2.43.0