fuse: change interrupt requests allocation algorithm

Using of two unconnected IDs req->in.h.unique and req->intr_unique does not
allow to link requests to a hash table. We need can't use none of them as a
key to calculate hash.

This patch changes the algorithm of allocation of IDs for a request. Plain
requests obtain even ID, while interrupt requests are encoded in the low
bit. So, in next patches we will be able to use the rest of ID bits to
calculate hash, and the hash will be the same for plain and interrupt
requests.

Signed-off-by: Kirill Tkhai <[e-mail]>
Signed-off-by: Miklos Szeredi <[e-mail]>

fs/fuse/dev.c

···
 MODULE_ALIAS_MISCDEV(FUSE_MINOR);
 MODULE_ALIAS("devname:fuse");
 
+/* Ordinary requests have even IDs, while interrupts IDs are odd */
+#define FUSE_INT_REQ_BIT (1ULL << 0)
+#define FUSE_REQ_ID_STEP (1ULL << 1)
+
 static struct kmem_cache *fuse_req_cachep;
 
 static struct fuse_dev *fuse_get_dev(struct file *file)
···
 
 static u64 fuse_get_unique(struct fuse_iqueue *fiq)
 {
-	return ++fiq->reqctr;
+	fiq->reqctr += FUSE_REQ_ID_STEP;
+	return fiq->reqctr;
 }
 
 static void queue_request(struct fuse_iqueue *fiq, struct fuse_req *req)
···
 	int err;
 
 	list_del_init(&req->intr_entry);
-	req->intr_unique = fuse_get_unique(fiq);
+	req->intr_unique = (req->in.h.unique | FUSE_INT_REQ_BIT);
 	memset(&ih, 0, sizeof(ih));
 	memset(&arg, 0, sizeof(arg));
 	ih.len = reqsize;