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Subject: [PATCH 1/3] fuse: Change interrupt requests allocation algorhythm
From:   Kirill Tkhai <ktkhai@virtuozzo.com>
To:     miklos@szeredi.hu, kuznet@virtuozzo.com, ktkhai@virtuozzo.com,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Date:   Tue, 11 Sep 2018 13:11:56 +0300
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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 algorhythm 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 caculate hash,
and the hash will be the same for plain and
interrupt requests.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
---
 fs/fuse/dev.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 11ea2c4a38ab..f24fd6f61a7a 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -25,6 +25,10 @@
 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)
@@ -319,7 +323,8 @@ static unsigned len_args(unsigned numargs, struct fuse_arg *args)
 
 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)
@@ -1084,7 +1089,7 @@ __releases(fiq->waitq.lock)
 	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;