ringbuffer: futexes?

3 files changed, 29 insertions, 1 deletions

diff --git a/fs/ringbuffer.c b/fs/ringbuffer.c
index 82e042c1c89b..8ba84fe299ae 100644
--- a/fs/ringbuffer.c
+++ b/fs/ringbuffer.c
@@ -6,6 +6,7 @@
 #include <linux/errname.h>
 #include <linux/file.h>
 #include <linux/fs.h>
+#include <linux/futex.h>
 #include <linux/init.h>
 #include <linux/mman.h>
 #include <linux/mount.h>
@@ -266,6 +267,14 @@ struct ringbuffer *ringbuffer_alloc(u32 size)
 	rb->ptrs->size	= size;
 	rb->ptrs->mask	= size - 1;
 	rb->ptrs->data_offset = PAGE_SIZE;
+
+	if (!rb->rb_file) {
+		int ret = ringbuffer_alloc_inode(rb);
+		if (ret) {
+			ringbuffer_free(rb);
+			return ERR_PTR(ret);
+		}
+	}
 	return rb;
 }
 
@@ -326,6 +335,19 @@ err:
 	return ret;
 }
 
+static void ringbuffer_futex_key(struct ringbuffer *rb, int rw,
+				 union futex_key *key)
+{
+	struct inode *inode = rb->rb_file->f_inode;
+
+	key->both.offset |= FUT_OFF_INODE; /* inode-based key */
+	key->shared.i_seq = get_inode_sequence_number(inode);
+	key->shared.pgoff = (1U << rb->order) - 1;
+	key->shared.offset = rw == READ
+		? offsetof(struct ringbuffer_ptrs, head)
+		: offsetof(struct ringbuffer_ptrs, tail);
+}
+
 ssize_t ringbuffer_read_iter(struct ringbuffer *rb, struct iov_iter *iter, bool nonblocking)
 {
 	u32 tail = rb->ptrs->tail, orig_tail = tail;
diff --git a/include/linux/futex.h b/include/linux/futex.h
index b70df27d7e85..5b86cd8f28ed 100644
--- a/include/linux/futex.h
+++ b/include/linux/futex.h
@@ -50,6 +50,8 @@ union futex_key {
 	} both;
 };
 
+u64 get_inode_sequence_number(struct inode *);
+
 #define FUTEX_KEY_INIT (union futex_key) { .both = { .ptr = 0ULL } }
 
 #ifdef CONFIG_FUTEX
diff --git a/kernel/futex/core.c b/kernel/futex/core.c
index 06a1f091be81..ffdd1f8c2491 100644
--- a/kernel/futex/core.c
+++ b/kernel/futex/core.c
@@ -169,7 +169,7 @@ futex_setup_timer(ktime_t *time, struct hrtimer_sleeper *timeout,
  * for PI futexes that can mess up the state. The above argues that false-negatives
  * are only possible for malformed programs.
  */
-static u64 get_inode_sequence_number(struct inode *inode)
+u64 get_inode_sequence_number(struct inode *inode)
 {
 	static atomic64_t i_seq;
 	u64 old;
@@ -191,6 +191,10 @@ static u64 get_inode_sequence_number(struct inode *inode)
 	}
 }
 
+static int inode_futex_key(union futex_key *key)
+{
+}
+
 /**
  * get_futex_key() - Get parameters which are the keys for a futex
  * @uaddr:	virtual address of the futex