Revert changes to convert to ->poll_mask() and aio IOCB_CMD_POLL

The poll() changes were not well thought out, and completely
unexplained.  They also caused a huge performance regression, because
"->poll()" was no longer a trivial file operation that just called down
to the underlying file operations, but instead did at least two indirect
calls.

Indirect calls are sadly slow now with the Spectre mitigation, but the
performance problem could at least be largely mitigated by changing the
"->get_poll_head()" operation to just have a per-file-descriptor pointer
to the poll head instead.  That gets rid of one of the new indirections.

But that doesn't fix the new complexity that is completely unwarranted
for the regular case.  The (undocumented) reason for the poll() changes
was some alleged AIO poll race fixing, but we don't make the common case
slower and more complex for some uncommon special case, so this all
really needs way more explanations and most likely a fundamental
redesign.

[ This revert is a revert of about 30 different commits, not reverted
  individually because that would just be unnecessarily messy  - Linus ]

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

12 files changed, 27 insertions, 20 deletions

diff --git a/include/crypto/if_alg.h b/include/crypto/if_alg.h
index cc414db9da0a..482461d8931d 100644
--- a/include/crypto/if_alg.h
+++ b/include/crypto/if_alg.h
@@ -245,7 +245,8 @@ ssize_t af_alg_sendpage(struct socket *sock, struct page *page,
 			int offset, size_t size, int flags);
 void af_alg_free_resources(struct af_alg_async_req *areq);
 void af_alg_async_cb(struct crypto_async_request *_req, int err);
-__poll_t af_alg_poll_mask(struct socket *sock, __poll_t events);
+__poll_t af_alg_poll(struct file *file, struct socket *sock,
+			 poll_table *wait);
 struct af_alg_async_req *af_alg_alloc_areq(struct sock *sk,
 					   unsigned int areqlen);
 int af_alg_get_rsgl(struct sock *sk, struct msghdr *msg, int flags,
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 5c91108846db..d78d146a98da 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1720,8 +1720,6 @@ struct file_operations {
 	int (*iterate) (struct file *, struct dir_context *);
 	int (*iterate_shared) (struct file *, struct dir_context *);
 	__poll_t (*poll) (struct file *, struct poll_table_struct *);
-	struct wait_queue_head * (*get_poll_head)(struct file *, __poll_t);
-	__poll_t (*poll_mask) (struct file *, __poll_t);
 	long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
 	long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
 	int (*mmap) (struct file *, struct vm_area_struct *);
diff --git a/include/linux/net.h b/include/linux/net.h
index 08b6eb964dd6..6554d3ba4396 100644
--- a/include/linux/net.h
+++ b/include/linux/net.h
@@ -147,7 +147,6 @@ struct proto_ops {
 	int		(*getname)   (struct socket *sock,
 				      struct sockaddr *addr,
 				      int peer);
-	__poll_t	(*poll_mask) (struct socket *sock, __poll_t events);
 	__poll_t	(*poll)	     (struct file *file, struct socket *sock,
 				      struct poll_table_struct *wait);
 	int		(*ioctl)     (struct socket *sock, unsigned int cmd,
diff --git a/include/linux/poll.h b/include/linux/poll.h
index fdf86b4cbc71..7e0fdcf905d2 100644
--- a/include/linux/poll.h
+++ b/include/linux/poll.h
@@ -74,18 +74,18 @@ static inline void init_poll_funcptr(poll_table *pt, poll_queue_proc qproc)
 	pt->_key   = ~(__poll_t)0; /* all events enabled */
 }
 
-static inline bool file_has_poll_mask(struct file *file)
+static inline bool file_can_poll(struct file *file)
 {
-	return file->f_op->get_poll_head && file->f_op->poll_mask;
+	return file->f_op->poll;
 }
 
-static inline bool file_can_poll(struct file *file)
+static inline __poll_t vfs_poll(struct file *file, struct poll_table_struct *pt)
 {
-	return file->f_op->poll || file_has_poll_mask(file);
+	if (unlikely(!file->f_op->poll))
+		return DEFAULT_POLLMASK;
+	return file->f_op->poll(file, pt);
 }
 
-__poll_t vfs_poll(struct file *file, struct poll_table_struct *pt);
-
 struct poll_table_entry {
 	struct file *filp;
 	__poll_t key;
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index c86885954994..164cdedf6012 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -3252,7 +3252,8 @@ struct sk_buff *__skb_recv_datagram(struct sock *sk, unsigned flags,
 				    int *peeked, int *off, int *err);
 struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned flags, int noblock,
 				  int *err);
-__poll_t datagram_poll_mask(struct socket *sock, __poll_t events);
+__poll_t datagram_poll(struct file *file, struct socket *sock,
+			   struct poll_table_struct *wait);
 int skb_copy_datagram_iter(const struct sk_buff *from, int offset,
 			   struct iov_iter *to, int size);
 static inline int skb_copy_datagram_msg(const struct sk_buff *from, int offset,
diff --git a/include/net/bluetooth/bluetooth.h b/include/net/bluetooth/bluetooth.h
index 53ce8176c313..ec9d6bc65855 100644
--- a/include/net/bluetooth/bluetooth.h
+++ b/include/net/bluetooth/bluetooth.h
@@ -271,7 +271,7 @@ int  bt_sock_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 		     int flags);
 int  bt_sock_stream_recvmsg(struct socket *sock, struct msghdr *msg,
 			    size_t len, int flags);
-__poll_t bt_sock_poll_mask(struct socket *sock, __poll_t events);
+__poll_t bt_sock_poll(struct file *file, struct socket *sock, poll_table *wait);
 int  bt_sock_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg);
 int  bt_sock_wait_state(struct sock *sk, int state, unsigned long timeo);
 int  bt_sock_wait_ready(struct sock *sk, unsigned long flags);
diff --git a/include/net/iucv/af_iucv.h b/include/net/iucv/af_iucv.h
index b0eaeb02d46d..f4c21b5a1242 100644
--- a/include/net/iucv/af_iucv.h
+++ b/include/net/iucv/af_iucv.h
@@ -153,6 +153,8 @@ struct iucv_sock_list {
 	atomic_t	  autobind_name;
 };
 
+__poll_t iucv_sock_poll(struct file *file, struct socket *sock,
+			    poll_table *wait);
 void iucv_sock_link(struct iucv_sock_list *l, struct sock *s);
 void iucv_sock_unlink(struct iucv_sock_list *l, struct sock *s);
 void iucv_accept_enqueue(struct sock *parent, struct sock *sk);
diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h
index 30b3e2fe240a..8c2caa370e0f 100644
--- a/include/net/sctp/sctp.h
+++ b/include/net/sctp/sctp.h
@@ -109,7 +109,8 @@ int sctp_backlog_rcv(struct sock *sk, struct sk_buff *skb);
 int sctp_inet_listen(struct socket *sock, int backlog);
 void sctp_write_space(struct sock *sk);
 void sctp_data_ready(struct sock *sk);
-__poll_t sctp_poll_mask(struct socket *sock, __poll_t events);
+__poll_t sctp_poll(struct file *file, struct socket *sock,
+		poll_table *wait);
 void sctp_sock_rfree(struct sk_buff *skb);
 void sctp_copy_sock(struct sock *newsk, struct sock *sk,
 		    struct sctp_association *asoc);
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 0448e7c5d2b4..800582b5dd54 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -388,7 +388,8 @@ bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst);
 void tcp_close(struct sock *sk, long timeout);
 void tcp_init_sock(struct sock *sk);
 void tcp_init_transfer(struct sock *sk, int bpf_op);
-__poll_t tcp_poll_mask(struct socket *sock, __poll_t events);
+__poll_t tcp_poll(struct file *file, struct socket *sock,
+		      struct poll_table_struct *wait);
 int tcp_getsockopt(struct sock *sk, int level, int optname,
 		   char __user *optval, int __user *optlen);
 int tcp_setsockopt(struct sock *sk, int level, int optname,
diff --git a/include/net/tls.h b/include/net/tls.h
index 7f84ea3e217c..70c273777fe9 100644
--- a/include/net/tls.h
+++ b/include/net/tls.h
@@ -109,7 +109,8 @@ struct tls_sw_context_rx {
 
 	struct strparser strp;
 	void (*saved_data_ready)(struct sock *sk);
-	__poll_t (*sk_poll_mask)(struct socket *sock, __poll_t events);
+	unsigned int (*sk_poll)(struct file *file, struct socket *sock,
+				struct poll_table_struct *wait);
 	struct sk_buff *recv_pkt;
 	u8 control;
 	bool decrypted;
@@ -224,7 +225,8 @@ void tls_sw_free_resources_tx(struct sock *sk);
 void tls_sw_free_resources_rx(struct sock *sk);
 int tls_sw_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 		   int nonblock, int flags, int *addr_len);
-__poll_t tls_sw_poll_mask(struct socket *sock, __poll_t events);
+unsigned int tls_sw_poll(struct file *file, struct socket *sock,
+			 struct poll_table_struct *wait);
 ssize_t tls_sw_splice_read(struct socket *sock, loff_t *ppos,
 			   struct pipe_inode_info *pipe,
 			   size_t len, unsigned int flags);
diff --git a/include/net/udp.h b/include/net/udp.h
index b1ea8b0f5e6a..81afdacd4fff 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -285,7 +285,7 @@ int udp_init_sock(struct sock *sk);
 int udp_pre_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
 int __udp_disconnect(struct sock *sk, int flags);
 int udp_disconnect(struct sock *sk, int flags);
-__poll_t udp_poll_mask(struct socket *sock, __poll_t events);
+__poll_t udp_poll(struct file *file, struct socket *sock, poll_table *wait);
 struct sk_buff *skb_udp_tunnel_segment(struct sk_buff *skb,
 				       netdev_features_t features,
 				       bool is_ipv6);
diff --git a/include/uapi/linux/aio_abi.h b/include/uapi/linux/aio_abi.h
index d00221345c19..d4e768d55d14 100644
--- a/include/uapi/linux/aio_abi.h
+++ b/include/uapi/linux/aio_abi.h
@@ -39,8 +39,10 @@ enum {
 	IOCB_CMD_PWRITE = 1,
 	IOCB_CMD_FSYNC = 2,
 	IOCB_CMD_FDSYNC = 3,
-	/* 4 was the experimental IOCB_CMD_PREADX */
-	IOCB_CMD_POLL = 5,
+	/* These two are experimental.
+	 * IOCB_CMD_PREADX = 4,
+	 * IOCB_CMD_POLL = 5,
+	 */
 	IOCB_CMD_NOOP = 6,
 	IOCB_CMD_PREADV = 7,
 	IOCB_CMD_PWRITEV = 8,
@@ -109,7 +111,7 @@ struct iocb {
 #undef IFLITTLE
 
 struct __aio_sigset {
-	const sigset_t __user	*sigmask;
+	sigset_t __user	*sigmask;
 	size_t		sigsetsize;
 };