v4.19.13 snapshot.
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
new file mode 100644
index 0000000..5a3bb3b
--- /dev/null
+++ b/include/linux/pipe_fs_i.h
@@ -0,0 +1,195 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_PIPE_FS_I_H
+#define _LINUX_PIPE_FS_I_H
+
+#define PIPE_DEF_BUFFERS 16
+
+#define PIPE_BUF_FLAG_LRU 0x01 /* page is on the LRU */
+#define PIPE_BUF_FLAG_ATOMIC 0x02 /* was atomically mapped */
+#define PIPE_BUF_FLAG_GIFT 0x04 /* page is a gift */
+#define PIPE_BUF_FLAG_PACKET 0x08 /* read() as a packet */
+
+/**
+ * struct pipe_buffer - a linux kernel pipe buffer
+ * @page: the page containing the data for the pipe buffer
+ * @offset: offset of data inside the @page
+ * @len: length of data inside the @page
+ * @ops: operations associated with this buffer. See @pipe_buf_operations.
+ * @flags: pipe buffer flags. See above.
+ * @private: private data owned by the ops.
+ **/
+struct pipe_buffer {
+ struct page *page;
+ unsigned int offset, len;
+ const struct pipe_buf_operations *ops;
+ unsigned int flags;
+ unsigned long private;
+};
+
+/**
+ * struct pipe_inode_info - a linux kernel pipe
+ * @mutex: mutex protecting the whole thing
+ * @wait: reader/writer wait point in case of empty/full pipe
+ * @nrbufs: the number of non-empty pipe buffers in this pipe
+ * @buffers: total number of buffers (should be a power of 2)
+ * @curbuf: the current pipe buffer entry
+ * @tmp_page: cached released page
+ * @readers: number of current readers of this pipe
+ * @writers: number of current writers of this pipe
+ * @files: number of struct file referring this pipe (protected by ->i_lock)
+ * @waiting_writers: number of writers blocked waiting for room
+ * @r_counter: reader counter
+ * @w_counter: writer counter
+ * @fasync_readers: reader side fasync
+ * @fasync_writers: writer side fasync
+ * @bufs: the circular array of pipe buffers
+ * @user: the user who created this pipe
+ **/
+struct pipe_inode_info {
+ struct mutex mutex;
+ wait_queue_head_t wait;
+ unsigned int nrbufs, curbuf, buffers;
+ unsigned int readers;
+ unsigned int writers;
+ unsigned int files;
+ unsigned int waiting_writers;
+ unsigned int r_counter;
+ unsigned int w_counter;
+ struct page *tmp_page;
+ struct fasync_struct *fasync_readers;
+ struct fasync_struct *fasync_writers;
+ struct pipe_buffer *bufs;
+ struct user_struct *user;
+};
+
+/*
+ * Note on the nesting of these functions:
+ *
+ * ->confirm()
+ * ->steal()
+ *
+ * That is, ->steal() must be called on a confirmed buffer.
+ * See below for the meaning of each operation. Also see kerneldoc
+ * in fs/pipe.c for the pipe and generic variants of these hooks.
+ */
+struct pipe_buf_operations {
+ /*
+ * This is set to 1, if the generic pipe read/write may coalesce
+ * data into an existing buffer. If this is set to 0, a new pipe
+ * page segment is always used for new data.
+ */
+ int can_merge;
+
+ /*
+ * ->confirm() verifies that the data in the pipe buffer is there
+ * and that the contents are good. If the pages in the pipe belong
+ * to a file system, we may need to wait for IO completion in this
+ * hook. Returns 0 for good, or a negative error value in case of
+ * error.
+ */
+ int (*confirm)(struct pipe_inode_info *, struct pipe_buffer *);
+
+ /*
+ * When the contents of this pipe buffer has been completely
+ * consumed by a reader, ->release() is called.
+ */
+ void (*release)(struct pipe_inode_info *, struct pipe_buffer *);
+
+ /*
+ * Attempt to take ownership of the pipe buffer and its contents.
+ * ->steal() returns 0 for success, in which case the contents
+ * of the pipe (the buf->page) is locked and now completely owned
+ * by the caller. The page may then be transferred to a different
+ * mapping, the most often used case is insertion into different
+ * file address space cache.
+ */
+ int (*steal)(struct pipe_inode_info *, struct pipe_buffer *);
+
+ /*
+ * Get a reference to the pipe buffer.
+ */
+ void (*get)(struct pipe_inode_info *, struct pipe_buffer *);
+};
+
+/**
+ * pipe_buf_get - get a reference to a pipe_buffer
+ * @pipe: the pipe that the buffer belongs to
+ * @buf: the buffer to get a reference to
+ */
+static inline void pipe_buf_get(struct pipe_inode_info *pipe,
+ struct pipe_buffer *buf)
+{
+ buf->ops->get(pipe, buf);
+}
+
+/**
+ * pipe_buf_release - put a reference to a pipe_buffer
+ * @pipe: the pipe that the buffer belongs to
+ * @buf: the buffer to put a reference to
+ */
+static inline void pipe_buf_release(struct pipe_inode_info *pipe,
+ struct pipe_buffer *buf)
+{
+ const struct pipe_buf_operations *ops = buf->ops;
+
+ buf->ops = NULL;
+ ops->release(pipe, buf);
+}
+
+/**
+ * pipe_buf_confirm - verify contents of the pipe buffer
+ * @pipe: the pipe that the buffer belongs to
+ * @buf: the buffer to confirm
+ */
+static inline int pipe_buf_confirm(struct pipe_inode_info *pipe,
+ struct pipe_buffer *buf)
+{
+ return buf->ops->confirm(pipe, buf);
+}
+
+/**
+ * pipe_buf_steal - attempt to take ownership of a pipe_buffer
+ * @pipe: the pipe that the buffer belongs to
+ * @buf: the buffer to attempt to steal
+ */
+static inline int pipe_buf_steal(struct pipe_inode_info *pipe,
+ struct pipe_buffer *buf)
+{
+ return buf->ops->steal(pipe, buf);
+}
+
+/* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
+ memory allocation, whereas PIPE_BUF makes atomicity guarantees. */
+#define PIPE_SIZE PAGE_SIZE
+
+/* Pipe lock and unlock operations */
+void pipe_lock(struct pipe_inode_info *);
+void pipe_unlock(struct pipe_inode_info *);
+void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
+
+extern unsigned int pipe_max_size;
+extern unsigned long pipe_user_pages_hard;
+extern unsigned long pipe_user_pages_soft;
+
+/* Drop the inode semaphore and wait for a pipe event, atomically */
+void pipe_wait(struct pipe_inode_info *pipe);
+
+struct pipe_inode_info *alloc_pipe_info(void);
+void free_pipe_info(struct pipe_inode_info *);
+
+/* Generic pipe buffer ops functions */
+void generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
+int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
+int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
+void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
+
+extern const struct pipe_buf_operations nosteal_pipe_buf_ops;
+
+/* for F_SETPIPE_SZ and F_GETPIPE_SZ */
+long pipe_fcntl(struct file *, unsigned int, unsigned long arg);
+struct pipe_inode_info *get_pipe_info(struct file *file);
+
+int create_pipe_files(struct file **, int);
+unsigned int round_pipe_size(unsigned long size);
+
+#endif