Commit f6dd9755 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Al Viro
Browse files

pipe: merge anon_pipe_buf*_ops 



All the op vectors are exactly the same, they are just used to encode
packet or nomerge behavior.  There already is a flag for the packet
behavior, so just add a new one to allow for merging.  Inverting it vs
the previous nomerge special casing actually allows for much nicer code.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 00c285d0

fs/pipe.c

+5 −40
Original line number Diff line number Diff line
@@ -231,7 +231,6 @@ void generic_pipe_buf_release(struct pipe_inode_info *pipe, 
}

EXPORT_SYMBOL(generic_pipe_buf_release);



/* New data written to a pipe may be appended to a buffer with this type. */

static const struct pipe_buf_operations anon_pipe_buf_ops = {

	.confirm = generic_pipe_buf_confirm,

	.release = anon_pipe_buf_release,
@@ -239,40 +238,6 @@ static const struct pipe_buf_operations anon_pipe_buf_ops = { 
	.get = generic_pipe_buf_get,

};



static const struct pipe_buf_operations anon_pipe_buf_nomerge_ops = {

	.confirm = generic_pipe_buf_confirm,

	.release = anon_pipe_buf_release,

	.steal = anon_pipe_buf_steal,

	.get = generic_pipe_buf_get,

};



static const struct pipe_buf_operations packet_pipe_buf_ops = {

	.confirm = generic_pipe_buf_confirm,

	.release = anon_pipe_buf_release,

	.steal = anon_pipe_buf_steal,

	.get = generic_pipe_buf_get,

};



/**

 * pipe_buf_mark_unmergeable - mark a &struct pipe_buffer as unmergeable

 * @buf:	the buffer to mark

 *

 * Description:

 *	This function ensures that no future writes will be merged into the

 *	given &struct pipe_buffer. This is necessary when multiple pipe buffers

 *	share the same backing page.

 */

void pipe_buf_mark_unmergeable(struct pipe_buffer *buf)

{

	if (buf->ops == &anon_pipe_buf_ops)

		buf->ops = &anon_pipe_buf_nomerge_ops;

}



static bool pipe_buf_can_merge(struct pipe_buffer *buf)

{

	return buf->ops == &anon_pipe_buf_ops;

}



/* Done while waiting without holding the pipe lock - thus the READ_ONCE() */

static inline bool pipe_readable(const struct pipe_inode_info *pipe)

{
@@ -478,7 +443,8 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from) 
		struct pipe_buffer *buf = &pipe->bufs[(head - 1) & mask];

		int offset = buf->offset + buf->len;



		if (pipe_buf_can_merge(buf) && offset + chars <= PAGE_SIZE) {

		if ((buf->flags & PIPE_BUF_FLAG_CAN_MERGE) &&

		    offset + chars <= PAGE_SIZE) {

			ret = pipe_buf_confirm(pipe, buf);

			if (ret)

				goto out;
@@ -541,11 +507,10 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from) 
			buf->ops = &anon_pipe_buf_ops;

			buf->offset = 0;

			buf->len = 0;

			buf->flags = 0;

			if (is_packetized(filp)) {

				buf->ops = &packet_pipe_buf_ops;

			if (is_packetized(filp))

				buf->flags = PIPE_BUF_FLAG_PACKET;

			}

			else

				buf->flags = PIPE_BUF_FLAG_CAN_MERGE;

			pipe->tmp_page = NULL;



			copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);

fs/splice.c

+5 −7
Original line number Diff line number Diff line
@@ -1624,12 +1624,11 @@ retry: 
			*obuf = *ibuf;



			/*

			 * Don't inherit the gift flag, we need to

			 * Don't inherit the gift and merge flags, we need to

			 * prevent multiple steals of this page.

			 */

			obuf->flags &= ~PIPE_BUF_FLAG_GIFT;



			pipe_buf_mark_unmergeable(obuf);

			obuf->flags &= ~PIPE_BUF_FLAG_CAN_MERGE;



			obuf->len = len;

			ibuf->offset += len;
@@ -1717,12 +1716,11 @@ static int link_pipe(struct pipe_inode_info *ipipe, 
		*obuf = *ibuf;



		/*

		 * Don't inherit the gift flag, we need to

		 * prevent multiple steals of this page.

		 * Don't inherit the gift and merge flag, we need to prevent

		 * multiple steals of this page.

		 */

		obuf->flags &= ~PIPE_BUF_FLAG_GIFT;



		pipe_buf_mark_unmergeable(obuf);

		obuf->flags &= ~PIPE_BUF_FLAG_CAN_MERGE;



		if (obuf->len > len)

			obuf->len = len;

include/linux/pipe_fs_i.h

+1 −1
Original line number Diff line number Diff line
@@ -8,6 +8,7 @@ 
#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 */

#define PIPE_BUF_FLAG_CAN_MERGE	0x10	/* can merge buffers */



/**

 *	struct pipe_buffer - a linux kernel pipe buffer
@@ -233,7 +234,6 @@ int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *); 
int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);

int generic_pipe_buf_nosteal(struct pipe_inode_info *, struct pipe_buffer *);

void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);

void pipe_buf_mark_unmergeable(struct pipe_buffer *buf);



extern const struct pipe_buf_operations nosteal_pipe_buf_ops;

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