Commit 01e7187b authored by Jann Horn's avatar Jann Horn Committed by Al Viro
Browse files

pipe: stop using ->can_merge 



Al Viro pointed out that since there is only one pipe buffer type to which
new data can be appended, it isn't necessary to have a ->can_merge field in
struct pipe_buf_operations, we can just check for a magic type.

Suggested-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarJann Horn <jannh@google.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent a0ce2f0a

fs/pipe.c

+16 −4
Original line number Diff line number Diff line
@@ -226,8 +226,8 @@ 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 = {

	.can_merge = 1,

	.confirm = generic_pipe_buf_confirm,

	.release = anon_pipe_buf_release,

	.steal = anon_pipe_buf_steal,
@@ -235,7 +235,6 @@ static const struct pipe_buf_operations anon_pipe_buf_ops = { 
};



static const struct pipe_buf_operations anon_pipe_buf_nomerge_ops = {

	.can_merge = 0,

	.confirm = generic_pipe_buf_confirm,

	.release = anon_pipe_buf_release,

	.steal = anon_pipe_buf_steal,
@@ -243,19 +242,32 @@ static const struct pipe_buf_operations anon_pipe_buf_nomerge_ops = { 
};



static const struct pipe_buf_operations packet_pipe_buf_ops = {

	.can_merge = 0,

	.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;

}



static ssize_t

pipe_read(struct kiocb *iocb, struct iov_iter *to)

{
@@ -393,7 +405,7 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from) 
		struct pipe_buffer *buf = pipe->bufs + lastbuf;

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



		if (buf->ops->can_merge && offset + chars <= PAGE_SIZE) {

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

			ret = pipe_buf_confirm(pipe, buf);

			if (ret)

				goto out;

fs/splice.c

+0 −4
Original line number Diff line number Diff line
@@ -138,7 +138,6 @@ error: 
}



const struct pipe_buf_operations page_cache_pipe_buf_ops = {

	.can_merge = 0,

	.confirm = page_cache_pipe_buf_confirm,

	.release = page_cache_pipe_buf_release,

	.steal = page_cache_pipe_buf_steal,
@@ -156,7 +155,6 @@ static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe, 
}



static const struct pipe_buf_operations user_page_pipe_buf_ops = {

	.can_merge = 0,

	.confirm = generic_pipe_buf_confirm,

	.release = page_cache_pipe_buf_release,

	.steal = user_page_pipe_buf_steal,
@@ -326,7 +324,6 @@ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos, 
EXPORT_SYMBOL(generic_file_splice_read);



const struct pipe_buf_operations default_pipe_buf_ops = {

	.can_merge = 0,

	.confirm = generic_pipe_buf_confirm,

	.release = generic_pipe_buf_release,

	.steal = generic_pipe_buf_steal,
@@ -341,7 +338,6 @@ static int generic_pipe_buf_nosteal(struct pipe_inode_info *pipe, 


/* Pipe buffer operations for a socket and similar. */

const struct pipe_buf_operations nosteal_pipe_buf_ops = {

	.can_merge = 0,

	.confirm = generic_pipe_buf_confirm,

	.release = generic_pipe_buf_release,

	.steal = generic_pipe_buf_nosteal,

include/linux/pipe_fs_i.h

+0 −7
Original line number Diff line number Diff line
@@ -73,13 +73,6 @@ struct pipe_inode_info { 
 * 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

kernel/relay.c

+0 −1
Original line number Diff line number Diff line
@@ -1175,7 +1175,6 @@ static void relay_pipe_buf_release(struct pipe_inode_info *pipe, 
}



static const struct pipe_buf_operations relay_pipe_buf_ops = {

	.can_merge = 0,

	.confirm = generic_pipe_buf_confirm,

	.release = relay_pipe_buf_release,

	.steal = generic_pipe_buf_steal,

kernel/trace/trace.c

+0 −2
Original line number Diff line number Diff line
@@ -5823,7 +5823,6 @@ static void tracing_spd_release_pipe(struct splice_pipe_desc *spd, 
}



static const struct pipe_buf_operations tracing_pipe_buf_ops = {

	.can_merge		= 0,

	.confirm		= generic_pipe_buf_confirm,

	.release		= generic_pipe_buf_release,

	.steal			= generic_pipe_buf_steal,
@@ -6843,7 +6842,6 @@ static void buffer_pipe_buf_get(struct pipe_inode_info *pipe, 


/* Pipe buffer operations for a buffer. */

static const struct pipe_buf_operations buffer_pipe_buf_ops = {

	.can_merge		= 0,

	.confirm		= generic_pipe_buf_confirm,

	.release		= buffer_pipe_buf_release,

	.steal			= generic_pipe_buf_steal,

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