Commit 4f6f0bd2 authored by Jens Axboe's avatar Jens Axboe
Browse files

[PATCH] splice: improve writeback and clean up page stealing 



By cleaning up the writeback logic (killing write_one_page() and the manual
set_page_dirty()), we can get rid of ->stolen inside the pipe_buffer and
just keep it local in pipe_to_file().

This also adds dirty page balancing logic and O_SYNC handling.

Signed-off-by: default avatarJens Axboe <axboe@suse.de>
parent 53cd9ae8

fs/pipe.c

+0 −1
Original line number Diff line number Diff line
@@ -124,7 +124,6 @@ static void anon_pipe_buf_unmap(struct pipe_inode_info *info, struct pipe_buffer 
static int anon_pipe_buf_steal(struct pipe_inode_info *info,

			       struct pipe_buffer *buf)

{

	buf->stolen = 1;

	return 0;

}

fs/splice.c

+48 −16
Original line number Diff line number Diff line
@@ -22,7 +22,10 @@ 
#include <linux/pipe_fs_i.h>

#include <linux/mm_inline.h>

#include <linux/swap.h>

#include <linux/writeback.h>

#include <linux/buffer_head.h>

#include <linux/module.h>

#include <linux/syscalls.h>



/*

 * Passed to the actors
@@ -38,11 +41,15 @@ static int page_cache_pipe_buf_steal(struct pipe_inode_info *info, 
				     struct pipe_buffer *buf)

{

	struct page *page = buf->page;

	struct address_space *mapping = page_mapping(page);



	WARN_ON(!PageLocked(page));

	WARN_ON(!PageUptodate(page));



	if (!remove_mapping(page_mapping(page), page))

	if (PagePrivate(page))

		try_to_release_page(page, mapping_gfp_mask(mapping));



	if (!remove_mapping(mapping, page))

		return 1;



	if (PageLRU(page)) {
@@ -55,7 +62,6 @@ static int page_cache_pipe_buf_steal(struct pipe_inode_info *info, 
		spin_unlock_irq(&zone->lru_lock);

	}



	buf->stolen = 1;

	return 0;

}
@@ -64,7 +70,6 @@ static void page_cache_pipe_buf_release(struct pipe_inode_info *info, 
{

	page_cache_release(buf->page);

	buf->page = NULL;

	buf->stolen = 0;

}



static void *page_cache_pipe_buf_map(struct file *file,
@@ -91,7 +96,6 @@ static void *page_cache_pipe_buf_map(struct file *file, 
static void page_cache_pipe_buf_unmap(struct pipe_inode_info *info,

				      struct pipe_buffer *buf)

{

	if (!buf->stolen)

	unlock_page(buf->page);

	kunmap(buf->page);

}
@@ -319,7 +323,8 @@ ssize_t generic_file_splice_read(struct file *in, struct inode *pipe, 
}



/*

 * Send 'len' bytes to socket from 'file' at position 'pos' using sendpage().

 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'

 * using sendpage().

 */

static int pipe_to_sendpage(struct pipe_inode_info *info,

			    struct pipe_buffer *buf, struct splice_desc *sd)
@@ -379,7 +384,7 @@ static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf, 
	struct page *page;

	pgoff_t index;

	char *src;

	int ret;

	int ret, stolen;



	/*

	 * after this, page will be locked and unmapped
@@ -390,6 +395,7 @@ static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf, 


	index = sd->pos >> PAGE_CACHE_SHIFT;

	offset = sd->pos & ~PAGE_CACHE_MASK;

	stolen = 0;



	/*

	 * reuse buf page, if SPLICE_F_MOVE is set
@@ -399,6 +405,7 @@ static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf, 
			goto find_page;



		page = buf->page;

		stolen = 1;

		if (add_to_page_cache_lru(page, mapping, index,

						mapping_gfp_mask(mapping)))

			goto find_page;
@@ -443,10 +450,13 @@ find_page: 
	}



	ret = mapping->a_ops->prepare_write(file, page, 0, sd->len);

	if (ret)

	if (ret == AOP_TRUNCATED_PAGE) {

		page_cache_release(page);

		goto find_page;

	} else if (ret)

		goto out;



	if (!buf->stolen) {

	if (!stolen) {

		char *dst = kmap_atomic(page, KM_USER0);



		memcpy(dst + offset, src + buf->offset, sd->len);
@@ -455,16 +465,18 @@ find_page: 
	}



	ret = mapping->a_ops->commit_write(file, page, 0, sd->len);

	if (ret < 0)

	if (ret == AOP_TRUNCATED_PAGE) {

		page_cache_release(page);

		goto find_page;

	} else if (ret)

		goto out;



	set_page_dirty(page);

	ret = write_one_page(page, 0);

	balance_dirty_pages_ratelimited(mapping);

out:

	if (ret < 0)

		unlock_page(page);

	if (!buf->stolen)

	if (!stolen) {

		page_cache_release(page);

		unlock_page(page);

	}

	buf->ops->unmap(info, buf);

	return ret;

}
@@ -576,7 +588,27 @@ static ssize_t move_from_pipe(struct inode *inode, struct file *out, 
ssize_t generic_file_splice_write(struct inode *inode, struct file *out,

				  size_t len, unsigned int flags)

{

	return move_from_pipe(inode, out, len, flags, pipe_to_file);

	struct address_space *mapping = out->f_mapping;

	ssize_t ret = move_from_pipe(inode, out, len, flags, pipe_to_file);



	/*

	 * if file or inode is SYNC and we actually wrote some data, sync it

	 */

	if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(mapping->host))

	    && ret > 0) {

		struct inode *inode = mapping->host;

		int err;



		mutex_lock(&inode->i_mutex);

		err = generic_osync_inode(mapping->host, mapping,

						OSYNC_METADATA|OSYNC_DATA);

		mutex_unlock(&inode->i_mutex);



		if (err)

			ret = err;

	}



	return ret;

}



ssize_t generic_splice_sendpage(struct inode *inode, struct file *out,

include/linux/pipe_fs_i.h

+0 −1
Original line number Diff line number Diff line
@@ -9,7 +9,6 @@ struct pipe_buffer { 
	struct page *page;

	unsigned int offset, len;

	struct pipe_buf_operations *ops;

	unsigned int stolen;

};



struct pipe_buf_operations {

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