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Commit 5abc97aa authored by Jens Axboe's avatar Jens Axboe Committed by Linus Torvalds
Browse files

[PATCH] splice: add support for SPLICE_F_MOVE flag 



This enables the caller to migrate pages from one address space page
cache to another.  In buzz word marketing, you can do zero-copy file
copies!

Signed-off-by: default avatarJens Axboe <axboe@suse.de>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 5274f052

fs/pipe.c

+8 −0
Original line number Diff line number Diff line
@@ -121,11 +121,19 @@ static void anon_pipe_buf_unmap(struct pipe_inode_info *info, struct pipe_buffer 
	kunmap(buf->page);

}



static int anon_pipe_buf_steal(struct pipe_inode_info *info,

			       struct pipe_buffer *buf)

{

	buf->stolen = 1;

	return 0;

}



static struct pipe_buf_operations anon_pipe_buf_ops = {

	.can_merge = 1,

	.map = anon_pipe_buf_map,

	.unmap = anon_pipe_buf_unmap,

	.release = anon_pipe_buf_release,

	.steal = anon_pipe_buf_steal,

};



static ssize_t

fs/splice.c

+84 −37
Original line number Diff line number Diff line
@@ -21,6 +21,7 @@ 
#include <linux/pagemap.h>

#include <linux/pipe_fs_i.h>

#include <linux/mm_inline.h>

#include <linux/swap.h>



/*

 * Passed to the actors
@@ -32,11 +33,37 @@ struct splice_desc { 
	loff_t pos;			/* file position */

};



static int page_cache_pipe_buf_steal(struct pipe_inode_info *info,

				     struct pipe_buffer *buf)

{

	struct page *page = buf->page;



	WARN_ON(!PageLocked(page));

	WARN_ON(!PageUptodate(page));



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

		return 1;



	if (PageLRU(page)) {

		struct zone *zone = page_zone(page);



		spin_lock_irq(&zone->lru_lock);

		BUG_ON(!PageLRU(page));

		__ClearPageLRU(page);

		del_page_from_lru(zone, page);

		spin_unlock_irq(&zone->lru_lock);

	}



	buf->stolen = 1;

	return 0;

}



static void page_cache_pipe_buf_release(struct pipe_inode_info *info,

					struct pipe_buffer *buf)

{

	page_cache_release(buf->page);

	buf->page = NULL;

	buf->stolen = 0;

}



static void *page_cache_pipe_buf_map(struct file *file,
@@ -63,6 +90,7 @@ 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);

}
@@ -72,6 +100,7 @@ static struct pipe_buf_operations page_cache_pipe_buf_ops = { 
	.map = page_cache_pipe_buf_map,

	.unmap = page_cache_pipe_buf_unmap,

	.release = page_cache_pipe_buf_release,

	.steal = page_cache_pipe_buf_steal,

};



static ssize_t move_to_pipe(struct inode *inode, struct page **pages,
@@ -336,8 +365,8 @@ static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf, 
	struct address_space *mapping = file->f_mapping;

	unsigned int offset;

	struct page *page;

	char *src, *dst;

	pgoff_t index;

	char *src;

	int ret;



	/*
@@ -350,9 +379,22 @@ 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;



	/*

	 * reuse buf page, if SPLICE_F_MOVE is set

	 */

	if (sd->flags & SPLICE_F_MOVE) {

		if (buf->ops->steal(info, buf))

			goto find_page;



		page = buf->page;

		if (add_to_page_cache_lru(page, mapping, index,

						mapping_gfp_mask(mapping)))

			goto find_page;

	} else {

find_page:

		ret = -ENOMEM;

	page = find_or_create_page(mapping, index, mapping_gfp_mask(mapping));

		page = find_or_create_page(mapping, index,

						mapping_gfp_mask(mapping));

		if (!page)

			goto out;
@@ -386,15 +428,19 @@ static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf, 
				SetPageUptodate(page);

			}

		}

	}



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

	if (ret)

		goto out;



	dst = kmap_atomic(page, KM_USER0);

	if (!buf->stolen) {

		char *dst = kmap_atomic(page, KM_USER0);



		memcpy(dst + offset, src + buf->offset, sd->len);

		flush_dcache_page(page);

		kunmap_atomic(dst, KM_USER0);

	}



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

	if (ret < 0)
@@ -405,6 +451,7 @@ static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf, 
out:

	if (ret < 0)

		unlock_page(page);

	if (!buf->stolen)

		page_cache_release(page);

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

	return ret;

include/linux/pipe_fs_i.h

+8 −0
Original line number Diff line number Diff line
@@ -9,6 +9,7 @@ struct pipe_buffer { 
	struct page *page;

	unsigned int offset, len;

	struct pipe_buf_operations *ops;

	unsigned int stolen;

};



struct pipe_buf_operations {
@@ -16,6 +17,7 @@ struct pipe_buf_operations { 
	void * (*map)(struct file *, struct pipe_inode_info *, struct pipe_buffer *);

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

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

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

};



struct pipe_inode_info {
@@ -53,4 +55,10 @@ void pipe_wait(struct inode * inode); 
struct inode* pipe_new(struct inode* inode);

void free_pipe_info(struct inode* inode);



/*

 * splice is tied to pipes as a transport (at least for now), so we'll just

 * add the splice flags here.

 */

#define SPLICE_F_MOVE	(0x01)	/* move pages instead of copying */



#endif