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Commit f84d7519 authored by Jens Axboe's avatar Jens Axboe
Browse files

[PATCH] pipe: introduce ->pin() buffer operation 



The ->map() function is really expensive on highmem machines right now,
since it has to use the slower kmap() instead of kmap_atomic(). Splice
rarely needs to access the virtual address of a page, so it's a waste
of time doing it.

Introduce ->pin() to take over the responsibility of making sure the
page data is valid. ->map() is then reduced to just kmap(). That way we
can also share a most of the pipe buffer ops between pipe.c and splice.c

Signed-off-by: default avatarJens Axboe <axboe@suse.de>
parent 0568b409

fs/pipe.c

+23 −16
Original line number Diff line number Diff line
@@ -110,13 +110,13 @@ static void anon_pipe_buf_release(struct pipe_inode_info *pipe, 
		page_cache_release(page);

}



static void * anon_pipe_buf_map(struct file *file, struct pipe_inode_info *pipe,

void *generic_pipe_buf_map(struct pipe_inode_info *pipe,

			   struct pipe_buffer *buf)

{

	return kmap(buf->page);

}



static void anon_pipe_buf_unmap(struct pipe_inode_info *pipe,

void generic_pipe_buf_unmap(struct pipe_inode_info *pipe,

			    struct pipe_buffer *buf)

{

	kunmap(buf->page);
@@ -135,19 +135,24 @@ static int anon_pipe_buf_steal(struct pipe_inode_info *pipe, 
	return 1;

}



static void anon_pipe_buf_get(struct pipe_inode_info *info,

			      struct pipe_buffer *buf)

void generic_pipe_buf_get(struct pipe_inode_info *info, struct pipe_buffer *buf)

{

	page_cache_get(buf->page);

}



int generic_pipe_buf_pin(struct pipe_inode_info *info, struct pipe_buffer *buf)

{

	return 0;

}



static struct pipe_buf_operations anon_pipe_buf_ops = {

	.can_merge = 1,

	.map = anon_pipe_buf_map,

	.unmap = anon_pipe_buf_unmap,

	.map = generic_pipe_buf_map,

	.unmap = generic_pipe_buf_unmap,

	.pin = generic_pipe_buf_pin,

	.release = anon_pipe_buf_release,

	.steal = anon_pipe_buf_steal,

	.get = anon_pipe_buf_get,

	.get = generic_pipe_buf_get,

};



static ssize_t
@@ -183,12 +188,14 @@ pipe_readv(struct file *filp, const struct iovec *_iov, 
			if (chars > total_len)

				chars = total_len;



			addr = ops->map(filp, pipe, buf);

			if (IS_ERR(addr)) {

			error = ops->pin(pipe, buf);

			if (error) {

				if (!ret)

					ret = PTR_ERR(addr);

					error = ret;

				break;

			}



			addr = ops->map(pipe, buf);

			error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars);

			ops->unmap(pipe, buf);

			if (unlikely(error)) {
@@ -300,11 +307,11 @@ pipe_writev(struct file *filp, const struct iovec *_iov, 
			void *addr;

			int error;



			addr = ops->map(filp, pipe, buf);

			if (IS_ERR(addr)) {

				error = PTR_ERR(addr);

			error = ops->pin(pipe, buf);

			if (error)

				goto out;

			}



			addr = ops->map(pipe, buf);

			error = pipe_iov_copy_from_user(offset + addr, iov,

							chars);

			ops->unmap(pipe, buf);

fs/splice.c

+30 −61
Original line number Diff line number Diff line
@@ -90,8 +90,7 @@ static void page_cache_pipe_buf_release(struct pipe_inode_info *info, 
	buf->flags &= ~PIPE_BUF_FLAG_LRU;

}



static void *page_cache_pipe_buf_map(struct file *file,

				     struct pipe_inode_info *info,

static int page_cache_pipe_buf_pin(struct pipe_inode_info *info,

				   struct pipe_buffer *buf)

{

	struct page *page = buf->page;
@@ -118,49 +117,25 @@ static void *page_cache_pipe_buf_map(struct file *file, 
		}



		/*

		 * Page is ok afterall, fall through to mapping.

		 * Page is ok afterall, we are done.

		 */

		unlock_page(page);

	}



	return kmap(page);

	return 0;

error:

	unlock_page(page);

	return ERR_PTR(err);

}



static void page_cache_pipe_buf_unmap(struct pipe_inode_info *info,

				      struct pipe_buffer *buf)

{

	kunmap(buf->page);

}



static void *user_page_pipe_buf_map(struct file *file,

				    struct pipe_inode_info *pipe,

				    struct pipe_buffer *buf)

{

	return kmap(buf->page);

}



static void user_page_pipe_buf_unmap(struct pipe_inode_info *pipe,

				     struct pipe_buffer *buf)

{

	kunmap(buf->page);

}



static void page_cache_pipe_buf_get(struct pipe_inode_info *info,

				    struct pipe_buffer *buf)

{

	page_cache_get(buf->page);

	return err;

}



static struct pipe_buf_operations page_cache_pipe_buf_ops = {

	.can_merge = 0,

	.map = page_cache_pipe_buf_map,

	.unmap = page_cache_pipe_buf_unmap,

	.map = generic_pipe_buf_map,

	.unmap = generic_pipe_buf_unmap,

	.pin = page_cache_pipe_buf_pin,

	.release = page_cache_pipe_buf_release,

	.steal = page_cache_pipe_buf_steal,

	.get = page_cache_pipe_buf_get,

	.get = generic_pipe_buf_get,

};



static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
@@ -171,11 +146,12 @@ static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe, 


static struct pipe_buf_operations user_page_pipe_buf_ops = {

	.can_merge = 0,

	.map = user_page_pipe_buf_map,

	.unmap = user_page_pipe_buf_unmap,

	.map = generic_pipe_buf_map,

	.unmap = generic_pipe_buf_unmap,

	.pin = generic_pipe_buf_pin,

	.release = page_cache_pipe_buf_release,

	.steal = user_page_pipe_buf_steal,

	.get = page_cache_pipe_buf_get,

	.get = generic_pipe_buf_get,

};



/*
@@ -517,26 +493,16 @@ static int pipe_to_sendpage(struct pipe_inode_info *info, 
{

	struct file *file = sd->file;

	loff_t pos = sd->pos;

	ssize_t ret;

	void *ptr;

	int more;



	/*

	 * Sub-optimal, but we are limited by the pipe ->map. We don't

	 * need a kmap'ed buffer here, we just want to make sure we

	 * have the page pinned if the pipe page originates from the

	 * page cache.

	 */

	ptr = buf->ops->map(file, info, buf);

	if (IS_ERR(ptr))

		return PTR_ERR(ptr);

	int ret, more;



	ret = buf->ops->pin(info, buf);

	if (!ret) {

		more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;



	ret = file->f_op->sendpage(file, buf->page, buf->offset, sd->len,

				   &pos, more);

		ret = file->f_op->sendpage(file, buf->page, buf->offset,

					   sd->len, &pos, more);

	}



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

	return ret;

}
@@ -569,15 +535,14 @@ static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf, 
	unsigned int offset, this_len;

	struct page *page;

	pgoff_t index;

	char *src;

	int ret;



	/*

	 * make sure the data in this buffer is uptodate

	 */

	src = buf->ops->map(file, info, buf);

	if (IS_ERR(src))

		return PTR_ERR(src);

	ret = buf->ops->pin(info, buf);

	if (unlikely(ret))

		return ret;



	index = sd->pos >> PAGE_CACHE_SHIFT;

	offset = sd->pos & ~PAGE_CACHE_MASK;
@@ -666,11 +631,16 @@ find_page: 
		goto out;



	if (buf->page != page) {

		char *dst = kmap_atomic(page, KM_USER0);

		/*

		 * Careful, ->map() uses KM_USER0!

		 */

		char *src = buf->ops->map(info, buf);

		char *dst = kmap_atomic(page, KM_USER1);



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

		flush_dcache_page(page);

		kunmap_atomic(dst, KM_USER0);

		kunmap_atomic(dst, KM_USER1);

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

	}



	ret = mapping->a_ops->commit_write(file, page, offset, offset+this_len);
@@ -690,7 +660,6 @@ out: 
	page_cache_release(page);

	unlock_page(page);

out_nomem:

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

	return ret;

}

include/linux/pipe_fs_i.h

+20 −1
Original line number Diff line number Diff line
@@ -14,10 +14,23 @@ struct pipe_buffer { 
	unsigned int flags;

};



/*

 * Note on the nesting of these functions:

 *

 * ->pin()

 *	->steal()

 *	...

 *	->map()

 *	...

 *	->unmap()

 *

 * That is, ->map() must be called on a pinned buffer, same goes for ->steal().

 */

struct pipe_buf_operations {

	int can_merge;

	void * (*map)(struct file *, struct pipe_inode_info *, struct pipe_buffer *);

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

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

	int (*pin)(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 *);

	void (*get)(struct pipe_inode_info *, struct pipe_buffer *);
@@ -50,6 +63,12 @@ struct pipe_inode_info * alloc_pipe_info(struct inode * inode); 
void free_pipe_info(struct inode * inode);

void __free_pipe_info(struct pipe_inode_info *);



/* Generic pipe buffer ops functions */

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

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

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

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



/*

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

 * add the splice flags here.