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

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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: Jens Axboe <axboe@suse.de>
This commit is contained in:
Jens Axboe 2006-05-01 19:59:03 +02:00
parent 0568b409c7
commit f84d751994
3 changed files with 73 additions and 78 deletions
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21
include/linux/pipe_fs_i.h
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@ -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.