[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: Jens Axboe <axboe@suse.de>
diff --git a/fs/pipe.c b/fs/pipe.c
index 888f265..d9644fd 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -110,14 +110,14 @@
page_cache_release(page);
}
-static void * anon_pipe_buf_map(struct file *file, struct pipe_inode_info *pipe,
- struct pipe_buffer *buf)
+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,
- struct pipe_buffer *buf)
+void generic_pipe_buf_unmap(struct pipe_inode_info *pipe,
+ struct pipe_buffer *buf)
{
kunmap(buf->page);
}
@@ -135,19 +135,24 @@
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 @@
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 @@
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);