[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/splice.c b/fs/splice.c
index 1633778..d7538d8 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -90,9 +90,8 @@
buf->flags &= ~PIPE_BUF_FLAG_LRU;
}
-static void *page_cache_pipe_buf_map(struct file *file,
- struct pipe_inode_info *info,
- struct pipe_buffer *buf)
+static int page_cache_pipe_buf_pin(struct pipe_inode_info *info,
+ struct pipe_buffer *buf)
{
struct page *page = buf->page;
int err;
@@ -118,49 +117,25 @@
}
/*
- * 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 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 @@
{
struct file *file = sd->file;
loff_t pos = sd->pos;
- ssize_t ret;
- void *ptr;
- int more;
+ int ret, 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);
+ ret = buf->ops->pin(info, buf);
+ if (!ret) {
+ more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
- 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 @@
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 @@
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 @@
page_cache_release(page);
unlock_page(page);
out_nomem:
- buf->ops->unmap(info, buf);
return ret;
}