[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);
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;
}
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index 3130977..b8aae1f 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -14,10 +14,23 @@
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 @@
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.