From: Miklos Szeredi <[email protected]>
The 'steal' operation hasn't been used for some time. Remove it and
the associated dead code. If it's needed in the future, it can always
be easily restored.
Signed-off-by: Miklos Szeredi <[email protected]>
---
fs/pipe.c | 31 -----------------------
fs/splice.c | 62 ----------------------------------------------
include/linux/pipe_fs_i.h | 20 ++------------
kernel/relay.c | 1
net/core/skbuff.c | 8 -----
5 files changed, 3 insertions(+), 119 deletions(-)
Index: linux-2.6/fs/pipe.c
===================================================================
--- linux-2.6.orig/fs/pipe.c 2008-06-21 10:17:43.000000000 +0200
+++ linux-2.6/fs/pipe.c 2008-06-21 11:46:52.000000000 +0200
@@ -209,36 +209,6 @@ void generic_pipe_buf_unmap(struct pipe_
}
/**
- * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
- * @pipe: the pipe that the buffer belongs to
- * @buf: the buffer to attempt to steal
- *
- * Description:
- * This function attempts to steal the &struct page attached to
- * @buf. If successful, this function returns 0 and returns with
- * the page locked. The caller may then reuse the page for whatever
- * he wishes; the typical use is insertion into a different file
- * page cache.
- */
-int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
- struct pipe_buffer *buf)
-{
- struct page *page = buf->page;
-
- /*
- * A reference of one is golden, that means that the owner of this
- * page is the only one holding a reference to it. lock the page
- * and return OK.
- */
- if (page_count(page) == 1) {
- lock_page(page);
- return 0;
- }
-
- return 1;
-}
-
-/**
* generic_pipe_buf_get - get a reference to a &struct pipe_buffer
* @pipe: the pipe that the buffer belongs to
* @buf: the buffer to get a reference to
@@ -274,7 +244,6 @@ static const struct pipe_buf_operations
.unmap = generic_pipe_buf_unmap,
.confirm = generic_pipe_buf_confirm,
.release = anon_pipe_buf_release,
- .steal = generic_pipe_buf_steal,
.get = generic_pipe_buf_get,
};
Index: linux-2.6/fs/splice.c
===================================================================
--- linux-2.6.orig/fs/splice.c 2008-06-21 10:19:01.000000000 +0200
+++ linux-2.6/fs/splice.c 2008-06-21 11:46:52.000000000 +0200
@@ -30,56 +30,6 @@
#include <linux/uio.h>
#include <linux/security.h>
-/*
- * Attempt to steal a page from a pipe buffer. This should perhaps go into
- * a vm helper function, it's already simplified quite a bit by the
- * addition of remove_mapping(). If success is returned, the caller may
- * attempt to reuse this page for another destination.
- */
-static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
- struct pipe_buffer *buf)
-{
- struct page *page = buf->page;
- struct address_space *mapping;
-
- lock_page(page);
-
- mapping = page_mapping(page);
- if (mapping) {
- WARN_ON(!PageUptodate(page));
-
- /*
- * At least for ext2 with nobh option, we need to wait on
- * writeback completing on this page, since we'll remove it
- * from the pagecache. Otherwise truncate wont wait on the
- * page, allowing the disk blocks to be reused by someone else
- * before we actually wrote our data to them. fs corruption
- * ensues.
- */
- wait_on_page_writeback(page);
-
- if (PagePrivate(page) && !try_to_release_page(page, GFP_KERNEL))
- goto out_unlock;
-
- /*
- * If we succeeded in removing the mapping, set LRU flag
- * and return good.
- */
- if (remove_mapping(mapping, page)) {
- buf->flags |= PIPE_BUF_FLAG_LRU;
- return 0;
- }
- }
-
- /*
- * Raced with truncate or failed to remove page from current
- * address space, unlock and return failure.
- */
-out_unlock:
- unlock_page(page);
- return 1;
-}
-
static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
struct pipe_buffer *buf)
{
@@ -135,27 +85,15 @@ static const struct pipe_buf_operations
.unmap = generic_pipe_buf_unmap,
.confirm = page_cache_pipe_buf_confirm,
.release = page_cache_pipe_buf_release,
- .steal = page_cache_pipe_buf_steal,
.get = generic_pipe_buf_get,
};
-static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
- struct pipe_buffer *buf)
-{
- if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
- return 1;
-
- buf->flags |= PIPE_BUF_FLAG_LRU;
- return generic_pipe_buf_steal(pipe, buf);
-}
-
static const struct pipe_buf_operations user_page_pipe_buf_ops = {
.can_merge = 0,
.map = generic_pipe_buf_map,
.unmap = generic_pipe_buf_unmap,
.confirm = generic_pipe_buf_confirm,
.release = page_cache_pipe_buf_release,
- .steal = user_page_pipe_buf_steal,
.get = generic_pipe_buf_get,
};
Index: linux-2.6/include/linux/pipe_fs_i.h
===================================================================
--- linux-2.6.orig/include/linux/pipe_fs_i.h 2008-06-21 10:17:43.000000000 +0200
+++ linux-2.6/include/linux/pipe_fs_i.h 2008-06-21 11:46:52.000000000 +0200
@@ -61,16 +61,13 @@ struct pipe_inode_info {
* Note on the nesting of these functions:
*
* ->confirm()
- * ->steal()
- * ...
* ->map()
* ...
* ->unmap()
*
- * That is, ->map() must be called on a confirmed buffer,
- * same goes for ->steal(). See below for the meaning of each
- * operation. Also see kerneldoc in fs/pipe.c for the pipe
- * and generic variants of these hooks.
+ * That is, ->map() must be called on a confirmed buffer. See below
+ * for the meaning of each operation. Also see kerneldoc in fs/pipe.c
+ * for the pipe and generic variants of these hooks.
*/
struct pipe_buf_operations {
/*
@@ -115,16 +112,6 @@ struct pipe_buf_operations {
void (*release)(struct pipe_inode_info *, struct pipe_buffer *);
/*
- * Attempt to take ownership of the pipe buffer and its contents.
- * ->steal() returns 0 for success, in which case the contents
- * of the pipe (the buf->page) is locked and now completely owned
- * by the caller. The page may then be transferred to a different
- * mapping, the most often used case is insertion into different
- * file address space cache.
- */
- int (*steal)(struct pipe_inode_info *, struct pipe_buffer *);
-
- /*
* Get a reference to the pipe buffer.
*/
void (*get)(struct pipe_inode_info *, struct pipe_buffer *);
@@ -146,6 +133,5 @@ void *generic_pipe_buf_map(struct pipe_i
void generic_pipe_buf_unmap(struct pipe_inode_info *, struct pipe_buffer *, void *);
void generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
-int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
#endif
Index: linux-2.6/net/core/skbuff.c
===================================================================
--- linux-2.6.orig/net/core/skbuff.c 2008-06-21 10:17:43.000000000 +0200
+++ linux-2.6/net/core/skbuff.c 2008-06-21 11:46:52.000000000 +0200
@@ -88,13 +88,6 @@ static void sock_pipe_buf_get(struct pip
skb_get(skb);
}
-static int sock_pipe_buf_steal(struct pipe_inode_info *pipe,
- struct pipe_buffer *buf)
-{
- return 1;
-}
-
-
/* Pipe buffer operations for a socket. */
static struct pipe_buf_operations sock_pipe_buf_ops = {
.can_merge = 0,
@@ -102,7 +95,6 @@ static struct pipe_buf_operations sock_p
.unmap = generic_pipe_buf_unmap,
.confirm = generic_pipe_buf_confirm,
.release = sock_pipe_buf_release,
- .steal = sock_pipe_buf_steal,
.get = sock_pipe_buf_get,
};
Index: linux-2.6/kernel/relay.c
===================================================================
--- linux-2.6.orig/kernel/relay.c 2008-06-21 11:46:52.000000000 +0200
+++ linux-2.6/kernel/relay.c 2008-06-21 11:47:05.000000000 +0200
@@ -1081,7 +1081,6 @@ static struct pipe_buf_operations relay_
.unmap = generic_pipe_buf_unmap,
.confirm = generic_pipe_buf_confirm,
.release = relay_pipe_buf_release,
- .steal = generic_pipe_buf_steal,
.get = generic_pipe_buf_get,
};
--
On Sat, Jun 21 2008, Miklos Szeredi wrote:
> From: Miklos Szeredi <[email protected]>
>
> The 'steal' operation hasn't been used for some time. Remove it and
> the associated dead code. If it's needed in the future, it can always
> be easily restored.
I'd rather not just remove this, it's basically waiting for Nick to make
good on his promise to make stealing work again (he disabled it).
--
Jens Axboe
> On Sat, Jun 21 2008, Miklos Szeredi wrote:
> > From: Miklos Szeredi <[email protected]>
> >
> > The 'steal' operation hasn't been used for some time. Remove it and
> > the associated dead code. If it's needed in the future, it can always
> > be easily restored.
>
> I'd rather not just remove this, it's basically waiting for Nick to make
> good on his promise to make stealing work again (he disabled it).
Yes, I read the commit log. He disabled it with the intent that we
may or may not want this interface back, and possibly in some other
form.
Jens, does somebody need this feature? What for? If not, then I
guess nobody will bother implementing it.
(Nick CC-d)
Thanks,
Miklos
On Tuesday 24 June 2008 18:50, Miklos Szeredi wrote:
> > On Sat, Jun 21 2008, Miklos Szeredi wrote:
> > > From: Miklos Szeredi <[email protected]>
> > >
> > > The 'steal' operation hasn't been used for some time. Remove it and
> > > the associated dead code. If it's needed in the future, it can always
> > > be easily restored.
> >
> > I'd rather not just remove this, it's basically waiting for Nick to make
> > good on his promise to make stealing work again (he disabled it).
>
> Yes, I read the commit log. He disabled it with the intent that we
> may or may not want this interface back, and possibly in some other
> form.
>
> Jens, does somebody need this feature? What for? If not, then I
> guess nobody will bother implementing it.
>
> (Nick CC-d)
I've kind of wanted to implement it "because it is cool", but also
because I hoped to ensure the new write_begin/write_end APIs would
be general enough to support it.
Unfortunately I'm not aware of a killer feature so it's kept going
down the todo pile. However it really is one of those things where
you need the API to work before you get programs emerging that make
interesting uses out of it. I think if it can be done without adding
complication to pagecache/filesystem code, then it would be nice.