From 0568b409c74f7a125d92a09a3f386785700ef688 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@suse.de>
Date: Mon, 1 May 2006 19:50:48 +0200
Subject: [PATCH] splice: fix bugs in pipe_to_file()

Found by Oleg Nesterov <oleg@tv-sign.ru>, fixed by me.

- Only allow full pages to go to the page cache.
- Check page != buf->page instead of using PIPE_BUF_FLAG_STOLEN.
- Remember to clear 'stolen' if add_to_page_cache() fails.

And as a cleanup on that:

- Make the bottom fall-through logic a little less convoluted. Also make
  the steal path hold an extra reference to the page, so we don't have
  to differentiate between stolen and non-stolen at the end.

Signed-off-by: Jens Axboe <axboe@suse.de>
---
 include/linux/pipe_fs_i.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

(limited to 'include/linux')

diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index 0008d4bd4059..3130977fc6ab 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -5,8 +5,7 @@
 
 #define PIPE_BUFFERS (16)
 
-#define PIPE_BUF_FLAG_STOLEN	0x01
-#define PIPE_BUF_FLAG_LRU	0x02
+#define PIPE_BUF_FLAG_LRU	0x01
 
 struct pipe_buffer {
 	struct page *page;
-- 
cgit v1.2.3-71-gd317


From f84d751994441292593523c7069ed147176f6cab Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@suse.de>
Date: Mon, 1 May 2006 19:59:03 +0200
Subject: [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>
---
 fs/pipe.c                 | 39 +++++++++++---------
 fs/splice.c               | 91 ++++++++++++++++-------------------------------
 include/linux/pipe_fs_i.h | 21 ++++++++++-
 3 files changed, 73 insertions(+), 78 deletions(-)

(limited to 'include/linux')

diff --git a/fs/pipe.c b/fs/pipe.c
index 888f265011bf..d9644fd9cc0d 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -110,14 +110,14 @@ static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
 		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 @@ static int anon_pipe_buf_steal(struct pipe_inode_info *pipe,
 	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 @@ pipe_readv(struct file *filp, const struct iovec *_iov,
 			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 @@ pipe_writev(struct file *filp, const struct iovec *_iov,
 			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 1633778f3652..d7538d83c367 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -90,9 +90,8 @@ static void page_cache_pipe_buf_release(struct pipe_inode_info *info,
 	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 @@ static void *page_cache_pipe_buf_map(struct file *file,
 		}
 
 		/*
-		 * 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 int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
 
 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 @@ static int pipe_to_sendpage(struct pipe_inode_info *info,
 {
 	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);
-
-	more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
+	ret = buf->ops->pin(info, buf);
+	if (!ret) {
+		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 @@ static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
 	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 @@ find_page:
 		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 @@ out:
 	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 3130977fc6ab..b8aae1fc5185 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -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.
-- 
cgit v1.2.3-71-gd317


From f6762b7ad8edd6abc802542ce845d3bc8adcb92f Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@suse.de>
Date: Mon, 1 May 2006 20:02:05 +0200
Subject: [PATCH] pipe: enable atomic copying of pipe data to/from user space

The pipe ->map() method uses kmap() to virtually map the pages, which
is both slow and has known scalability issues on SMP. This patch enables
atomic copying of pipe pages, by pre-faulting data and using kmap_atomic()
instead.

lmbench bw_pipe and lat_pipe measurements agree this is a Good Thing. Here
are results from that on a UP machine with highmem (1.5GiB of RAM), running
first a UP kernel, SMP kernel, and SMP kernel patched.

Vanilla-UP:
Pipe bandwidth: 1622.28 MB/sec
Pipe bandwidth: 1610.59 MB/sec
Pipe bandwidth: 1608.30 MB/sec
Pipe latency: 7.3275 microseconds
Pipe latency: 7.2995 microseconds
Pipe latency: 7.3097 microseconds

Vanilla-SMP:
Pipe bandwidth: 1382.19 MB/sec
Pipe bandwidth: 1317.27 MB/sec
Pipe bandwidth: 1355.61 MB/sec
Pipe latency: 9.6402 microseconds
Pipe latency: 9.6696 microseconds
Pipe latency: 9.6153 microseconds

Patched-SMP:
Pipe bandwidth: 1578.70 MB/sec
Pipe bandwidth: 1579.95 MB/sec
Pipe bandwidth: 1578.63 MB/sec
Pipe latency: 9.1654 microseconds
Pipe latency: 9.2266 microseconds
Pipe latency: 9.1527 microseconds

Signed-off-by: Jens Axboe <axboe@suse.de>
---
 fs/pipe.c                 | 141 ++++++++++++++++++++++++++++++++++++++--------
 fs/splice.c               |   4 +-
 include/linux/pipe_fs_i.h |  11 ++--
 3 files changed, 126 insertions(+), 30 deletions(-)

(limited to 'include/linux')

diff --git a/fs/pipe.c b/fs/pipe.c
index d9644fd9cc0d..3941a7f78b5d 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -55,7 +55,8 @@ void pipe_wait(struct pipe_inode_info *pipe)
 }
 
 static int
-pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len)
+pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len,
+			int atomic)
 {
 	unsigned long copy;
 
@@ -64,8 +65,13 @@ pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len)
 			iov++;
 		copy = min_t(unsigned long, len, iov->iov_len);
 
-		if (copy_from_user(to, iov->iov_base, copy))
-			return -EFAULT;
+		if (atomic) {
+			if (__copy_from_user_inatomic(to, iov->iov_base, copy))
+				return -EFAULT;
+		} else {
+			if (copy_from_user(to, iov->iov_base, copy))
+				return -EFAULT;
+		}
 		to += copy;
 		len -= copy;
 		iov->iov_base += copy;
@@ -75,7 +81,8 @@ pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len)
 }
 
 static int
-pipe_iov_copy_to_user(struct iovec *iov, const void *from, unsigned long len)
+pipe_iov_copy_to_user(struct iovec *iov, const void *from, unsigned long len,
+		      int atomic)
 {
 	unsigned long copy;
 
@@ -84,8 +91,13 @@ pipe_iov_copy_to_user(struct iovec *iov, const void *from, unsigned long len)
 			iov++;
 		copy = min_t(unsigned long, len, iov->iov_len);
 
-		if (copy_to_user(iov->iov_base, from, copy))
-			return -EFAULT;
+		if (atomic) {
+			if (__copy_to_user_inatomic(iov->iov_base, from, copy))
+				return -EFAULT;
+		} else {
+			if (copy_to_user(iov->iov_base, from, copy))
+				return -EFAULT;
+		}
 		from += copy;
 		len -= copy;
 		iov->iov_base += copy;
@@ -94,6 +106,47 @@ pipe_iov_copy_to_user(struct iovec *iov, const void *from, unsigned long len)
 	return 0;
 }
 
+/*
+ * Attempt to pre-fault in the user memory, so we can use atomic copies.
+ * Returns the number of bytes not faulted in.
+ */
+static int iov_fault_in_pages_write(struct iovec *iov, unsigned long len)
+{
+	while (!iov->iov_len)
+		iov++;
+
+	while (len > 0) {
+		unsigned long this_len;
+
+		this_len = min_t(unsigned long, len, iov->iov_len);
+		if (fault_in_pages_writeable(iov->iov_base, this_len))
+			break;
+
+		len -= this_len;
+		iov++;
+	}
+
+	return len;
+}
+
+/*
+ * Pre-fault in the user memory, so we can use atomic copies.
+ */
+static void iov_fault_in_pages_read(struct iovec *iov, unsigned long len)
+{
+	while (!iov->iov_len)
+		iov++;
+
+	while (len > 0) {
+		unsigned long this_len;
+
+		this_len = min_t(unsigned long, len, iov->iov_len);
+		fault_in_pages_readable(iov->iov_base, this_len);
+		len -= this_len;
+		iov++;
+	}
+}
+
 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
 				  struct pipe_buffer *buf)
 {
@@ -111,15 +164,24 @@ static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
 }
 
 void *generic_pipe_buf_map(struct pipe_inode_info *pipe,
-			   struct pipe_buffer *buf)
+			   struct pipe_buffer *buf, int atomic)
 {
+	if (atomic) {
+		buf->flags |= PIPE_BUF_FLAG_ATOMIC;
+		return kmap_atomic(buf->page, KM_USER0);
+	}
+
 	return kmap(buf->page);
 }
 
 void generic_pipe_buf_unmap(struct pipe_inode_info *pipe,
-			    struct pipe_buffer *buf)
+			    struct pipe_buffer *buf, void *map_data)
 {
-	kunmap(buf->page);
+	if (buf->flags & PIPE_BUF_FLAG_ATOMIC) {
+		buf->flags &= ~PIPE_BUF_FLAG_ATOMIC;
+		kunmap_atomic(map_data, KM_USER0);
+	} else
+		kunmap(buf->page);
 }
 
 static int anon_pipe_buf_steal(struct pipe_inode_info *pipe,
@@ -183,7 +245,7 @@ pipe_readv(struct file *filp, const struct iovec *_iov,
 			struct pipe_buf_operations *ops = buf->ops;
 			void *addr;
 			size_t chars = buf->len;
-			int error;
+			int error, atomic;
 
 			if (chars > total_len)
 				chars = total_len;
@@ -195,12 +257,21 @@ pipe_readv(struct file *filp, const struct iovec *_iov,
 				break;
 			}
 
-			addr = ops->map(pipe, buf);
-			error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars);
-			ops->unmap(pipe, buf);
+			atomic = !iov_fault_in_pages_write(iov, chars);
+redo:
+			addr = ops->map(pipe, buf, atomic);
+			error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars, atomic);
+			ops->unmap(pipe, buf, addr);
 			if (unlikely(error)) {
+				/*
+				 * Just retry with the slow path if we failed.
+				 */
+				if (atomic) {
+					atomic = 0;
+					goto redo;
+				}
 				if (!ret)
-					ret = -EFAULT;
+					ret = error;
 				break;
 			}
 			ret += chars;
@@ -304,21 +375,28 @@ pipe_writev(struct file *filp, const struct iovec *_iov,
 		int offset = buf->offset + buf->len;
 
 		if (ops->can_merge && offset + chars <= PAGE_SIZE) {
+			int error, atomic = 1;
 			void *addr;
-			int error;
 
 			error = ops->pin(pipe, buf);
 			if (error)
 				goto out;
 
-			addr = ops->map(pipe, buf);
+			iov_fault_in_pages_read(iov, chars);
+redo1:
+			addr = ops->map(pipe, buf, atomic);
 			error = pipe_iov_copy_from_user(offset + addr, iov,
-							chars);
-			ops->unmap(pipe, buf);
+							chars, atomic);
+			ops->unmap(pipe, buf, addr);
 			ret = error;
 			do_wakeup = 1;
-			if (error)
+			if (error) {
+				if (atomic) {
+					atomic = 0;
+					goto redo1;
+				}
 				goto out;
+			}
 			buf->len += chars;
 			total_len -= chars;
 			ret = chars;
@@ -341,7 +419,8 @@ pipe_writev(struct file *filp, const struct iovec *_iov,
 			int newbuf = (pipe->curbuf + bufs) & (PIPE_BUFFERS-1);
 			struct pipe_buffer *buf = pipe->bufs + newbuf;
 			struct page *page = pipe->tmp_page;
-			int error;
+			char *src;
+			int error, atomic = 1;
 
 			if (!page) {
 				page = alloc_page(GFP_HIGHUSER);
@@ -361,11 +440,27 @@ pipe_writev(struct file *filp, const struct iovec *_iov,
 			if (chars > total_len)
 				chars = total_len;
 
-			error = pipe_iov_copy_from_user(kmap(page), iov, chars);
-			kunmap(page);
+			iov_fault_in_pages_read(iov, chars);
+redo2:
+			if (atomic)
+				src = kmap_atomic(page, KM_USER0);
+			else
+				src = kmap(page);
+
+			error = pipe_iov_copy_from_user(src, iov, chars,
+							atomic);
+			if (atomic)
+				kunmap_atomic(src, KM_USER0);
+			else
+				kunmap(page);
+
 			if (unlikely(error)) {
+				if (atomic) {
+					atomic = 0;
+					goto redo2;
+				}
 				if (!ret)
-					ret = -EFAULT;
+					ret = error;
 				break;
 			}
 			ret += chars;
diff --git a/fs/splice.c b/fs/splice.c
index 0a6916423e7d..d4664a297bab 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -640,13 +640,13 @@ find_page:
 		/*
 		 * Careful, ->map() uses KM_USER0!
 		 */
-		char *src = buf->ops->map(info, buf);
+		char *src = buf->ops->map(info, buf, 1);
 		char *dst = kmap_atomic(page, KM_USER1);
 
 		memcpy(dst + offset, src + buf->offset, this_len);
 		flush_dcache_page(page);
 		kunmap_atomic(dst, KM_USER1);
-		buf->ops->unmap(info, buf);
+		buf->ops->unmap(info, buf, src);
 	}
 
 	ret = mapping->a_ops->commit_write(file, page, offset, offset+this_len);
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index b8aae1fc5185..4c054491e38e 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -5,7 +5,8 @@
 
 #define PIPE_BUFFERS (16)
 
-#define PIPE_BUF_FLAG_LRU	0x01
+#define PIPE_BUF_FLAG_LRU	0x01	/* page is on the LRU */
+#define PIPE_BUF_FLAG_ATOMIC	0x02	/* was atomically mapped */
 
 struct pipe_buffer {
 	struct page *page;
@@ -28,8 +29,8 @@ struct pipe_buffer {
  */
 struct pipe_buf_operations {
 	int can_merge;
-	void * (*map)(struct pipe_inode_info *, struct pipe_buffer *);
-	void (*unmap)(struct pipe_inode_info *, struct pipe_buffer *);
+	void * (*map)(struct pipe_inode_info *, struct pipe_buffer *, int);
+	void (*unmap)(struct pipe_inode_info *, struct pipe_buffer *, void *);
 	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 *);
@@ -64,8 +65,8 @@ 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_map(struct pipe_inode_info *, struct pipe_buffer *, int);
+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_pin(struct pipe_inode_info *, struct pipe_buffer *);
 
-- 
cgit v1.2.3-71-gd317


From 7afa6fd037e51e95d322990cb127bb2b1217251a Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@suse.de>
Date: Mon, 1 May 2006 20:02:33 +0200
Subject: [PATCH] vmsplice: allow user to pass in gift pages

If SPLICE_F_GIFT is set, the user is basically giving this pages away to
the kernel. That means we can steal them for eg page cache uses instead
of copying it.

The data must be properly page aligned and also a multiple of the page size
in length.

Signed-off-by: Jens Axboe <axboe@suse.de>
---
 fs/splice.c               | 28 +++++++++++++++++++++++++---
 include/linux/pipe_fs_i.h |  2 ++
 2 files changed, 27 insertions(+), 3 deletions(-)

(limited to 'include/linux')

diff --git a/fs/splice.c b/fs/splice.c
index d4664a297bab..b150493b6fc3 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -141,7 +141,10 @@ static struct pipe_buf_operations page_cache_pipe_buf_ops = {
 static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
 				    struct pipe_buffer *buf)
 {
-	return 1;
+	if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
+		return 1;
+
+	return 0;
 }
 
 static struct pipe_buf_operations user_page_pipe_buf_ops = {
@@ -186,6 +189,9 @@ static ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
 			buf->offset = spd->partial[page_nr].offset;
 			buf->len = spd->partial[page_nr].len;
 			buf->ops = spd->ops;
+			if (spd->flags & SPLICE_F_GIFT)
+				buf->flags |= PIPE_BUF_FLAG_GIFT;
+
 			pipe->nrbufs++;
 			page_nr++;
 			ret += buf->len;
@@ -1073,7 +1079,7 @@ static long do_splice(struct file *in, loff_t __user *off_in,
  */
 static int get_iovec_page_array(const struct iovec __user *iov,
 				unsigned int nr_vecs, struct page **pages,
-				struct partial_page *partial)
+				struct partial_page *partial, int aligned)
 {
 	int buffers = 0, error = 0;
 
@@ -1113,6 +1119,15 @@ static int get_iovec_page_array(const struct iovec __user *iov,
 		 * in the user pages.
 		 */
 		off = (unsigned long) base & ~PAGE_MASK;
+
+		/*
+		 * If asked for alignment, the offset must be zero and the
+		 * length a multiple of the PAGE_SIZE.
+		 */
+		error = -EINVAL;
+		if (aligned && (off || len & ~PAGE_MASK))
+			break;
+
 		npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
 		if (npages > PIPE_BUFFERS - buffers)
 			npages = PIPE_BUFFERS - buffers;
@@ -1206,7 +1221,8 @@ static long do_vmsplice(struct file *file, const struct iovec __user *iov,
 	else if (unlikely(!nr_segs))
 		return 0;
 
-	spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial);
+	spd.nr_pages = get_iovec_page_array(iov, nr_segs, pages, partial,
+					    flags & SPLICE_F_GIFT);
 	if (spd.nr_pages <= 0)
 		return spd.nr_pages;
 
@@ -1314,6 +1330,12 @@ static int link_pipe(struct pipe_inode_info *ipipe,
 				obuf = opipe->bufs + nbuf;
 				*obuf = *ibuf;
 
+				/*
+				 * Don't inherit the gift flag, we need to
+				 * prevent multiple steals of this page.
+				 */
+				obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
+
 				if (obuf->len > len)
 					obuf->len = len;
 
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index 4c054491e38e..df4d3fa7d3dc 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -7,6 +7,7 @@
 
 #define PIPE_BUF_FLAG_LRU	0x01	/* page is on the LRU */
 #define PIPE_BUF_FLAG_ATOMIC	0x02	/* was atomically mapped */
+#define PIPE_BUF_FLAG_GIFT	0x04	/* page is a gift */
 
 struct pipe_buffer {
 	struct page *page;
@@ -79,6 +80,7 @@ int generic_pipe_buf_pin(struct pipe_inode_info *, struct pipe_buffer *);
 				 /* we may still block on the fd we splice */
 				 /* from/to, of course */
 #define SPLICE_F_MORE	(0x04)	/* expect more data */
+#define SPLICE_F_GIFT	(0x08)	/* pages passed in are a gift */
 
 /*
  * Passed to the actors
-- 
cgit v1.2.3-71-gd317