X-Git-Url: http://pilppa.org/gitweb/gitweb.cgi?a=blobdiff_plain;f=fs%2Fpipe.c;h=d007830d9c870fabb4b887d3f81afcb8e7160642;hb=c4a7808fc3d7a346d5d12e0d69d76d66d821488b;hp=ebafde7d6abab948f9fa3a23e71f39360c757c71;hpb=2aa6eb313e57a8254b17e60b8bb5e0a2570d7776;p=linux-2.6-omap-h63xx.git

diff --git a/fs/pipe.c b/fs/pipe.c
index ebafde7d6ab..d007830d9c8 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -164,6 +164,20 @@ static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
 		page_cache_release(page);
 }
 
+/**
+ * generic_pipe_buf_map - virtually map a pipe buffer
+ * @pipe:	the pipe that the buffer belongs to
+ * @buf:	the buffer that should be mapped
+ * @atomic:	whether to use an atomic map
+ *
+ * Description:
+ *	This function returns a kernel virtual address mapping for the
+ *	passed in @pipe_buffer. If @atomic is set, an atomic map is provided
+ *	and the caller has to be careful not to fault before calling
+ *	the unmap function.
+ *
+ *	Note that this function occupies KM_USER0 if @atomic != 0.
+ */
 void *generic_pipe_buf_map(struct pipe_inode_info *pipe,
 			   struct pipe_buffer *buf, int atomic)
 {
@@ -175,6 +189,15 @@ void *generic_pipe_buf_map(struct pipe_inode_info *pipe,
 	return kmap(buf->page);
 }
 
+/**
+ * generic_pipe_buf_unmap - unmap a previously mapped pipe buffer
+ * @pipe:	the pipe that the buffer belongs to
+ * @buf:	the buffer that should be unmapped
+ * @map_data:	the data that the mapping function returned
+ *
+ * Description:
+ *	This function undoes the mapping that ->map() provided.
+ */
 void generic_pipe_buf_unmap(struct pipe_inode_info *pipe,
 			    struct pipe_buffer *buf, void *map_data)
 {
@@ -185,11 +208,28 @@ void generic_pipe_buf_unmap(struct pipe_inode_info *pipe,
 		kunmap(buf->page);
 }
 
+/**
+ * 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;
@@ -198,12 +238,32 @@ int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
 	return 1;
 }
 
-void generic_pipe_buf_get(struct pipe_inode_info *info, struct pipe_buffer *buf)
+/**
+ * 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
+ *
+ * Description:
+ *	This function grabs an extra reference to @buf. It's used in
+ *	in the tee() system call, when we duplicate the buffers in one
+ *	pipe into another.
+ */
+void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 {
 	page_cache_get(buf->page);
 }
 
-int generic_pipe_buf_pin(struct pipe_inode_info *info, struct pipe_buffer *buf)
+/**
+ * generic_pipe_buf_confirm - verify contents of the pipe buffer
+ * @pipe:	the pipe that the buffer belongs to
+ * @buf:	the buffer to confirm
+ *
+ * Description:
+ *	This function does nothing, because the generic pipe code uses
+ *	pages that are always good when inserted into the pipe.
+ */
+int generic_pipe_buf_confirm(struct pipe_inode_info *info,
+			     struct pipe_buffer *buf)
 {
 	return 0;
 }
@@ -212,7 +272,7 @@ static const struct pipe_buf_operations anon_pipe_buf_ops = {
 	.can_merge = 1,
 	.map = generic_pipe_buf_map,
 	.unmap = generic_pipe_buf_unmap,
-	.pin = generic_pipe_buf_pin,
+	.confirm = generic_pipe_buf_confirm,
 	.release = anon_pipe_buf_release,
 	.steal = generic_pipe_buf_steal,
 	.get = generic_pipe_buf_get,
@@ -252,7 +312,7 @@ pipe_read(struct kiocb *iocb, const struct iovec *_iov,
 			if (chars > total_len)
 				chars = total_len;
 
-			error = ops->pin(pipe, buf);
+			error = ops->confirm(pipe, buf);
 			if (error) {
 				if (!ret)
 					error = ret;
@@ -373,7 +433,7 @@ pipe_write(struct kiocb *iocb, const struct iovec *_iov,
 			int error, atomic = 1;
 			void *addr;
 
-			error = ops->pin(pipe, buf);
+			error = ops->confirm(pipe, buf);
 			if (error)
 				goto out;
 
@@ -841,8 +901,18 @@ static int pipefs_delete_dentry(struct dentry *dentry)
 	return 0;
 }
 
+/*
+ * pipefs_dname() is called from d_path().
+ */
+static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
+{
+	return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
+				dentry->d_inode->i_ino);
+}
+
 static struct dentry_operations pipefs_dentry_operations = {
 	.d_delete	= pipefs_delete_dentry,
+	.d_dname	= pipefs_dname,
 };
 
 static struct inode * get_pipe_inode(void)
@@ -888,8 +958,7 @@ struct file *create_write_pipe(void)
 	struct inode *inode;
 	struct file *f;
 	struct dentry *dentry;
-	char name[32];
-	struct qstr this;
+	struct qstr name = { .name = "" };
 
 	f = get_empty_filp();
 	if (!f)
@@ -899,11 +968,8 @@ struct file *create_write_pipe(void)
 	if (!inode)
 		goto err_file;
 
-	this.len = sprintf(name, "[%lu]", inode->i_ino);
-	this.name = name;
-	this.hash = 0;
 	err = -ENOMEM;
-	dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &this);
+	dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &name);
 	if (!dentry)
 		goto err_inode;