knfsd: nfsd4: return nfserr_wrongsec

[safe/jmp/linux-2.6] / fs / pipe.c

diff --git a/fs/pipe.c b/fs/pipe.c
index 3694af1..d007830 100644 (file)
--- 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;
@@ -198,11 +238,30 @@ 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);
 }
 
+/**
+ * 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)
 {