Merge git://git.kernel.org/pub/scm/linux/kernel/git/sam/kbuild

[sfrench/cifs-2.6.git] / fs / pipe.c

diff --git a/fs/pipe.c b/fs/pipe.c
index 3a89592bdf577930b4c1698c4811261aa467cbf2..e66ec48e95d8f44223ba960e5fe82a9c7acd962d 100644 (file)
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -45,8 +45,7 @@ void pipe_wait(struct pipe_inode_info *pipe)
         * Pipes are system-local resources, so sleeping on them
         * is considered a noninteractive wait:
         */
-       prepare_to_wait(&pipe->wait, &wait,
-                       TASK_INTERRUPTIBLE | TASK_NONINTERACTIVE);
+       prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
        if (pipe->inode)
                mutex_unlock(&pipe->inode->i_mutex);
        schedule();
@@ -164,6 +163,20 @@ 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 +188,15 @@ 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 +207,28 @@ 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 +237,32 @@ 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
+ * @info:      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 +271,7 @@ 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 +311,7 @@ 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;
@@ -323,7 +382,7 @@ redo:
 
        /* Signal writers asynchronously that there is more room. */
        if (do_wakeup) {
-               wake_up_interruptible(&pipe->wait);
+               wake_up_interruptible_sync(&pipe->wait);
                kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
        }
        if (ret > 0)
@@ -373,7 +432,7 @@ 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;
 
@@ -496,7 +555,7 @@ redo2:
 out:
        mutex_unlock(&inode->i_mutex);
        if (do_wakeup) {
-               wake_up_interruptible(&pipe->wait);
+               wake_up_interruptible_sync(&pipe->wait);
                kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
        }
        if (ret > 0)
@@ -590,7 +649,7 @@ pipe_release(struct inode *inode, int decr, int decw)
        if (!pipe->readers && !pipe->writers) {
                free_pipe_info(inode);
        } else {
-               wake_up_interruptible(&pipe->wait);
+               wake_up_interruptible_sync(&pipe->wait);
                kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
                kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
        }