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-rw-r--r--fs/pipe.c20
1 files changed, 16 insertions, 4 deletions
diff --git a/fs/pipe.c b/fs/pipe.c
index c51750ed4011..0ff09b490ddf 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -226,8 +226,8 @@ void generic_pipe_buf_release(struct pipe_inode_info *pipe,
}
EXPORT_SYMBOL(generic_pipe_buf_release);
+/* New data written to a pipe may be appended to a buffer with this type. */
static const struct pipe_buf_operations anon_pipe_buf_ops = {
- .can_merge = 1,
.confirm = generic_pipe_buf_confirm,
.release = anon_pipe_buf_release,
.steal = anon_pipe_buf_steal,
@@ -235,7 +235,6 @@ static const struct pipe_buf_operations anon_pipe_buf_ops = {
};
static const struct pipe_buf_operations anon_pipe_buf_nomerge_ops = {
- .can_merge = 0,
.confirm = generic_pipe_buf_confirm,
.release = anon_pipe_buf_release,
.steal = anon_pipe_buf_steal,
@@ -243,19 +242,32 @@ static const struct pipe_buf_operations anon_pipe_buf_nomerge_ops = {
};
static const struct pipe_buf_operations packet_pipe_buf_ops = {
- .can_merge = 0,
.confirm = generic_pipe_buf_confirm,
.release = anon_pipe_buf_release,
.steal = anon_pipe_buf_steal,
.get = generic_pipe_buf_get,
};
+/**
+ * pipe_buf_mark_unmergeable - mark a &struct pipe_buffer as unmergeable
+ * @buf: the buffer to mark
+ *
+ * Description:
+ * This function ensures that no future writes will be merged into the
+ * given &struct pipe_buffer. This is necessary when multiple pipe buffers
+ * share the same backing page.
+ */
void pipe_buf_mark_unmergeable(struct pipe_buffer *buf)
{
if (buf->ops == &anon_pipe_buf_ops)
buf->ops = &anon_pipe_buf_nomerge_ops;
}
+static bool pipe_buf_can_merge(struct pipe_buffer *buf)
+{
+ return buf->ops == &anon_pipe_buf_ops;
+}
+
static ssize_t
pipe_read(struct kiocb *iocb, struct iov_iter *to)
{
@@ -393,7 +405,7 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
struct pipe_buffer *buf = pipe->bufs + lastbuf;
int offset = buf->offset + buf->len;
- if (buf->ops->can_merge && offset + chars <= PAGE_SIZE) {
+ if (pipe_buf_can_merge(buf) && offset + chars <= PAGE_SIZE) {
ret = pipe_buf_confirm(pipe, buf);
if (ret)
goto out;