Merge tag 'erofs-for-5.5-rc2-fixes' of git://git.kernel.org/pub/scm/linux/kernel...

[linux-2.6-microblaze.git] / fs / pipe.c

diff --git a/fs/pipe.c b/fs/pipe.c
index 87109e7..04d004e 100644 (file)
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -364,17 +364,39 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
                        ret = -EAGAIN;
                        break;
                }
-               if (signal_pending(current)) {
-                       if (!ret)
-                               ret = -ERESTARTSYS;
-                       break;
-               }
                __pipe_unlock(pipe);
-               if (was_full) {
+
+               /*
+                * We only get here if we didn't actually read anything.
+                *
+                * However, we could have seen (and removed) a zero-sized
+                * pipe buffer, and might have made space in the buffers
+                * that way.
+                *
+                * You can't make zero-sized pipe buffers by doing an empty
+                * write (not even in packet mode), but they can happen if
+                * the writer gets an EFAULT when trying to fill a buffer
+                * that already got allocated and inserted in the buffer
+                * array.
+                *
+                * So we still need to wake up any pending writers in the
+                * _very_ unlikely case that the pipe was full, but we got
+                * no data.
+                */
+               if (unlikely(was_full)) {
                        wake_up_interruptible_sync_poll(&pipe->wait, EPOLLOUT | EPOLLWRNORM);
                        kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
                }
-               wait_event_interruptible(pipe->wait, pipe_readable(pipe));
+
+               /*
+                * But because we didn't read anything, at this point we can
+                * just return directly with -ERESTARTSYS if we're interrupted,
+                * since we've done any required wakeups and there's no need
+                * to mark anything accessed. And we've dropped the lock.
+                */
+               if (wait_event_interruptible(pipe->wait, pipe_readable(pipe)) < 0)
+                       return -ERESTARTSYS;
+
                __pipe_lock(pipe);
                was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
        }