linux-kernel - [PATCH] pipe: read/write_iter() handler should check for IOCB

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Date:   Thu, 30 Apr 2020 10:24:46 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Alexander Viro <viro@...iv.linux.org.uk>
Cc:     linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] pipe: read/write_iter() handler should check for IOCB_NOWAIT

Pipe read/write only checks for the file O_NONBLOCK flag, but we should
also check for IOCB_NOWAIT for whether or not we should handle this read
or write in a non-blocking fashion. If we don't, then we will block on
data or space for iocbs that explicitly asked for non-blocking
operation. This messes up callers that explicitly ask for non-blocking
operations.

Signed-off-by: Jens Axboe <axboe@...nel.dk>

---

diff --git a/fs/pipe.c b/fs/pipe.c
index 16fb72e9abf7..5711e6bca12d 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -363,7 +363,8 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
 			break;
 		if (ret)
 			break;
-		if (filp->f_flags & O_NONBLOCK) {
+		if ((filp->f_flags & O_NONBLOCK) ||
+		    (iocb->ki_flags & IOCB_NOWAIT)) {
 			ret = -EAGAIN;
 			break;
 		}
@@ -566,7 +567,8 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
 			continue;
 
 		/* Wait for buffer space to become available. */
-		if (filp->f_flags & O_NONBLOCK) {
+		if ((filp->f_flags & O_NONBLOCK) ||
+		    (iocb->ki_flags & IOCB_NOWAIT)) {
 			if (!ret)
 				ret = -EAGAIN;
 			break;

-- 
Jens Axboe