Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Thu, 30 Apr 2020 10:58:56 -0700
From:   Matthew Wilcox <willy@infradead.org>
To:     Jens Axboe <axboe@kernel.dk>
Cc:     Alexander Viro <viro@zeniv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] pipe: read/write_iter() handler should check for
 IOCB_NOWAIT
Message-ID: <20200430175856.GX29705@bombadil.infradead.org>
References: <273d8294-2508-a4c2-f96e-a6a394f94166@kernel.dk>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <273d8294-2508-a4c2-f96e-a6a394f94166@kernel.dk>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, Apr 30, 2020 at 10:24:46AM -0600, Jens Axboe wrote:
> 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@kernel.dk>

Wouldn't this be better?

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

diff --git a/fs/pipe.c b/fs/pipe.c
index 16fb72e9abf7..d4cf3ea9ad49 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -363,7 +363,7 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
 			break;
 		if (ret)
 			break;
-		if (filp->f_flags & O_NONBLOCK) {
+		if (iocb->ki_flags & IOCB_NOWAIT) {
 			ret = -EAGAIN;
 			break;
 		}
@@ -566,7 +566,7 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
 			continue;
 
 		/* Wait for buffer space to become available. */
-		if (filp->f_flags & O_NONBLOCK) {
+		if (iocb->ki_flags & IOCB_NOWAIT) {
 			if (!ret)
 				ret = -EAGAIN;
 			break;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 4f6f59b4f22a..2790c956bd4f 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3429,6 +3429,8 @@ static inline int iocb_flags(struct file *file)
 		res |= IOCB_DSYNC;
 	if (file->f_flags & __O_SYNC)
 		res |= IOCB_SYNC;
+	if (file->f_flags & O_NONBLOCK)
+		res |= IOCB_NOWAIT;
 	return res;
 }