Re: [PATCH] pipe: read/write_iter() handler should check for IOCB_NOWAIT

[Matthew Wilcox]

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 <ax...@kernel.dk>

Wouldn't this be better?

Signed-off-by: Matthew Wilcox (Oracle) <wi...@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;
 }