From: Jens Axboe <axboe@kernel.dk>
To: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel <linux-fsdevel@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: [PATCH] pipe: honor IOCB_NOWAIT
Date: Mon, 7 Sep 2020 09:21:02 -0600 [thread overview]
Message-ID: <cedfa436-47a3-7cbc-1948-75d0e28cfdc5@kernel.dk> (raw)
Pipe only looks at O_NONBLOCK for non-blocking operation, which means that
io_uring can't easily poll for it or attempt non-blocking issues. Check for
IOCB_NOWAIT in locking the pipe for reads and writes, and ditto when we
decide on whether or not to block or return -EAGAIN.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
If this is acceptable, then I can add S_ISFIFO to the whitelist on file
descriptors we can IOCB_NOWAIT try for, then poll if we get -EAGAIN
instead of using thread offload.
diff --git a/fs/pipe.c b/fs/pipe.c
index 60dbee457143..3cee28e35985 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -82,6 +82,13 @@ void pipe_unlock(struct pipe_inode_info *pipe)
}
EXPORT_SYMBOL(pipe_unlock);
+static inline bool __pipe_lock_nonblock(struct pipe_inode_info *pipe)
+{
+ if (mutex_trylock(&pipe->mutex))
+ return true;
+ return false;
+}
+
static inline void __pipe_lock(struct pipe_inode_info *pipe)
{
mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
@@ -244,7 +251,12 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
return 0;
ret = 0;
- __pipe_lock(pipe);
+ if (iocb->ki_flags & IOCB_NOWAIT) {
+ if (!__pipe_lock_nonblock(pipe))
+ return -EAGAIN;
+ } else {
+ __pipe_lock(pipe);
+ }
/*
* We only wake up writers if the pipe was full when we started
@@ -344,7 +356,8 @@ 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;
}
@@ -432,7 +445,12 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
if (unlikely(total_len == 0))
return 0;
- __pipe_lock(pipe);
+ if (iocb->ki_flags & IOCB_NOWAIT) {
+ if (!__pipe_lock_nonblock(pipe))
+ return -EAGAIN;
+ } else {
+ __pipe_lock(pipe);
+ }
if (!pipe->readers) {
send_sig(SIGPIPE, current, 0);
@@ -554,7 +572,8 @@ 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
next reply other threads:[~2020-09-07 15:26 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-07 15:21 Jens Axboe [this message]
2020-09-11 1:12 ` [PATCH] pipe: honor IOCB_NOWAIT Al Viro
2020-09-11 11:21 ` Jens Axboe
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