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FAILED: patch "[PATCH] io_uring: don't use poll handler if file can't be nonblocking" failed to apply to 5.8-stable tree

PATCH [email protected] 2 participants 2 messages Aug 31, 2020

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#0 lore raw

The patch below does not apply to the 5.8-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 9dab14b81807a40dab8e464ec87043935c562c2c Mon Sep 17 00:00:00 2001
From: Jens Axboe <[email protected]>
Date: Tue, 25 Aug 2020 12:27:50 -0600
Subject: [PATCH] io_uring: don't use poll handler if file can't be nonblocking
read/written

There's no point in using the poll handler if we can't do a nonblocking IO attempt of the operation, since we'll need to go async anyway. In fact this is actively harmful, as reading from eg pipes won't return 0 to indicate EOF.

Cc [email protected] # v5.7+
Reported-by Benedikt Ames <[email protected]>
Signed-off-by Jens Axboe <[email protected]>
fs/io_uring.c +9 -1
index 384df86dfc69..d15139088e4c 100644
@@ -4889,12 +4889,20 @@ static bool io_arm_poll_handler(struct io_kiocb *req)
 	struct async_poll *apoll;
 	struct io_poll_table ipt;
 	__poll_t mask, ret;
+	int rw;
 
 	if (!req->file || !file_can_poll(req->file))
 		return false;
 	if (req->flags & REQ_F_POLLED)
 		return false;
-	if (!def->pollin && !def->pollout)
+	if (def->pollin)
+		rw = READ;
+	else if (def->pollout)
+		rw = WRITE;
+	else
+		return false;
+	/* if we can't nonblock try, then no point in arming a poll handler */
+	if (!io_file_supports_async(req->file, rw))
 		return false;
 
 	apoll = kmalloc(sizeof(*apoll), GFP_ATOMIC);
#1 lore raw
Quoted 5 lines · On 8/31/20 3:58 AM, [email protected] wrote:

The patch below does not apply to the 5.8-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

Here's a backport:

From 84f81565a00f353c503d5b5bd98c77625af73b60 Mon Sep 17 00:00:00 2001
From: Jens Axboe <[email protected]>
Date: Tue, 25 Aug 2020 12:27:50 -0600
Subject: [PATCH 2/3] io_uring: don't use poll handler if file can't be
nonblocking read/written

There's no point in using the poll handler if we can't do a nonblocking IO attempt of the operation, since we'll need to go async anyway. In fact this is actively harmful, as reading from eg pipes won't return 0 to indicate EOF.

Cc [email protected] # v5.7+
Reported-by Benedikt Ames <[email protected]>
Signed-off-by Jens Axboe <[email protected]>
---
 fs/io_uring.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)
fs/io_uring.c +9 -1
index c384caad6466..2b7018456091 100644
@@ -4503,12 +4503,20 @@ static bool io_arm_poll_handler(struct io_kiocb *req)
 	struct async_poll *apoll;
 	struct io_poll_table ipt;
 	__poll_t mask, ret;
+	int rw;
 
 	if (!req->file || !file_can_poll(req->file))
 		return false;
 	if (req->flags & (REQ_F_MUST_PUNT | REQ_F_POLLED))
 		return false;
-	if (!def->pollin && !def->pollout)
+	if (def->pollin)
+		rw = READ;
+	else if (def->pollout)
+		rw = WRITE;
+	else
+		return false;
+	/* if we can't nonblock try, then no point in arming a poll handler */
+	if (!io_file_supports_async(req->file, rw))
 		return false;
 
 	apoll = kmalloc(sizeof(*apoll), GFP_ATOMIC);
Signature · 5 lines
2.28.0


-- 
Jens Axboe