This is a note to let you know that I've just added the patch titled
io_uring/net: introduce IORING_SEND_ZC_REPORT_USAGE flag
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
io_uring-net-introduce-ioring_send_zc_report_usage-flag.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From e307e6698165ca6508ed42c69cb1be76c8eb6a3c Mon Sep 17 00:00:00 2001
From: Stefan Metzmacher <metze@xxxxxxxxx>
Date: Thu, 27 Oct 2022 20:34:45 +0200
Subject: io_uring/net: introduce IORING_SEND_ZC_REPORT_USAGE flag
From: Stefan Metzmacher <metze@xxxxxxxxx>
commit e307e6698165ca6508ed42c69cb1be76c8eb6a3c upstream.
It might be useful for applications to detect if a zero copy transfer with
SEND[MSG]_ZC was actually possible or not. The application can fallback to
plain SEND[MSG] in order to avoid the overhead of two cqes per request. Or
it can generate a log message that could indicate to an administrator that
no zero copy was possible and could explain degraded performance.
Cc: stable@xxxxxxxxxxxxxxx # 6.1
Link: https://lore.kernel.org/io-uring/fb6a7599-8a9b-15e5-9b64-6cd9d01c6ff4@xxxxxxxxx/T/#m2b0d9df94ce43b0e69e6c089bdff0ce6babbdfaa
Signed-off-by: Stefan Metzmacher <metze@xxxxxxxxx>
Reviewed-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
Link: https://lore.kernel.org/r/8945b01756d902f5d5b0667f20b957ad3f742e5e.1666895626.git.metze@xxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/uapi/linux/io_uring.h | 18 ++++++++++++++++++
io_uring/net.c | 6 +++++-
io_uring/notif.c | 12 ++++++++++++
io_uring/notif.h | 3 +++
4 files changed, 38 insertions(+), 1 deletion(-)
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -296,10 +296,28 @@ enum io_uring_op {
*
* IORING_RECVSEND_FIXED_BUF Use registered buffers, the index is stored in
* the buf_index field.
+ *
+ * IORING_SEND_ZC_REPORT_USAGE
+ * If set, SEND[MSG]_ZC should report
+ * the zerocopy usage in cqe.res
+ * for the IORING_CQE_F_NOTIF cqe.
+ * 0 is reported if zerocopy was actually possible.
+ * IORING_NOTIF_USAGE_ZC_COPIED if data was copied
+ * (at least partially).
*/
#define IORING_RECVSEND_POLL_FIRST (1U << 0)
#define IORING_RECV_MULTISHOT (1U << 1)
#define IORING_RECVSEND_FIXED_BUF (1U << 2)
+#define IORING_SEND_ZC_REPORT_USAGE (1U << 3)
+
+/*
+ * cqe.res for IORING_CQE_F_NOTIF if
+ * IORING_SEND_ZC_REPORT_USAGE was requested
+ *
+ * It should be treated as a flag, all other
+ * bits of cqe.res should be treated as reserved!
+ */
+#define IORING_NOTIF_USAGE_ZC_COPIED (1U << 31)
/*
* accept flags stored in sqe->ioprio
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -937,7 +937,8 @@ int io_send_zc_prep(struct io_kiocb *req
zc->flags = READ_ONCE(sqe->ioprio);
if (zc->flags & ~(IORING_RECVSEND_POLL_FIRST |
- IORING_RECVSEND_FIXED_BUF))
+ IORING_RECVSEND_FIXED_BUF |
+ IORING_SEND_ZC_REPORT_USAGE))
return -EINVAL;
notif = zc->notif = io_alloc_notif(ctx);
if (!notif)
@@ -955,6 +956,9 @@ int io_send_zc_prep(struct io_kiocb *req
req->imu = READ_ONCE(ctx->user_bufs[idx]);
io_req_set_rsrc_node(notif, ctx, 0);
}
+ if (zc->flags & IORING_SEND_ZC_REPORT_USAGE) {
+ io_notif_to_data(notif)->zc_report = true;
+ }
if (req->opcode == IORING_OP_SEND_ZC) {
if (READ_ONCE(sqe->__pad3[0]))
--- a/io_uring/notif.c
+++ b/io_uring/notif.c
@@ -18,6 +18,10 @@ static void __io_notif_complete_tw(struc
__io_unaccount_mem(ctx->user, nd->account_pages);
nd->account_pages = 0;
}
+
+ if (nd->zc_report && (nd->zc_copied || !nd->zc_used))
+ notif->cqe.res |= IORING_NOTIF_USAGE_ZC_COPIED;
+
io_req_task_complete(notif, locked);
}
@@ -28,6 +32,13 @@ static void io_uring_tx_zerocopy_callbac
struct io_notif_data *nd = container_of(uarg, struct io_notif_data, uarg);
struct io_kiocb *notif = cmd_to_io_kiocb(nd);
+ if (nd->zc_report) {
+ if (success && !nd->zc_used && skb)
+ WRITE_ONCE(nd->zc_used, true);
+ else if (!success && !nd->zc_copied)
+ WRITE_ONCE(nd->zc_copied, true);
+ }
+
if (refcount_dec_and_test(&uarg->refcnt)) {
notif->io_task_work.func = __io_notif_complete_tw;
io_req_task_work_add(notif);
@@ -55,6 +66,7 @@ struct io_kiocb *io_alloc_notif(struct i
nd->account_pages = 0;
nd->uarg.flags = SKBFL_ZEROCOPY_FRAG | SKBFL_DONT_ORPHAN;
nd->uarg.callback = io_uring_tx_zerocopy_callback;
+ nd->zc_report = nd->zc_used = nd->zc_copied = false;
refcount_set(&nd->uarg.refcnt, 1);
return notif;
}
--- a/io_uring/notif.h
+++ b/io_uring/notif.h
@@ -13,6 +13,9 @@ struct io_notif_data {
struct file *file;
struct ubuf_info uarg;
unsigned long account_pages;
+ bool zc_report;
+ bool zc_used;
+ bool zc_copied;
};
void io_notif_flush(struct io_kiocb *notif);
Patches currently in stable-queue which might be from metze@xxxxxxxxx are
queue-6.1/io_uring-net-introduce-ioring_send_zc_report_usage-flag.patch
