From a2416e1ec23c6b79010d03d69c0e4e035339b4ad Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <asml.silence@gmail.com>
Date: Mon, 9 Aug 2021 13:04:09 +0100
Subject: [PATCH] io_uring: don't halt iopoll too early
Git-commit: a2416e1ec23c6b79010d03d69c0e4e035339b4ad
Patch-mainline: v5.15-rc1
References: bsc#1199011
IOPOLL users should care more about getting completions for requests
they submitted, but not in "device did/completed something". Currently,
io_do_iopoll() may return a positive number, which will instruct
io_iopoll_check() to break the loop and end the syscall, even if there
is not enough CQEs or none at all.
Don't return positive numbers, so io_iopoll_check() exits only when it
gets an actual error, need reschedule or got enough CQEs.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/641a88f751623b6758303b3171f0a4141f06726e.1628471125.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: David Disseldorp <ddiss@suse.de>
---
fs/io_uring.c | 15 ++++++---------
1 file changed, 6 insertions(+), 9 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 8892747bd173..6a3079a038fb 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2288,7 +2288,6 @@ static int io_do_iopoll(struct io_ring_ctx *ctx, unsigned int *nr_events,
struct io_kiocb *req, *tmp;
LIST_HEAD(done);
bool spin;
- int ret;
/*
* Only spin for completions if we don't have multiple devices hanging
@@ -2296,9 +2295,9 @@ static int io_do_iopoll(struct io_ring_ctx *ctx, unsigned int *nr_events,
*/
spin = !ctx->poll_multi_queue && *nr_events < min;
- ret = 0;
list_for_each_entry_safe(req, tmp, &ctx->iopoll_list, inflight_entry) {
struct kiocb *kiocb = &req->rw.kiocb;
+ int ret;
/*
* Move completed and retryable entries to our local lists.
@@ -2313,22 +2312,20 @@ static int io_do_iopoll(struct io_ring_ctx *ctx, unsigned int *nr_events,
break;
ret = kiocb->ki_filp->f_op->iopoll(kiocb, spin);
- if (ret < 0)
- break;
+ if (unlikely(ret < 0))
+ return ret;
+ else if (ret)
+ spin = false;
/* iopoll may have completed current req */
if (READ_ONCE(req->iopoll_completed))
list_move_tail(&req->inflight_entry, &done);
-
- if (ret && spin)
- spin = false;
- ret = 0;
}
if (!list_empty(&done))
io_iopoll_complete(ctx, nr_events, &done, resubmit);
- return ret;
+ return 0;
}
/*
--
2.34.1