linux-kernel - [PATCH AUTOSEL 5.14 37/40] io_uring: allow conditional reschedule for intensive iterators

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Date:   Tue, 28 Sep 2021 01:55:21 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Jens Axboe <axboe@...nel.dk>,
        syzbot+111d2a03f51f5ae73775@...kaller.appspotmail.com,
        Sasha Levin <sashal@...nel.org>, io-uring@...r.kernel.org
Subject: [PATCH AUTOSEL 5.14 37/40] io_uring: allow conditional reschedule for intensive iterators

From: Jens Axboe <axboe@...nel.dk>

[ Upstream commit 8bab4c09f24ec8d4a7a78ab343620f89d3a24804 ]

If we have a lot of threads and rings, the tctx list can get quite big.
This is especially true if we keep creating new threads and rings.
Likewise for the provided buffers list. Be nice and insert a conditional
reschedule point while iterating the nodes for deletion.

Link: https://lore.kernel.org/io-uring/00000000000064b6b405ccb41113@google.com/
Reported-by: syzbot+111d2a03f51f5ae73775@...kaller.appspotmail.com
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/io_uring.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 754d59f734d8..ddd241b28f91 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -8649,8 +8649,10 @@ static void io_destroy_buffers(struct io_ring_ctx *ctx)
 	struct io_buffer *buf;
 	unsigned long index;
 
-	xa_for_each(&ctx->io_buffers, index, buf)
+	xa_for_each(&ctx->io_buffers, index, buf) {
 		__io_remove_buffers(ctx, buf, index, -1U);
+		cond_resched();
+	}
 }
 
 static void io_req_cache_free(struct list_head *list, struct task_struct *tsk)
@@ -9146,8 +9148,10 @@ static void io_uring_clean_tctx(struct io_uring_task *tctx)
 	struct io_tctx_node *node;
 	unsigned long index;
 
-	xa_for_each(&tctx->xa, index, node)
+	xa_for_each(&tctx->xa, index, node) {
 		io_uring_del_tctx_node(index);
+		cond_resched();
+	}
 	if (wq) {
 		/*
 		 * Must be after io_uring_del_task_file() (removes nodes under
-- 
2.33.0