From 8bab4c09f24ec8d4a7a78ab343620f89d3a24804 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Fri, 24 Sep 2021 07:12:27 -0600
Subject: [PATCH] io_uring: allow conditional reschedule for intensive
 iterators
Git-commit: 8bab4c09f24ec8d4a7a78ab343620f89d3a24804
Patch-mainline: v5.15-rc3
References: bsc#1199011

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@syzkaller.appspotmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Takashi Iwai <tiwai@suse.de>
[ddiss: revert from stable-5.14.11 to mainline fix]
Acked-by: David Disseldorp <ddiss@suse.de>

---
 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 7707cdb7b372..ef3c94a55fbd 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -9173,8 +9173,10 @@ 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)
@@ -9672,8 +9674,10 @@ 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
-- 
2.34.1