From c7b04d27c9107fbc0d22dee67316f8584439df35 Mon Sep 17 00:00:00 2001 From: Pavel Begunkov Date: Thu, 17 Dec 2020 00:24:36 +0000 Subject: [PATCH] io_uring: remove racy overflow list fast checks [ Upstream commit 9cd2be519d05ee78876d55e8e902b7125f78b74f ] list_empty_careful() is not racy only if some conditions are met, i.e. no re-adds after del_init. io_cqring_overflow_flush() does list_move(), so it's actually racy. Remove those checks, we have ->cq_check_overflow for the fast path. Signed-off-by: Pavel Begunkov Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- fs/io_uring.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index e28eeda..1f798c5 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -1636,8 +1636,6 @@ static bool io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force, LIST_HEAD(list); if (!force) { - if (list_empty_careful(&ctx->cq_overflow_list)) - return true; if ((ctx->cached_cq_tail - READ_ONCE(rings->cq.head) == rings->cq_ring_entries)) return false; @@ -6579,8 +6577,7 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr) /* if we have a backlog and couldn't flush it all, return BUSY */ if (test_bit(0, &ctx->sq_check_overflow)) { - if (!list_empty(&ctx->cq_overflow_list) && - !io_cqring_overflow_flush(ctx, false, NULL, NULL)) + if (!io_cqring_overflow_flush(ctx, false, NULL, NULL)) return -EBUSY; } -- 2.7.4