From 31af27c7cc9f675d93a135dca99e6413f9096f1d Mon Sep 17 00:00:00 2001 From: Pavel Begunkov Date: Wed, 15 Apr 2020 00:39:50 +0300 Subject: [PATCH] io_uring: don't count rqs failed after current one When checking for draining with __req_need_defer(), it tries to match how many requests were sent before a current one with number of already completed. Dropped SQEs are included in req->sequence, and they won't ever appear in CQ. To compensate for that, __req_need_defer() substracts ctx->cached_sq_dropped. However, what it should really use is number of SQEs dropped __before__ the current one. In other words, any submitted request shouldn't shouldn't affect dequeueing from the drain queue of previously submitted ones. Instead of saving proper ctx->cached_sq_dropped in each request, substract from req->sequence it at initialisation, so it includes number of properly submitted requests. note: it also changes behaviour of timeouts, but 1. it's already diverge from the description because of using SQ 2. the description is ambiguous regarding dropped SQEs Signed-off-by: Pavel Begunkov Signed-off-by: Jens Axboe --- fs/io_uring.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index 3fc33ba4855d..381d50becd04 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -957,8 +957,8 @@ static inline bool __req_need_defer(struct io_kiocb *req) { struct io_ring_ctx *ctx = req->ctx; - return req->sequence != ctx->cached_cq_tail + ctx->cached_sq_dropped - + atomic_read(&ctx->cached_cq_overflow); + return req->sequence != ctx->cached_cq_tail + + atomic_read(&ctx->cached_cq_overflow); } static inline bool req_need_defer(struct io_kiocb *req) @@ -5801,7 +5801,7 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req, * it can be used to mark the position of the first IO in the * link list. */ - req->sequence = ctx->cached_sq_head; + req->sequence = ctx->cached_sq_head - ctx->cached_sq_dropped; req->opcode = READ_ONCE(sqe->opcode); req->user_data = READ_ONCE(sqe->user_data); req->io = NULL;