From f7be9c72d1de9307a7fbc0c394996268d4fdc4e9 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Fri, 23 Jul 2021 11:49:29 -0600 Subject: [PATCH] io_uring: never attempt iopoll reissue from release path [ Upstream commit 3c30ef0f78cfb36fdb13753794b0384cf7e37cc9 ] There are two reasons why this shouldn't be done: 1) Ring is exiting, and we're canceling requests anyway. Any request should be canceled anyway. In theory, this could iterate for a number of times if someone else is also driving the target block queue into request starvation, however the likelihood of this happening is miniscule. 2) If the original task decided to pass the ring to another task, then we don't want to be reissuing from this context as it may be an unrelated task or context. No assumptions should be made about the context in which ->release() is run. This can only happen for pure read/write, and we'll get -EFAULT on them anyway. Link: https://lore.kernel.org/io-uring/YPr4OaHv0iv0KTOc@zeniv-ca.linux.org.uk/ Reported-by: Al Viro Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- fs/io_uring.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index d465e99971574..86f609fa761cc 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -2252,7 +2252,7 @@ static inline bool io_run_task_work(void) * Find and free completed poll iocbs */ static void io_iopoll_complete(struct io_ring_ctx *ctx, unsigned int *nr_events, - struct list_head *done) + struct list_head *done, bool resubmit) { struct req_batch rb; struct io_kiocb *req; @@ -2267,7 +2267,7 @@ static void io_iopoll_complete(struct io_ring_ctx *ctx, unsigned int *nr_events, req = list_first_entry(done, struct io_kiocb, inflight_entry); list_del(&req->inflight_entry); - if (READ_ONCE(req->result) == -EAGAIN && + if (READ_ONCE(req->result) == -EAGAIN && resubmit && !(req->flags & REQ_F_DONT_REISSUE)) { req->iopoll_completed = 0; req_ref_get(req); @@ -2291,7 +2291,7 @@ static void io_iopoll_complete(struct io_ring_ctx *ctx, unsigned int *nr_events, } static int io_do_iopoll(struct io_ring_ctx *ctx, unsigned int *nr_events, - long min) + long min, bool resubmit) { struct io_kiocb *req, *tmp; LIST_HEAD(done); @@ -2334,7 +2334,7 @@ static int io_do_iopoll(struct io_ring_ctx *ctx, unsigned int *nr_events, } if (!list_empty(&done)) - io_iopoll_complete(ctx, nr_events, &done); + io_iopoll_complete(ctx, nr_events, &done, resubmit); return ret; } @@ -2352,7 +2352,7 @@ static void io_iopoll_try_reap_events(struct io_ring_ctx *ctx) while (!list_empty(&ctx->iopoll_list)) { unsigned int nr_events = 0; - io_do_iopoll(ctx, &nr_events, 0); + io_do_iopoll(ctx, &nr_events, 0, false); /* let it sleep and repeat later if can't complete a request */ if (nr_events == 0) @@ -2410,7 +2410,7 @@ static int io_iopoll_check(struct io_ring_ctx *ctx, long min) if (list_empty(&ctx->iopoll_list)) break; } - ret = io_do_iopoll(ctx, &nr_events, min); + ret = io_do_iopoll(ctx, &nr_events, min, true); } while (!ret && nr_events < min && !need_resched()); out: mutex_unlock(&ctx->uring_lock); @@ -6804,7 +6804,7 @@ static int __io_sq_thread(struct io_ring_ctx *ctx, bool cap_entries) mutex_lock(&ctx->uring_lock); if (!list_empty(&ctx->iopoll_list)) - io_do_iopoll(ctx, &nr_events, 0); + io_do_iopoll(ctx, &nr_events, 0, true); /* * Don't submit if refs are dying, good for io_uring_register(),