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Wed, 23 Apr 2025 08:55:05 -0700 (PDT) Content-Type: multipart/mixed; boundary="------------q5NDZdvobEhcchbgiQ1tLFB4" Message-ID: <52d55891-36e3-43e7-9726-a2cd113f5327@kernel.dk> Date: Wed, 23 Apr 2025 09:55:04 -0600 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/2] io_uring: Add new functions to handle user fault scenarios From: Jens Axboe To: =?UTF-8?B?5aec5pm65Lyf?= Cc: viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, akpm@linux-foundation.org, peterx@redhat.com, asml.silence@gmail.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, io-uring@vger.kernel.org References: <20250422162913.1242057-1-qq282012236@gmail.com> <20250422162913.1242057-2-qq282012236@gmail.com> <14195206-47b1-4483-996d-3315aa7c33aa@kernel.dk> <7bea9c74-7551-4312-bece-86c4ad5c982f@kernel.dk> Content-Language: en-US In-Reply-To: <7bea9c74-7551-4312-bece-86c4ad5c982f@kernel.dk> This is a multi-part message in MIME format. --------------q5NDZdvobEhcchbgiQ1tLFB4 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Something like this, perhaps - it'll ensure that io-wq workers get a chance to flush out pending work, which should prevent the looping. I've attached a basic test case. It'll issue a write that will fault, and then try and cancel that as a way to trigger the TIF_NOTIFY_SIGNAL based looping. diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index d80f94346199..e18926dbf20a 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -32,6 +32,7 @@ #include #include #include +#include static int sysctl_unprivileged_userfaultfd __read_mostly; @@ -376,6 +377,8 @@ vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason) */ if (current->flags & (PF_EXITING|PF_DUMPCORE)) goto out; + else if (current->flags & PF_IO_WORKER) + io_worker_fault(); assert_fault_locked(vmf); diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h index 85fe4e6b275c..d93dd7402a28 100644 --- a/include/linux/io_uring.h +++ b/include/linux/io_uring.h @@ -28,6 +28,7 @@ static inline void io_uring_free(struct task_struct *tsk) if (tsk->io_uring) __io_uring_free(tsk); } +void io_worker_fault(void); #else static inline void io_uring_task_cancel(void) { @@ -46,6 +47,9 @@ static inline bool io_is_uring_fops(struct file *file) { return false; } +static inline void io_worker_fault(void) +{ +} #endif #endif diff --git a/io_uring/io-wq.c b/io_uring/io-wq.c index d52069b1177b..f74bea028ec7 100644 --- a/io_uring/io-wq.c +++ b/io_uring/io-wq.c @@ -1438,3 +1438,13 @@ static __init int io_wq_init(void) return 0; } subsys_initcall(io_wq_init); + +void io_worker_fault(void) +{ + if (test_thread_flag(TIF_NOTIFY_SIGNAL)) + clear_notify_signal(); + if (test_thread_flag(TIF_NOTIFY_RESUME)) + resume_user_mode_work(NULL); + if (task_work_pending(current)) + task_work_run(); +} -- Jens Axboe --------------q5NDZdvobEhcchbgiQ1tLFB4 Content-Type: text/x-csrc; charset=UTF-8; name="ufd.c" Content-Disposition: attachment; filename="ufd.c" Content-Transfer-Encoding: base64 I2luY2x1ZGUgPHN0ZGlvLmg+CiNpbmNsdWRlIDxzdGRsaWIuaD4KI2luY2x1ZGUgPHVuaXN0 ZC5oPgojaW5jbHVkZSA8c3RyaW5nLmg+CiNpbmNsdWRlIDxwb2xsLmg+CiNpbmNsdWRlIDxz 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