[PATCH 3/4] kernel/io_uring: cancel io_uring before task works

Pavel Begunkov
2020-12-30T21:38:49Z

For cancelling io_uring requests it needs either to be able to run
currently enqueued task_wokrs or having it shut down by that moment.
Otherwise io_uring_cancel_files() may be waiting for requests that won't
ever complete.

Go with the first way and do cancellations before setting PF_EXITING and
so before putting the task_work infrastructure into a transition state
where task_work_run() would better not be called.

Cc: stable@vger.kernel.org # 5.5+
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
fs/file.c | 2 --
kernel/exit.c | 2 ++
2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/file.c b/fs/file.c
index c0b60961c672..dab120b71e44 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -21,7 +21,6 @@
#include <linux/rcupdate.h>
#include <linux/close_range.h>
#include <net/sock.h>
-#include <linux/io_uring.h>

unsigned int sysctl_nr_open __read_mostly = 1024*1024;
unsigned int sysctl_nr_open_min = BITS_PER_LONG;
@@ -428,7 +427,6 @@ void exit_files(struct task_struct *tsk)
struct files_struct * files = tsk->files;

if (files) {
- io_uring_files_cancel(files);
task_lock(tsk);
tsk->files = NULL;
task_unlock(tsk);
diff --git a/kernel/exit.c b/kernel/exit.c
index 3594291a8542..04029e35e69a 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -63,6 +63,7 @@
#include <linux/random.h>
#include <linux/rcuwait.h>
#include <linux/compat.h>
+#include <linux/io_uring.h>

#include <linux/uaccess.h>
#include <asm/unistd.h>
@@ -776,6 +777,7 @@ void __noreturn do_exit(long code)
schedule();
}

+ io_uring_files_cancel(tsk->files);
exit_signals(tsk); /* sets PF_EXITING */

/* sync mm's RSS info before statistics gathering */
--
2.24.0