[ldv-project] [PATCH 5.10 1/2] io_uring: cancel files inflight counting

[Fedor Pchelkin]

From: Pavel Begunkov <asml.silence at gmail.com>

To not skip events, io_uring_cancel_files() is pretty much counts on
io_uring_count_inflight() to be monotonous for the time it's used.
That's  not the case when it includes requests of other thats that are
PF_EXITING.

Cancel as before, but don't account extra in io_uring_count_inflight(),
we can hang otherwise.

Signed-off-by: Pavel Begunkov <asml.silence at gmail.com>
Signed-off-by: Fedor Pchelkin <pchelkin at ispras.ru>
---
 fs/io_uring.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index a952288b2ab8..25f2b87673bf 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1028,15 +1028,14 @@ static void io_refs_resurrect(struct percpu_ref *ref, struct completion *compl)
 		percpu_ref_put(ref);
 }
 
-static bool io_match_task(struct io_kiocb *head,
-			  struct task_struct *task,
-			  struct files_struct *files)
+static bool __io_match_task(struct io_kiocb *head, struct task_struct *task,
+			    struct files_struct *files, bool match_exiting)
 {
 	struct io_kiocb *link;
 
 	if (task && head->task != task) {
 		/* in terms of cancelation, always match if req task is dead */
-		if (head->task->flags & PF_EXITING)
+		if (match_exiting && (head->task->flags & PF_EXITING))
 			return true;
 		return false;
 	}
@@ -1053,6 +1052,12 @@ static bool io_match_task(struct io_kiocb *head,
 	return false;
 }
 
+static bool io_match_task(struct io_kiocb *head,
+			  struct task_struct *task,
+			  struct files_struct *files)
+{
+	return __io_match_task(head, task, files, true);
+}
 
 static void io_sq_thread_drop_mm(void)
 {
@@ -8656,7 +8661,7 @@ static int io_uring_count_inflight(struct io_ring_ctx *ctx,
 
 	spin_lock_irq(&ctx->inflight_lock);
 	list_for_each_entry(req, &ctx->inflight_list, inflight_entry)
-		cnt += io_match_task(req, task, files);
+		cnt += __io_match_task(req, task, files, false);
 	spin_unlock_irq(&ctx->inflight_lock);
 	return cnt;
 }
-- 
2.25.1