Merge tag 'io_uring-6.6-2023-10-27' of git://git.kernel.dk/linux

Pull io_uring fixes from Jens Axboe:
 "Fix for an issue reported where reading fdinfo could find a NULL
  thread as we didn't properly synchronize, and then a disable for the
  IOCB_DIO_CALLER_COMP optimization as a recent reported highlighted how
  that could lead to deadlocks if the task issued async O_DIRECT writes
  and then proceeded to do sync fallocate() calls"

* tag 'io_uring-6.6-2023-10-27' of git://git.kernel.dk/linux:
  io_uring/rw: disable IOCB_DIO_CALLER_COMP
  io_uring/fdinfo: lock SQ thread while retrieving thread cpu/pid

Author: torvalds

io_uring/fdinfo.c

@@ -53,7 +53,6 @@ static __cold int io_uring_show_cred(struct seq_file *m, unsigned int id,
 __cold void io_uring_show_fdinfo(struct seq_file *m, struct file *f)
 {
 	struct io_ring_ctx *ctx = f->private_data;
-	struct io_sq_data *sq = NULL;
 	struct io_overflow_cqe *ocqe;
 	struct io_rings *r = ctx->rings;
 	unsigned int sq_mask = ctx->sq_entries - 1, cq_mask = ctx->cq_entries - 1;
@@ -64,6 +63,7 @@ __cold void io_uring_show_fdinfo(struct seq_file *m, struct file *f)
 	unsigned int cq_shift = 0;
 	unsigned int sq_shift = 0;
 	unsigned int sq_entries, cq_entries;
+	int sq_pid = -1, sq_cpu = -1;
 	bool has_lock;
 	unsigned int i;
 
@@ -143,13 +143,19 @@ __cold void io_uring_show_fdinfo(struct seq_file *m, struct file *f)
 	has_lock = mutex_trylock(&ctx->uring_lock);
 
 	if (has_lock && (ctx->flags & IORING_SETUP_SQPOLL)) {
-		sq = ctx->sq_data;
-		if (!sq->thread)
-			sq = NULL;
+		struct io_sq_data *sq = ctx->sq_data;
+
+		if (mutex_trylock(&sq->lock)) {
+			if (sq->thread) {
+				sq_pid = task_pid_nr(sq->thread);
+				sq_cpu = task_cpu(sq->thread);
+			}
+			mutex_unlock(&sq->lock);
+		}
 	}
 
-	seq_printf(m, "SqThread:\t%d\n", sq ? task_pid_nr(sq->thread) : -1);
-	seq_printf(m, "SqThreadCpu:\t%d\n", sq ? task_cpu(sq->thread) : -1);
+	seq_printf(m, "SqThread:\t%d\n", sq_pid);
+	seq_printf(m, "SqThreadCpu:\t%d\n", sq_cpu);
 	seq_printf(m, "UserFiles:\t%u\n", ctx->nr_user_files);
 	for (i = 0; has_lock && i < ctx->nr_user_files; i++) {
 		struct file *f = io_file_from_index(&ctx->file_table, i);

io_uring/rw.c

@@ -913,15 +913,6 @@ int io_write(struct io_kiocb *req, unsigned int issue_flags)
 		kiocb_start_write(kiocb);
 	kiocb->ki_flags |= IOCB_WRITE;
 
-	/*
-	 * For non-polled IO, set IOCB_DIO_CALLER_COMP, stating that our handler
-	 * groks deferring the completion to task context. This isn't
-	 * necessary and useful for polled IO as that can always complete
-	 * directly.
-	 */
-	if (!(kiocb->ki_flags & IOCB_HIPRI))
-		kiocb->ki_flags |= IOCB_DIO_CALLER_COMP;
-
 	if (likely(req->file->f_op->write_iter))
 		ret2 = call_write_iter(req->file, kiocb, &s->iter);
 	else if (req->file->f_op->write)