Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 205 insertions, 0 deletions

diff --git a/drivers/md/dm-vdo/wait-queue.c b/drivers/md/dm-vdo/wait-queue.c
new file mode 100644
index 000000000..f81ed0cee
--- /dev/null
+++ b/drivers/md/dm-vdo/wait-queue.c
@@ -0,0 +1,205 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2023 Red Hat
+ */
+
+#include "wait-queue.h"
+
+#include <linux/device-mapper.h>
+
+#include "permassert.h"
+
+#include "status-codes.h"
+
+/**
+ * vdo_waitq_enqueue_waiter() - Add a waiter to the tail end of a waitq.
+ * @waitq: The vdo_wait_queue to which to add the waiter.
+ * @waiter: The waiter to add to the waitq.
+ *
+ * The waiter must not already be waiting in a waitq.
+ */
+void vdo_waitq_enqueue_waiter(struct vdo_wait_queue *waitq, struct vdo_waiter *waiter)
+{
+	BUG_ON(waiter->next_waiter != NULL);
+
+	if (waitq->last_waiter == NULL) {
+		/*
+		 * The waitq is empty, so form the initial circular list by self-linking the
+		 * initial waiter.
+		 */
+		waiter->next_waiter = waiter;
+	} else {
+		/* Splice the new waiter in at the end of the waitq. */
+		waiter->next_waiter = waitq->last_waiter->next_waiter;
+		waitq->last_waiter->next_waiter = waiter;
+	}
+
+	/* In both cases, the waiter we added to the list becomes the last waiter. */
+	waitq->last_waiter = waiter;
+	waitq->length += 1;
+}
+
+/**
+ * vdo_waitq_transfer_all_waiters() - Transfer all waiters from one waitq to
+ *                                    a second waitq, emptying the first waitq.
+ * @from_waitq: The waitq containing the waiters to move.
+ * @to_waitq: The waitq that will receive the waiters from the first waitq.
+ */
+void vdo_waitq_transfer_all_waiters(struct vdo_wait_queue *from_waitq,
+				    struct vdo_wait_queue *to_waitq)
+{
+	/* If the source waitq is empty, there's nothing to do. */
+	if (!vdo_waitq_has_waiters(from_waitq))
+		return;
+
+	if (vdo_waitq_has_waiters(to_waitq)) {
+		/*
+		 * Both are non-empty. Splice the two circular lists together
+		 * by swapping the next (head) pointers in the list tails.
+		 */
+		struct vdo_waiter *from_head = from_waitq->last_waiter->next_waiter;
+		struct vdo_waiter *to_head = to_waitq->last_waiter->next_waiter;
+
+		to_waitq->last_waiter->next_waiter = from_head;
+		from_waitq->last_waiter->next_waiter = to_head;
+	}
+
+	to_waitq->last_waiter = from_waitq->last_waiter;
+	to_waitq->length += from_waitq->length;
+	vdo_waitq_init(from_waitq);
+}
+
+/**
+ * vdo_waitq_notify_all_waiters() - Notify all the entries waiting in a waitq.
+ * @waitq: The vdo_wait_queue containing the waiters to notify.
+ * @callback: The function to call to notify each waiter, or NULL to invoke the callback field
+ *            registered in each waiter.
+ * @context: The context to pass to the callback function.
+ *
+ * Notifies all the entries waiting in a waitq to continue execution by invoking a callback
+ * function on each of them in turn. The waitq is copied and emptied before invoking any callbacks,
+ * and only the waiters that were in the waitq at the start of the call will be notified.
+ */
+void vdo_waitq_notify_all_waiters(struct vdo_wait_queue *waitq,
+				  vdo_waiter_callback_fn callback, void *context)
+{
+	/*
+	 * Copy and empty the waitq first, avoiding the possibility of an infinite
+	 * loop if entries are returned to the waitq by the callback function.
+	 */
+	struct vdo_wait_queue waiters;
+
+	vdo_waitq_init(&waiters);
+	vdo_waitq_transfer_all_waiters(waitq, &waiters);
+
+	/* Drain the copied waitq, invoking the callback on every entry. */
+	while (vdo_waitq_has_waiters(&waiters))
+		vdo_waitq_notify_next_waiter(&waiters, callback, context);
+}
+
+/**
+ * vdo_waitq_get_first_waiter() - Return the waiter that is at the head end of a waitq.
+ * @waitq: The vdo_wait_queue from which to get the first waiter.
+ *
+ * Return: The first (oldest) waiter in the waitq, or NULL if the waitq is empty.
+ */
+struct vdo_waiter *vdo_waitq_get_first_waiter(const struct vdo_wait_queue *waitq)
+{
+	struct vdo_waiter *last_waiter = waitq->last_waiter;
+
+	if (last_waiter == NULL) {
+		/* There are no waiters, so we're done. */
+		return NULL;
+	}
+
+	/* The waitq is circular, so the last entry links to the head of the waitq. */
+	return last_waiter->next_waiter;
+}
+
+/**
+ * vdo_waitq_dequeue_matching_waiters() - Remove all waiters that match based on the specified
+ *                                        matching method and append them to a vdo_wait_queue.
+ * @waitq: The vdo_wait_queue to process.
+ * @waiter_match: The method to determine matching.
+ * @match_context: Contextual info for the match method.
+ * @matched_waitq: A wait_waitq to store matches.
+ */
+void vdo_waitq_dequeue_matching_waiters(struct vdo_wait_queue *waitq,
+					vdo_waiter_match_fn waiter_match,
+					void *match_context,
+					struct vdo_wait_queue *matched_waitq)
+{
+	struct vdo_wait_queue iteration_waitq;
+
+	vdo_waitq_init(&iteration_waitq);
+	vdo_waitq_transfer_all_waiters(waitq, &iteration_waitq);
+
+	while (vdo_waitq_has_waiters(&iteration_waitq)) {
+		struct vdo_waiter *waiter = vdo_waitq_dequeue_waiter(&iteration_waitq);
+
+		vdo_waitq_enqueue_waiter((waiter_match(waiter, match_context) ?
+					  matched_waitq : waitq), waiter);
+	}
+}
+
+/**
+ * vdo_waitq_dequeue_waiter() - Remove the first (oldest) waiter from a waitq.
+ * @waitq: The vdo_wait_queue from which to remove the first entry.
+ *
+ * The caller will be responsible for waking the waiter by continuing its
+ * execution appropriately.
+ *
+ * Return: The first (oldest) waiter in the waitq, or NULL if the waitq is empty.
+ */
+struct vdo_waiter *vdo_waitq_dequeue_waiter(struct vdo_wait_queue *waitq)
+{
+	struct vdo_waiter *first_waiter = vdo_waitq_get_first_waiter(waitq);
+	struct vdo_waiter *last_waiter = waitq->last_waiter;
+
+	if (first_waiter == NULL)
+		return NULL;
+
+	if (first_waiter == last_waiter) {
+		/* The waitq has a single entry, so empty it by nulling the tail. */
+		waitq->last_waiter = NULL;
+	} else {
+		/*
+		 * The waitq has multiple waiters, so splice the first waiter out
+		 * of the circular waitq.
+		 */
+		last_waiter->next_waiter = first_waiter->next_waiter;
+	}
+
+	/* The waiter is no longer in a waitq. */
+	first_waiter->next_waiter = NULL;
+	waitq->length -= 1;
+
+	return first_waiter;
+}
+
+/**
+ * vdo_waitq_notify_next_waiter() - Notify the next entry waiting in a waitq.
+ * @waitq: The vdo_wait_queue containing the waiter to notify.
+ * @callback: The function to call to notify the waiter, or NULL to invoke the callback field
+ *            registered in the waiter.
+ * @context: The context to pass to the callback function.
+ *
+ * Notifies the next entry waiting in a waitq to continue execution by invoking a callback function
+ * on it after removing it from the waitq.
+ *
+ * Return: true if there was a waiter in the waitq.
+ */
+bool vdo_waitq_notify_next_waiter(struct vdo_wait_queue *waitq,
+				  vdo_waiter_callback_fn callback, void *context)
+{
+	struct vdo_waiter *waiter = vdo_waitq_dequeue_waiter(waitq);
+
+	if (waiter == NULL)
+		return false;
+
+	if (callback == NULL)
+		callback = waiter->callback;
+	callback(waiter, context);
+
+	return true;
+}