Commit 21386765 authored by Daniel Verkamp's avatar Daniel Verkamp Committed by Jim Harris
Browse files

bdev: defer completions from within submit_request 



If a blockdev module calls spdk_bdev_io_complete() within its
submit_request function, and the user's completion callback issues a new
I/O, it is possible to cause infinite recursion, consuming all available
stack space.

To avoid this, track whether a bdev_io is being processed by
submit_request, and if io_complete() is called in this case, defer the
completion via an event.

Change-Id: I6ccdb8ed4ee0d5738e6c9840d35431de52bd5fa2
Signed-off-by: default avatarDaniel Verkamp <daniel.verkamp@intel.com>
parent 360a3da3

include/spdk/bdev.h

+8 −0
Original line number Diff line number Diff line
@@ -265,6 +265,14 @@ struct spdk_bdev_io { 
	/** Status for the IO */

	enum spdk_bdev_io_status status;



	/**

	 * Set to true while the bdev module submit_request function is in progress.

	 *

	 * This is used to decide whether spdk_bdev_io_complete() can complete the I/O directly

	 * or if completion must be deferred via an event.

	 */

	bool in_submit_request;



	/** Used in virtual device (e.g., RAID), indicates its parent spdk_bdev_io **/

	struct spdk_bdev_io *parent;

lib/bdev/bdev.c

+26 −0
Original line number Diff line number Diff line
@@ -415,7 +415,9 @@ __submit_request(struct spdk_bdev *bdev, struct spdk_bdev_io *bdev_io) 
	if (bdev_io->type == SPDK_BDEV_IO_TYPE_RESET) {

		spdk_bdev_cleanup_pending_rbuf_io(bdev);

	}

	bdev_io->in_submit_request = true;

	bdev->fn_table->submit_request(bdev_io);

	bdev_io->in_submit_request = false;

}



static int
@@ -438,6 +440,7 @@ spdk_bdev_io_init(struct spdk_bdev_io *bdev_io, 
	bdev_io->cb = cb;

	bdev_io->gencnt = bdev->gencnt;

	bdev_io->status = SPDK_BDEV_IO_STATUS_PENDING;

	bdev_io->in_submit_request = false;

	TAILQ_INIT(&bdev_io->child_io);

}
@@ -798,9 +801,32 @@ spdk_bdev_free_io(struct spdk_bdev_io *bdev_io) 
	return 0;

}



static void

bdev_io_deferred_completion(void *arg1, void *arg2)

{

	struct spdk_bdev_io *bdev_io = arg1;

	enum spdk_bdev_io_status status = (enum spdk_bdev_io_status)arg2;



	assert(bdev_io->in_submit_request == false);



	spdk_bdev_io_complete(bdev_io, status);

}



void

spdk_bdev_io_complete(struct spdk_bdev_io *bdev_io, enum spdk_bdev_io_status status)

{

	if (bdev_io->in_submit_request) {

		/*

		 * Defer completion via an event to avoid potential infinite recursion if the

		 * user's completion callback issues a new I/O.

		 */

		spdk_event_call(spdk_event_allocate(spdk_app_get_current_core(),

						    bdev_io_deferred_completion,

						    bdev_io,

						    (void *)status));

		return;

	}



	if (bdev_io->type == SPDK_BDEV_IO_TYPE_RESET) {

		/* Successful reset */

		if (status == SPDK_BDEV_IO_STATUS_SUCCESS) {