Commit 27f204c2 authored by Benjamin Marzinski's avatar Benjamin Marzinski Committed by Mikulas Patocka
Browse files

dm-mpath: Simplify the setup_scsi_dh code 



There's no point to the MPATHF_RETAIN_ATTACHED_HW_HANDLER flag any more.
The way setup_scsi_dh() worked, if that flag wasn't set, it would
attempt to attach any passed in hardware handler. This would always fail
if a different hardware handler was attached, which caused
setup_scsi_dh() to rerun as if the flag was set. So the code would
already retain any attached handler, because attaching a different one
would always fail.

Also, the code had a bug. If attached_handler_name was NULL but there
was a scsi device handler attached (because either
scsi_dh_attached_handler_name failed() to allocate a name, a handler got
attached after it was called) the code would loop endlessly.

Instead, ignore MPATHF_RETAIN_ATTACHED_HW_HANDLER, and always free the
passed in handler if *attached_handler_name is set. This simplifies the
code, and avoids the endless loop bug, while keeping the functionality
the same.

Signed-off-by: default avatarBenjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
parent 4efe85b0

drivers/md/dm-mpath.c

+23 −38
Original line number Diff line number Diff line
@@ -131,7 +131,7 @@ static void queue_if_no_path_timeout_work(struct timer_list *t); 
#define MPATHF_QUEUE_IO 0			/* Must we queue all I/O? */

#define MPATHF_QUEUE_IF_NO_PATH 1		/* Queue I/O if last path fails? */

#define MPATHF_SAVED_QUEUE_IF_NO_PATH 2		/* Saved state during suspension */

#define MPATHF_RETAIN_ATTACHED_HW_HANDLER 3	/* If there's already a hw_handler present, don't change it. */

/* MPATHF_RETAIN_ATTACHED_HW_HANDLER no longer has any effect */

#define MPATHF_PG_INIT_DISABLED 4		/* pg_init is not currently allowed */

#define MPATHF_PG_INIT_REQUIRED 5		/* pg_init needs calling? */

#define MPATHF_PG_INIT_DELAY_RETRY 6		/* Delay pg_init retry? */
@@ -237,16 +237,10 @@ static struct multipath *alloc_multipath(struct dm_target *ti) 


static int alloc_multipath_stage2(struct dm_target *ti, struct multipath *m)

{

	if (m->queue_mode == DM_TYPE_NONE) {

	if (m->queue_mode == DM_TYPE_NONE)

		m->queue_mode = DM_TYPE_REQUEST_BASED;

	} else if (m->queue_mode == DM_TYPE_BIO_BASED) {

	else if (m->queue_mode == DM_TYPE_BIO_BASED)

		INIT_WORK(&m->process_queued_bios, process_queued_bios);

		/*

		 * bio-based doesn't support any direct scsi_dh management;

		 * it just discovers if a scsi_dh is attached.

		 */

		set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);

	}



	dm_table_set_type(ti->table, m->queue_mode);
@@ -887,14 +881,13 @@ static int setup_scsi_dh(struct block_device *bdev, struct multipath *m, 
	struct request_queue *q = bdev_get_queue(bdev);

	int r;



	if (mpath_double_check_test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, m)) {

retain:

	if (*attached_handler_name) {

		/*

		 * Clear any hw_handler_params associated with a

		 * handler that isn't already attached.

		 */

			if (m->hw_handler_name && strcmp(*attached_handler_name, m->hw_handler_name)) {

		if (m->hw_handler_name && strcmp(*attached_handler_name,

						 m->hw_handler_name)) {

			kfree(m->hw_handler_params);

			m->hw_handler_params = NULL;

		}
@@ -909,14 +902,9 @@ static int setup_scsi_dh(struct block_device *bdev, struct multipath *m, 
		m->hw_handler_name = *attached_handler_name;

		*attached_handler_name = NULL;

	}

	}



	if (m->hw_handler_name) {

		r = scsi_dh_attach(q, m->hw_handler_name);

		if (r == -EBUSY) {

			DMINFO("retaining handler on device %pg", bdev);

			goto retain;

		}

		if (r < 0) {

			*error = "error attaching hardware handler";

			return r;
@@ -1138,7 +1126,7 @@ static int parse_features(struct dm_arg_set *as, struct multipath *m) 
		}



		if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {

			set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);

			/* no longer has any effect */

			continue;

		}
@@ -1823,7 +1811,6 @@ static void multipath_status(struct dm_target *ti, status_type_t type, 
		DMEMIT("%u ", test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) +

			      (m->pg_init_retries > 0) * 2 +

			      (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +

			      test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) +

			      (m->queue_mode != DM_TYPE_REQUEST_BASED) * 2);



		if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
@@ -1832,8 +1819,6 @@ static void multipath_status(struct dm_target *ti, status_type_t type, 
			DMEMIT("pg_init_retries %u ", m->pg_init_retries);

		if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)

			DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);

		if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags))

			DMEMIT("retain_attached_hw_handler ");

		if (m->queue_mode != DM_TYPE_REQUEST_BASED) {

			switch (m->queue_mode) {

			case DM_TYPE_BIO_BASED: