[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

Re: [dm-devel] [PATCH 3/3] dm-multipath: 'default_hw_handler' feature

On 05/08/2012 04:46 PM, Mike Snitzer wrote:
On Tue, May 08 2012 at 10:18am -0400,
Hannes Reinecke<hare suse de>  wrote:

This patch introduces a 'default_hw_handler' feature for
dm-mpath. When specifying the feature 'default_hw_handler'
dm-multipath will be using the currently attached hardware
handler instead of trying to re-attach with the one
specified during table creation.
If no hardware handler is attached the specified hardware
handler will be used.

Signed-off-by: Hannes Reinecke<hare suse de>
  drivers/md/dm-mpath.c |   25 ++++++++++++++++++++++---
  1 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
index 6d3f2a8..c1ef41d 100644
--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -57,6 +57,7 @@ struct priority_group {


  /* Multipath context */
  struct multipath {
@@ -589,14 +590,24 @@ static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps

  	if (m->hw_handler_name) {
  		struct request_queue *q = bdev_get_queue(p->path.dev->bdev);
+		const char *hw_handler_name = m->hw_handler_name;

-		r = scsi_dh_attach(q, m->hw_handler_name);
+		if (m->features&  FEATURE_DEFAULT_HW_HANDLER)
+			hw_handler_name = NULL;
+		r = scsi_dh_attach(q, hw_handler_name);
  		if (r == -EBUSY) {
  			 * Already attached to different hw_handler,
  			 * try to reattach with correct one.
+			r = scsi_dh_attach(q, hw_handler_name);
+		} else if (r == -EINVAL) {
+			/*
+			 * No hardware handler attached, use
+			 * the specified one.
+			 */
  			r = scsi_dh_attach(q, m->hw_handler_name);

I like what you've done with the 'default_hw_handler' feature.  But
you're not establishing m->hw_handler_name.  As such the rest of the
dm-mpath.c code that keys off of m->hw_handler_name (e.g. reinstate_path,
pg_init_done, free_pgpaths) will not work.

Ah. True.

Would you be OK with a hybrid of both our approaches?  Use your
'default_hw_handler' feature and, rather than pass a NULL name to
scsi_dh_attach, use scsi_dh_attached_handler_name like I provided?

Yes, sure. That sounds like the best approach here.

I'm not _that_ keen on my 'NULL' hw handler name approach, so your idea
of having a function for that looks like a better idea.

(I don't see a problem with altering m->hw_handler_name to reflect the
scsi_dh that is used by the path.. Babu agreed with this too).


I'd be happy to merge our dm-mpath patches and attribute authorship to

Oh, cool.
Please do.


Dr. Hannes Reinecke		      zSeries & Storage
hare suse de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Markus Rex, HRB 16746 (AG Nürnberg)

[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]