[dm-devel] [PATCH] multipath: reference count on pgpath

[Menny_Hamburger at Dell.com]

Hi,

Here is the patch I am currently testing to solve the OOPs  in  pg_init_done (from send_mode_select).
The patch  adds a reference count to pgpath, which  ensures that activate_path has the pgpath intact when the call to scsi_dh_activate returns; thus any call to send_mode_select from within scsi_dh_rdac will call pg_init_done with a valid pgpath.


This patch is over RHEL5.4.

diff -r -U 2 a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c
--- a/drivers/md/dm-mpath.c    2011-01-23 14:26:51.483249000 +0200
+++ b/drivers/md/dm-mpath.c 2011-01-23 14:26:51.521889000 +0200
@@ -21,4 +21,5 @@
#include <linux/time.h>
#include <linux/workqueue.h>
+#include <linux/kref.h>
#include <scsi/scsi_dh.h>
#include <asm/atomic.h>
@@ -34,4 +35,5 @@
                struct priority_group *pg;            /* Owning PG */
                unsigned fail_count;                       /* Cumulative failure count */
+             struct kref ref_count;

                struct path path;
@@ -129,4 +131,6 @@
                                memset(pgpath, 0, sizeof(*pgpath));
                                pgpath->path.is_active = 1;
+                             kref_init(&pgpath->ref_count);
+                             kref_get(&pgpath->ref_count);
                                INIT_WORK(&pgpath->activate_path, activate_path, pgpath);
                }
@@ -140,4 +144,11 @@
}

+static void release_pgpath(struct kref *kref)
+{
+        struct pgpath *pgpath = container_of(kref, struct pgpath, ref_count);
+             free_pgpath(pgpath);
+
+}
+
static struct priority_group *alloc_priority_group(void)
{
@@ -164,5 +175,5 @@
                                                scsi_dh_detach(bdev_get_queue(pgpath->path.dev->bdev));
                                dm_put_device(ti, pgpath->path.dev);
-                              free_pgpath(pgpath);
+                             kref_put(&pgpath->ref_count, release_pgpath);
                }
}
@@ -449,6 +460,8 @@
                                                                if (queue_delayed_work(kmpath_handlerd,
                                                                    &tmp->activate_path, m->pg_init_delay ?
-                                                                  m->pg_init_delay_secs * HZ : 0))
+                                                                 m->pg_init_delay_secs * HZ : 0)) {
+                                                                             kref_get(&pgpath->ref_count);
                                                                                m->pg_init_in_progress++;
+                                                             }
                                                }
                                }
@@ -971,6 +984,8 @@
                                queue_work(kmultipathd, &m->process_queued_ios);
                } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
-                              if (queue_work(kmpath_handlerd, &pgpath->activate_path))
+                             if (queue_work(kmpath_handlerd, &pgpath->activate_path)) {
+                                             kref_get(&pgpath->ref_count);
                                                m->pg_init_in_progress++;
+                             }
                }

@@ -1215,4 +1230,5 @@
                scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev),
                                                                pg_init_done, &pgpath->path);
+             kref_put(&pgpath->ref_count, release_pgpath);
}

Menny Hamburger
Engineer
Dell | IDC
office +972 97698789,  fax +972 97698889
Dell IDC. 4 Hacharoshet St, Raanana 43657, Israel

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