cciss: Do not automatically rescan on UNIT ATTENTION/LUN DATA CHANGED

[linux-2.6-block.git] / drivers / block / cciss.c

diff --git a/drivers/block/cciss.c b/drivers/block/cciss.c
index 42eaddb543807ed7aece9bcdcbfcf824143e8b43..bf2d1c80b788abfd72242ed35905d3c344e9ec61 100644 (file)
--- a/drivers/block/cciss.c
+++ b/drivers/block/cciss.c
@@ -3416,8 +3416,22 @@ static int check_for_unit_attention(ctlr_info_t *h, CommandList_struct *c)
        case REPORT_LUNS_CHANGED:
                printk(KERN_WARNING "cciss%d: report LUN data "
                        "changed\n", h->ctlr);
-               add_to_scan_list(h);
-               wake_up_process(cciss_scan_thread);
+       /*
+        * Here, we could call add_to_scan_list and wake up the scan thread,
+        * except that it's quite likely that we will get more than one
+        * REPORT_LUNS_CHANGED condition in quick succession, which means
+        * that those which occur after the first one will likely happen
+        * *during* the scan_thread's rescan.  And the rescan code is not
+        * robust enough to restart in the middle, undoing what it has already
+        * done, and it's not clear that it's even possible to do this, since
+        * part of what it does is notify the block layer, which starts
+        * doing it's own i/o to read partition tables and so on, and the
+        * driver doesn't have visibility to know what might need undoing.
+        * In any event, if possible, it is horribly complicated to get right
+        * so we just don't do it for now.
+        *
+        * Note: this REPORT_LUNS_CHANGED condition only occurs on the MSA2012.
+        */
                return 1;
        break;
        case POWER_OR_RESET: