cciss: fix lost command issue

commit 1ddd5049545e0aa1a0ed19bca4d9c9c3ce1ac8a2 upstream.

Under certain workloads a command may seem to get lost. IOW, the Smart Array
thinks all commands have been completed but we still have commands in our
completion queue. This may lead to system instability, filesystems going
read-only, or even panics depending on the affected filesystem. We add an
extra read to force the write to complete.

Testing shows this extra read avoids the problem.

Signed-off-by: Mike Miller <mike.miller@hp.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/block/cciss.h b/drivers/block/cciss.h
index 31524cf42c77360645424a9c85e68a9651ba8422..5ae1b1c4fc44a16789df85de859f72f18cb36939 100644 (file)
--- a/drivers/block/cciss.h
+++ b/drivers/block/cciss.h
@@ -165,6 +165,7 @@ static void SA5_submit_command( ctlr_info_t *h, CommandList_struct *c)
         printk("Sending %x - down to controller\n", c->busaddr );
 #endif /* CCISS_DEBUG */ 
          writel(c->busaddr, h->vaddr + SA5_REQUEST_PORT_OFFSET);
+       readl(h->vaddr + SA5_REQUEST_PORT_OFFSET);
         h->commands_outstanding++;
         if ( h->commands_outstanding > h->max_outstanding)
                h->max_outstanding = h->commands_outstanding;