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: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/drivers/block/cciss.h b/drivers/block/cciss.h
index c5d411174db0fb282d019a391c94f723513a84ae..37a2d4fb01d8fbd4444d977314b020e46b3288fd 100644 (file)
--- a/drivers/block/cciss.h
+++ b/drivers/block/cciss.h
@@ -173,6 +173,7 @@ 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;