libata: make EH fail gracefully if no reset method is available

When no reset method is available, libata currently oopses.  Although
the condition can't happen unless there's a bug in a low level driver,
oopsing isn't the best way to report the error condition.  Complain,
dump stack and fail reset instead.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
index ecbb8e90cb8d..d94359a24d41 100644
--- a/drivers/ata/libata-eh.c
+++ b/drivers/ata/libata-eh.c
@@ -2137,9 +2137,14 @@ int ata_eh_reset(struct ata_link *link, int classify,
         if (hardreset) {
                 reset = hardreset;
                 ehc->i.action = ATA_EH_HARDRESET;
-        } else {
+        } else if (softreset) {
                 reset = softreset;
                 ehc->i.action = ATA_EH_SOFTRESET;
+        } else {
+                ata_link_printk(link, KERN_ERR, "BUG: no reset method, "
+                                "please report to linux-ide@vger.kernel.org\n");
+                dump_stack();
+                return -EINVAL;
         }
 
         if (prereset) {