libata: Fix a potential race condition in ata_scsi_park_show()

Peter Moulder has pointed out that there is a slight chance that a
negative value might be passed to jiffies_to_msecs() in
ata_scsi_park_show(). This is fixed by saving the value of jiffies in a
local variable, thus also reducing code since the volatile variable
jiffies is accessed only once.

Signed-off-by: Elias Oltmanns <eo@nebensachen.de>
Signed-off-by: Tejun Heo <tj.kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index bbb30d8..3fa75ea 100644 (file)
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -190,7 +190,7 @@ static ssize_t ata_scsi_park_show(struct device *device,
        struct ata_port *ap;
        struct ata_link *link;
        struct ata_device *dev;
-       unsigned long flags;
+       unsigned long flags, now;
        unsigned int uninitialized_var(msecs);
        int rc = 0;
 
@@ -208,10 +208,11 @@ static ssize_t ata_scsi_park_show(struct device *device,
        }
 
        link = dev->link;
+       now = jiffies;
        if (ap->pflags & ATA_PFLAG_EH_IN_PROGRESS &&
            link->eh_context.unloaded_mask & (1 << dev->devno) &&
-           time_after(dev->unpark_deadline, jiffies))
-               msecs = jiffies_to_msecs(dev->unpark_deadline - jiffies);
+           time_after(dev->unpark_deadline, now))
+               msecs = jiffies_to_msecs(dev->unpark_deadline - now);
        else
                msecs = 0;