ide: fix locking for manual DMA enable/disable ("hdparm -d")
Since hwif->ide_dma_check and hwif->ide_dma_on never queue any commands
(ide_config_drive_speed() sets transfer mode using polling and has no error
recovery) we are safe with setting hwgroup->busy for the time while DMA
setting for a drive is changed (so it won't race against I/O commands in fly).
I audited briefly all ->ide_dma_check/->ide_dma_on/->tuneproc/->speedproc
implementations and they all look OK wrt to this change.
This patch finally allowed me to close kernel bugzilla bug #8169
(once again thanks to Patrick Horn for reporting the issue & testing patches).
Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/drivers/ide/ide.c b/drivers/ide/ide.c
index 695610f..a6f098f 100644
--- a/drivers/ide/ide.c
+++ b/drivers/ide/ide.c
@@ -1124,17 +1124,40 @@
static int set_using_dma (ide_drive_t *drive, int arg)
{
#ifdef CONFIG_BLK_DEV_IDEDMA
+ ide_hwif_t *hwif = drive->hwif;
+ int err = -EPERM;
+
if (!drive->id || !(drive->id->capability & 1))
- return -EPERM;
- if (HWIF(drive)->ide_dma_check == NULL)
- return -EPERM;
+ goto out;
+
+ if (hwif->ide_dma_check == NULL)
+ goto out;
+
+ err = -EBUSY;
+ if (ide_spin_wait_hwgroup(drive))
+ goto out;
+ /*
+ * set ->busy flag, unlock and let it ride
+ */
+ hwif->hwgroup->busy = 1;
+ spin_unlock_irq(&ide_lock);
+
+ err = 0;
+
if (arg) {
- if (ide_set_dma(drive))
- return -EIO;
- if (HWIF(drive)->ide_dma_on(drive)) return -EIO;
+ if (ide_set_dma(drive) || hwif->ide_dma_on(drive))
+ err = -EIO;
} else
ide_dma_off(drive);
- return 0;
+
+ /*
+ * lock, clear ->busy flag and unlock before leaving
+ */
+ spin_lock_irq(&ide_lock);
+ hwif->hwgroup->busy = 0;
+ spin_unlock_irq(&ide_lock);
+out:
+ return err;
#else
return -EPERM;
#endif