I would like to merge it for 2.6.21-final because this issue become quite
urgent thanks to /etc/udev/scripts/hdparm.conf (the race is triggered
by udev/hdparm tuning master device while the slave device is still being
probed by the driver). Reviews/comments are greatly appreciated.
[PATCH] 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.
Cc: Sergei Shtylyov <[EMAIL PROTECTED]>
Cc: Alan Cox <[EMAIL PROTECTED]>
Signed-off-by: Bartlomiej Zolnierkiewicz <[EMAIL PROTECTED]>
---
drivers/ide/ide.c | 37 ++++++++++++++++++++++++++++++-------
1 file changed, 30 insertions(+), 7 deletions(-)
Index: b/drivers/ide/ide.c
===================================================================
--- a/drivers/ide/ide.c
+++ b/drivers/ide/ide.c
@@ -1124,17 +1124,40 @@ static int set_io_32bit(ide_drive_t *dri
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
-
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