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Commit 87996204 authored by Bartlomiej Zolnierkiewicz's avatar Bartlomiej Zolnierkiewicz
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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: default avatarBartlomiej Zolnierkiewicz <bzolnier@gmail.com>
parent f68d9320

drivers/ide/ide.c

+30 −7
Original line number Diff line number Diff line
@@ -1124,17 +1124,40 @@ static int set_io_32bit(ide_drive_t *drive, int arg) 
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